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Introduction



•Mollusca is the Latin
for “soft”
•Includes snails, squids,
nautilus, octopus,
clams, etc.
•2nd largest ph...
Phylum Mollusca; the most malleable body plan in the animal kingdom
•Have adapted to a wide variety of habitats
   •Terrestrial, marine, benthic, and
   accomplished swimmers.
•Molluscs evol...
Edible mussels
                                  (Mytilus edulis)




•Humans use molluscs in a variety
of ways:
    •As f...
“If a grain of sand, parasite or other foreign particle
becomes trapped between the mantle and the shells’ inner
surface, ...
Mollusc Phylogeny

                    • ~50-80K extant
                      species
                    • ~40K extinct
 ...
The first molluscs probably arose
during Precambrian times.
      Diverse molluscs found in the early
   Cambrian.
  It is...
o“Hypothetical Ancestral Mollusc”
  oProbably lacked a shell or crawling
  foot.
  oProbably small (about 1 mm).
  oLikely...
1. Dorsal Epithelium forming a mantle which
   secretes calcareous spicules or one or more
   shells
2. Cuticular band of ...
• Most but not all mollusc have shells consisting
  primarily of calcium carbonate set in a protein
  matrix.
• The Mollus...
An example of mollusc illustrating their common body plan
The Head-Foot Region
• Most molluscs have well developed head ends
  with sensory structures including
  photosensory rece...
The Head-Foot Region

                  • The radula is a
                    rasping, protrusible
                    fee...
The Head-Foot Region

• The foot of a mollusc
  may be adapted for
  locomotion, attachme
  nt, or both.
• Pelagic forms m...
Muscular foot
Mantle and Mantle Cavity
When present, the calcareous shell is secreted by the mantle
and is lined by it. It has 3 layers:
   •Periostracum – outer...
Pearl is formed between the mantle and the shell.
• Many molluscs have an open circulatory
  system with a pumping heart, blood vessels
  and blood sinuses.
• Most cephalop...
• Most molluscs are
  dioecious, some are
  hermaphroditic.
• The life cycle of many
  molluscs includes a free
  swimming...
The trochophore larval stage is followed by a free-swimming veliger larva in most species
Mollusc Taxonomy


Major classes
  Polyplacophora – the chitons
  Aplacophora-
  Monoplacophora
  Gastropoda- snails ...
Class Polyplacophora

Greek: many plate bearing
Defining characteristics: Shell forms as a series of 7
to 8 separate plate...
• Pair of osphradia serves as sense organ.
• Light sensitive esthetes form eyes in some species – pierce plates.
• Blood p...
Class Aplacophora

                               •Quite small– usually only a few millimeters
                           ...
Two subclasses:
      Neomeniomorpha or Solenogastres
      Chaetodermomorpha or Caudofoveata
Solenogastres               ...
•Caudofoveata are small (1-30
mm), mainly deep sea molluscs.
They are worm-like, lacking
shells or distinct muscular feet;...
Subclass Solenogaster
•do not have true ctenidia, although their gill-like structures resemble them
•during development ma...
Solenogasters feed on
cnidaria and
ctenophores, either sucking
their bodily fluids or eating
their tissue.
Class Monoplacophora


