Class-Classification of Mollusca upto class.ppt
- 1. Phylum Mollusca Phylum Mollusca By By Dr. Dipanwita Sarkar (Paria) Dr. Dipanwita Sarkar (Paria)
- 2. Phylum Mollusca Phylum Mollusca Protostomes Protostomes Lophotrochozoan group Lophotrochozoan group Eucoelomates (coelomates) Eucoelomates (coelomates) Tridacna squamosa Tridacna gigas
- 3. The majority of coelomate invertebrates develop as protostomes ("first mouth") in which the oral end of the animal develops from the first developmental opening, the blastopore. In the deuterostomes ("second mouth": cf. Deuteronomy, "second book of the law"), including Echinodermata and the ancestors of the Chordata, the oral end of the animal develops from a second opening on the dorsal surface of the animal; the blastopore becomes the anus.
- 4. The name Lophotrochozoa Lophotrochozoa comes from the names of the larval type of the two major animal groups (annelida & Mollusca) included: the Lophophorata and the Trochozoa. It might seem strange at first to group earthworms and squid together. They don't look much alike as adult but many annelids and molluscs share patterns of development in early embryonic stages. When these larvae hatch, each is a microscopic swimmer known as a trochophore larva There are six phyla which are considered eucoelomates. A (eu)coelomate has a true coelom (fluid filled body cavity) which surrounds the gut and is lined on both sides by mesoderm.
- 5. Phylum Mollusca (mollis, soft) Phylum Mollusca (mollis, soft) Body usually an anterior Body usually an anterior head, head, ventral foot ventral foot and a and a dorsal dorsal visceral mass visceral mass. . Covered by a fleshy Covered by a fleshy outgrowth of the body wall outgrowth of the body wall called a called a mantle mantle. . Shell if present is Shell if present is secreted by the mantle secreted by the mantle Good phylum for Good phylum for demonstrating demonstrating Adaptive Adaptive Radiation. Radiation. With the exception of With the exception of Monoplacophora, the Monoplacophora, the phylum is phylum is unsegmented. unsegmented.
- 6. Phylum Mollusca Phylum Mollusca Complete digestive tract Complete digestive tract Digestive glands with salivary Digestive glands with salivary glands glands Specialized feeding Specialized feeding structures and Rasping structures and Rasping tongue ( tongue (Radula Radula) ) Circulatory system Circulatory system Heart (2 chambers) Heart (2 chambers) usually in pericardial cavity usually in pericardial cavity Open system in most Open system in most groups groups Closed in cephalopods Closed in cephalopods Respiratory Respiratory system system Ctenidia ( Ctenidia (gills gills) in mantle ) in mantle cavity, respiratory pigment is cavity, respiratory pigment is copper copper. .
- 7. Phylum Mollusca Phylum Mollusca Advanced nervous system Advanced nervous system Brain Brain Sensory organs Sensory organs Eyes (simple and camera) Eyes (simple and camera) Sensory papillae Sensory papillae Excretory system Excretory system Kidney-like nephridia Kidney-like nephridia Reproduction Reproduction Monoecious and dioecious Monoecious and dioecious External development External development External & internal fertilization External & internal fertilization Larva in marine = Larva in marine = trochophore trochophore and and veliger veliger, in , in freshwater clam is freshwater clam is g glochidium lochidium. .
- 8. Mollusc Phylogeny Mollusc Phylogeny ~50-80K extant ~50-80K extant species species ~40K extinct ~40K extinct species species Fossil records from Fossil records from precambrian period precambrian period of proterozoic eon of proterozoic eon (>570my BP) (>570my BP)
- 9. Classification Of Mollusca Classification Of Mollusca Classes: Classes: Aplacophora Aplacophora Monoplacophora (no specimens) Monoplacophora (no specimens) Polyplacophora Polyplacophora Scaphopoda Scaphopoda Gastropoda Gastropoda Bivalvia Bivalvia Cephalopoda Cephalopoda
- 10. Worm like mollusc, body covered by cuticle. Shell Worm like mollusc, body covered by cuticle. Shell absent absent Foot absent or reduced to ventral ridge Foot absent or reduced to ventral ridge Mantle thick with calcareous spicules. Mantle thick with calcareous spicules. Head poorly marled and without eyes or sensory Head poorly marled and without eyes or sensory tentacles tentacles No excretory organ No excretory organ I. Class Aplacophora I. Class Aplacophora
- 12. II. Class Monoplacophora II. Class Monoplacophora The word is Latinized but is derived from the Greek ktenidion which means "little comb" MONOPECTINATE TYPE: The ctenidia consists of flattened gill filaments arranged in a single row on one side of the ctenidial axis
- 13. III. Class Polyplacophora (Chitons) III. Class Polyplacophora (Chitons) Elliptical body with dorsal surface Elliptical body with dorsal surface bearing eight overlapping limy bearing eight overlapping limy plates (valves) plates (valves) Chitons are marine. Chitons are marine. They live mostly in shallow water. They live mostly in shallow water. All are similar in morphology All are similar in morphology and ecology. and ecology. They are slow moving They are slow moving microphagous feeders microphagous feeders ( (food in the form of tiny particles), , scraping algae scraping algae and other small invertebrates and other small invertebrates from substrate with their radula. from substrate with their radula. Chiton radula Chiton radula is reinforced with is reinforced with iron mineral iron mineral Genera •Katherina •Cryptochiton Chiton tuberculatus Chiton tuberculatus
- 14. Polyplacophora Polyplacophora representative genera. representative genera. Katherina Katherina Cryptochiton Cryptochiton
- 15. Mossy Chiton - hairs and bristles aid in defense Polyplacophora Polyplacophora representative genera. representative genera.
