Zoology Chapter 16

Mollusks

Have a saclike cavity called a coelom that encloses internal organs; most have hard external skeleton (shell); aquatic and terrestrial; includes snails, oysters, clams, octopuses and squids.

Gills

Help extract oxygen from water

Torsion

In gastropods, a developmental process in which the visceral mass rotates up to 180°, causing the animal's anus and mantle cavity to be positioned above its head.

Umbo

Oldest part of the shell

Style Sac

Opens into the stomach and secretes a gelatinous rod.

Mantle

Secretes the shell

Esthetes

So-called "shell eyes" of chitons

Coiling

Special winding of the shell and visceral mass is not the same as torsion

Head Foot

What does cephalopoda mean?

Caudofoveata

Wormlike marine organisms ranging from 2 to 140 mm in length

Crystalline Style

a gelatinous rod which projects into the stomach and is kept whirling by means of cilia in the style sac layers freeing digestive enzymes.

Rhinophores

a pair of tentacles that is modified with platelike folds to increase chemoreception (Opisthobranchs)

Solenogastres

a small group of about 250 species of marine animals similar to caudofoveata however have no radula and no gills and instead have a secondary respiratory system.

Planospiral Shell

all whorls lay in the same plane

Visceral Mass

area beneath the mantle of a mollusk that contains the internal organs

Chromatophores

cells in the skin that contain pigment granules

Suprabranchial Chamber

channels on top of the gills which conducts wastes to the excurrent siphon

Prismatic Layer

composed of densely packed prisms of calcium carbonate laid down in a protein matrix.

Siphuncle

cord of tissue that runs through the chambers of nautilus shell and functions in the removal of seawater from the chambers and in the regulation of the gas content of the chambers

Veliger

free swimming larva of most marine snails, tusk shells, and bivalves; develops from the trochophore and has the beginning of a foot, shell, and mantle

Conglutinate

in females, many glochidia are contained in a packet called?

Glochidium Larva

larva of some freshwater bivalve species which parasitizes fish gills

Nacreous Layer

lies next to the mantle and is secreted continuously by the mantle surface.

Conispiral

more advanced kind of Gastropod shell where the right kidney, auricle and kidney are lost to allow the Gastropod to completely withdraw into the cell.

Periostracum

outer organic layer composed of an organic substance called conchiolin which consists of quinone tanned protein.

Nephrostome

the funnel-shaped opening of the nephridium of some invertebrates such as earthworms; coelomic fluid is drawn into the nephrostome for filtration

Scaphopoda

tusk shells or tooth shells are benthic marine molluscs from the subtidal zone to over 6000 ft in depth.

Hectocotylus

used to pluck a spermatophore from the male mantle cavity and insert it into the female

Gastropoda

A class of the phylum Mollusca that includes snails, slugs, and limpets. These organisms use radula for feeding on algae and protozoa, and have a long foot and cephalized body. They also have simple eyes on eyestalks and a primitive nervous system. They use nephridium to filter and remove waste, and can be monoecious or dioecious.

Sepia

A dark fluid containing the pigment melanin, ink

Open Circulatory System

A pumping heart, blood vessels, and blood sinuses.

Odontophore

A structure at the base of the mouth of most mollusks over which the radula is drawn back and forth in breaking up food.

Opisthobranchs

A subclass of Gastropoda that includes sea slugs and sea hares; mantle cavity lateral/posterior due to detorsion, tend to have a reduction or loss in the shell, operculum (in adulthood), mantle cavity, osphradium, and ctenidia; has structures analogous to ctenidia/osphradium (cerata/rhinophores)

Metanephridia

A type of nephridia in which the inner end opens into the coelom by a nephrostome

Brachial Hearts

Accessory hearts at the base of each gill to increase the pressure of blood going through those cappilaries

Cephalopoda

An active marine predator is found possessing these characteristics: a series of tentacles (modified from the foot), a highly developed nervous system, and elaborate eyes. To which of the following animal classes does this organism most likely belong

Radula

An organ covered with teeth that mollusks use to scrape food into their mouths

Prosobranchs

Anterior gill. Mantle cavity is generally anterior due to torsion.

Bivalvia

Aquatic; clams, oysters, mussels, scallops

Boring

Burrowing into sand

Class Polyplacophora

Chitons , Chitons. Eight valve (shells) imbedded in a thick mantle; large muscular foot.

Capacula

Ciliated adhesive knobs of long tentacles

Monoplacophora

Class of Mollusks that are very primitive. They are abundant as fossils and were thought to be extinct . Characterized by single, cap-like shell resembling that of limpets. They retain some internal segmentation of hear and kidney