Greek : one shell bearing
Defining characteristics:
1. 3 to 6 pairs of ctenidia, 6 to 7 pairs of ne...
Class Gastropoda
Greek: stomach foot
Defining Characteristics:
1. Visceral mass and nervous system become
   twisted 90-18...
• Gastropods show bilateral symmetry, but due to a twisting
  process called torsion that occurs during the veliger larval...
Torsion is an anticlockwise twisting of most of the body (the visceral mass) through 180⁰ during
                         ...
• The shell of a gastropod is
  always one piece –
  univalve – and may be
  coiled or uncoiled.
   – The apex contains th...
• Coiling is not the same as
  torsion.
• Early gastropods had a
  planospiral shell where
  each whorl lies outside the
 ...
• herbivores and feed by
  scraping algae off hard
  surfaces using the radula.
• scavengers of dead
  organisms, again te...
• Snails in the genus Conus feed on fish, worms, and
  molluscs.
   – Highly modified radula used for prey capture.
   – T...
• Flamingo tongue snails
  feed on gorgonians.
• Mantle is brightly
  colored and envelops
  the shell.
• Pulmonates lack gills.
   – Have a highly vascular area in
     mantle that serves as lung.
   – Lung opens to outside b...
• Most have a single nephridium and well-
  developed circulatory and nervous systems.
• Sense organs include eyes, statoc...
• Respiration in many
  performed by ctenidia in
  mantle cavity.
• Derived prosobranchs lost
  one gill and half of
  rem...
• Slugs lack
Pneumostome shells
           • Mantle
             thickened
           • Pneumostome
              – Air in...
• Monoecious and dioecious species.
• Young may emerge as veliger larvae or pass
  this stage inside the egg.
• Some speci...
Greek: Anterior Gill
Defining Characteristic:
1. Mantle Cavity generally anterior
due to torsion

                        ...
Greek: Posterior Gill
Defining Characteristic:
1. Mantle cavity lateral or posterior due to detorsion,
or lost




       ...
– Most are marine, shallow-water.
– Partial to complete detorsion -
  anus and gill(s) are displaced to
  right side.
– Tw...
Locomotion is generally made by cilia
and pedal waves along the ventral
surface of the foot
  Some opisthobranchs, ex. sea...
Latin : Lung
Defining Characteristic:
1. Mantle cavity highly vascularized and other
modified to form a lung

            ...
Class Bivalvia
Latin: Two valved [Greek: hatched foot]
Pelecypoda
Defining Characteristics:
1. Two valved shell
2. Body fl...
• Bivalves are laterally
  (right-left) compressed
  and their two shells are
  held together by a
  hinge ligament on the...
• Part of the mantle is
  modified to form
  incurrent and excurrent
  siphons.
  – Used to pump water
    through the org...
• Shipworms can be destructive to wharves & ships.
• The valves have tiny teeth that act as wood rasps and
  allow these b...
• Bivalves move around by extending the muscular foot
  between the shells.
• Scallops and file shells swim by clapping th...
• Like other
  molluscs, bivalves
  have a coelom
  and an open
  circulatory
  system.
• The mantle cavity
  of a bivalve...
• Scallops have a row of small blue eyes along the mantle
  edge. Each eye has a cornea, lens, retina, and pigmented
  lay...
Suspended organic matter enters incurrent siphon.
Gland cells on gills and labial palps secrete mucus to entangle particle...
• Bivalves usually
  have separate
  sexes.
• Zygotes develop
  into
  trochophore, vel
  iger, and spat
  (tiny bivalve)
...
In freshwater clams,
fertilized eggs develop
into glochidium larvae
which is a specialized
veliger.
     Glochidia live as...
Greek: first gill
Defining Characteristics:
1. Gills small, functioning primarily as gas
   exchange surfaces
2. Food coll...
-Entirely marine, and all species live in soft substrate
- feed on sediments taken in and the organic fraction is digested...
Greek: plate gill
Defining Characteristics:
1. Gills modified to collect suspended food particles, in
   addition to servi...
Greek: Fence gill
                   Defining Characteristic:
                   Gills highly modified to form a muscular
...
Septibranchs feed as organic vacuum (suck small crustaceans
and annelids).
The stomach is lined with hardened chitin, to g...
Class Scaphopoda
Greek: Spade foot
Defining Characteristics:
1. Tusk-shaped, conical shell, open at both
   ends
2. Develo...
The scaphopod shell is
never spirally wound, but rather
grows linearly as hollow, curved
table; hence known as “tooth
shel...
-capture small food particles, including Foraminiferans ,from the
surrounding sediment and water using specialized, thin t...
Rear end, through which water is
                                              driven
                             into th...
Scaphopoda shells (many of them from
Vancouver Is, British Columbia) were the
shells used to make the North American
India...
Scaphopods have separate sexes, and external
fertilisation. They have a single gonad occupying
much of the posterior part...
Class Cephalopoda
  Greek: Head foot
  Defining Characteristic:
  1. Shell divided by septa, with
     chambers connected ...
• Cephalopods include
  octopuses, squid, nautiluses
  and cuttlefish.
• Marine carnivores with beak-
  like jaws surround...
Cephalopods are the supreme testament to the
impressive plasticity of the basic molluscan body plan.
Ctenidia and a radu...
•   Cephalopod fossils go back to Cambrian (570 mya) times.
•   The earliest had straight cone-shaped shells.
•   Later ex...
Anatomy of Nautilus
• Shells of Nautilus and early
  nautiloid and ammonoid
  cephalopods were made
  buoyant by a series of gas     • Nautilu...
Cuttlefishes have a small curved shell, completely enclosed by the mantle.
The squid shell is also internal, but it is little more than a thin, stiff, proteinaceous
                                ...
FUN FACT: The largest
cephalopod Mesonychoteuthis
hamiltoni, (Fig. 17) called the
colossal squid, is longer than a city
bu...
General Anatomy Cephalopod
         Anatomy
All cephalopods have arms, but not all
cephalopods have tentacles .
Octopuses, cuttlefish, and squid have eight
non-retr...
Anatomy of an Octopus
•Cephalopods have a closed
circulatory system.
•Nervous and sensory systems are
more elaborate in cephalopods
than in othe...
Communication

