Terminology Description
Terminology Description
Abdomen A body region of an animal that corresponds to the belly. In arthropods this region is usually muscular and may contain gills.
aboral surface The surface opposite the mouth of, for example, a sea star.
adductor muscle A large muscle that closes a bivalve’s shell.
ambulacral groove A groove through which the tube feet of an echinoderm extend.
amphipod A type of crustacean with a body similar to a shrimp belonging to the order Amphipoda.
ampulla An expanded area of a tubular structure; in echinoderms, a saclike structure attached to the tube foot.
annelid A segmented worm belonging to the phylum Annelida.
aperture An opening, such as the opening into a gastropod’s shell.
Aristotle’s lantern A chewing structure composed of five teeth found in the mouths of sea urchins.
arrowworm A planktonic animal belonging to the phylum Chaetognatha.
arthropod An animal belonging to the phylum Arthropoda. Arthropods are characterized by jointed appendages and a hard exterior covering (exoskeleton).
autotomize To purposely cast off a body part.
barnacle A sessile crustacean whose body is usually covered by plates composed of calcium carbonate.
beardworm An animal belonging to the annelid class Pogonophora.
bivalve A type of mollusc whose body is covered by a two-pieced, hinged shell.
bulb gland A gland found in molluscs of the family Conidae which produces the toxin that coats their radulae.
byssal threads Strong protein fibers secreted by mussels that fasten the animal to a rock or another solid surface.
byssus A tough protein secreted by a gland in the foot of some bivalves that commonly takes the form of threads. It is used to attach the bivalve to a solid surface such as rock or coral.
carapace The hard dorsal covering of the bodies of animals such as arthropods and turtles.
carnivore An animal that feeds on other animals.
casting A pile of organic material and minerals defecated by deposit feeders. Also known asfecal cast.
cephalochordate An animal belonging to the subphylum Cephalochordata. Also known as alancelet.
cephalopod An animal belonging to the molluscan class Cephalopoda, which includes squids, octopods, cuttlefish, and nautiloids.
cephalothorax The combination of two body regions: the head and the thorax.
cerata Projections on the body of a nudibranch that function in gas exchange.
chelicera An appendage in chelicerates that is modified for feeding and takes the place of mouthparts.
chelicerate An animal belonging to the arthropod subphylum Chelicerata; they have a pair of oral appendages calledcheliceraethat are used in feeding.
chelipeds Legs bearing clawlike structures (chela) in arthropods.
chitin A polysaccharide found in the cell walls of fungi and in the exoskeletons of many arthropods.
chiton A mollusc belonging to the class Polyplacophora. Chitons are characterized by a shell composed of eight separate plates bound together by a leathery girdle.
chordate An animal belonging to the phylum Chordata characterized by having a notochord, pharyngeal gill slits, postanal tail, and dorsal, hollow nerve tube sometime in its life cycle.
chromatophore A special cell in an animal’s skin that contains pigment molecules.
cirri Grasping structures found on some species of sea lily.
cirriped Feathery appendage used by barnacles to filter food from the surrounding water.
coleoid A cephalopod belonging to the subclass Coleoidea that does not have an external shell.
conchiolin The protein that makes up the periostracum of a molluscan shell.
copepod A crustacean belonging to the class Copepoda, usually the most abundant member of the marine zooplankton.
copulatorypleopod Specialized appendage on the abdomens of male decapods used for transferring sperm to females.
crinoid An animal belonging to the echinoderm class Crinoidea. These generally sessile animals have bodies that resemble flowers and are commonly referred to as sea lilies.
crop A digestive organ found in some animals that stores food before it is processed.
crustacean An animal belonging to the arthropod class Crustacea, which includes crabs, lobsters, shrimp, and barnacles.
