Invertebrates

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Some terms or names of body parts for your reference



Abapical 

Located at the opposite end of a shell from the apex. 


Abatement 

Reducing the degree or intensity of, or eliminating 


Abductor muscle scar 

The area or depression on the inside of a bivalve shell where the foot muscle was attached. 


Acrosphere 

The knobbed tentacle tip of an anthozoan, usually bearing numerous nematocysts 


Aeolid 

A member of the suborder aeolidacea, nudibranches having cerata containing branches of the digestive gland 


Aeolidiform 

Resembling an aeolid in body plan. 


Air bladder 

A gas filled sac used for floatation in the portuguese man o war and some gastropods. also called a pneumatophore. 


Alcyonarian 

A soft coral of the order alcyonacea, class anthozoa 


Algae 

Unicellular, multicellular, solitary, or colonial organisms that contain chlorophyll. they lack roots, stems, leaves, flowers, and seeds. algae are in the kingdom protista 


Algal bloom 

A sudden spurt of algal growth that can indicate potentially hazardous changes in local water chemistry 


Algal reef 

A reef, usually exposed to wave action, composed of coralline algae and vermatid gastropods. the coralline algae occur in forms of cups or funnels 


Allopatric species 

Species that do not have overlapping ranges 


Anastomatising 

Branches have re-fused during growth 


Annulate rhinophores 

Rhinophores with well defined circular ridges or collars 


Anterior 

Toward the front of the animal; opposite of posterior. 


Aperture 

The main opening in a gastropod shell where the foot and head extrude. 


Apex 

The part of gastropod shell that was formed first, typically pointed, at the posterior end of the shell. 


Apical 

Toward the tip of a shell or other structure 


Apical orifice 

An opening at the apex of a structure 


Aposematic 

Coloration that stands out in contrast to its background, presumably acts as a warning to predators 


Arborescent 

Tree -like in form 


Arcuate 

Arc -like in shape 


Arms (of a cephalopod) 

Shorter, thicker (as opposed to tentacles), fleshy extensions hanging beneath the head of the cephalopod. usually has suckers most of its length. 


Atoll 

A ring-shaped coral reef including a coral rim that encircles a lagoon partially or completely, usually atop a volcano. 


Autotomize 

To drop body parts when disturbed, presumably as a distraction to predators 


Axial 

Being located at the tip of a branch 


Axial (gastropods) 

Running longitudinally across the whorls in gastropods. 


Axial corallite 

An individual corallite located at the tip of a branch 


Azooxanthellate 

Lacking the symbiotic algae, zooxanthellae 


Basal disk 

The base of a sea anemone that attaches to the substrate. 


Batesian mimicry 

When a palatable species closely resembles an unpalatable species 


Beak 

In bivalves, the pointed or rounded end of the shell in the hinge area. also called apex or umbo. in cephalopods, the pair of curved sharp teeth at the opening of the mouth. 


Bell 

The gelatinous, radially symmetrical covering of a jellyfish. the mouth is on the underside of the bell. 


Benthic 

Refers to organisms that live on or in the ocean bed. benthic epifauna are organisms that live on the ocean floor or upon bottom objects sch as sea anemones and barnacles, whereas benthic infauna are organisms that live within the surface sediments such as clams and worms. 


Bifid rhinophores 

Rhinophores that divide into two branches 


Bifurcate 

Splitting into two branches or tips. 


Bilabiate 

Having two lips or edges 


Bipinnate 

Having two series of branches 


Bivalve 

A mollusk that is surrounded by 2 hinged shells. includes clams, oysters, and mussels. 


Body whorl 

The lowest and largest whorl of a gastropod shell 


Branchial lamellae 

Folds of the gills in nudibranches. 


Calice 

The upper surface, or the opening of a corralite bounded by the wall 


Calumella (plural calumellae) 

Skeletal structures at the axis of corallites 


Calyx (pl. calyces) 

The depression or extension in a coral skeleton that houses the polyp. 


Caruncle 

The elevated crest between the rhinophores in some arminids 


Caryophyllidia 

Tubercles surrounded by spicules that are found on the dorsal surfaces of some dorids 


Cephalopod 

A marine mollusk having bilateral symmetry, a well developed head and eyes, having arms and tentacles. includes octopuses, squids, cuttlefishes and the nautilus. 


Ceras (pl cerata) 

Dorsal and lateral outgrowths on the upper surfaces of the body of nudibranches. 