Visual signals allow
cephalopods to communicate.
    Movement of body and
    arms
    Color changes effect...
Cephalopods have an amazing ability to change
color very rapidly. They accomplish this feat
using numerous pigment-filled ...
Cephalopods
  have two eyes
 Nautilus spp. Eyes
    are simple and
  function as on the
    pinhole camera
   principle;...
Octopuses are the only cephalopods with a completely protected
"closed" cornea. This structure is probably the most sophis...
Reproduction

• Sexes are separate in cephalopods.
• Juveniles hatch directly from eggs – no free-
  swimming larvae.
• On...
Reproduction
•Most females then lay large yolky eggs in clusters on the
ocean floor or on any other hard substrate.
•Eggs develop by di...
The brain. Finally, one of the most intriguing aspects
of cephalopods is their intelligence. With a
centralized brain, the...
phylum mollusca
phylum mollusca
phylum mollusca
phylum mollusca
phylum mollusca
phylum mollusca
phylum mollusca
phylum mollusca
phylum mollusca
phylum mollusca
phylum mollusca
phylum mollusca
phylum mollusca
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Phylum Mollusca-my report..

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phylum mollusca

  1. 1. Introduction •Mollusca is the Latin for “soft” •Includes snails, squids, nautilus, octopus, clams, etc. •2nd largest phylum after Phylum Arthropods (Animal Kingdom)
  2. 2. Phylum Mollusca; the most malleable body plan in the animal kingdom
  3. 3. •Have adapted to a wide variety of habitats •Terrestrial, marine, benthic, and accomplished swimmers. •Molluscs evolved in the sea and most molluscs are still marine. •Some gastropods and bivalves inhabit freshwater. •A few gastropods (slugs & snails) are terrestrial
  4. 4. Edible mussels (Mytilus edulis) •Humans use molluscs in a variety of ways: •As food – mussels, clams, oysters, abalon e, calamari (squid), octopus, escargot (snails), etc. •Pearls – formed in oysters and clams. •Shiny inner layer of some shells used to make buttons.
  5. 5. “If a grain of sand, parasite or other foreign particle becomes trapped between the mantle and the shells’ inner surface, a pearl may form over a period of years. Natural pearl formation is a fairly rare event; perhaps only one oyster in 1,000 is likely to harbor a valuable pearl naturally”
  6. 6. Mollusc Phylogeny • ~50-80K extant species • ~40K extinct species • Fossil records from precambrian period of proterozoic eon (>570my BP)
  7. 7. The first molluscs probably arose during Precambrian times. Diverse molluscs found in the early Cambrian. It is likely that molluscs split off from the line that led to annelids after coelom formation, but before segmentation appeared.
  8. 8. o“Hypothetical Ancestral Mollusc” oProbably lacked a shell or crawling foot. oProbably small (about 1 mm). oLikely was a worm-like organism with a ventral gliding surface. oProbably possessed a dorsal mantle, a chitinous cuticle and calcareous scales.
  9. 9. 1. Dorsal Epithelium forming a mantle which secretes calcareous spicules or one or more shells 2. Cuticular band of teeth(radula) in the esophagus used for feeding (not present- lost? in bivalves) 3. Ventral body wall muscles develop into a locomotory or clinging foot
  10. 10. • Most but not all mollusc have shells consisting primarily of calcium carbonate set in a protein matrix. • The Molluscan body plan includes – Head-foot – Visceral Mass -containing digestive, circulatory, respiratory and reproductive organs.
  11. 11. An example of mollusc illustrating their common body plan
  12. 12. The Head-Foot Region • Most molluscs have well developed head ends with sensory structures including photosensory receptors that may be simple light detectors or complex eyes (cephalopods)
  13. 13. The Head-Foot Region • The radula is a rasping, protrusible feeding structure found in most molluscs (not bivalves). – Ribbon-like membrane with rows of tiny teeth.