Cuvierian tubule Small, sticky tube expelled from the anus of some sea cucumbers to distract predators.
cyprid larva A planktonic larval stage of barnacles that develops from a nauplius larva and has compound eyes and a carapace composed of two shell plates.
decapod An animal with five pairs of walking legs that belongs to the arthropod order Decapoda, which includes crabs, lobsters, and shrimp.
deposit feeder An animal that feeds on bottom sediments.
echinoderm An animal belonging to the phylum Echinodermata, which includes sea stars, brittle stars, sea urchins, sea cucumbers, and crinoids.
echinoid An echinoderm belonging to the class Echinoidea, which includes sea urchins, heart urchins, sand dollars, and sea biscuits.
echiuran An animal that belongs to the class Echiura in the phylum Annelida. Also known as aspoonworm.
ectoparasite A parasite that attaches to the outer covering of its host.
endoskeleton An internal skeleton.
epitoke The pelagic, reproductive individual formed by some errant polychaetes.
epitoky A type of reproduction that occurs in some polychaetes that involves the production of a reproductive individual (epitoke) adapted for a pelagic existence from a nonreproductive individual adapted for a benthic existence.
errant polychaete An actively mobile polychaete that has a mouth equipped with jaws or teeth.
eviscerate The release of internal organs from the mouth or anus. This behavior is used by sea cucumbers to deter predation.
exhalant opening The opening of a bivalve’s or tunicate’s siphon, through which water is expelled from the body.
exoskeleton A hard, protective exterior skeleton such as that found in arthropods.
fecal cast A pile of organic material and minerals defecated by deposit feeders. Also known ascasting.
fertilizin A chemical released by some female epitokes that stimulates males to shed their sperm.
filter-feeder An organism that filters its food from the water.
gastrodermis The cellular lining of the gastrovascular cavity of cnidarians and ctenophores.
gastropod A member of the molluscan class Gastropoda, which includes snails, limpets, abalones, and nudibranchs.
gastrovascular cavity A central cavity in the body of cnidarians and flatworms that functions in digestion and in the movement of materials within the animal.
gnathopods Specialized appendages found on amphipods that are used for collecting food.
grasping spine A structure on the head of an arrowworm used to capture prey.
head-foot The region of the gastropod body that contains the head, with its mouth and sensory organs, and the foot, which is the animal’s organ of locomotion.
hemichordate An animal in the phylum Hemichordata. Also known as anacorn worm.
herbivore An animal that eats only plants and algae.
holothurin A poison from the flesh of sea cucumbers that protects the animal from predation by fishes and that is used by Pacific islanders to poison fishes.
hydroid A colonial organism belonging to the cnidarian class Hydrozoa. Also known as ahydrozoan.
hydrostatic skeleton A body support that results from fluids under pressure in an animal’s body cavity.
inhalant opening The opening of a bivalve’s or tunicate’s siphon through which water is drawn into the body.
irregular echinoid An echinoid such as a heart urchin or sand dollar that is adapted to a burrowing lifestyle.
krill Pelagic, shrimplike creatures that belong to the arthropod order Euphausiacea.
lancelet An animal belonging to the subphylum Cephalochordata. Also known as acephalochordate.
larvacean A free-swimming tunicate that resembles a tadpole.
madreporite The structure at which water enters the water vascular system of an echinoderm.
mandible One component of the third pair of chewing or grinding appendages of crustaceans.
mandibulate A member of the arthropod subphylum Mandibulata, which includes the crustaceans.
mantle (mollusc) The part of a mollusc’s body that secretes its shell.
mantle cavity The space between a mollusc’s mantle and its body
melanin A brown or brown-black pigment found in many animals.
mollusc A soft-bodied animal that is a member of the phylum Mollusca. The bodies of most molluscs are covered by a shell.
molting In arthropods, the process by which an old exoskeleton is shed and a new one is formed.
mother-of-pearl layer Another term for the nacreous layer of pearl oysters.
nacreous layer The innermost layer of a molluscan shell. In oysters, it also is known as themother-of-pearl layer.
nauplius larva A larval stage in the life cycle of many crustaceans Nauplius larvae are characterized by three pairs of appendages and a median eye.
nautiloid A cephalopod that has an external shell belonging to the subclass Nautiloidea.
nematode A round, wormlike animal that belongs to the phylum Nematoda.
nonselective deposit feeder An animal that ingests both organic and mineral particles and then digests the organic material, especially the bacteria that grow on the surface of the mineral particles.
notochord A flexible supporting structure that runs the length of the body between the gut and the nerve cord. It is present in all chordates at some stage in their development.
nudibranch A gastropod mollusc that does not have a shell and has many projections from its body calledcerata.
operculum A hard or tough covering found in some molluscan gastropods that closes the opening to the shell when the animal retracts inside. In fishes, the protective covering of the animal’s gills.
