Maddison D.R., Moore W., Baker M.D., Ellis T.M., Ober K.A., Cannone J.J., and Gutell R.R. (2009).
Monophyly of terrestrial adephagan beetles as indicated by three nuclear genes (Coleoptera: Carabidae and Trachypachidae).
Zoologica Scripta, 38(1):43-62.
“Distributional patterns of the order Gomphales (fungi: basidiomycota) in Nor...astridGonzalez29
ASTRID GONZÁLEZ-ÁVILA and DAVID ESPINOSA-ORGANISTA
Facultad de Estudios Superiores Zaragoza, Universidad Nacional Autónoma de México, Batalla del 5 de mayo s/n, Ejército de Oriente, Iztapalapa, CP 09230, Ciudad de México, México.
First attempts using NGS in Senecio (Asteraceae)
Building a robust phylogeny of Culcitium group: a baseline for addressing further evolutionary questions for the genus in the Andes
In order to assess the Myxosporeans fauna of Cameroon fresh water fishes so
as to find the fight strategies, 655 specimens (350 Oreochromis niloticus and 305
Barbus callipterus) were sampled in Mapé river (Sanaga basin) and examined.
Standard methods were used for the sampling of fishes, conservation and microscopy.
Morphometric characteristics of the spores were used for species identification. Two
new species belonging to the genus Myxobolus Büstchli, 1882 were described namely
Myxobolus tchoumbouei n. sp in Barbus callipterus which formed cysts within various
organs (fins, skin and operculum); Myxobolus mapei n. sp parasite of kidneys and liver
in Oreochromis niloticus and Barbus callipterus. Myxobolus tchoumbouei exhibited
very long spores (19.19 x 8.89 μm), pear-shaped with rounded anterior end
sometimes flattened. Polar capsules were dissymmetrical. They measured 7.60 x 3.00
μm for the bigger and 7.06 x 2.62 μm for the smaller. Myxobolus mapei n. sp had
ellipsoidal spores (13.50 x 6.83 μm) with unequal polar capsules. The larger polar
capsule (6.44 X 2.88 μm) was about 1.5 times longer than the smaller one (4.13 X 1.61
μm) and filled half of the spiral cavity. The awareness about these parasites is useful
to find fighting strategies.
Maddison D.R., Moore W., Baker M.D., Ellis T.M., Ober K.A., Cannone J.J., and Gutell R.R. (2009).
Monophyly of terrestrial adephagan beetles as indicated by three nuclear genes (Coleoptera: Carabidae and Trachypachidae).
Zoologica Scripta, 38(1):43-62.
“Distributional patterns of the order Gomphales (fungi: basidiomycota) in Nor...astridGonzalez29
ASTRID GONZÁLEZ-ÁVILA and DAVID ESPINOSA-ORGANISTA
Facultad de Estudios Superiores Zaragoza, Universidad Nacional Autónoma de México, Batalla del 5 de mayo s/n, Ejército de Oriente, Iztapalapa, CP 09230, Ciudad de México, México.
First attempts using NGS in Senecio (Asteraceae)
Building a robust phylogeny of Culcitium group: a baseline for addressing further evolutionary questions for the genus in the Andes
In order to assess the Myxosporeans fauna of Cameroon fresh water fishes so
as to find the fight strategies, 655 specimens (350 Oreochromis niloticus and 305
Barbus callipterus) were sampled in Mapé river (Sanaga basin) and examined.
Standard methods were used for the sampling of fishes, conservation and microscopy.
Morphometric characteristics of the spores were used for species identification. Two
new species belonging to the genus Myxobolus Büstchli, 1882 were described namely
Myxobolus tchoumbouei n. sp in Barbus callipterus which formed cysts within various
organs (fins, skin and operculum); Myxobolus mapei n. sp parasite of kidneys and liver
in Oreochromis niloticus and Barbus callipterus. Myxobolus tchoumbouei exhibited
very long spores (19.19 x 8.89 μm), pear-shaped with rounded anterior end
sometimes flattened. Polar capsules were dissymmetrical. They measured 7.60 x 3.00
μm for the bigger and 7.06 x 2.62 μm for the smaller. Myxobolus mapei n. sp had
ellipsoidal spores (13.50 x 6.83 μm) with unequal polar capsules. The larger polar
capsule (6.44 X 2.88 μm) was about 1.5 times longer than the smaller one (4.13 X 1.61
μm) and filled half of the spiral cavity. The awareness about these parasites is useful
to find fighting strategies.
Radiation and Radiation toxins are responsible for causing severe pathology and toxicity following moderate and high doses of radiation including cytotoxicity - necrosis, apoptosis, neurotoxicity, cardiotoxicity, profuse hemorrhage, and disruption of blood homeostasis.
Introduction
Ostracoderms (shell-skinned) are of several groups of extinct, primitive, jawless fishes that were covered in an armour of bony plates.
They appeared in the Cambrian, about 510 million years ago, and became extinct towards the end of the Devonian, about 377 million years ago. They were quite abundant during the upper Silurian and Devonian periods. Most of fossils of Ostracodermi were preserved in the bottom sediments of freshwater streams.
However, the opinion is sharply divided as to whether their habitat was freshwater or marine.
The first fossil fishes that were discovered were ostracoderms.
The Swiss anatomist Louis Agassiz received some fossils of bony armored fish from Scotland in the 1830s.
The ostracoderms resembled the present day cyclostomes (lampreys and hagfishes) in many respects and together with them constitute a special group of jawless vertebrates, the Agnatha.
Characteristics: They use gills exclusively for respiration but not for feeding . Earlier chordates with gills used them for both respiration and feeding. Ostracoderms had separate pharyngeal gill pouches along the side of the head, which were permanently open with no protective operculum. mostly small to medium-sized fishes, protected by a heavy, bony dermal (derived from skin) armor. bottom-dwellers; filter-feeders or grazers. no paired fins, but many with stabilizing paired flaps on either side of head.
(1) Ostracoderms were the first vertebrates.
(2) They were popularly called armoured fishes.
(4) They lived in freshwater.