  14. 14. The Head-Foot Region • The foot of a mollusc may be adapted for locomotion, attachme nt, or both. • Pelagic forms may have a foot modified into wing-like parapodia.
  15. 15. Muscular foot
  16. 16. Mantle and Mantle Cavity
  17. 17. When present, the calcareous shell is secreted by the mantle and is lined by it. It has 3 layers: •Periostracum – outer organic layer helps to protect inner layers from boring organisms. •Prismatic layer – densely packed prisms of calcium carbonate. •Nacreous layer – iridescent lining secreted continuously by the mantle – surrounds foreign objects to form pearls in some.
  18. 18. Pearl is formed between the mantle and the shell.
  19. 19. • Many molluscs have an open circulatory system with a pumping heart, blood vessels and blood sinuses. • Most cephalopods have a closed circulatory system with a heart, blood vessels and capillaries.
  20. 20. • Most molluscs are dioecious, some are hermaphroditic. • The life cycle of many molluscs includes a free swimming, ciliated larval stage called a trochophore. – Similar to annelid larvae.
  21. 21. The trochophore larval stage is followed by a free-swimming veliger larva in most species
  22. 22. Mollusc Taxonomy Major classes Polyplacophora – the chitons Aplacophora- Monoplacophora Gastropoda- snails and slugs Bivalvia- clams, mussel and oysters Scaphopoda- tusk shells Cephalopoda- octopus and squids
  23. 23. Class Polyplacophora Greek: many plate bearing Defining characteristics: Shell forms as a series of 7 to 8 separate plates •Use radula to scrape algae off rocks •Live on rocky intertidal zones •Gills are suspended from roof of mantle cavity. •Water flows from anterior to posterior ; linear digestive tract Tonicella lineata
  24. 24. • Pair of osphradia serves as sense organ. • Light sensitive esthetes form eyes in some species – pierce plates. • Blood pumped by a three-chambered heart. – Travels through aorta and sinuses to gills. • Pair of metanephridia carries wastes from pericardial cavity to exterior. • Sexes are separate. • Trochophore larvae metamorphose into juveniles without a veliger stage.
  25. 25. Class Aplacophora •Quite small– usually only a few millimeters •Entirely marine •No true shell •The body is unsegmented and bears numerous calcareous spines or scales embedded in an outer cuticle Greek: no shell bearing Defining Characteristic: Cylindrical, vermiform body with the foot forming a narrow keel
  26. 26. Two subclasses: Neomeniomorpha or Solenogastres Chaetodermomorpha or Caudofoveata Solenogastres Caudofoveata
  27. 27. •Caudofoveata are small (1-30 mm), mainly deep sea molluscs. They are worm-like, lacking shells or distinct muscular feet; they instead have scales and calcareous spines called sclerites, for movement. •live by burrowing through soft sediment and feed by lying vertically in the sediment with just the mouthparts exposed and taking in passing organic detritus.
  28. 28. Subclass Solenogaster •do not have true ctenidia, although their gill-like structures resemble them •during development many solenogastres are covered by a spiny scleritome comprising spines or scale-like plates; this has been likened to the halwaxiid scleritome
  29. 29. Solenogasters feed on cnidaria and ctenophores, either sucking their bodily fluids or eating their tissue.
  30. 30. Class Monoplacophora Greek : one shell bearing Defining characteristics: 1. 3 to 6 pairs of ctenidia, 6 to 7 pairs of nephridia 2. Multiple (usually 8) pairs of foot (pedal) retractor muscles -Was known only from fossils until 1952 -Entirely marine and all collected from depth at least 2000 m -A single unhinged cap shaped shell is present -The largest species is about 37 mm
  31. 31. Class Gastropoda Greek: stomach foot Defining Characteristics: 1. Visceral mass and nervous system become twisted 90-180 ⁰ (exhibiting torsion) during embryonic development 2. Proteinaceous shield on the foot (operculum) to which columellar muscles attaches ______________________________________ Gastropoda is the largest of the molluscan classes. – 40,000 to 75,000 living species. – Include snails, slugs, sea hares, sea slugs, sea butterflies. – Marine, freshwater, terrestrial. • Benthic or pelagic
