This document provides an overview of the phylum Arthropoda. It discusses that arthropods make up about 85% of animal species and are found in nearly all environments. They are defined by having a jointed exoskeleton and losing motile cilia as adults. The exoskeleton allows them to be successful across habitats. Body segments are commonly fused for specialized functions. Respiration varies with habitat and vision involves simple or compound eyes. The circulatory system is open and fertilization can be internal or external.

1. Arthropods
Introduction
The phylum accounts for about 85% of all animal species described so far represented in almost
all types of environment: freshwater, marine, and terrestrial. Some members are also
endoparasites and ectoparasites of an array of host species. The group is composed of bilaterally
symmetric, triploblastic, coelomates with protostome – like development. Members are defined
by the presence of epidermis producing a segmented, jointed, and hardened chitinous
exoskeleton with intrinsic musculature between individual joints of appendages and the complete
loss of motile cilia in adult and larval stages. Metamerism is also commonly observed coupled by
tagmatization – fusion and modification of different regions of the body for highly specialized
functions. The exoskeleton (which is periodically molted) is secreted by epidermal cells with the
outer layer being water impermeable. The presence of this structure is one of the reasons why
arthropods are successful in invading all types of habitat. The body cavity of arthropods is part of
the circulatory system as in the molluscs. The nervous system consists of a dorsal brain and a
ventral, ganglionated longitudinal nerve cord from which lateral nerves extend in each segment.
The presence of striated muscles also made flight possible allowing some arthropods to invade
previously uninhabited areas. The circulatory system of arthropods is an open one with blood
entering the heart directly from the hemocoel through perforations called ostia. The diverse
respiratory strategies are adaptations to the habitat they are found (i.e., terrestrial species possess
tracheae, book lungs, and gills). The visual system is either simple ocelli or compound eyes.
Most species are gonochoristic, but some species, especially sedentary and parasitic ones are
hermaphroditic. While internal fertilization is favored among terrestrial representatives, aquatic
ones exhibit external fertilization and spawning. As mentioned, majority of the known animal
species are under this phylum so most invertebrates you see are arthropods. In this exercise, we
take a closer look at the distribution, morphology, and adaptations of arthropod representatives.
Phylum Arthro • poda (Greek: jointed foot) ar-throp´-ō-dah
Defining Characteristic:
1 1) Epidermis produces a segmented, jointed, and hardened (sclerotized) chitinous exoskeleton,
with intrinsic musculature between individual joints of appendages;
2) complete loss of motile cilia in adult and larval stages
Introduction and General Characteristics
Nearly 85% of all animal species described to date belong to the phylum Arthropoda, making the
arthropod body plan by far the best represented in the animal kingdom. Arthropods also
dominate the fossil record. Insects, spiders, scorpions, pseudoscorpions, centipedes, crabs,
lobsters, brine shrimp, copepods, and barnacles are all arthropods. Like annelids, arthropods are
basically metameric, with new segments arising during development from a specific budding
zone at the rear of the animal. In most modern members of the phylum, however, the underlying
metameric, serial repetition of like segments is masked by the fusion and modification of
different regions of the body for highly specialized functions. This specialization of groups of
segments, known as tagmatization, is also seen in some polychaete annelids, but it reaches its
greatest extent in the Arthropoda. Two of the major arthropod groups (Insecta and Crustacea)
have 3 distinct tagmata: head, thorax, and abdomen. Arthropods are unusual in lacking cilia,
even in the larval stages.

2. louse, (order Phthiraptera), any of a group of small wingless parasitic insects divisible into two
main groups: the Amblycera and Ischnocera, or chewing or biting lice, which are parasites of
birds and mammals, and the Anoplura, or sucking lice, parasites of mammals only. One of the
sucking lice, the human louse, thrives in conditions of filth and overcrowding and is the carrier
of typhus and louse-borne relapsing fever.