(5) They were bottom dwellers.
(6) Their body was fish-like and did not exceed 30 cm in size.
(7) Paired fins were absent.
(8) Median and caudal fins were present.
(9) The caudal fin was of heterocercal type.
(10) The head and thorax were covered by heavy armour of bones. It protected ostracoderms from the giant scorpion like arthropods, eurypterids.
(11) Bony skull was well developed.
(12) Mouth was mostly present on the ventral side.
(13) They were having large number of gill slits.
(14) The nervous system had 10 pairs of cranial nerves.
(15) The head had a pair of lateral eyes, and a median pineal eye.
(16) They were filter feeders, feeding like a vacuum cleaner.
(17) The endoskeleton was either bony or cartilaginous.
ARTICLE IN PRESShttpwww.elsevier.deprotisPublished onl.docxfredharris32
ARTICLE IN PRESS
http://www.elsevier.de/protis
Published online date 7 August 2006
1
Correspondin
fax +81 29 853
e-mail iinouye
2Current addr
Parkville, Victo
& 2006 Elsev
doi:10.1016/j
157, 401—419, August 2006
Protist, Vol.
ORIGINAL PAPER
Hatena arenicola gen. et sp. nov., a Katablepharid
Undergoing Probable Plastid Acquisition
Noriko Okamoto2, and Isao Inouye1
Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba,
Ibaraki 305-8572, Japan
Submitted February 27, 2006; Accepted May 27, 2006
Monitoring Editor: Robert A. Andersen
Hatena arenicola gen. et sp. nov., an enigmatic flagellate of the katablepharids, is described. It shows
ultrastructural affinities to the katablepharids, including large and small ejectisomes, cell covering,
and a feeding apparatus. Although molecular phylogenies of the 18S ribosomal DNA support its
classification into the katablepharids, the cell is characterized by a dorsiventrally compressed cell
shape and a crawling motion, both of which are unusual within this group. The most distinctive feature
of Hatena arenicola is that it harbors a Nephroselmis symbiont. This symbiosis is distinct from
previously reported cases of ongoing symbiosis in that the symbiont plastid is selectively enlarged,
while other structures such as the mitochondria, Golgi body, cytoskeleton, and endomembrane
system are degraded; the host and symbiont have developed a morphological association, i.e., the
eyespot of the symbiont is always at the cell apex of Hatena arenicola; and only one daughter cell
inherits the symbiont during cell division, resulting in a symbiont-bearing green cell and a symbiont-
lacking colorless cell. Interestingly, the colorless cells have a feeding apparatus that corresponds to
the location of the eyespot in symbiont-bearing cells, and they are able to feed on prey cells. This
indicates that the morphology of the host depends on the presence or absence of the symbiont. These
observations suggest that Hatena arenicola has a unique ‘‘half-plant, half-predator’’ life cycle; one cell
divides into an autotrophic cell possessing a symbiotic Nephroselmis species, and a symbiont-lacking
colorless cell, which later develops a feeding apparatus de novo. The evolutionary implications of
Hatena arenicola as an intermediate step in plastid acquisition are discussed in the context of other
examples of ongoing endosymbioses in dinoflagellates.
& 2006 Elsevier GmbH. All rights reserved.
Key words: Hatena arenicola; Katablepharidophyta/Kathablepharida; Nephroselmis symbiont; plant
evolution; plastid acquisition via secondary endosymbiosis; ultrastructure.
Abbreviations: EM ¼ electron microscopy; ER ¼
endoplasmic reticulum; ICBN ¼ International Code
of Botanical Nomenclature; ICZN ¼ International
Code of Zoological Nomenclature; LM ¼ light mi-
croscopy; SEM ¼ scanning electron microscopy;
SSU rDNA ¼ small subunit ribosomal DNA; TEM ¼
transmission electron microscopy.
g author;
4533
...
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...
Evolution venom app82_2
1. Mem. Inst. Butantan
46: 106-118, 1982
THE EVOLUTION OF THE VENOM APPARATUS IN
SNAKES FROM COLUBRIDS TO VIPERIDS & ELAPIDS
Kenneth V. KARDONG *
ABSTRACT: The venom apparatus of poisonous snakes consists
of a fang and associated venom gland (or glands). Venomous
snakes evolved from nonvenomous ancestors. The course of this
evolution, the adaptive advantages of the changes at each stage,
and the implications of the findings to snake phylogeny, phar-macology,
and clinical strategies of treatment of envenomations
are the subject of this paper.
In particular, it is argued in this paper that: (1) both viperid
and elapid snakes evolved from opisthodont ancestors; (2) the
Duvernoy's gland in most colubrid snakes should not be seen as
a gland "on its way" to becoming a venom gland, but should be
examined for the immediate biological role it plays in the life of
those snakes possessing such a gland; (3) it would be useful to
distinguish between a property of an oral secretion (e.g. toxin)
and its biological role (e.g. venom) ; (4) strategies of treatment
of envenomation would profit if it were more fully appreciated
why venom is composed of more than just a suite of toxins.
INTRODUCTION
The venom apparatus of poisonous snakes consists primarily of two
components: a modified tooth, the fang by which venom is delivered into
prey, and the venom gland (or glands) where toxin is produced and
stored. Venomous snakes use the venom apparatus to rapidly kill prey
and secondarily in defense from their own enemies.
The structure of fangs and venom glands are the subject of many
revealing descriptive papers (e.g. Kochva and Gans, 1966; Rosenberg,
1967; Nickerson, 1969; Gabe and Saint Girons, 1971 ; Halstead et al.,
1978). However, clarifying the evolution of the venom apparatus has
proved to be a more contentious and elusive task (Smith and Bellairs,
1947; Kroll, 1976). In part, this arises from phylogenies of snakes
constructed upon only a general or anecdotal knowledge of the functional
morphology of the jaw apparatus. Thus, the first purpose of this paper
is to review the functional role of both the apparatus and the evolutio-nary
antecedants of the venom apparatus. This will lead to the formu-lation
of focused hypotheses that yield testable predictions.
* Department of Zoology. Washington State University-U.S.A
2. KARDONG,
elapids.
