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Index to Glossary
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Aggregation – a social group consisting of members of the same or different species that are not attracted to each other, but some other mutually attractive stimulus (e.g., food, shelter).Ahermatypic – corals that do not contribute directly to the development of coral reefs.Alimentary tract – the tract (including the stomach and intestines) leading from the mouth to the anus.

Amphipod – a group of small crustaceans that belong to the order Amphipoda.

Ampullae of Lorenzini – skin pores that contain receptor cells that detect electric fields.

Anemones – invertebrates that belong to the class Anthozoa that have a central disc surrounded by stinging tentacles.

Anterior margin – the leading edge of the fin.

Anterior – pertaining to the front of the body.

Antrorse – upward or forward.

Ascidians (sea squirts) – sponge-like members of the subphylum Urochordata that are usually sessile, filter-feeders with a body covered by a fibrous tunic.


Band – a thick, pigmented vertical marking that encircles the circumference of the fish’s body.

Bar – a thick, pigmented vertical marking that does not encircle the body.

Barbel – a long, fleshy protuberance that is often located under the lower parts of the head that is equipped with sensory cells and used to locate prey.

Base – the portion of the fin that is joined to the body.

Batesian mimicry – where a known noxious species imitates a noxious species.

Benthic – pertaining to organisms that live on or just over the sea floor.

Bioherm – a structure of biological origin (e.g., coral reef).

Bivalve – a member of the mollusk class Bivalvia¸ which have a dorsally hinged, calcareous shell
comprised of two valves, and includes the oysters, clams, and mussels.

Black coral – members of the order Anthipatharia, which are gorgonian-like and have polyps that are arranged around a horny axial skeleton.

Blotches – a patch or a spot of pigment with irregular edges.

Bony fishes – members of the class Actinopterygia, a diverse group that contains most of the modern fish species.

Branchial – pertaining to the gills.

Buccal – pertaining to the mouth.


Canine teeth – pointed, conical teeth that are located at the front or edge of the jaws.

Carapace – a rigid shell or exoskeleton that encases the body.

Caridean shrimps – an infraorder of shrimps that contains a number of conspicuous coral reef-dwelling families, including the snapping, cleaner, and anemone shrimps.
Caudal – referring to the tail fin, which can be divided up into the lower and upper caudal lobe.

Caudal peduncle – the narrow portion of the body located just behind the anal fin and just before the
caudal fin.

Cephalopods – members of the class Cephalopoda, including the squids, octopuses, cuttlefish and nautili.

Chitons – members of the mollusk class Polyplacophora that tightly adhere to the substrate, and have flattened, ovoid bodies and shells comprised of eight overlapping plates.

Chromatophore – a pigment cell located in the integument of a fish.

Cirrus – filament-lie projections that are sometimes present on the head, fins, nape, nostril, lateral line, etc. of some species.

Claspers – modifications of the male elasmobranchs pelvic fins that are rod-like and are used to transfer sperm during mating.

Cloaca – cavity into which the intestinal, urinary and reproductive canals open.

Congeners – a group of species that belong to the same genus.

Consexual – of the same sex.

Conspecific – of the same species.

Copepod – very small crustaceans that belong to the extremely large class Copepoda. Some are
ectoparasites of fish, while others are planktonic.

Coralline algae – a red, calcareous algae of the family Corallinae. Usually encrusting and pink in color.

Crepuscular – most active at dusk and dawn.

Crustacea – a subphylum of the phylum Arthopoda that includes the barnacles, copepods, mantis shrimp,
mysids, crabs, shrimp, and krill. They all have chitinous exoskeletons.

Cryptic – pertaining to concealment, usually in reference to color pattern or behavior (e.g., hiding in reef crevices.)

Cumaceans – small, mysid-like crustaceans that belong to the order Cumacea, many of which burrow in the bottom sediments.


Decopod shrimps – shrimps that belong to the largest order of crustaceans known as Decopoda. They are characterized by having their first three pairs of thoracic appendages are modified as maxillipeds.