With the exception of the human body louse, lice spend their entire life cycle, from egg to adult,
on the host. The females are usually larger than the males and often outnumber them on any one
host. In some species males are rarely found, and reproduction is by unfertilized eggs
(parthenogenetic). The eggs are laid singly or in clumps, usually cemented to a feather or hair.
The human body louse lays its eggs on clothing next to the skin.
Head lice reproduce sexually, and copulation is necessary for the female to produce fertile eggs.
Parthenogenesis, the production of viable offspring by virgin females, does not occur in
Pediculus humanus.
pinnata
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Psocodea
Suborder: Troctomorpha
Infraorder: Nanopsocetae
Parvorder: Phthiraptera
Activity/Exercise 9: Nematodes
[Schedule: 29 and 30 November 2022]
Introduction
The roundworms are the most abundant multicellular animals today. They are non –
metameric, bilaterally symmetric acoelomates/pseudocoelomates with vermiform shape. They
represent the smallest molting animals. Members of the phylum are defined by the presence of
paired lateral sensory organs on the head derived from cilia and opening to the outside through
a small pore called the amphids. They are common parasites of vertebrates, invertebrates, and
plants. Common parasitic representatives of the phylum include Ascaris, Trichuris,
hookworms, pinworms, and filarial worms. They are also represented in freshwater, marine,
and terrestrial environments. The typical body of a roundworm is tapered at both ends with no
external segmentation covered by a thick, multilayered cuticle (permeable to water and gases).

3. The cuticle is shed and resecreted 4 times during development from the juvenile to the adult
form. The fluid of the pseudocoel serves as the circulatory medium which contains hemoglobin
in some species. A closed circulatory system is wanting. Free – living representatives must live
in water or at least a film of water. The body wall contains no circular muscles resulting in the
generation of sinusoidal waves by undulating the body. In general, the nematode design is not
well suited for swimming. The nervous system is a simple one consisting of an anterior brain
and four or more major lateral nerve cords. There are no specialized organs for gas exchange
and excretion. Sexual dimorphism is observed in roundworms and sexual reproduction is
preferred but parthenogenesis is possible in some species.
Objectives
After completing this activity, you must be able to:
1. identify different nematode representatives from environmental samples;
2. perform simple experiments to collect nematodes;
3. conduct simple techniques in concentrating and detecting nematode eggs from
environmental samples; and
4. correlate nematode egg morphologies to their life cycle.
Materials and Methods
microscope microscope slides
clear, transparent scotch tape (2”) falcon tubes
10% formaldehyde ethyl acetate
gauze glass funnel
iron stand iron ring
applicator stick iodine
vortex mixer centrifuge
test tubes test tube rack
1.2 SG sucrose solution 1.3 SG sucrose solution
10 cc syringe cover slips
wash bottle 600 mL beaker
Pasteur pipette 10 mL pipette
aspirator forceps
Students need to bring:
Camera
animal fecal samples
soil samples
A. Scotch tape method for pinworm detection
1. Specimen must be collected from the perianal skin of a child suspected of pinworm
infection (common symptom is itching in the anal region). Samples must be
collected early in the morning before the child bathes or uses the toilet.
2. Wear gloves during collection since pinworm eggs are infectious if swallowed.
3. Cut 4 inches (10 cm) of your transparent (not frosted) tape.
4. Hold the tape between your thumbs and forefingers with the sticky side facing
upward.
5. While the child is still asleep in the morning, press the sticky side of the tape against
the skin across the anal opening with even, through pressure. Eggs, if present,
should stick to the tape.
6. Gently place the sticky side of the tape down against the surface of a clear glass
slide.

4. 7. Label the slide and bring it to the laboratory for microscopic examination. You can
get multiple samples from the same child or collect from different suspected
children.
8. Examine your samples and record your observations.
B. Sucrose floatation method for soil samples
1. From the dried soil samples provided by your instructor, place approximately 2
grams into a test tube. Make sure that the tubes are properly labeled based on the
sample you are preparing.