Ceras (plural cerata) 

An elongate projection from the dorsal surfaces of aeolids, dendronotids, arminaceans and sacoglossans, sometimes applied only to those of aeolids 


Ceratal group 

A cluster of cerata 


Ceratal insertion 

The point at which cerata attach to the animal 


Ceroid 

Polyps that share common walls 


Chloroplasts 

Photosynthetic organelles in the cells of alga and other plants that contain the pigment chlorophyll 


Choanocyte 

Choanocytes (also known as "collar cells") are cells that line the interior of asconoid, syconoid and leuconoid body type sponges.


Cilia 

Minute hair-like structures that can move rhythmically and are used for locomotion or moving fluids and particles along a structure. 


Circumtropical 

Having a global distribution in tropical waters 


Clavus 

The club-shaped tip of a rhinophore 


Cnidosac 

A sack in the tip of a ceras that contains nematocysts extracted by aeolids from their food 


Cochleariform 

A short, stout, erect cylindrical calicle, with a broad apex and the upper side partly wanting 


Coenenchyme 

The common tissue that connects colonial polyps. 


Coenosteum 

Skeletal material between the walls of the corallites of a coral. 


Collines 

Skeletal ridges composed of coenosteum which separate corallites 


Columella 

The inner margin of the aperture in a gastropod shell 


Columella - coral 

The central part of the calyx of a coral skeleton where the lower elements of the septa fuse. 


Columella - mollusk 

The central pillar of a gastropod shell around which the whorls form. it is partially or totally hidden inside the shell. 


Columellae 

Skeletal structures at the center of corallites 


Columellar 

Relating to the columella 


Commensal 

An animal that lives in close association with another species without harming its host 


Concave 

Curving inward. 


Convex 

Curving outward. 


Coral bleaching 

When the relationship between the coral host and zooxanthallae, which give coral much of their colour, breaks down. causes include:

- stress caused by a sustained increase water temperature (even as low as 1 degree) for a period of 4 weeks or more. (most common)

- fresh water inundation (low salinity)

- poor water quality from sediment or pollution


Corallite 

The skeleton of an individual polyp 


Corallum (pl. coralla) 

The entire coral skeleton. 


Corralum (plural corolla) 

The skeleton of a colony 


Corralum (plural: corolla) 

The skeleton of a colony 


Cosmopolitan 

Having a global distribution in tropical and temperate waters 


Costa (pl. costae) - coral 

Radial skeletal elements outside the corallite wall 


Costa (pl. costae) - mollusk 

Tubular or circular ridge on the surface of a shell. 


Costa (plural: costae) 

Radial skeletal elements outside the corallite wall 


Costae (singular costa) 

Radial skeletal elements outside the corallite wall 


Costae (singular: costa) 

Radial skeletal elements outside the corallite wall 


Crenate 

Having a round-tooth or scalloped edge. 


Crenulate 

Having margins that are scalloped, indented, wrinkled or notched. 


Crustacean 

Crustaceans form a very large group of arthropods, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. 


Cryptic 

A species that is difficult to see against it's usual background 


Cryptobranch 

Dorids that can fully withdraw their gills (or that have evolved from such species) 


Cyanobacteria 

Photosynthetic bacteria, also known as blue-green algae 


Dextral 

Right -handed. in gastropods, when the whorls wind clockwise. 


Digestive gland 

The primary organ responsible for digestion in opisthobranchs, often highly elaborate 


Digitiform 

Resembling fingers 


Dimidiate 

A tublular calicle bisected vertically nearly to its base 


Distal 

The portion of a structure furthest from the center of the body 


Dorid 

A member of the suborder doridacea 


Doridiform 

Resembling a dorid in body plan 


Dorsal 

Referring to the upper surface of an animal; opposite of ventral. 


Dorsum 

The upper surface of an animal 


Endemic 

A species found only in the region under discussion 


Endostyle 

An endostyle is a longitudinal groove on the ventral wall which produces mucus to gather food particles. 


Endosymbiont 

An endosymbiont is any organism that lives within the body or cells of another organism. 


Excretory 

The excretory system is a passive biological system that removes excess and unnecessary materials. 


Exsert 

Projecting above the surrounding structure 


Extra-branchial appendage 

A projection from the body located near the branchia in some dorids 


Extra-rhinophoral appendage 

A projection from the body located near the rhinophores in some dorids 


Extra-tentacular budding 

Polyp duplication where daughter polyps form on the side of a parent polyp. 


Flabello-meandroid 

Valleys elongate with separate walls 


Foot 

The muscular part of a mollusk's body used for crawling. 


Foot corners 

The anterior corners of the foot 


Frontal veil 

The expanded anterior portion of the head in many dendronotids 


Gastropod 

A mollusk typically having a single, coiled shell (cap-shaped in limpets, absent in nudibranches), a flattened muscular foot used for locomotion, and eyes and tentacles on a distinct head. includes snails, whelks, limpets and slugs. 