K. V. The evolution of the venom apparatus in snakes from colubrids
Men. Inst. Butantan. 46:105-118, 1982.
viperids 6t
The conclusions reached herein about the evolution of the snake
venom apparatus shed a different light upon ophidian taxonomy and
phylogeny, venom pharmacology, and even upon clinical treatment of
snakebite. Thus, the second purpose of this paper is to discuss the
implications of these conclusions for these related areas.
RESULTS
A) Evolution of the Fang
1 . Morphological Series
Venomous snakes evolved from nonvenomous ancestors. Three
families of snakes are immediately involved: Colubridae, Viperidae, and
Elapidae (including sea snakes). Viperids and elapids are poisonous
snakes with sophisticated venom apparatuses used to quickly kill prey.
However, most colubrid snakes are basically nonvenomous. True, some
such as Dispholidus seem to parallel viperids and elapids in that they
possess a highly toxic venom apparatus and use it to rapidly kill prey.
But, the vast majority of colubrids are truely nonvenomous.
The origin of viperid and elapid snakes from colubrids has been a
longstanding concern among those interested in advanced snakes (Bou-lenger,
1893, 1896, 1917; West, 1895; Alcock and Rogers, 1902; Phisalix,
1912, 1922). Several relationships have been proposed. One suggests
a single origin of venomous snakes from colubrids (Cope, 1900; Mosauer,
1935) ; another that elapids arose from opisthoglyphous colubrids, and
viperids from proteroglyphous colubrids (Anthony, 1955). The rela-tionship
I use here is that both elapids and viperids evolved from
opisthoglyphous colubrid ancestors, but independently (Kardong, 1980).
This evolution of venomous snakes from opisthoglyphs probably occurred
several times (Kochva et al., 1967; Bprrgeois, 1968; McDowell, 1968;
Savitzky, 1980). However, despite a lipfely polyphyletic origin of veno-mous
snakes, these fall along but two pathways, one leading to viperids
and viper-like snakes, and the other to elapids and elapid-like snakes.
It is beyond the scope of this paper to identify how many times each
of these paths was traveled by evolving snakes. Instead, the purpose
is to analyze the general adaptive advantage of changes on each evolu-ti
onary highway.
If we focus our attention on the maxillary bone and the teeth it
hears, then one can construct a simple morphological series (sensu Maslin,
1952) through which the maxilla and its teeth transform into the short-ened
maxilla and fang of elapids on the one hand, and viperids on
the other (Fig. 1). Notice that within colubrids, there exists a range of
morphological conditions. The first state, and presumbly phylogenetically
the most primitive, is exhibited here by Pituophis wherein the shaft of
the maxilla is long, its teeth numerous, and the dentition basically homo-dont
(sensu EZdmund, 1969). In a more derived condition, as exhibited
by Dispholidus, the maxilla is shortened, the teeth reduced in number,
3. KARDONG, K. V. The evolution of the venom apparatus in snakes from eolubrids to viperidr &
elapids. Mem. Znst. Rutantan, 46:105-118, 1982.
and the dentition heterodont. Heterodonty is achieved by the differen-tiation
of the posterior maxillary teeth that lengthen through this series,
change shape, and eventually come to bear a groove along their sides.
ELAPl DAE
i COLUBRI DAE
Fig. 1 - Transformation series of the maxilla and teeth it bears within the family Colubridae and to
In elapids, this tooth has migrated forward to a more rostra1 position on the maxilla.
In viperids, this tooth resddes at the posterior end of the maxilla, but kinetically rotates
forward during the stri Actual skulls depicted among the colubrids are those of
Pituophis (left) and Dispkolidus (right). A Naja and Vipera skull represent Elapidae and
Viperidae, respectively.
Evolution of the maxilla and its teeth within colubrids thus proceeds
from an aglyphous to an opisthoglyphous condition. Between these two
extremes lie most colubrids showing graded, intermediate states. For
instance, next after the initial condition would follow snakes that posses-sed
maxillae with slightly elongated maxillary teeth (e.g. Thamnophis).
Next would lie snakes possessing long, rear maxillary teeth, but with
secretion groves (e.g. Crotaphopeltis) . A secretion channel too appears
4. KARDONG, K. V. The evolution of the venom apparatus in snakes from colubrids to viperids &
elapids. Mem. Inst. Butantan, 46:106-118, 1982.
in gradual stages. It would appear first, in this transformation series,
as a corner between two adjacent teeth (Taub, 1967) and later as a
groove within a tooth (Sarker, 1923).
This trend within colubrids to a shortened maxilla, reduced number
of teeth, and elongated posterior tooth continues into the two venomous
families. But, the continuation of these trends is established in two
different ways. In viperids, the elongate posterior tooth (now a fang)
lies at the rear of the shortened maxillary bone. In elapids, the elongated
posterior tooth (now also a fang) lies not at the rear of the shortened
maxillary bone, but forward on the remaining shaft. Occasionally, small
teeth remain at; the posterior end of the elapid maxilla marking the point
at which the fang once resided in elapid ancestors.
2. Adaptive Advantages
a) Accretion Hypothesis
A common view holds that these evolutionary changes in the maxilla
and its teeth are driven by the increasing and additive advantages long
teeth serve in venom injection. Thus, by tie accretion of progressive toxic
benefits, a venom system develops. This hypothesis predicts that the
initial and the subsequent role played by these teeth was in prey capture.
To test this prediction, several living species (Thamnophis, Crota-phopeltis)
falling within the middle stages of the transformation series
among colubrids were examined to see just how they used their maxillae
and posterior maxillary teeth. These species possess long posterior maxil-lary
teeth. The results (Kardong, 1979, 1980; Wright, et al., 1979)
showed that, i11 fact, they did not use these teeth extensively during prey
capture. Instead, they used these teeth to manipulate prey once already
caught (see also Minton, 1944; Platt, 1969; Kroll, 1976). Thus, these
teeth, even though slightly elongated, did not serve to inject a venom
during prey capture, but instead aided swallowing by acting like small
hooks to give better purchase an the slippery or uncertain surface of
the prey. Further, comparison of the posterior maxillary teeth and of
a venom fang revealed that the two are quite unalike (Schaefer, 1976;
Kardong, 1979; Wright et al., 1979).