2. Add 6 mL of distilled water to the sample and mix the suspension thoroughly using
a vortex mixer.
3. Centrifuge the mixture at 1800 rpm for 10 minutes.
4. After centrifugation, decant the supernatant from the tube.
5. Add 8 mL of 1.2 specific gravity sucrose solution.
6. Mix the resulting suspension using a vortex mixer and centrifuge for 10 minutes at
1800 rpm.
7. After centrifugation, fill the tube with 1.3 specific gravity sucrose solution up to
the brim using a 10cc syringe.
8. Using a coverslip, collect the topmost portion of the sucrose suspension.
9. Place the coverslip in a glass slide and observe under a microscope.
10. Record and photograph parasite eggs and other developmental stages.
C. Formalin - Ethyl Acetate Concentration technique (FEACT) for fecal samples
1. Collect animal fecal samples from different animals. Fresh samples are better.
Preserve the samples in denatured alcohol making sure that the feces is submerged
in the preservative. Bring the samples to the laboratory for processing.
2. In the laboratory, place 2 grams of ethanol - fixed fecal sample in a beaker.
3. Homogenize it using 7 mL 10% formalin and strain using three layers of surgical
gauze into a tube.
4. Add 3 mL of ethyl acetate into the tube.
5. Cover the suspension with electrical tape and shake vigorously for 60 seconds.
6. Release the gas and centrifuge it for 5 minutes at 1500 rpm.
7. Following centrifugation, you will observe 4 layers composed of ethyl acetate on
top, followed by debris, formalin layer and the sediment containing parasite eggs
and other developmental stages.
8. Decant ethyl acetate - formalin leaving only a small portion of the concentrate.
9. Thoroughly mix the concentrate and place a drop into a glass slide.
10. Add iodine stain and view under the microscope.
11. Record parasite eggs and other developmental stages.
12. Identify the parasites using available guides on the internet.
Many nematodes are parasitic, and are modified accordingly. Nearly every major animal group,
from sponges to mammals, plays host to some parasitic nematode species; nematodes of some
species even parasitize members of other nematode species. According to a recent cladistic
interpretation of gene sequence data, 5 parasitism arose independently among nematodes at least
seven times. Happily for biologists, much research on nematode biology has been driven by the
need to control the potentially devastating impact of these parasitic species ( Fig. 16.8 ).
Nematodes parasitize humans, cats, dogs, and many and sheep. Considerable veterinary and
clinical research activity is now focused on how the various parasitic species suppress or
otherwise outfox the host’s immune response, and on why some individuals appear less
susceptible to infection than others. Nematodes also parasitize the roots, stems, leaves, and

5. flowers of plants, including species of great economic importance, such as soybeans, potatoes,
oats, tobacco, onions, and sugar beets. Some of these parasitic nematodes attain great length,
although they may be extremely thin. The largest nematode so far described is 9 m long and
resides in the placenta of female sperm whales. Hookworms and pinworms are two groups of
nematodes well known to many humans
Nematodes have well-developed reproductive systems that distinguish them as female and male
nematodes. The females lay eggs, usually after fertilization by males but in some cases without
fertilization. Many species lack males. Nematode eggs hatch into juveniles that resemble the
adult nematodes but are smaller.
How does the nematodes reproduce?
Sexually reproducing nematodes relies on the union of sperm and oocytes for generating zygote.
Most of the sexually reproducing nematodes exist as male and female (gonochorism), wherein
the sperm from the male are ejaculated in to the female during mating.
Family Oxyuridae. This family contains parasites of vertebrates and invertebrates. Enterobius
vermicularis —pinworm.