Gillnet 

A net set upright in the water to catch fish by entangling their gills in its mesh. 


Gladius 

The internal pen (hard structure) of a squid. 


Hemispherical 

Shaped with an appearance similar to a dome 


Hermaphrodite 

Being both male and female 


Hermatypic 

With symbiotic algae present in the polyp tissue 


Holoplanktonic 

Organisms that spend there entire life cycle in the plankton 


Intra-tentacular budding 

Polyp duplication where the polyp divides into two or more polyps 


Labellate 

Long -lipped, or in shape nearly like the blade of a shovel, the upper side of the calicle being entirely wanting, and the lower thin and nearly flat. 


Lamella (pl. lamellae) 

A thin plate or fold of hard or soft tissue. 


Lamella (plural lamellae) 

A leaf-like fold 


Lamellate rhinophores 

Rhinophores having leaf-like folds 


Mantle 

Need definition 


Massive 

A colony shape where all dimensions are approximately the same. 


Meandroid 

Polyps that form valleys 


Median 

Pertaining to the center 


Mesohyl 

The mesohyl is the gelatinous matrix within a sponge. 


Mimicry 

When one species resembles another, presumably gaining some selective advantage 


Monotypic 

A taxon that contains only one species 


Mullerian mimicry 

When two unpalatable species resemble each other 


Nariform 

A compressed calicle, resembling in shape to an inverted nose 


Nematocyst 

A stinging cell produced by cnidarians (jellyfish, sea anemones, fire coral, etc) 


Nomenclatural 

Having to do with names 


Notum 

The upper surface of an animal 


Oblique 

Angled, either upward or downward, usually refers to mouths, stripes or lines. 


Octocoral 

A member of the cnidarian subclass octocorallia, one of the groups known as "soft corals"


Oral arms 

Soft, sometimes convoluted, structures that hang beneath the bell of a jellyfish that are used to pass food to the mouth. 


Oral cavity 

Mouth . 


Oral disk 

The membranous disk that contains the mouth in sea anemones. 


Oral hood 

The expanded "net" used by the genus melibe to catch food


Oral veil 

The expanded front of the head in many dendronotids 


Osculum 

The osculum is an excretory structure in the living sponge, a large opening to the outside through which the current of water exits after passing through the spongocoel. 


Outer slope 

A slope that is steeper anc can be exposed to strong hydrodynamic forces. 


Paliform lobe 

Upright skeletal rods or plates at the inner margin of septa formed by upward growth of septum 


Palmate cerata 

Cerata resembling an open hand 


Papilla (plural papillae) 

A small, finger-like projection or bump 


Papillae 

Finger -like projections of reticulum with a diameter less than or equal to the corallites. papillae may encircle the corallites or may be scattered independently of the corallites. 


Papillate rhinophores 

Rhinophores having papillae 


Pedalia (sing. pedalium) 

Gelatinous, muscular extensions of the bell of some jellyfish. 


Pelagic 

Refers to the plants and animals that live in the water column or in the open waters of the ocean rather than the ocean floor (see benthic). 


Petaloid 

Septa with a flower-like appearance 


Phaceloid 

Polyps that are extremely prominent 


Phanerobranch 

Dorids that cannot fully retract their gills 


Photosynthesis 

Photosynthesis is a process used by plants and other organisms to convert light energy, normally from the sun. 


Pinacocyte 

Pinacocytes are flat cells found on the outermost layer of a sponge (phylum porifera). 


Plankton 

Pelagic organisms that float through the water column, not attached to any substrate and unable to move against the currents and tides. plankton can be further divided into phytoplankton and zooplankton, meroplankton and holoplankton. 


Planktonic 

Drifting passively in the open ocean 


Plastids 

Pigment containing organelles in the cells of algae and other plants 


Pleurobranch 

A member of the order pleurobranchomorpha (formerly included tylodinoidea) 


Plocoid 

Polyps that have separate walls 


Polyp 

An individual organism, usually cylindrical in shape with an oral end surrounded by tentacles and a base for attachment. when in colonies, each polyp usually serves only one function, such as digestion or reproduction. 


Posterior 

Pertaining to the rear of the body; opposite of anterior. 


Proximal 

Nearest the center of the body or point of attachment to body. 


Punctate 

Covered with small pits or depressions 


Rachis 

The stem or main shaft of a structure. 


Radial 

Being located around the perimeter of a branch along its length extending out from a common point 


Reef pediment 

A gentle slop in front of the reef, descending to depths of 30 to 50 m. 


Reticulum 

The coenosteum and associated structures of montipora. essentially represents the structure of the colony surface. 