  32. 32. • Gastropods show bilateral symmetry, but due to a twisting process called torsion that occurs during the veliger larval stage, the visceral mass is asymmetrical.
  33. 33. Torsion is an anticlockwise twisting of most of the body (the visceral mass) through 180⁰ during early development
  34. 34. • The shell of a gastropod is always one piece – univalve – and may be coiled or uncoiled. – The apex contains the oldest and smallest whorl. – Shells may coil to the right or left – this is genetically controlled.
  35. 35. • Coiling is not the same as torsion. • Early gastropods had a planospiral shell where each whorl lies outside the others. – Bulky • Conispiral shells have each whorl to the side of the preceding one. – Unbalanced • Shell shifts over for better weight distribution.
  36. 36. • herbivores and feed by scraping algae off hard surfaces using the radula. • scavengers of dead organisms, again tearing off pieces with radular teeth. • carnivores and have a radula modified into a drill to bore through the shells of other molluscs. They use chemicals to soften the shell.
  37. 37. • Snails in the genus Conus feed on fish, worms, and molluscs. – Highly modified radula used for prey capture. – They secrete a toxin that paralyzes their prey. • Some are painful, even lethal, to humans.
  38. 38. • Flamingo tongue snails feed on gorgonians. • Mantle is brightly colored and envelops the shell.
  39. 39. • Pulmonates lack gills. – Have a highly vascular area in mantle that serves as lung. – Lung opens to outside by small opening, the pneumostome. – Aquatic pulmonates surface to expel a gas bubble and inhale by curling, thus forming a siphon. In Terrestrial gastropods: The mantle cavity serves as a “lung”
  40. 40. • Most have a single nephridium and well- developed circulatory and nervous systems. • Sense organs include eyes, statocysts, tactile organs, and chemoreceptors. • Eyes vary from simple cups holding photoreceptors to a complex eye with a lens and cornea. • Sensory osphradium at base of the incurrent siphon may be chemosensory or mechanoreceptive.
  41. 41. • Respiration in many performed by ctenidia in mantle cavity. • Derived prosobranchs lost one gill and half of remaining gill. – Resulting attachment to wall of mantle cavity provided respiratory efficiency.
  42. 42. • Slugs lack Pneumostome shells • Mantle thickened • Pneumostome – Air intake into mantle cavity
  43. 43. • Monoecious and dioecious species. • Young may emerge as veliger larvae or pass this stage inside the egg. • Some species, including most freshwater snails, are ovoviviparous.
  44. 44. Greek: Anterior Gill Defining Characteristic: 1. Mantle Cavity generally anterior due to torsion •Prosobranchia includes most marine snails and some freshwater and terrestrial gastropods. •Largest of three subclasses; mostly marine •Generally free-living and mobile; some have evolved sessile or even parasitic lifestyles •Warm water cone snails (Conus sp.) are carnivorous produce potent venoms •Most primitive of gastropods; two other subclasses evolved from prosobranch like ancestors
  45. 45. Greek: Posterior Gill Defining Characteristic: 1. Mantle cavity lateral or posterior due to detorsion, or lost Opisthobranchia includes sea slugs, sea hares, sea butterflies, and canoe shells Sea hare Aplysia has large anterior tentacles and a vestigial shell.
  46. 46. – Most are marine, shallow-water. – Partial to complete detorsion - anus and gill(s) are displaced to right side. – Two pairs of tentacles, one pair modified to increase chemo- absorption. – Shell is reduced or absent. – Monoecious Compared to Prosobranchia: 1. A trend toward reduction or loss of the shell 2. Reduction or loss of the operculum 3. Limited torsion during embryogenesis 4. Reduction or loss of the mantle cavity 5. Reduction or loss of the ctenidia