Thus, no support was found for the predictions of the accretion
hypothesis, at least as applied to snakes within the middle of the trans-formation
series.
b) Deglutition Hypothesis
Altg2atively, I propose (Kardong, 1979; 1980) that these teeth
borne by,,maxillary bone initially functioned as hooks or gaffs to improve
purchase during swallowing. This role favored, (1) elongation of the
teeth, and (2) shortening of the maxillary bone, two changes, in fact,
present in the jaws of many colubrid snakes. Once long teeth along the
maxillary bone had arisen to serve the requirements of swallowing, then
they would be preadapted to subsequent evolution into a new function,
that of venom injection. But, the initial adaptive avantage of long
maxillary teeth was not related to venom injection, but instead to
swallowing.
5. KARDONG. K. V. The evolution of the venom apparatus in snakes from colubrids to viperids &
elapids. Mem. Inst. Butantan. 46:105-118. 1962.
B) Evolution of the Venom Gland
1. Morphological Series
The evolution of the venom gland, like the previous evolution of
the fang, begins within colubrid snakes. Within colubrids, the Duvernoy's
gland is the evolutionary predecessor of the venom gland (Gans and
Elliott, 1968 ; Kochva, 1978). A morphological series constructed now
for the Duvernoy's gland shows its transformation into the venom gland
of viperid and of elapid snakes (Fig. 2).
E LAPI DAE Vl PERIDAE
- GLAND 1
Fig. 2 - Transformation series of Ddvernoy's gland. This gland appears first within the middle
of the colubrid series. It arises near the posterior end of the supralabial gland (SLG).
Through the morphocline, the Duvernoy's gland transforms independently into the venom
gland (VG) of elapid and viperid snakes.
2 . Adaptive Advantages
a) Accretion Hypothesis
Again, the conentional view is that the Duvernoy's gland was
always slightly venomous and that the increasing, additive advantages
of venom injection drove the changes leading eventually to appearance
of a fully venomous gland. But, again there is reason to doubt this
hypothesis. First, as just mentioned, eventhough the teeth of colubrids
6. KARDONG, K. V. The evolution of the venom apparatus in snakes from colubrids to viperids &
elapids. Mem. Znst. Butantan, 46:105-118, 1982.
are long, they are otherwise structurally quite unlike fangs. Second,
most colubrid snakes do not have large storage areas to hold venom
(Taub, 1967) to inject and rapidly kill prey.
Further, those who subscribe to this accretion hypothesis face a
self-imposed paradox, what may be termed the "paradox of imperfec-tion".
By the accretion hypothesis, possessors of a Duvernoy's gland are
"on their way" to becoming highly venomous, but, as yet, possess only
a mild venomous capacity. But, in fact, most living colubrids are so
endowed with long, posterior maxillary teeth (Marx and Rabb, 1972)
and a Duvernoy's gland (Taub, 1967). In most parts of the world, such
colubrids live sympatrically with and outnumber in terms of species,
venomous snakes such as viperids and elapids. The paradox lies in the
fact that such colubrids with a presumed mildly venomous secretion,
but "imperfect" venom apparatus, could be so successful with these two
families that possess a highly venomous and efficient venom apparatus.
It does seem contradictory that colubrid species could compete and thrive
using an "imperfect" venom injection system as successful contempora-ries
with elapids and viperids.
Perhaps, I have overstated or misstated the paradox. On the other
hand, the paredox may arise from a flawed hypothesis, the accretion
hypothesis. Tyis, in fact, is my view. Most colubrids simply do not seem
to use their oral secretions as venoms. Eventhough the oral secretions
of many colubrids are proving to be more toxic than previously suspected
(McAlister, 1963 ; Heatwole and Banuchi, 1966 ; Vest, 1981), still these
same species do not, in fact, use their oral secretions to rapidly kill prey
as do truely venomous snakes possessing fangs.
2. Deglutition Hypothesis
Duvernoy's gland secretion (in most colubrids) serves not as a
venom. This is to say, it does not serve to help rapidly kill prey during
prey capture. Instead, it must serve some other primary biological role
or roles for these species. Being associated with the swallowing behavior
of snakes, the secretion of Duvernoy's gland may reasonably be expected
to play a role in swallowing and/or digestion. However, without further
broad study of both the pharmacology of Duvernoy's gland secretions
together with studies of the feeding behavior, it is premature to propose
any careful alternative hypothesis.
CONCLUSIONS
Early in the evolu,tion of the venom apparatus among snakes, the
posterior maxillary teeth were long, but not yet fangs. Instead they
served as spikes to help the snake grip slippery, bulky, or difficult prey
during swallowing. So too, the Duvernoy's gland was not yet a venom
gland, but likely served some other biological role.
Certainly once these teeth were long and the Duvernoy's gland well
established, then this system was preadapted for the quite different role
7. KARDONG, K. V. The evolution of the venom apparatus in snakes from colubrids to viperids &
elapids. Men. Inat. Butantan, 46:105-118, 1982.
of quickly subduing prey. Later in its evolution, the tooth/gland system
then evolved under the increasing advantages derived from the ease and
efficiency of rapidly killing prey. But, prehension and envenomation
were not the initial roles that drove the early evolution of the glandular
and dental elements in the jaws of colubrid snakes toward long, posterior
teeth on a shortened maxilla.
IMPLICATIONS
A) Snake Evolution
1) Viperidis and Elapids - two venom modes
Both viperid and elapid snakes evolved independently from opistho-glyph
ancestors. At least, this is the view I take based upon the arguments
presented herein. The alternative view that elapids (or viperids) arose
from proteroglyph ancestors is contradicted by the position of the venom
gland (McDowell, 1968), embryonic development (Martin, 1899a,b.c ;
Kochva 1963; 1965), and rear maxillary tooth structure, position, and
function (Kardong, 1980 :273-274).