- 16. IV Class Gastropoda IV Class Gastropoda Most diverse class Most diverse class Over 70,000 living Over 70,000 living Forms range from marine forms to air- Forms range from marine forms to air- breathing terrestrial snails and slugs breathing terrestrial snails and slugs Shells Shells, if present, are chief defense , if present, are chief defense Some produce Some produce distasteful or toxic secretions distasteful or toxic secretions distinct head, scraping radula. distinct head, scraping radula. Use process of Use process of Torsion Torsion ( (Visceral mass typically Visceral mass typically turned 180° counterclockwise = turned 180° counterclockwise = torsion torsion.)And the .)And the visceral mass is coiled in shell. visceral mass is coiled in shell.
- 17. Gastropod Gastropod Shells Shells One-piece (univalve) One-piece (univalve) Apex Apex is smallest and oldest is smallest and oldest whorl whorl Whorls become larger and Whorls become larger and spiral around spiral around central axis central axis Giant marine gastropods Giant marine gastropods have shell up to 60 cm long have shell up to 60 cm long Some fossil forms are 2 Some fossil forms are 2 meters long meters long Terrestrial gastropods shells Terrestrial gastropods shells are restricted by soil mineral are restricted by soil mineral content, temperature, content, temperature, dryness, and acidity dryness, and acidity
- 18. Some Gastropods Some Gastropods Abalone shells Conch Examples of gastropoda
- 19. Pila Haliotis
- 20. Helix Helix (garden snail) (garden snail) Busycon (Whelk)
- 21. Spotted sea hare ( Spotted sea hare (Aplysia Aplysia) ) Phidiana zebra sea goddess ( zebra sea goddess (Hypselodoris Hypselodoris) )
- 22. Gills absent Gills absent Mantle cavity on right side converted into an Mantle cavity on right side converted into an air-breathing lung with a contractile opening, air-breathing lung with a contractile opening, the pneumostome the pneumostome Shell present-operculum absent Shell present-operculum absent Nervous system symmetrical Nervous system symmetrical Example-Achatina, Helix Example-Achatina, Helix Sub-class-Pulmonata
- 23. V. Class Scaphopoda V. Class Scaphopoda Tooth shells (or Tusk shells) Tooth shells (or Tusk shells) Shell and mantle slender, tubular, and slightly Shell and mantle slender, tubular, and slightly curved. It is curved. It is open at both ends open at both ends Elongated body completely enclosed by mantle. Elongated body completely enclosed by mantle. From ventral opening conical or cylindrical From ventral opening conical or cylindrical burrowing foot and buccal region are projected burrowing foot and buccal region are projected Gills absent-instead a part of mantle serves for Gills absent-instead a part of mantle serves for gaseous exchange. gaseous exchange. Single gonad-discharges via the right kidney. Single gonad-discharges via the right kidney. Example Example-Dentalium, Cadulus -Dentalium, Cadulus
- 24. Dentalium
- 25. VI. Class Bivalvia VI. Class Bivalvia Mussels, clams, scallops, oysters Mussels, clams, scallops, oysters Laterally compressed body enclosed in Laterally compressed body enclosed in a pair of shell valves. a pair of shell valves. Range in size from 1–2 mm in length to Range in size from 1–2 mm in length to the giant South Pacific clams (1m) the giant South Pacific clams (1m) Foot blade like or reduced Foot blade like or reduced Mouth with 2 pairs of labial palps Mouth with 2 pairs of labial palps Most are Most are sedentary filter feeders sedentary filter feeders Bivalves Bivalves lack a head, radula, or other lack a head, radula, or other aspects of cephalization aspects of cephalization Contain Contain Siphons Siphons
- 26. Scallop - developed sensory organs along mantle edges (tentacles and blue eyes)
- 27. Clam - Symbiotic relationship with Algae to gain most nutrients Siphonal Area
- 28. Mytilus Ostrea
- 29. VII. Class Cephalopoda VII. Class Cephalopoda Squids, octopuses, nautiluses, and Squids, octopuses, nautiluses, and cuttlefish cuttlefish All All marine predators marine predators Foot is in the head region Foot is in the head region Modified for Modified for expelling water expelling water from from mantle cavity mantle cavity Range from 2 cm to 60 ft (the giant Range from 2 cm to 60 ft (the giant squid) squid) Largest invertebrate Largest invertebrate Nautilus - only one with external shell Nautilus - only one with external shell Series of gas chambers in shell Series of gas chambers in shell helps helps maintain neutral buoyancy maintain neutral buoyancy
