(1) CLASS - MONOPLACOPHORA
• Body bilaterally symmetrical, with a dome-shaped mantle.
• Radula in a radular sac, intestine much coiled.
• lnternalsegmentation.
• Marine.
Examples : Neopilina galatheae (living fossil) and considered as connecting link between annelida and
mollusca.
(2) CLASS - AMPHTNEURA
Shell as eight dorsal plates or as spicules or absent.
. Fertilization external, larva trochophore.
Marine.
Examples:
Aplacophora - Neomenia, Chaetoderma Polyplacophora - Lepidopleurus,
chaetopleura, chiton, etc.
(3) CLASS - SCAPHOPODA :
Tusk-shells.
Body within a tubular shell, open at both ends.
Examples : Dentalium (Elephant tusk shell), Cadulus, Pulsellum.
(4) CLASS - GASTROPODA
Snails and slugs.
Calcareous shell
Torsion (coiling) of body mass at sometime in development is responsible for asymmetry.
Well developed head with eyes and tentacles, radula present.
Foot large and flat.
Shell present or absent univalve and usually coiled.
Mostly marine, some freshwater or terrestrial.
Examples : Fissurella (Key-hole limpet), Patella (limpet), Trochus (Top shell), Pila (Apple snail), Crepidula
(Slipper shell), Cypraea (Cowries), Natica (Star shell), Aplysia (Sea hare), Doris (Sea lemon), Helix (Land
snail), Turbinella (Shankh) etc.
(5) CLASS - PELECYPODA (BIVALV|A OR LAMELLIBRANCHIAE) :
o Body enclosed in a bivalve shelland laterally compressed.
o Usually dioecious, veliger or glochidium larva.
o Mostly marine, a few freshwater.
Examples : Nucula, Melletia, Mytilus (Mussel), Spondylus (Edible oyster), Pecten (Scallop). Teredo (Shipworm),
Ensis (Razor calm), Unio, Lamellidens, Pinctada (Pearl oyster). P. vulgaris, P. chemniEi, P. margaritifera, P. mentensi,
P. anomioides, P. atropurpurea are pearl oyster of
lndian water.
• Necrous layer - lnner lining of shell helps in pearl formation.
• Periastracum layer - Outer lining of shell.
• Mikimoto of Japan - Father of artificial pearl formation.
(6) CLASS - CEPHALOPODA (S|PHONOPODA) :
Head distinct with well-developed eyes (considered as homologous to vertebrate eye), foot as tentacles
and siphon, radula present.
Dioecious, development direct.
Marine and free-swimming.
Examples : Nautilus, Pachydiscus, Loligo (Squid or sea arrow), Sepia (Cuttle-fish), Spirula (spiral shell),
Octopus ( Devil fish), Architeuthis (G iant squ id) - Largest invertebrates.
Neopillina - Connective link b/w Annelida and Mollusca.
Pila -Apple snail
Pinctada- Pearloyster
Sepia - Cuttle fish
Loligo - Squid
Acbpus- Devilfish
Aplysia- Sea hare
Dentalium - Elephant tusk shell
Chaetopleura- Chiton
Larval forms
Trochophore-Dentalium,Chiton
Velliger - Mussel
Glochidium - Mussel and Pila
• Body bilaterally symmetrical, with a dome-shaped mantle.
• Radula in a radular sac, intestine much coiled.
• lnternalsegmentation.
• Marine.
Examples : Neopilina galatheae (living fossil) and considered as connecting link between annelida and
mollusca.
(2) CLASS - AMPHTNEURA
Shell as eight dorsal plates or as spicules or absent.
. Fertilization external, larva trochophore.
Marine.
Examples:
Aplacophora - Neomenia, Chaetoderma Polyplacophora - Lepidopleurus,
chaetopleura, chiton, etc.
(3) CLASS - SCAPHOPODA :
Tusk-shells.
Body within a tubular shell, open at both ends.
Examples : Dentalium (Elephant tusk shell), Cadulus, Pulsellum.
(4) CLASS - GASTROPODA
Snails and slugs.
Calcareous shell
Torsion (coiling) of body mass at sometime in development is responsible for asymmetry.
Well developed head with eyes and tentacles, radula present.
Foot large and flat.
Shell present or absent univalve and usually coiled.
Mostly marine, some freshwater or terrestrial.
Examples : Fissurella (Key-hole limpet), Patella (limpet), Trochus (Top shell), Pila (Apple snail), Crepidula
(Slipper shell), Cypraea (Cowries), Natica (Star shell), Aplysia (Sea hare), Doris (Sea lemon), Helix (Land
snail), Turbinella (Shankh) etc.
(5) CLASS - PELECYPODA (BIVALV|A OR LAMELLIBRANCHIAE) :
o Body enclosed in a bivalve shelland laterally compressed.
o Usually dioecious, veliger or glochidium larva.
o Mostly marine, a few freshwater.
Examples : Nucula, Melletia, Mytilus (Mussel), Spondylus (Edible oyster), Pecten (Scallop). Teredo (Shipworm),
Ensis (Razor calm), Unio, Lamellidens, Pinctada (Pearl oyster). P. vulgaris, P. chemniEi, P. margaritifera, P. mentensi,
P. anomioides, P. atropurpurea are pearl oyster of
lndian water.
• Necrous layer - lnner lining of shell helps in pearl formation.
• Periastracum layer - Outer lining of shell.
• Mikimoto of Japan - Father of artificial pearl formation.
(6) CLASS - CEPHALOPODA (S|PHONOPODA) :
Head distinct with well-developed eyes (considered as homologous to vertebrate eye), foot as tentacles
and siphon, radula present.
Dioecious, development direct.
Marine and free-swimming.
Examples : Nautilus, Pachydiscus, Loligo (Squid or sea arrow), Sepia (Cuttle-fish), Spirula (spiral shell),
Octopus ( Devil fish), Architeuthis (G iant squ id) - Largest invertebrates.
Neopillina - Connective link b/w Annelida and Mollusca.
Pila -Apple snail
Pinctada- Pearloyster
Sepia - Cuttle fish
Loligo - Squid
Acbpus- Devilfish
Aplysia- Sea hare
Dentalium - Elephant tusk shell
Chaetopleura- Chiton
Larval forms
Trochophore-Dentalium,Chiton
Velliger - Mussel
Glochidium - Mussel and Pila
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