Upper jaw teeth in colubrids serve in two primary capacities-preh-ension
and swallowing. Rut, these two activities are not always shared
equally among the teeth. Anterior teeth of the mouth tend more often
to be involved in prehension because they are first to come into the vicinity
of the prey and because they bear responsibility for snagging elusive
prey. Correspondingly, anterior teeth are often long and recurved reflect-ing
their special role in prey capture (Frazzetta, 1966). Posterior teeth,
on the other hand, tend to be involved in preingestion/swallowing mani-pulations.
Because of the kinetic motion of the maxilla, rear teeth it
bears lie at an especially favorable mechanical position to aid in swallow-ing
(Kardong, 1979). Consequently; posterior maxillary teeth are often
long and blade-shaped (Wright et al. 1979).
The fang borne by the maxilla in elapids and viperids is, like anterior
teeth of colubrids, deployed principally during prey capture. It is thus
fashioned similarly. For instance, the fang is conical and often recurved
(Klauber, 1956) ; it is located, during the strike, in the anterior part
of the mouth. !n this latter feature, however, this forward position in
the mouth is accomplished in two different ways. In viperids, the fang
rides upon a highly kinetic maxilla that erects during the strike to bring
the fang well forward in the mouth (van Riper, 1953; Kardong, 1975).
In elapids, the fang rides on a less kinetic maxilla, but has undergone
during its evolution a forward migration so that it sits in a more anterior
position along the shaft of the maxilla (Fig. 1). Thus, fangs in the two
groups enjoy the advantages of an anterior position in the mouth, but
this is achieved differently-phylogenetic migration along the maxilla in
elapids, kinematic rotation in viperids. Although elapids and viperids
are venomous snakes, they seem to be separately derived styles of a
venomous mode of life. They differ in the structural features of the
8. KARDONG, K. V. The evolntion of the venom apparatus in snakes from colubrids to viperids &
elapids. Mem. Inst. Butantan. 463105-118. 1982.
maxilla and fang just mentioned, relative toxicity of tlieir venoms (e.g.
Minbn and Minton, 1969), and perhaps even in behavioral styles in their
strategies of prey capture (Naulleau, 1965 ; Kardong, 1982).
2) Duvernoy's gland
The Duveriioy's gland in most colubrid snakes is unlikely a gland
"on its way" to being a venom gland, but sh~uldb e examined for the
immediate biological role it plays in the life oj~th ose snakes possessing
such a gland.
B) Pharmacology
1) Toxin and Venom
A distinction should be made between a secretion that is a "toxin"
and one that is a "venom", at least as applied to snake secretions in a
biological context. These two terms have grown up in the medical lite-rature
with closely related meanings (e.g. Russell, 1980). I don't intend
to propose redefinition in a medical or clinical context. However, the
transference of these terms into a biological context has led to confusion.
As a result, some animals live with an undeserved reputation for danger
and even some medical strategies of treatment of suspected envenoma-tions
suffer from the confusion.
In a biological context, by "toxic" I mean the letha! property of a
chemical expressed as an LD.,, or LD,,,, for example; it is usually
identified and characterized under defined laboratory conditions. However,
by the term "venomous" I mean the function of the secretion, specifically
the biological role (Bock, 1980) of the substance in the life of the animal
producing it. Observation of the free ranging animal in its natural
habitat is usually or ideally the basis for concluding (or not) that a
secretion is used as a venom. The two terms rest on different concepts
so more is at issue than mere semantics.
If Duvernoy's gland secretion is shown to be toxic, some suggest
from this alone that the snake is likely venomous. However, there are
two reasons for resisting such a hasty conclusion.
2) Incidental Byproduct
First, to prove a substance toxic in character is insufficient to prove
it venomous in practice. Toxicity can occasionally be an incidental
byproduct. For example, some components of human saliva are toxic and
possess an@ LD50 (Bonilla et aJ, 1971). Yet, no food humans consume
require envenomation to make it safe to eat, nor are there enemies
thwarted by threat of saliva injection. Toxicity is incidental and those
seeking the biological role of saliva look, quite rightly, beyond this
property to its digestive roles to understand its chemical character. How-ever,
analysis of oral secretions from "nonvenomous" snakes has not
always been so sensible. Too often, only the property of toxicity of
these secretions seems to have been seriously considered. Certainly, this
9. KARDONG, K. V. The evolution of the venom apparatus in snakes from colubrida to viperids &
elapids. Mem. Znst. Butantan, 46: 105-118, 1982.
is understandable. Lethal dose, if any, can be relatively easily demons-trated,
and hence toxicity discovered; also, the toxicity alone makes the
substance medically important regardless of its actual biological function.
Yet, in many colubrid secretions, toxicity might be, as with human saliva,
incidental, a property with no or only secondary biological significance.
It would be misleading to call humans "venomous" simply because they
possessed a "toxic" saliva. Similarly with snakes. In a biological context,
distinguishing conceptually between a toxin and a venom should help
avoid such confusion.
3) Other Functions
There is a second reason for resisting the temptation to conclude
that a toxic secretion is also automatically a venom. In most colubrids,
Duvernoy's gland secretion functions in capacities other than as a venom.
Many colubrids possess well developed Duvernoy's glands, yet do not use
its secretion to rapidly kill prey. To take an example, the wandering
garter snake (Thamnophis elegans) possesses a Duvernny's gland secret-ion
of alarming toxicity approaching that of some viperid snakes (Vest,
1981 ; 1982), yet lacks the teeth to inject much secretion (Wright et al.,
1979), and does not feed by bringing rapid death to the prey (Peterson,
1978). It possesses the toxicity, but lacks the equipment and behavior
to use the secretion as a venom. The secretion from Duvernoy's gland
or, for that matter, any secretion released from a specialized organ or
group of cells may serve several functions. It may function as a venom,
it may paralyze prey, it may tranquilize, it may aid digestion, and so on.
In Thamnophis and similar colubrids, what then could be this secretion's
function ?