Nematodes
Intestinal Nematodes
Ancylostoma duodenale / Necator americanus
Ascaris lumbricoides
Enterobius vermicularis
Trichuris trichiura
Strongyloides stercoralis
Filarial Nematodes
Brugia malayi
Wuchereria bancrofti
Loa loa
Mansonella perstans
Mansonella streptocerca
Onchocerca volvulus
Activity/Exercise 10: Echinoderms
[Schedule: 1 December 2022]
Introduction

6. Phylum Echinodermata has ~6,500 living species and another ~13,000 species known from
fossil records. Echinoderms can be found on the seafloor from the intertidal zone to the ocean
depths. Members of this phylum share these defining characteristics: 1) has a series of fluid
filled canals (the water vascular system) derived from a pair of coelomic compartments and
which service numerous flexible feeding and locomotory appendages (tube feet); 2) 5 pointed
(pentamerous) radial symmetry in adults; 3) calcareous ossicles (mesodermal) form the
endoskeleton; 4) connective tissue is mutable.
Sea urchins and sand dollars are examples of Echinoidea. These echinoderms do not have arms
but are hemispherical or flattened with five rows of tube feet that help them in slow movement;
tube feet are extruded through pores of a continuous internal shell called a test. Like other
echinoderms, sea urchins are bilaterians. Their early larvae have bilateral symmetry, but they
develop fivefold symmetry as they mature. This is most apparent in the “regular” sea urchins,
which have roughly spherical bodies, with five equally sized parts radiating out from their
central axes. Several sea urchins, however, including the sand dollars, are oval, with distinct
front and rear ends, giving them a degree of bilateral symmetry. In these urchins, the upper
surface of the body is slightly domed, but the underside is flat, while the sides are devoid of
tube feet. This “irregular” body form has evolved to allow the animals to burrow through sand
or other soft materials.
Although they vary in color, most holothurians are black, brown, or olive green. Ranging from
three cm to one m long, the largest sea cucumbers may have a diameter of 24 cm. Holothurians
generally look long and worm-like but retain the pentaradial symmetry characteristic of the
Echinodermata. Some may be spherical in body shape. The mouth and anus are located on
opposite poles, and five rows of tube feet run from the mouth to the anus along the cylindrical
body. Ten to 30 branching tentacles surround the mouth. The tentacles are part of the water
vascular system. In the Holothuroidea, the madreporite is unattached to the coelom and is
internal, lying beneath the pharynx. A short stone canal follows the madreporite. While support
in most echinoderms is from the skeletal structure, in sea cucumbers, thick sheets of body wall
muscles provide support. Microscopic ossicles (or sclerites) are on the dermal layer and are
used in taxonomic identification. Respiratory trees, which branch out near the rectum of the
animal, are used for gas exchange as water is pumped through the anus. The respiratory trees
are part of the organs that are expelled occasionally by the sea cucumber.
Objectives
After completing this activity, you must be able to:
1. identify the sex of the collected specimens,
2. classify collected representative echinoderms;
3. explain adaptations of echinoderms based on their observed anatomy; and
4. perform simple spawning and fertilization experiments on sea urchins.
Materials and Methods
microscope microscope slides
petri plates 0.5 M KCl
beaker droppers
depression slide
Students need to bring:
camera
live sea urchins placed in seawater from the collection site
A. Spawning

7. 1. Collect sea urchins as instructed in our Exercise 8 Study Guide (Echinoderms).
2. Place the live urchins in pail/s containing seawater from the collection site. Make
sure that all of them are submerged so that they stay alive during transport to the
laboratory.
3. In preparation for spawning, cut the spines of the live sea urchins for easy handling
and place them individually in small plastic containers with sea water. Use thick
gloves when doing this. Make sure to keep them separate so that they do not induce
unnecessary spawning before you start with the activity proper.
4. Place one specimen in a petri dish (with the oral side facing you) and Induce
individual spawning by injecting 1-2 ml of 0.5 M KCl using a syringe. Make sure
to inject it through the membrane of the oral side into the perivisceral cavity. This
will cause the smooth muscle of the gonads to contract and spawn the gametes.