  47. 47. Locomotion is generally made by cilia and pedal waves along the ventral surface of the foot Some opisthobranchs, ex. sea hares, can swim in short spurts by flapping lateral folds called parapodia
  48. 48. Latin : Lung Defining Characteristic: 1. Mantle cavity highly vascularized and other modified to form a lung Compare to other subclasses, only few of these species are marine and those few species occur only in intertidal and in estuaries
  49. 49. Class Bivalvia Latin: Two valved [Greek: hatched foot] Pelecypoda Defining Characteristics: 1. Two valved shell 2. Body flattened laterally -Includes clams, scallops, mussels , shipworms and oyster Mostly sessile filter feeders. No head or radula. Two major subclasses: •Protobranchia •Lamellibranchia -and one very small subclass; The Septibranchia
  50. 50. • Bivalves are laterally (right-left) compressed and their two shells are held together by a hinge ligament on the dorsal surface. • The Umbo is the oldest part of the shell, growth occurs in concentric rings around it.
  51. 51. • Part of the mantle is modified to form incurrent and excurrent siphons. – Used to pump water through the organism for gas exchange and filter feeding. – Sometimes used for jet propulsion.
  52. 52. • Shipworms can be destructive to wharves & ships. • The valves have tiny teeth that act as wood rasps and allow these bivalves to burrow through wood. • They feed on wood particles with the help of symbiotic bacteria that produce cellulase and fix nitrogen.
  53. 53. • Bivalves move around by extending the muscular foot between the shells. • Scallops and file shells swim by clapping their shells together to create jet propulsion.
  54. 54. • Like other molluscs, bivalves have a coelom and an open circulatory system. • The mantle cavity of a bivalve contains gills that are used for feeding as well as gas exchange.
  55. 55. • Scallops have a row of small blue eyes along the mantle edge. Each eye has a cornea, lens, retina, and pigmented layer.
  56. 56. Suspended organic matter enters incurrent siphon. Gland cells on gills and labial palps secrete mucus to entangle particles. Food in mucous masses slides to food grooves at lower edge of gills. Cilia and grooves on the labial palps direct the mucous mass into mouth. Some bivalves feed on deposits in sand.
  57. 57. • Bivalves usually have separate sexes. • Zygotes develop into trochophore, vel iger, and spat (tiny bivalve) stages.
  58. 58. In freshwater clams, fertilized eggs develop into glochidium larvae which is a specialized veliger. Glochidia live as parasites on fish and then drop off to complete their development. Glochidia – Unique Larval Stage of Freshwater Bivalves
  59. 59. Greek: first gill Defining Characteristics: 1. Gills small, functioning primarily as gas exchange surfaces 2. Food collecting by long , thin, muscular extensions of tissue surrounding the mouth (palp proboscides)
  60. 60. -Entirely marine, and all species live in soft substrate - feed on sediments taken in and the organic fraction is digested (deposit feeding) -Palp boscides, long, thin muscular extensions of the tissue surrounding the mouth is responsible for food collection , not in the gills -Much more common in deep water
  61. 61. Greek: plate gill Defining Characteristics: 1. Gills modified to collect suspended food particles, in addition to serving as gas exchange surfaces 2. Secretion of proteinaceous attachment material (usually in the form of threads) by a specialized gland (the byssus gland) in the foot Most bivalves are lamellibranchs. Majority are marine, and some belong to Unionidae, freshwater bivalve species. Commercially important for many years as food (e.g., Oysters and scallops) Widely used to assess environmental pollution