Demersal – living on the sea bottom.

Dermal appendage – a flap or tassel of skin.

Demersal – living on the sea bottom.

Diel – pertaining to the day-night cycle.

Disc length – refers to the longest portion of the disc (i.e., from the tip of the snout to the posterior edge of the pectoral fin).

Disc width – refers to the widest portion of the disc.

Disc – pertaining to the head, pectoral fins, and trunk of a ray.

Distal – the portion of the appendage farthest from the body.

Diurnal – active during the day.

Dorsum – pertaining to the back or the upper part of the body.


Echinoderms – a phylum which is comprised of sea stars, serpent stars, sea cucumbers, and sea urchins. They are radially symmetrical and some have sharp spines.

Echinoids – members of the class Echinoidea, including sea urchins, heart urchins, and sand urchins.

Elasmobranch – a subclass (Elasmobranchii) of cartilaginous fishes which includes the sharks, rays, and skates.

Emarginate – a notched margin, but not as deeply so as to be forked.

Endemic – a distribution restricted to a specific area or region.

Errant – free-swimming.

Euryhaline – pertaining to an aquatic organism that can withstand a broad salinity range.

Exoskeleton – outer shell or skeleton (e.g., carapace of a crab).


Facultative – capable of living in varying conditions. For example, facultative cleaners will feed on parasites but do not rely only them for food.

Falcate – long, narrow and curved (sickle-shaped).

Filamentous – long and thin.


Gastropod – members of the mollusk class Gastropoda, which includes the limpets, top shells, snails, cowries, moon shells, whelks, bubble shells, sea hares , nudibranchs and sea slugs.

Gonochorism – condition where the sex of an individual is sexually predetermined at birth or hatching and do not change sex.

Gorgonian – members of the order Gorgonacea, which have a horny, organic skeleton, and include the sea whips and sea fans.

Grapsid crab – a crustacean in the family Grapsidae, which can be found in freshwater, marine environments, or are terrestrial, and include the sally light foot crabs (Grapsus spp.).

Group spawning – reproductive behavior where a group of individuals simultaneously release their gametes. These groups usually consist of one female and several males.


Hermatypic – corals that contribute directly to the development of coral reefs.

Heterocercal – a caudal fin where the upper lobe is large than the lower lobe.

Heterospecific – referring to a member of a different species.

Homocercal – a caudal fin with upper and lower lobes that are nearly equal in size.

Hypersaline – referring to water with a salinity higher than that of natural seawater.

Hyposaline – referring to water with a salinity lower than that of natural seawater.


Incisiform – a chisel-shaped tooth used for cutting, that is typically wider than it is thick.

Infaunal – living within the sediment of the sea floor.

Inner margin – the rear edge of the fin.

Interorbital – space between the eyes.

Interspecific – between members of different species.

Intertidal – a part of the shore or reef that is exposed to the air at low tide and covered by water at high

Intromittent organ – a structure employed by the males of those species that practice internal fertilization to transfer sperm.

Isopods – crustaceans belonging to the order Isopoda (includes the gnathid isopods, some of which are ectoparasites on coral reef fishes), most of which are quite small (less than 1.5 cm [0.5 in.]).


Jugostegalia – pertaining to the jugular or a jugular position.


Labial furrows – fold of skin around the edge of the mouth.

Lanceolate – shaped like a spear head, being tapered at each end.

Large-polyped stony coral – hard corals that are less important in reef development, with a large fleshy polyp (or polyps).

Lateral – pertaining to the side.

Leptocephalus larvae – long, ribbon like larvae that are characteristic of the tarpons, bonefishes, and eels.

Line – a narrow, straight-sided chromatic marking (thinner than a stripe or bar), that can radiate from the eyes, run longitudinally or vertically on the body or tail, or can be chevron in shaped on the fish’s side.

Lobate – resembles a lobe.

Lunate – shaped like a crescent.