Rhinophore shaft 

The stalk or "trunk" of a rhinophore


Rhinophore sheath 

The collar or cup surrounding the base of a rhinophore 


Rhinophores 

A pair of tentacles, on the head of nudibranches, which contain scent or taste receptors. 


Rolled rhinophores 

Flattened rhinophores that have inrolled margins forming a tube 


Rosette 

A circular cluster of branches or projections 


Sail 

A stiff, upright structure on some hydroids that is used to catch the wind to enable movement. 


Scleractinian 

A member of the cnidarian order scleractinia, most species referred to as "hard corals"


Sclerite 

A skeletal element in soft corals, composed of calcium spicules. 


Sea hare 

A member of the order notaspidea 


Sea slug 

A member of the subclass opisthobranchia, particularly those that lack shells 


Septa 

Radial elements of corallites situated inside the corallite wall 


Septo-costae 

Radial elements of corallites that are continuous between corallites 


Septum (pl. septa) - coral 

Skeletal radiating plates inside the calyx of a coral. 


Septum (plural septa) 

Skeletal elements projecting inwards from the corallite wall 


Side-gilled slug 

A member of the order pleurobranchomorpha (formerly included tylodinoidea) 


Simple rhinophores 

Rhinophores that lack any obvious ridges, lamellae or other "decorations"


Siphon 

A tubular structure for bringing in or expelling fluids. 


Siphonal canal 

A channeled extension from which the siphon extends. 


Siphonal notch 

A notch at the base of the siphonal canal in gastropods. 


Spicule 

A a tiny, reinforcing structure formed by sponges and some opisthobranchs (among others)

- minute hard pointed projections.


Spire 

The coiling whorls above the aperture of a gastropod. 


Stolon 

In bryozoans, branch-like extensions (not considered "true" branches as in plants).


Stria (plural striae) 

A fine line or ridge 


Stromboid notch 

A notch or indentation in the lower outer lip of conch gastropods, used to extend 1 of its stalked eyes out of the shell. 


Subapical 

Immediately below the apex of a structure 


Submarginal 

Located bellow the edge or margin of a structure such as a parapodium 


Submassive 

Growth that is mostly in two dimensions (encrusting) but with distinct bumps or mounds growing from the surface. 


Subterminal 

Immediately below the end of a structure 


Suture 

The place where two structures join, particularly two whorls of a gastropod shell 


Symbiont 

An animal that lives in close association with another animal 


Symbiosis 

A pair of animals that lives in close association with one another 


Synapticulae 

Horizontal rods between septa 


Taxon (plural taxa) 

A group used in the classification of organisms such as genus, family, order, class, etc. 


Taxonomy 

The theory and practice of describing, naming and classifying plants and animals. 


Tentacle 

A long projection, usually sensory in function 


Tentacle (cephalopods) 

In cephalopods, an elongated arm use to capture prey (usually with suckers on the distal ends). tentacles contain the stinging cells. 


Tentacle (gastropods) 

An elongated projection of the body. 


Tentacle (jellyfishes) 

One of several narrow elongated string-like processes projecting from the lower surface of the bell. tentacles contain the stinging cells. 


Tentacle (sea anemones) 

One of many motile and retractable arms surrounding the oral cavity. tentacles contain the stinging cells. 


Theca 

The wall of a corallite of a coral. 


Tripinate 

Branching in three cycles from the central axis 


Tubcrculae 

Large papillae and may be much larger the diameter of the corallite. 


Tubercle 

A calcified and hard protuberance projection, or lump, usually larger than a papilla 


Tuberculae 

Reticulum structures that are bigger than the corallites of montipora. 


Tubiform 

Cylindrical in shape 


Umbilicus 

A sunken or depressed area at the base of a gastropod. 


Varix (pl. varices) 

Longitudinal thickened ridge found in some gastropods. 


Veliger 

The larvae of gastropod mollusks 


Velum 

A ciliated structure in gastropod larvae used for swimming 


Ventral 

Pertaining to the lower side; opposite of dorsal. 


Verrucae 

Wart -like growths found on species of pocillopora. 


Verrucose rhinophores 

Rhinophores having irregular wrinkles 


Villous 

Covered with small, hair-like projections 


Wall (theca) 

The skeleton enclosing a calice 


Wall reticulum 

Number of rings of vertical rods (trabeculae) forming the wall between corallites 


Whorl 

One "turn" of the spiral in a gastropod shell


Zooid 

An individual polyp in a colony, as in bryozoans 


Zooplankton 

Animal component of the plankton that feed on phytoplankton and other zooplankton 


Zooxanthellae 

The symbiotic algae that live within the bodies of cnidarians, mollusks, etc.

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