  62. 62. Greek: Fence gill Defining Characteristic: Gills highly modified to form a muscular septum, which pumps water through the mantle cavity for respiration and feeding Small groups of carnivorous bivalves that feed on zooplanktons and on pieces of decomposing animal tissue All species are marine and found in very deep water The septibranch ctenidium is highly modified, lacking filaments and forming a muscular septum
  63. 63. Septibranchs feed as organic vacuum (suck small crustaceans and annelids). The stomach is lined with hardened chitin, to grind up ingested food.
  64. 64. Class Scaphopoda Greek: Spade foot Defining Characteristics: 1. Tusk-shaped, conical shell, open at both ends 2. Development of anterior, threadlike, adhesive feeding tentales Young group, first appearing in the fossil records in the middle Ordovician (450 years ago) 300-400 species, Entirely marine, lives sedentary lives in sand or mud substrate Possess no ctenidia
  65. 65. The scaphopod shell is never spirally wound, but rather grows linearly as hollow, curved table; hence known as “tooth shell” and “tusk shell”.
  66. 66. -capture small food particles, including Foraminiferans ,from the surrounding sediment and water using specialized, thin tentacles known as captacula.
  67. 67. Rear end, through which water is driven into the pallial cavity by ciliary action Burrowing foot pulling the animal into the ground
  68. 68. Scaphopoda shells (many of them from Vancouver Is, British Columbia) were the shells used to make the North American Indian trade money "Wampum“. Scaphopod shells have been used as decoration, jewellery and money by many peoples.
  69. 69. Scaphopods have separate sexes, and external fertilisation. They have a single gonad occupying much of the posterior part of the body, and shed their gametes into the water through the nephridium. Once fertilised, the eggs hatch into a free- living trochophore larva, which develops into a veliger larva that more closely resembles the adult, but lacks the extreme elongation of the adult body.
  70. 70. Class Cephalopoda Greek: Head foot Defining Characteristic: 1. Shell divided by septa, with chambers connected by the siphuncle: a vascularized strand of tissue contained within a tube of calcium carbonate (shell reduced or lost in many species) 2. Closed circulatory system 3. Foot modified to form flexible arms and siphon 4. Ganglia fused to form a large brain encased in a cartilaginous cranium
  71. 71. • Cephalopods include octopuses, squid, nautiluses and cuttlefish. • Marine carnivores with beak- like jaws surrounded by tentacles of their modified foot. – Modified foot is a funnel for expelling water from the mantle cavity.
  72. 72. Cephalopods are the supreme testament to the impressive plasticity of the basic molluscan body plan. Ctenidia and a radula are present in all cephalopod species The head and associated sensory organs are extremely well-developed. Nautilus locomotes by jet propulsion, expelling water from the mantle cavity through flexible, hollow tube called the siphon or funnel Cephalopods swim by expelling water from the mantle cavity through a ventral funnel. They can aim the funnel to control the direction they are swimming.
  73. 73. • Cephalopod fossils go back to Cambrian (570 mya) times. • The earliest had straight cone-shaped shells. • Later examples had coiled shells similar to Nautilus. • Ammonoids were a very successful group, some had quite elaborate shells.
  74. 74. Anatomy of Nautilus
  75. 75. • Shells of Nautilus and early nautiloid and ammonoid cephalopods were made buoyant by a series of gas • Nautilus shells differ chambers. from gastropod because they are divided into chambers. The animal lives in the last chamber. A cord of living tissue extends through each chamber.
  76. 76. Cuttlefishes have a small curved shell, completely enclosed by the mantle.
  77. 77. The squid shell is also internal, but it is little more than a thin, stiff, proteinaceous sheet, called the pen