4) Alternative or Addition~~Flu nctions
To date pharmacological and biological analysis of Duvernoy's gland
secretion has been preoccupied with toxicity (e.g. Philpot et al., 1977),
so one is left to speculation about alternative functions. However, several
seem likely.
a) Lubrication
Besides Duvernoy's and venom glands, snakes possess additional
strips of glandular tissue along upper and lower lips (Taub, 1966) that
release their products over the prey to lubricate its passage into the
esophagus. Duvernoy's gland secretion, released at the base of rear
maxillary teeth, trickles down the sides of these teeth to likely finds its
way to the surface of the prey. Thus it could be an additional source of
lubricant to facilitate swallowing.
b) Digestion
In viperid and elapid snakes, venom certainly contributes to rapid
prey death, but has also been suspected of promtting digestion (Reichert,
1936 ; Zeller, 1948). Experimental work - injebting venom into mice and
then comparing rates of their digestion to controls - indicates that
rattlesnake venom actually speeds digestion (Thomas and Pough, 1979).
10. KARDONG. K. V. The evolution of the venom np~~aratuIsn snakes from eolubrids to viperids &
elapids. Mem. Znst. Butantan, 46: 105-118, 1 0%.
Such venom attributes may be of adaptive value for snakes feeding on
large numbers of prey in short periods of time or to enhance digestion
in snakes from cold or temperate climates. Similar tests have not been
done for the secretion from Duvernoy's gland, but the possibility it
serves a similar function seems worth investigating.
Snakes swallow their food without tearing or chewing. Digestive
enzymes released from the wall of the gut may not always complete the
inward spread of digestion before tissues within the center of the bolus
putrefy. Venom injected deep (Thomas and Pough, 1979) or Duvernoy's
gland secretion inoculated subcutaneously within the prey before swallow-ing
may retard this putrefaction.
d) Detoxify Prey Sscretions
Many snakes, especially colubrids, feed on amphibians possessing
skin glands which contain, depending upon the amphibian species, irritat-ing
to actually poisonous secretions (Habermeihl, 1971 ; Lutz, 1971 ;
Brodie and Tumbarello, 1978). Duvernoy's gland secretion in those
colubrids regularly feeding on amphibians may help neutralize these skin
secretions released by the amphibian prey.
Further, these oral secretions could contribute to improved oral
hygiene or prevent sticky material elaborated by prey from fouling the
jaws during swallowing (Gans, 1978; Jansen, 1982). My intent is not
to settle the questions of what functions snake oral secretions serve.
Instead, I wish to emphasize that snakes, faced with a variety of problems
while catching and swallowing prey, might possess various components
in the Duvernoy's gland or venom gland secretions that serve a variety
of biological roles besides or in addition to envenomation.
Even though introduced into the prey in small quantities compared
to a true venom, some propose that the Duvernoy's gland secretion may
slow or tranquilize the prey, thus making prey capture less risky and
swallowing easier. Perhaps it does. But, tranquilizing prey differs from
envenomation. Tooth form (Kardong, 1979 ; Wright et ag., 1979), maxil-lary
bone structure (e. g. Bogert, 1943; Brattstrom, 1964), and behavior
(e.g. van Riper, 1953; Klauber, 1956; Dullemeijer, 1961; Greene and
Burghardt, 1978) differ from species that use venom predominantly to
capture and dispatch rather than just quiet prey. Consequently, tran-quilization
seems distinct from true envenomation as a prey handling
technique.
C ) Clinical Significance
Venom& are complex. Laboratory analysis proceeds by fractiona-tion
into molecular components then to separate analysis of each fraction.
Some components exhibit toxicity while other components seem to be
without toxic effect (e.g. van Mierop, 1976; Russell, 1980). These nontoxic
fractions are usually classified as potentiators, activators, or amplifiers
(gg. spreading factors) of the toxic components. Generally this conclusion
sems on mark. However, some of these components of venom may lack
to%icity, because they are present for biological reasons other than to
11. KARDONG, K. V. The evolution of the venom apparatus in snakes from colubrids to viperids Q
elapids. Mem. Inst. Butantan, 46:105-118, 1982.
promote rapid prey death (e.g. Thomas & Pough, 1979). In fact, even
demonstrating toxicity in a particular component does not or ought not
to end the search for its possible function. Other attributes, besides
toxicity, should be considered if one is to eventually understand the
biochemical action and interaction of all venom components.
One fruitful place to begin such an analysis may be with the secretion
from Duvernoy's gland. The venom gland of viperids and elapid snakes
evolved from the Ijuvernoy's gland; these venomous snakes feed upon
similar foods and thus face generally similar problems with prey as
many "nonvenomous" colubrids. Certainly the venom of viperids and
elapids functions primarily to rapidly kill prey, but components serving
secondary functions are most likely present as well. Venom is a suite of
chemicals, all of which go into a victim - toxins and nontoxins alike.
Consequently, it seems advisable for strategies of treatment of enveno-mations
to be founded upon a knowledge of all components and their
biological roles, not just upon the action of the toxins. Perhaps, somewhat
ironically, one place to focus such an analysis of snake venoms, is on
"nonvenomous" colubrid snakes.
ACKNOWLEDGMENTS
My thanks go in particular to several institutions and persons who
over several years have helped me secure needed comparative specimens,
namely the American Museum of Natural History (C. W. Bleyers, R. G.
Zweifel), California Academy of Sciences (A. E. Leviton), Field Museum
of Natural History (H. Marx, R. Inger), Museum of Comparative Zoology
(E. E. Williams) National Museums of Rhodesia (D. G. Broadley),
Smithsonian Institution (R. I. Crombie, F. I. McCullough, G. R. Zug),
University of Florida (W. Auffenberg), and University of Kansas Mu-seum
of Natural History (W. E. Duellman). I appreciate the help of J.
Visser, Wildlife Documentaries (South Africa) for securing living
specimens. My special thanks and sincere appreciation go to Prof. A. R.
Hoge and other organizers of the symposium on "Serpentes em Geral
e Arthrop6des Pe(;onhentos" for their invitation, help, and support.
