Unit 2 Vocab

Adductor muscles

Muscles that work in opposition to the hinge ligament and draw the valves together in molluscs

Book gills

Abdominal appendages that are modified into flat, leaf‐like gills

Carapace

A hard dorsal shield found in horseshoe crabs

Chela

An enlarged strong claw that is used for defense

Cuticle

A nonliving external layer secreted by the epidermis of roundworms

and arthropod

Ecdysis

The process of shedding the outer layer of the cuticle in arthropods.

Halter

The hind wings of Diptera that vibrate and are responsible for

equilibrium during flight

Hemolymph

An extracellular fluid made by combination of blood plasma

and lymph

Hydrostatic skeleton

The fluid filled coelom of most annelids that moves by alternating waves of contraction of longitudinal and circular muscles

Hyperparasitism

A parasitic insect that is itself parasitized by other insects

Instar

The stage between molts of inse

Lophophore

A crown of tentacles covered with cilia that is borne on a ridge

or fold of the body wall

Malpighian tubules

The unique excretory system of spiders and insects that works with specialized rectal glands

Mantle

A sheath of skin, extending dorsally from the visceral mass, that

wraps around each side of the body of a mollusc, protecting the soft

parts and creating the mantle cavity between itself and the visceral

mass. The outer surface of this sheath secretes the shell.

Maxillipeds

The first three pairs of thoracic appendages of crayfishes’

Nacreous layer

inner layer of a molluscs shell that is composed of calcium carbonate sheets laid down over a thin protein matrix

Operculum

A hard proteinaceous plate that covers the shell aperture when

the body withdraws into the shell

Ovigers

A pair of modified legs of male sea spiders that are used to carry egg masses

Periostracum

The outer organic of a mollusk’s shell that is composed of resistant protein called conchiolin

Radula

A rasping, protrusible, tongue‐like organ found in all molluscs except bivalves and some gastropods and some solenogasters.

Siphuncle

A cord of living tissue that connects the internal chambers of the shell of Nautilus, which are used for buoyancy

Spermatophores

A bundle of sperm

Spiracles

The external openings of the tracheae of spiders

Tagmata

A functional group of combined or fused segments

Telson

A long spike‐like tailpiece

Trochophore

A free‐swimming, feeding, larval stage having a ring of large ciliated cells in front of the mouth

Umbo

The oldest part of a bivalve shell that projects above the hinge ligament on each valve

Uropods

The last pair of crustacean appendages that are wide and serve as paddles for swift backward movements

Veliger

A free‐swimming larva of most marine snails, tusk shells, and bivalves, and it has the beginning of a foot, shell and mantle

Visceral mass

One of two parts of a molluscs body that contains the digestive, circulatory, respiratory, and reproductive organs, and it depends primarily on ciliary tracts for its functioning