  78. 78. FUN FACT: The largest cephalopod Mesonychoteuthis hamiltoni, (Fig. 17) called the colossal squid, is longer than a city bus, while the smallest cephalopod, Idiosepius notoides, the pygmy squid, could fit on your fingernail.
  79. 79. General Anatomy Cephalopod Anatomy
  80. 80. All cephalopods have arms, but not all cephalopods have tentacles . Octopuses, cuttlefish, and squid have eight non-retractable arms, but only cuttlefish and squid (Sepioidea and Teuthoidea) have tentacles (two each). Arms usually have cirri (fleshy papillae/palps), often suckers, and sometimes hooks (modified suckers) along their undersides.  Tentacles are longer than arms, are retractable, and usually have a blade-shaped or flattened tip, called a club, which is covered in suckers
  81. 81. Anatomy of an Octopus
  82. 82. •Cephalopods have a closed circulatory system. •Nervous and sensory systems are more elaborate in cephalopods than in other molluscs. •The brain is the largest of any invertebrate. •Most cephalopods’ skin contains several layers of tiny colored cells called chromatophores, which overlay reflective cells called iridocytes- responsible for coloration of skin
  83. 83. Communication Visual signals allow cephalopods to communicate. Movement of body and arms Color changes effected by chromatophores Most cephalopods have an ink sac that secretes sepia, a dark fluid containing the pigment melanin. When a predator tries to attack, the animal ejects the ink into the water where it hangs between the animal and the predator screening a quick escape
  84. 84. Cephalopods have an amazing ability to change color very rapidly. They accomplish this feat using numerous pigment-filled bags, called chromatophores. Chromatophores are found in the skin, and expand and contract to reveal or conceal small dots of color (left). Additionally, an iridescent dermal tissue can also be manipulated by some cephalopods to aid in camouflage, courtship rituals, or accompany color changes.
  85. 85. Cephalopods have two eyes Nautilus spp. Eyes are simple and function as on the pinhole camera principle; no lens While other cephalopods eyes are incredibly similar to mammals
  86. 86. Octopuses are the only cephalopods with a completely protected "closed" cornea. This structure is probably the most sophisticated eye of all invertebrates and is as complex as the vertebrate eye. Differing eye morphologies in cephalopods. From left, a squid (Loligo), octopus, cuttlefish, and Nautilus. Note the hyponome below the octopus eye — this is a muscular tube, that when contracted, expels water in a jet, propelling the octopus backwards. The hyponome can be aimed in various directions, giving the octopus finer control over its escape route.
  87. 87. Reproduction • Sexes are separate in cephalopods. • Juveniles hatch directly from eggs – no free- swimming larvae. • One arm of male is modified as an intromittent organ, the hectocotylus. – Removes a spermatophore from mantle cavity and inserts it into female.
  88. 88. Reproduction
  89. 89. •Most females then lay large yolky eggs in clusters on the ocean floor or on any other hard substrate. •Eggs develop by dividing unequally instead of in the spiral pattern of other molluscs. It is thought this is a derived mode of development. •After a period of development within the egg, juveniles hatch out directly without the swimming larval stage common to many other molluscs. Most males and females die shortly after spawning.
  90. 90. The brain. Finally, one of the most intriguing aspects of cephalopods is their intelligence. With a centralized brain, the largest of all invertebrates, and highly developed eyes and other sense organs, they are able to remember and learn by example or through trial and error.
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Phylum Mollusca-my report.. sorry for some overlapping of texts... i was not able to edit it..it is actually because of the animations that i put it..... i just uploaded it directly :)

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