BIBLIOGRAPHIC REFERENCES
ALCOCK, A. & ROGERS, L. On the toxic properties of the saliva of certain
"non-poisonous" colubrines. Proc. Roy. Soc. (Lond.) , 70 :446-454, 1902.
ANTHONY, J. Essai sur 1'Bvolution anatomique de I'appareil venimeus des Ophidiens.
Ann Sci. Natur. Zool., 17:7-53, 1955.
BOCK, W.J. The definition and recognition of biological adaptation. Amer. Zool.,
20 :217-227, 1980.
ROGERT, C.M. Dentitionaf phenomena in cobras and other elapids, with notes
on the adaptive modifications of their fangs. Bull. Amer. Mus. Nut. Hist.,
81 :285-360, 1943.
BONILLA, C.A.; FIERO, M.K. & SEIFERT', W. Comparative biochemistry and
pharmacology of salivary gland secretions. I. Electrophoretic analysis of the
proteins in the secretions from human parotid and reptilian (Duvernoy's) glands.
J. Chromatogr., 56:368-372, 1971.
12. KARDONG. K. V. The evolution of the venom apparatus in snakes from colubrids to viperids L
elapids. Mem. Inst. Butantan, 46:105-118, 1982.
BOULENGER, G.A. Catalogue of the snakes in the British Museum (Natural
History). Vol. 1. London, British Museum (Natural History), 1893. pp. 448.
Remarks on the dentition of sqakes and on the evolution of the poison
fangs. Proc. Zool. Soc. London 1896:614-616.
Sur l'bvolution de l'appareil a venin des serpents. Compt. Rend.,
165 :92-94, 1917.
BOURGEOIS, M. Contribution la morphologie comparbe du crane des ophidiens
de I'Afrique centrale. Publ. Univ. Off. Congo Lubwmbashi, 18:l-292, 1968.
BRATTSTROM, B.H. Evolution of the pit vipers. Trans. Sun Diego Soc. Nut.
Hist., 13 :185-268, 1964.
BRODIE, E.D. Jr. & TUMBARELLO, M.S. The antipredator functions of Dendro-bates
auratus (Amphibia, Anura, Dendrobatidae) skin secretion in regard to a
snake predator (Thamnophis). J. Herpet., 12:264-265, 1978.
COPE, E.D. The crocodilians, lizards, and snakes of North America. Annu. Rep.
Smithson. Inst. for 1898, U.S. National Museum, Washington, D.C., 1900 pp.
153-1270.
DULLEMEIJER, P. Some remarks on the feeding behavior of rattlesnakes. Proc.
Xon. Ned. Akad., 64:383-396, 1961.
EDMUND, A.B. Dentition. In "Biology of the Reptilia" ( C . Gans, A. Bellairs,
T. S. Parsons, eds.). Academic Press, 1969. v. I, p. 117-200.
FRAZZETTA, T.H. Studies on the morphology and function of the skull in the
Boidae (Serpentes). Part 11. Morphology and function of the jaw apparatus
in Python sebae and Python molurus. J. Morph., 118:217-296, 1966.
GABE, M. & SAINT GIRONS, H. Histologies compar6e des glandes salivaires due
vestibule buccal chez less lbzards et les serpentes et bvolution de la fonction
venimeuse. In "Toxins of Animal and Plant Origin." (A. de Vries and F.
Kochva, eds.). London, Gordon and Beach, v. 1, p. 65-68, 1971.
GANS, C. Reptilian venom: Some evolutionary considerations. In "Biology of
the Reptilia" (C. Gans and K. A. Gans, eds.). London, Academic Press, 1978.
v. 8, p. 1-42.
& ELLIOT, W.B. Snake venoms: production, injection, action. Ad. Oral
Biol., 3:45-81, 1968.
GREEN, H.W. & BURGHARDT, G.M. Behavior and phylogeny: Constriction in
ancient and modern snakes. Science, 200:74-77, 1978.
HABERMEIHL, G. Toxicology, pharmacology, chemistry, and biochemistry of
salamander venom. In "Venomous animals and their venoms" (W. Biicherl and
E. E. Buckley, eds.). New York, Academic Press, 1971. v. 2, p. 569-584.
HALSTEAD, B.W.; ENGEN, P.C. & TU, A.T. The venom and venom apparatus
of the sea snake Lapemis hardwicki Gray. Zool. J. Linn. Soc., 63:371-396, 1978.
HEATWOLE, H. & BANUCHI, I.B. Envenomation by the colubrid snake Alsophis
portoricensis. Herpetologica, 22 : 132-134, 1966.
JANSEN, D.W. A possible function of the secretion of Duvernoy's gland. Copeia,
1982. (in press).
KARDONG, KV. Prey capture in the cottonmouth snake (Agkistrodo~l piscivom).
J. Herp., 9:169-175, 1975.
"Protovipers" and the evolution of snake fangs. Evolution, 33 :433-443,
1979.
Evolutionary patterns in advanced snakes. Amer. Zool., 20:269-282,
1980.
Comparative study of changes in prey capture behavior in the cotton-mouth
(Agkistrodon piscivorus) and Egyptian cobra (Naja haie). Copeia,
1982. (in press).
KLAUBER, L.M. Rattlesnakes, their habits, life histories, and influence on mankind.
Univ. Calif. Press, 1956. v. 1, p. 1-708; v. 2, p. 709-1476.
KOCHVA, E. Development of the venom gland and the trigeminal muscles in
Vipera palaestinae. Acta Anatomica, 52 :49-89, 1963.
13. KARDONG. K. V. The evolution of the venom apparatus in snakes from colubrids to viperids &
elapids. Mem. Inst. Butantan. 46:105-118, 1982.
The development of the venom gland in the opisthoglyph snake Telescopus
fallax with remarks on Thamnophis sirtalis (Colubridae, Reptilia). Copeia,
147-154, 1965.
Oral glands of the reptilia. In C. Gans and K. A. Gans (eds.).
"Biology of the Reptilia". New York, Academic Press, 1978. v. 1, p. 43-161.
& GANS, C. Histology and histochemistry of venom glands of some
crotaline snakes. Copeia, 506-515, 1966.
