Gastropods Flashcards

1
Q

8 mollusc clades

A
  1. Caudofoveata\ Aplacophora
  2. Solenogastres
  3. Monoplacophora
  4. Scaphopoda: tusk shells
  5. Polyplacophora: chitons
  6. Gastropoda: snails, limpets, slugs etc.
  7. Bivalvia: clams, mussels, etc
  8. Cephlapoda: octopi, squid
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2
Q

Characteristics of the Phylum Mollusca

A

One of the largest phyla - ~93,000 species (35,000 fossils)
Microscopic to ~18m (454kg)
Marine, fresh water and terrestrial
Grazers, carnivores, filter feeders
Most Gonochoristic, some hermaphrodites
All soft bodied (no skeleton), most secrete a hard shell
Coelomates

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3
Q

Three main parts

A

Muscular foot: involved in movement, contains sensory organs
Visceral mass: digestive, circulatory, respiratory, reproductive and sensory organs
Mantle: fold of tissue draped over visceral mass. Excretes the shell (where present)

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4
Q

Development

A

Most marine & aquatic molluscs have planktonic trochophore and veliger larval stages

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5
Q

Snails, slugs, limpets, whelks, conch, sea hares, periwinkles, sea slugs, sea butterflies

A

75% all mollusc species
Only molluscs to have invaded land
Univalve coiled shell typical
Variously coiled

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6
Q

Functional beauty of shells

A

The outer layer consists of conchiolin (tough protein)
The inner layers consist of calcium carbonate
The colours result from pigment in the calcareous layers

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7
Q

Circulationin of snails, slugs, limpets etc

A

Heat delivers blood (haemolymph) to head/foot and viscera in mantle cavity
Open circulation
Blood also has role in hydrostatic skeleton

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8
Q

Excretion (snails, slugs, limpets etc)

A

Only one nephridium (kidney) retained in gastropods
Waste from heart ultra-filtered into pericardial cavity
Drains into nephridium/kidney

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9
Q

Feeding (Snails, slugs, limpets etc)

A

Highly varied
Most herbivorous (grazers/browsers)
Ciliary feeders (slipper limpets)
Scavengers
Predators (Mollusca, invertebrates & vertebrates)
Mostly use radula which may be extremely modified
E.g. venomous Conus spp.

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10
Q

Gastropoda divided into 3 informal subclasses

A

Prosobranchia, Opisthobranchia, Pulmonata

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11
Q

Prosobranchia

A

Periwinkles, limpets, whelk, conch, abalone, slipper shells, oyster borers, rock shells, cowries

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12
Q

Opisthobranchia

A

Sea hares (vestigal shell), sea slugs, nudibranchs (cerata), canoe shells

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13
Q

Pulmonata

A

Land and freshwater snails and slugs, lack gills, mantle cavity acts as lung.

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14
Q

Nudibranchs

A

Nudibranchs have lost shells and brightly coloued
Dorid nudibranchs – make or accumulate toxins from food (sponges) secrete in mucus
Aeolid nudibranchs – graze on Cnidaria- have chitin coated gut & accumulate nematocysts in tips of protusions
APOSEMATISM- warning colouration

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15
Q

Pulmonata Reproduction

A

Penises are everted
Sperm exchange is external
1. The shelled Helicidea the vagina contains an oval dart sac
2. The sac secretes a calcareous spicule- the ‘love dart’
3. Dart secretes hormones that increase sperm survival & paternity
4. Copulating limacid slugs hang from a cord of mucus attached to a tree
5. The penes are 10 – 25cm long

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