- 30. Nautilus Nautilus (South Pacific and Indian Ocean) (South Pacific and Indian Ocean)
- 31. Locomotion Locomotion Cephalopods Cephalopods swim by forcefully expelling water swim by forcefully expelling water through a ventral funnel or siphon through a ventral funnel or siphon Control direction and force of the water, thus Control direction and force of the water, thus determining its speed determining its speed Lateral fins of Lateral fins of squids and cuttlefishes squids and cuttlefishes are stabilizers are stabilizers Nautilus Nautilus swims mainly at night swims mainly at night Octopuse Octopuses s mainly crawl on the bottom but can swim mainly crawl on the bottom but can swim Some with webbing between their arms swim with Some with webbing between their arms swim with a medusa-like action a medusa-like action Respiration and Circulation Respiration and Circulation With higher oxygen demands, With higher oxygen demands, cephalopods have a cephalopods have a muscular pumping system to keep water flowing muscular pumping system to keep water flowing through the mantle cavity through the mantle cavity Circulatory system has a network of vessels Circulatory system has a network of vessels conducting blood through gill filaments ( conducting blood through gill filaments (Closed Closed Circulatory System!! Circulatory System!!) )
- 32. Nervous and Sensory Systems Nervous and Sensory Systems Cephalopod brain Cephalopod brain is the largest of any invertebrate is the largest of any invertebrate Squids Squids have giant nerve fibers have giant nerve fibers Sense organs are well-developed Sense organs are well-developed Eyes are complex, complete with cornea, lens, and retina Eyes are complex, complete with cornea, lens, and retina Can learn by reward and punishment, and by observation of Can learn by reward and punishment, and by observation of others others Cephalopods lack a sense of hearing but have tactile and Cephalopods lack a sense of hearing but have tactile and chemoreceptor cells in their arms chemoreceptor cells in their arms
- 33. Communication Communication Use Use chemical and visual signals chemical and visual signals to communicate to communicate Chromatophores Chromatophores are cells in the skin that contain pigment are cells in the skin that contain pigment granules granules Contractions of the muscle fibers attached to the cell causes Contractions of the muscle fibers attached to the cell causes the cell to expand and the cell to expand and change the color pattern change the color pattern Color patterns can be changed rapidly Color patterns can be changed rapidly Deep-water cephalopods Deep-water cephalopods have elaborate luminescent organs have elaborate luminescent organs Ink sac Ink sac empties into rectum; (Not in Nautiloids) empties into rectum; (Not in Nautiloids) Contains ink gland that secretes sepia (dark fluid) when Contains ink gland that secretes sepia (dark fluid) when animal is alarmed animal is alarmed Reproduction Reproduction Sexes are Sexes are separate separate One arm of male is modified as an intromittent organ, the One arm of male is modified as an intromittent organ, the hectocotylus hectocotylus Fertilized eggs leave oviduct and are attached to stones, etc. Fertilized eggs leave oviduct and are attached to stones, etc. Large, yolky eggs undergo Large, yolky eggs undergo meroblastic cleavage (not full meroblastic cleavage (not full cleavage) cleavage) Hatch into juveniles with Hatch into juveniles with no free-swimming larval stage no free-swimming larval stage
- 34. Giant cuttlefish ( Giant cuttlefish (Sepia latimanus Sepia latimanus) ) Octopus sp
- 35. Octopus Octopus Eight arms Eight arms
- 37. Sepia Sepia Cuttlebone (internal skeleton) Cuttlebone (internal skeleton)
- 39. Marine Gastropods Marine Gastropods Sea Hare – Aplysia sp
- 40. Marine Gastropods - Nudibranch Marine Gastropods - Nudibranch
- 42. Squid are the largest Cephalopods Squid are the largest Cephalopods
- 43. Color & Morphology Changes for Color & Morphology Changes for Camouflage Camouflage