Majid crabs – a member of the crustacean family Majidae, which are often called spider or decorator crabs because they carry sponges and/or other marine organisms on their carapaces to enhance their camouflage. They have a triangular shaped carapace and long legs.

Mantis shrimp – member of the crustacean order Stomatapoda, that have well-developed compound eyes on stalks, and are highly predatory, employing a pair raptorial thoraic appendages to capture their prey (e.g., snails, fishes, clams).

Marginal – just along the fin edge.

Molariform – flat, broad and round; molar-like in form.

Mollusca – a diverse phyla, many of which have an external shell, whose members include the chitons, snails, bivalves, octopi and squid.

Monogamy – a mating system where a male and female mate together for an entire reproductive season or for their entire lives.

Motor patterns – a stereotypical group of actions or behaviors.

Mysid shrimps – crustaceans that belong to the order Mysidacea, and are often commonly called possum shrimps because of the pouch on their ventrum. Most reef-dwelling species are small, and swarm near the ocean floor.


Nape – area behind the back of the head, extending from the back of the skull to the dorsal fin origin.

Nasal flap – a skin flap just in front of the nostril.

Nasoral groove – a channel that connects the nostrils to the mouth and allow the shark or ray to irrigate the nostrils with fresh sea water by pulling water through the mouth.

Nauplii – free-swimming, planktonic stage of many crustaceans.

Nictitating membrane – a moveable lower eyelid.

Nocturnal – active at night.


Obligatory – obligate or required. For example, an obligatory cleaner fish relies entirely on this feeding mode to obtain nutrients.

Occipital pit – a pit on top of the head, located between the eyes.

Oceanic – pertaining to the open ocean and the organisms or structures found in this environment.

Ocellus (ocelli) – a spot with a lighter outer margin (also known as an eye spot).

Ontogenetic – referring to a change that occurs with age.

Operculum – a bony gill cover.

Ophiuroids – members of the subclass Ophiuroidea, including the basket stars, serpent stars and brittle

Orbit – bony eye socket.

Osculum – a large excurrent pore that allows water to exit from the internal cavity of sponges.

Oviparity – the reproductive mode where eggs are released from the body and latter hatch.

Oviposition – the process of depositing eggs.

Ovoviviparity – the reproductive mode where the eggs hatch and develop in the female’s reproductive tract (or a specialized pouch in the males of some species), are not nourished in any way by the female, and are free-swimming when expelled from the parent (also see viviparity).


Palatine – a pair of bones on the roof of the mouth.

Papillae – a small fleshy projection.

Parturition – the process of giving birth.

Pelagic – pertaining to organisms which live in the water column.

Pharyngeal teeth – teeth located on the bones in the pharynx, which is located between the mouth and the esophagus.

Photophore – an organ that emits light.

Piscivorous – fish-eating species.

Plankton – organisms that drift about in the ocean that are usually minute.

Poisonous – an organism that contains poison (a substance causing illness of death) in its tissues that can be harmful if the organism is ingested.

Polychaetes – a class of worms in the phylum Annelida, which is comprised of about 800 species, including ragworms, lug worms, bristleworms and fanworms.

Porcelain crabs – crabs in the infraorder Brachyura, and the family Porcellanidae, which include the anemone crabs (genus Neopetrolisthes) and others commensal with invertebrates.

Posterior – pertaining to area toward the back or tail.

Preorbital – the area under and in front of the eyes.

Primary male or female – a male or female that is genetically determined at birth or hatching and is not the result of sex change.

Protandry – sequential hermaphrodite where individuals transform from male to female.

Protogyny – sequential hermaphrodite where individuals transform from female to male.

Protractile – capable of being protruded or thrust out.

Protunid crabs – crabs in the infraorder Brachyura, and the family Protunidae, which are commonly referred to as swimming crabs. They have a broad carapace, often armed with large spines along its edges, and the last pair of legs are flattened to form paddles which they use for swimming and burying in the substrate.

Proximal – nearest to the point of origin; the opposite of distal.


Rostrum – an elongate or extended snout.