5. Sex identification can be done during spawning. If the animal is ripe, spawning will
happen within minutes. Allow males to spawn in the petri plate. Sperm is creamy
white in color. Collect the sperm and place them in a small beaker containing a
small amount of filtered sea water.
6. Females would spawn eggs that are yellow, orange, pink, or red in color depending
on the species. Allow the female sea urchins to spawn in a beaker containing filtered
sea water by placing them aboral up (inverted). The eggs would settle down as
spawning continues.
7. Observe the sperm cells and the egg cells under a microscope by making separate
wet mounts. Note how unfertilized gametes look like.
8. Photograph the gametes.
9. Record the male to female ratio of the collected samples and proceed with
fertilization.
B. Fertilization
1. After the shedding of eggs is done, decant the seawater.
2. From the collected sperm earlier, prepare a standard sperm suspension by adding 1
- 2 drops of dry sperm into 10 ml of seawater.
3. Use the suspension to fertilize the egg by adding 2 drops of the standard sperm
suspension into 10 ml of seawater with eggs.
4. Repeat procedure 3 after 2 minutes.
5. Allow the suspension to stand for 10 minutes before observation.
6. After 10 minutes, collect enough samples and place it on a depression slide.
7. Observe normal sea urchin fertilization under the microscope.
8. Compare how a fertilized egg differs from an unfertilized one observed earlier.
9. Observe different fertilization stages.
10. Photograph the mount.
The major unifying characteristic of the phylum
Echinodermata is the presence of what is known as the
water vascular system
Sea urchins (/ˈɜːrtʃɪnz/) are spiny, globular echinoderms in the class Echinoidea.
Class Echinoidea Class Echin • oidea (G: spine-like) ek-in-oy´-dē-ah

8. Defining Characteristics: 1) Ossicles are joined to form a rigid test; 2) podia pores pass through
the ambulacral plates; 3) adults generally possess a complex system of ossicles and muscles
(Aristotle’s lantern) that can be partially protruded from the mouth for grazing and chewing
The last two classes of the Echinodermata remaining to be discussed consist of species that lack
arms. The Echinoidea include the sea urchins, heart urchins, and sand dollars, somewhat less
than 1,000 species in total. The class is perhaps best represented by the sea urchins, which
possess large numbers of long, rigid, calcium carbonate spines. The Greek word “ echinus ”
means, literally, “a hedgehog.” The spines serve for protection and, in some species, are actively
involved in locomotion. Most sea urchins are free-living, roaming individuals, but a number of
species bore into rock. Class Echin • oidea (G: spine-like) ek-in-oy´-dē-a
sea urchins belong to the class Echinoidea, named for the movable spines projecting from their
body like a hedgehog’s spines (from the Greek word echinoid meaning like a hedgehog). Sea
urchins (Fig. 3.83 A) are common around the world, from the ocean’s shoreline to great depths
and from tropical waters to polar waters. Sea urchins are relatively small; most species could fit
in the palm of your hand. The spines are adaptations that protect the urchins from predators.
Spines and tube feet help urchins move and get food. The long, thin, sharp spines of some sea
urchins easily penetrate flesh and in some species, toxic chemicals on the tissue covering the
sharp spines make its stab extremely painful (Fig. 3.87 A and B). Other species, with short, thick,
or blunt spines are safe to handle (Fig. 3.87 C and D). A few species that have adapted to live in
the wave surge zone of rocky coastlines have flattened spines (Fig. 3.87 D). Flat, broad plate
spines give these urchins a low profile and prevent them from getting swept away by powerful
waves. Sand dollars have fine velvet-textured spines that help these animals burrow into sand
(Fig. 3.87 E).
Sea urchins reproduce by sending clouds of eggs and sperm into the water. Millions of larvae
are formed, but only a handful make it back to the shoreline to grow into adults.
Just like many other sea creatures, sea urchins reproduce by releasing eggs and sperm cells in the
water. This type of reproduction is called external fertilization.