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adductor muscle scar

Region on interior of bivalve shell where the muscles attach to hold shell closed


Sponge body type; simple non-branching spongocoel

Byssus threads

Protein threads secreted by glands in the foot of bivalves; holds animal to substrate


Secondary gill on dorsal surface of Opisthobranchs (Phylum Mollusca, Class Gastropoda)


Flagellated cell lining interior canals of sponges; creates currents; captures particles in collar of microvilli held together by mucus; responsible for intracellular digestion and meiosis


Body cavity formed within mesoderm; created by layer of epithelium called the peritoneum; holds organs in place


Cells on tentacles of ctenophores that secrete glue for prey capture


Ciliated "wheels" at anterior of rotifers; used for movement of water to capture suspended organic particles, such as bacteria, for feeding


Gill in molluscs; consists of an axis that holds layers of thin, vascularized sheets of tissue (has comb-like appearance, hence the name); also used for feeding in bivalves


Defensive zooid with many nematocysts in polymorphic hydrozoa


Development from embryos that have two layers of cells, the endoderm and ectoderm; adult organism has epidermis and gastrodermis (Cnidaria and Ctenophora are diploblastic)


Sexual stage of some polychaete worms; separates from adult and swims up to spawn


Development in which all adults have the same, fixed number of cells (rotifers, nematodes, tardigrades)

flame bulb

Protonephridia found in flatworms, nemerteans, rotifers; ciliated "flame cell" pulls water from the coelom into a canal system for excretion; appears to function mostly for osmoregulation rather than excretion of wastes; Annelida have similar structure, but flame cell is flagellated (called a solenocyte)


Muscular portion of mollusk used for movement

Gastrovascular cavity

Fluid filled cavity in Cnidaria (Ctenophores?)and Flatworms; serves for digestion and for hydroskeleton


Feeding zooid of a polymorphic Hydrozoan


Reproductive zooid of a polymorphic Hyrdozoan


Annelid body type in which segments in different regions are specialize for certain functions

hinge & teeth

Portions of a bivalve shell; holds two sides of shell together


Annelid body type in which segments are more or less the same

hydrostatic skeleton

Support structure in cnidarians and flatworms based on a fluid filled cavity surrounded by muscles that can put pressure on the cavity to stiffen and contract the animal; or release pressure to soften and extend the animal

labial palp

Extensions of tissue near the mouth of bivalves; selects appropriate particles to consume and creates pseudofeces of rejected particles


Sponge body type characterized by extensively branching canals


Characteristic of molluscs; fold of epidermis that covers the vis the visceral mass and forms a cavity in which the ctenidia, anus, nephridiopore and gonopore are located; mantle secretes the shell and forms siphons, tentacles, and other structures

mantle cavity

Cavity in molluscs formed by the mantle; ctenidia lie in cavity and anus, gonopore, and nephridiopore open into cavity


Body form in Cnidaria; upside down sac with tentacles


Non-cellular layer of "jelly" and fibers between the epidermis and gastrodermis in cnidarian


Non-cellular material in the wall of a sponge; contains spicules, amoebocytes; lies between the choanocyte layer and the pinacocyte layer


Structure in Annelids that serves for both excretion of wastes from mesonephridia to the outside of the body, as well as for transport of gametes


Organelle in cnidocytes of Cnidaria; when triggered by touch, shoots out a harpoon like hook with poisons, attached by a thread of protein; used to subdue prey and for defense


Opening for excurrent water flow in sponges


Sensory structure in bivalves; water flows that enters siphon flows first across this organ, which has chemosensors; enables siphon to "sniff out" directions in which food or mates might be found


Opening for incurrent water flow in sponges

pallial line

Scar on shell that marks the edge where the mantle was attached


Extensions of the body in polychaetes that serve as legs; contain setae

pericardial cavity

Region of coelom that encloses heart (in molluscs)


External, organic layer of a molluscan shell


The first segment in an Annelid; contains the mouth


Body type in Cnidaria; upright sac with tentacles


"head" of a polychaete worm; region at anterior of peristomium


Simple kidney-like structures that serve as osmoregulatory and (in some) waste removal in flatworms, nematodes, nemerteans, and annelids)


Body cavity that is not lined with tissue and that does not originate from mesoderm


Bolus of particles rejected by bivalve labial palps, bound up in mucus, and expelled into the mantle cavity


Strip of stiff organic material holding chitinous teeth; used for feeding in molluscs


Chemosensory tentacles characteristic of Opisthobranchs


Repeating body unit in Annelids


Chitinous bristles found in Annelids


Specialization of mantle for directing incurrent and excurrent water flow through body cavity in bivalves


Crystal of CaCO3 or glass; forms skeleton in sponges


Choanocyte cavities in sponges


Organelle of maintenance of balance; found in Cnidaria, Ctenophores, molluscs


Spong body type with branched choanocyte lined channels


Developmental process in gastropods that results in anus of adult located near mouth


Oldest part of each valve in a bivalve shell

visceral mass

Tissue that contains gonad and digestive glands and structures in molluscs

Dioecious (gonochoristic)

Individual produces either eggs or sperm; includes members of phyla: nematodes, rotifers, annelids, molluscs, and tardigrades


Individual produces eggs and sperm (serial hermaphrodite produces eggs and sperm but not at the same time); includes members of phyla: sponges, cnidarian, ctenophores, flatworms, annelida


Ability to replace a body structure that has been lost

Trocophore larvae

Larval type characterized by an anterior tuft of cilia and a band of cilia; found in annelids and molluscs

Planula larvae

Larval stage in cnidaria

Veliger larvae

Larval stage in mollusca


Animals that lack body cavities (sponges, cnidarian, ctenophores)


Animals that have a body cavity that is not derived from mesoderm; the cavity usually contains proteins, fibers, non-cellular material, and organs; nematodes, nemerteans, and rotifers


Organisms that have a body cavity derived from mesoderm; include annelids and molluscs and other "higher" animals

Asexual reproduction

Ability to reproduce via mitotically derived cells; common in sponges, cnidarian, Platyhelminthes, nemerteans, and annelida,


Non-sexual reproduction in which females produce eggs that don't require fertilization and that produce only female offspring

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