ophiuroid Echinoderm commonly referred to as brittle star or serpent star, belonging to the class Ophiuroidea.
oral tentacles Modified tube feet that are located around the mouth of a sea cucumber and used in acquiring food.
ossicles Plates of calcium carbonate that make up the endoskeleton of echinoderms.
oviduct A tube that carries eggs to the outside of a female’s body.
palp (bivalve) A pair of structures located near the mouth that forms filtered food into a mass and then moves it to the bivalve’s mouth.
palp (sea spider) A pair of sensory structures.
pedicellariae Tiny pincerlike structures, found in some echinoderms, that keep the surface of the body clean and free of parasites and the settling larvae of fouling species. In some echinoderm species, they may also aid in obtaining food.
pen An internal strip of hard protein that helps support the mantle of a squid.
periostracum The outermost layer of a molluscan shell. The periostracum is composed of the proteinconchiolin.
pharyngeal gill slits Perforated, slitlike openings that lead from the pharyngeal cavity to the outside. They are present in all chordates at some stage in their development.
pheromone A hormone released into the environment by one individual that controls the behavior or development of other individuals of the same species.
photophore A specialized organ in some organisms that produces bioluminescence.
podia The tube feet of sea stars.
pogonophoran An animal that belongs to the class Pogonophora of the phylum Annelida. Also known asbeardworms.
polychaete A type of annelid worm belonging to the class Polychaeta.
postanal tail A tail that extends beyond an animal’s digestive tract. It is present in all chordates at some stage in their development.
priapulid A benthic worm belonging to the phylum Priapulida.
prismatic layer The middle layer of a molluscan shell and the layer that contains most of the mass of the shell.
radula A ribbon of tissue that contains teeth. This structure is unique to molluscs.
regular echinoid An echinoid with a spherical body. Also known as asea urchin.
respiratory tree A system of tubules found in most sea cucumbers that functions in gas exchange.
roe An ovary with eggs.
salp A free-swimming tunicate belonging to the class Thaliacea.
scaphopod A mollusc belonging to the class Scaphopoda. Scaphopods are also known astusk shellsbecause their shells are shaped like the tusks of elephants.
sedentary polychaete A sessile polychaete that usually forms some sort of tube to cover its body.
selective deposit feeder An animal that separates organic material from minerals in sediments and ingests only the organic material.
sepia A dark fluid produced in the ink glands of cephalopods.
septa A divider or partition.
setae Bristles on the bodies of annelid worms.
shipworm A bivalve mollusc with a wormlike body belonging to the genusTeredoorBankiathat can burrow into wood.
siphon Tubular structure in some invertebrates that directs the flow of water in and out of the animal’s body.
siphuncle A cord of tissue that runs through the chambers of a nautilus shell and functions in the removal of seawater from the chambers and in the regulation of the gas content of the chambers.
sipunculid Solitary worms belonging to the phylum Sipuncula.
spermatophore A package of sperm.
spoonworm An animal that belongs to the class Echiura in the phylum Annelida. Also known as anechiuran.
swarm A large mass of krill.
swarming A behavior exhibited by some errant polychaetes in which the males and females congregate at the surface of the water to reproduce.
swimmeret An appendage modified for swimming in some crustaceans.
telson A long spike attached to the posterior end of a horseshoe crab’s abdomen; used for steering and defense.
trochophore larva A free-swimming ciliated larva in the life cycles of many marine molluscs as well as some other marine organisms.
tube feet Tubular structures in echinoderms that function in locomotion and feeding.
tunic The body covering of animals known as tunicates, phylum Urochordata, which is composed of a molecule similar to cellulose.
tunicate Animals belonging to the subphylum Urochordata. Tunicates are named for their body covering: a tunic composed of a substance similar to cellulose.
umbo The area around the hinge of a bivalve’s shell. This area represents the oldest part of the shell.
univalve A shell composed of one piece.
veliger larva A free-swimming larval stage that develops from the trochophore larva of some molluscs.
visceral mass The dorsal region of the gastropod body that contains the circulatory, digestive, respiratory, excretory, and reproductive systems.
water vascular system A hydraulic system unique to echinoderms that functions in locomotion, feeding, gas exchange, and excretion.
whorls The turns of a gastropod’s spiral shell.
zoea larva The planktonic larval stage of decapod crustaceans.