SHAYER-WOLLBERG, M. & SOBOL, R. The special pattern of
the venom gland in Atractaspis and its bearing on the taxonomic status of the
genus. Copeia, 763-772, 1967.
KROLL, J.C. Feeding adaptations of hognose snakes. Southwestern Nut. 20:
537-557, 1976.
LUTZ, B. Venomous toads and frogs. In "Venomous &nimuls and their venoms"
(W. Bucherl and E. E. Buckley, eds.). New York, Academic Press, 1971, v. 2,
p. 523-473.
MARTIN, H. Sur le ddveloppement le l'appareil venimeux de la Vipera aspis
Bvolution du canal venimeux. C. R. 28 Sess. Sec. part. Ass. franc. Avanc Sci.
522-527, 1899a.
Recherches sur le ddveloppement de I'appareil venimeux de la Vipera
aspis. Compt. Rend. Ass. Anat., 1 :56-66, 1899b.
Etude de I'appareil glandulaire venimeux chez un embryon de Vipera
aspis. Bull. Soc. Zool. France, 24:106-116, 1899c.
MARX, H. & RABB, G.B. Phyletic analysis of fifty characters of advanced snake.
Fieldiana, Zoology, 63 : 1-321, 1972.
MASLIN, T.P. Morphological criteria of phyletic relationships. Syst. Zool., 1:
49-70, 1952.
MCALISTER, W.H. Evidence of mild toxicity in the saliva of the hognose snake
(Heterodon). Herpetologica, 19 :132-137, 1963.
MCDOWELL, S.B. Affinities of the snakes usually called Elaps lacteus and E.
dorsalis. J. Linn. Soc. (Zool.), 473561-578, 1968.
MIEROP, L.H.S. VAN. Poisonous snakebite: A review. I. Snakes and their venom.
J. Florida Med. Assoc., 63 : 191-210, 1976.
MINTON, S.A. Introduction to the study of reptiles of Indiana. Amer. Midl. Nut.,
32 3438-477, 1944.
- & MINTON, S.R. Venomous reptiles. New York. Charles Scribner's
Sons, 1969, 274 p.
MOSAUER, W. The myology of the trunk region of snakes and its significance
for ophidian taxonomy and phylogeny. Publ. Univ. Calif. Los Angeles. Biol.
Sci., 1 :81-120, 1935.
NAULLEAU, G. La biologie et le comportment prkdateur de Vipera aspis au
laboratoire et dans la nature. Bull Biol. France Belique, 99:295-524, 1965.
NICKERSON, M.A. A study of the ultrastructure and histochemistry of the venom
apparatus of some elapid snakes. Univ. Microfilms 60-1285, 1969.
PETERSON, C. Constriction in the wandering garter snake. Amer. Zool., 28:649,
1978. (Abstract).
PHILPOT, VAN B. Jr.; EZEKIEL, E.; YEAGER, R.G. Jr. & STJERNHOLM,
R.L. Lethal action of saliva from non-venomous snakes. Fed. Proc., 36:860,
1977. (Abstr.).
PHISALIX, M. Modifications que la formation venimeuse imprime Ir la tet osseuse
et aux dents chez des serpents. Ann. des Sci. Nut. Zool. 90th ser t . xvi:161-205,
1912.
Animaux venimeux et venins. 2 vols. Faris, Masson & Cie, 1922.
PLATT, D.R. Natural history of the hognose snakes Heterodon platyrhinos and
Heterodon nmicus. Univ. Kansas Publ., Mua. Nat. Hist., 18:253-420, 1969.
REICHERT, E. Bothrops jaracussu. B1. Aquar. K., 47:228-231, 1936.
14. KARDONG, K. V. The evolution of the venom apparatus in snakes from colubrids to viperids &
elapids. Mem. Inst. Butantan. 46:105-118, 1942.
RIPER, W., VAN. How a rattlesnake strikes. Sci. Amer., 189:100-102, 1953.
ROSENBERG, H.I. Histology, histochemistry, and emptying mechanism of the
venom glands of some elapid snakes. J. Morph., 123:133-156, 196?.
RUSSELL, F. Snake venom poisoning. Lippincott, 1980, p. 562.
QARKER, S.C. A comparative study of the buccal glands and teeth of the Opis-thoglypha,
and a discussion of the evolution of the order from the A.glypha.
Proc. 2001. Soc. Lond. (1) :295-322, 1923.
SAVITZKY, A.H. The role of venom delivery stratyies in snake evolution. Evo-lution,
34:1194-1204, 1980.
SCHAEFER, N. The mechanism of venom transfer from the venom duct to the
fang in snakes. Herpetologica, 32 :71-76, 1976.
SMITH, M. & BELLAIRS, A. The head glands of snakes with remarks on the
evolution of the parotid gland and teeth of Opisthoglypha. Linn. Soc. J. Zool.,
41 :351-368, 1947.
TAUB, A.M. Ophidian cephalic glands. J. Morph., 118:529-542, 1966.
Comparative histological studies on Duvernoy's gland of colubrid snakes.
Bull. Amer. Mus. Nut. Hist., 138:l-50, 1967.
THOMAS, R.B. & POUGH, F.H. The effect of rattlesnake venom on digestion of
prey. Toxicon, 17 :221-228, 1979.
VEST, D.K. Envenomation following the bite of a wandering garter snake (Tham-nophis
elegans vagrans) Clin. Tox., 18 :573-579, 1981.
The toxic Duvernoy's secretion of the wandergin garter snake (Tham-nophis
elegans vagrans). Toxicon, 1982 (in press).
WEST, G.S. On the buccal glands and teeth of certain poisonous snakes. Proc.
2001. SOC. Lond., 812-826, 1895.
WRIGHT, D.L.; KARDONG, K.V. & BENTLEY, D.L. The functional anatomy of
the teeth of the western terrestrial garter snake, Thamnophis elegans. Herpeto-logica,
35:223-228, 1979.
ZELLER, E.A. Enzyms of snake venoms and their biological significance. In F. F.
Nord (ed.), "Advances in enzymology", New York, Interscience Publ., 8:459-495,
1948.