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WCHS Zoology Chapter 12

Molluscs a triploblastic; the phylum of coelomate animals whose members posess a head-foot, visceral masses, mantle and mantle cavity. Most molluscs also possess a radula and a shell. The molluscs are related to bivalves, snails, octopuses.
head-foot The body region of a mollusc that contains the head and is responsible for locomotion as well as retracting the visceral mass into the shell.
visceral mass The region of a mollusc's body that contains visceral organs.
mantle usually attaches to the the visceral mass, enfolds most of the body and may secrete a shell that overlies the mantle
mantle cavity a space between the mantle and the foot
radula the mouth of most molluscs is a rasping sturcture
odontophore the radula overlies tongue like sturcture supported by a cartilaginous
torsion a 180 degree, counterclockwise twisting of the visceral mass, mantle, and mantle cavity. It positions the gills, anus, and opening from the excertory and reproductive systems just behind the head an nerve cords, and twists the digestive tract into a U.
operculum In snails, a proteinaceous and in some a calcareous, covering, on the dorsal, posteior margin of the foot enhances protection
protostyle a rotating mucoid mass into which food is incorporated in the gut of a gastropod (phylum Mollusca)
siphon a tubular structure through which fluid flows. Sophons of some molluscs allow water to enter and leave the mantle cavity.
open circulatory system a circulatory system found in insects and some other other invertebrates in which blood is not confined to vessels in part of its circuit. Blood bathes tissues in blood sinuses.
hydraulic skeleton the use of body fluids in open circulatory systems to give support and dacilitate movement. Muscles contracting in one part of the body force body dluids into some distant tisssue space, thus causing a part of the body to extend or become turgid.
trochophore larva a larval stage characteristic of many molluscs, annelids, and some other protostomate
veliger larva the second free-swimming larval stage of many molluscs. Develops from the trochophore and forms rudiments of the shell, visceral mass, and head-foot before settling to the substrate and undergoing metamorposis.
pneumostrome The outside opening of the gas exchange structure (lung) in land snails and slugs
umbo the rounded prominence at the anterior margin of the hinge of a bivalve (Mollusca) shell. It is the oldest part of the shell
labial palps 1. Chemosensroy appendage found on the labium of insects (Arthropoda) 2. Flaplike lobe surrounding the mouth of bivalve molluscs that directs food toward the mouth.
crystalline style a proteinaceous, rodlike structure in the digestive tract of a bivalve (mollusca) that rotates against a gastric sheild and releases digestive enzymes.
gastric shield a chitinized plate in the stomach of a bivalve (phylum mollusca) on which the crystalline style rotates
glochidium a larval stage of freshwater bivalves in the family Unionidae. It lives as a parasite on the gills or fins of fishes
closed circulatory system a circulatory system in an animal (vertibrates) in which blood is confined to vessels throughtout its circuit.
chromatophores cells containing pigment that, through contraction and expansion, produce temporary color changes.
spermatophore encapsulated sperm that a male can deposit on a substrate for a female to pick up or that a male can transfer directly to a female
hectocotylus a motified arm of some male cephalopods that is used in sperm transfer
Created by: dmoudy