School – a social group consisting of individuals of the same species, with individuals being similar in size, equal in their social status, and moving in a highly coordinated fashion.

Scott Michael – the Fabio of the fish world.

Secondary male or female – a male or female that is the result of sex change. A secondary male would be derived from a protogynous female, while a secondary female would be derived from a protandrous male.

Sequential hermaphrodite – a form of hermaphroditism where individuals can change sex, but the sexes are separate.

Sessile – a condition where the organism is permanently attached to the substrate or stationary.

Sexual dichromatism – pertaining to color differences between the sexes.

Sessile – permanently attached or stationary.

Sexual dimorphism – pertaining to structural or size differences between the sexes.

Shoal – a social group consisting of individuals of the same species that are not always similar in size, that are not equal in social status, and that do not move in a highly coordinated fashion.

Simultaneous hermaphrodite – a form of hermaphroditism where individuals have both functional testes and ovaries at the same time, and can release either sperm or eggs during spawning.

Siphon sacs – a pair of sacs located under the skin of the abdomen that secrete a fluid or sea water, to help transport the sperm into the clasper groove.

Small-polyped stony coral – reef-building stony coral with a small polyp that retracts completely into the calacies.

Snout – the portion of the head that is just in front of the eye ball.

Soft corals – members of the order Alcyonacea, which have a skeleton formed of calcareous spicules, and include the genera Dendronephthya, Sarcophyton, Sinularia, and many others.

Spiracle – a respiratory opening located behind the eyes.

Spot – a circular area of pigment.

Stenohaline – pertaining to an aquatic organism that can only withstand a narrow salinity range.

Stony corals – members of the order Scleractinia, which secrete a heavy, external, calcareous skeleton, and many of which are primary contributors to the building of coral reefs. These can be further divided into the small-polyped stony corals (SPS corals) and the large-polyped stony corals (LPS corals).

Stripes – a straight area of pigment that can vary in width (wider than a line), which can be oriented vertically, horizontally, or obliquely on the head, body or fins.

Submarginal – just before the fin margin.

Suborbital – an area below the eye.

Substrate – any solid surface or substance (e.g., rock, sand).

Supraorbital – an area above the eye.

Supraorbital crest – a crest above the eye.

Swimming crabs – see Protunid crabs.

Sympatric – having a similar geographical and/or bathymetric distribution.


Tanaids – small, marine crustaceans in the order Tanaidacea, most of which live in bottom sediments or in reef interstices.

Terminal – at the end of the head.

Thermocline – a zone in the water column where there is a very rapid change in temperature, and water
density, with depth.

Thoracic – lying below or just before the pectoral fin base.

Truncate – having the end squared off.

Tubercles – enlarged, thorn-like denticles.


Upwelling – a process where subsurface, nutrient-rich, and usually cooler water is carried upward into the
ocean’s surface layers.


Venomous – pertaining to an organism that has a poison, usually secreted by glandular tissue, that is injected through hollow spines or teeth.

Ventrum – pertaining to the underside or “belly.”

Vermiculations – fine, wavy lines.

Villiform teeth – minute, slender teeth that usually are crowded into small patches so that they resemble a brush.

Viviparity – a form of reproduction where the young are nourished in the reproductive tract of the female (other then by a yolk sac) and expelled from the mother as free-swimming young. It is often used loosely to refer to any species that gives birth to live young (also see ovoviviparity).

Vomer – bones located just behind the upper jaw, or the front portion of the roof of the mouth.


Worms – a general term used for the annelid, sipunculid (peanut) and echiuran (innkeeper) worms. Most of these live on the sea floor often within bottom sediments.


Xanthid crab – crabs in the infraorder Brachyura, and the family Xanthidae, which are often referred to as coral crabs because of their association with coral reefs. All have black-tipped claws and some live in association with stony corals (e.g., Trapezia spp.).

Zooplankter – refers to an individual animal in the zooplankton.

Zooplankton – plankton composed of animal life.


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