Definitions of terms relating to Opisthobranchs.
aeolid - A nudibranch belonging to the major group (suborder) Aeolidina.
anterior - Toward the front of the body.
autotomy - A defensive behaviour in which an animal deliberately casts off part of its body (usually the mantle or cerata).
benthic - Refers to an organism living on or in the substrate.
bipinnate - With small side branches arising on two sides of the main stem or axis (refers to the gill).
branchial pocket - A cavity in the posterior midline of a dorid’s body into which the gills can be retracted.
buccal - Referring to the mouth or mouth cavity.
carnivorous - Literally a meat-eater; but in this context relates to a nudibranch feeding on a diet of animal material (e.g. sponges, bryozoans, bristle worms, cnidarians, or sea squirts).
caryophyllidia - Specialised spiculose tubercles on the mantle surface of some cryptobranch dorids.
cerata - (singular ceras) Finger-like processes arising in groups from the notum of aeolid and zephyrinid nudibranchs and containing diverticula of the digestive gland. Function in respiration, digestion and (in aeolids) in defense.
clavus - The distal portion of the rhinophore above the stalk. It is often expanded and ornamented with lamellae or papillae.
cnidosac - A small cavity at the apex of each ceras of aeolids in which unexploded nematocysts aquired from the cnidarian food are stored.
crenulate - Finely notched; regularly indented.
cryptic - Body camouflaged to resemble part of the microhabitat; or possessing secretive behaviour.
cryptobranch gill - Gills of dorid nudibranchs which can be retracted completely into a branchial pocket below the notum.
distal - That section of an organ or appendage which is most remote from the point of attachment to the body.
digestive diverticulum - A branch of the digestive gland within a ceras.
dorid - Nudibranchs with a circle of gills surrounding the anus in the midline towards the rear of the body, belonging to the major group (suborder) Doridina.
dorsal - The top surface of the animal.
dorsum - (= notum) The exposed back or top surface of a nudibranch mantle.
endemic - A species that is restricted to one or few localities in its distribution.
gill - (= branchia) The respiratory organ. Either in the form of single leaflets (hence pinnate) or with side branches (bipinnate or tripinnate).
herbivorous - Feeding on plant material (e.g. seaweed, encrusting microalgae).
hermaphrodite - Bisexual; an individual possessing functional male and female reproductive organs and capable of producing both sperm and eggs.
hyponotum - The under surface of the mantle.
in situ - Refers to the natural environment of an animal.
infrapallial lobe - Posterior fold of body enclosing shell of cephalaspideans.
intraspecific variation - Refers to natural variation in one or more charcters between individuals of the same species.
involute - Refers to the spire of the shell of the family Bullidae, which is sunk below the level of the apex.
jaws - Thickened, horny plates within the buccal cavity.
lamellate - (= perfoliate) Rhinophores bearing plates on the posterior face of the stalk or clavus.
lecithotrophic - Relates to the type of development in which larvae utilise only the reserves of yolk in the egg to nourish themselves.
|
mantle - The organ secreting the shell of molluscs. It develops into the layer that covers the body in opisthobranchs without a shell.
margin - The outer edge of the mantle.
nekton - Permanently floating at the surface of the ocean.
nematocyst - The stinging organ of the Cnidaria (a microscopic capsule with a coiled thread that rapidly unwinds on discharge). Present in hydroids, sea anemones, corals, etc. Aeolid nudibranchs separate the nematocysts from the remainder of the hydroid tissues and pass them, unexpoded, through the digestive diverticulum in the cerata to the cnidosac at the tip where they are used for the aeolid’s own defense.
notum - (= dorsum) The exposed back or top surface of a nudibranch mantle.
nudibranch - Technically a member of the order Nudibranchia of the subclass Opisthobranchia (sea slugs). Equivalent of Opisthobranch in much popular literature.
opisthobranch - Technically a member of the subclass Gastropoda (includes bubble snails, sea hares, sea butterflies, caddis slugs, sap-sucking slugs and side-gilled slugs as well as nudibranchs).
oral tentacle - Tentacle (or flap) around the mouth; used for food location and recognition.
oral veil - A membranous extension of the head above the mouth.
papilla - (plural papillae) A small, delicate, finger-like projection.
parapodia - Flap-like extensions from the sides of the foot in cephalaspidean, sacoglossan and thecosomatous opisthobranchs. They enclose the body and can be used for swimming.
pelagic - Passively drifting or floating at the sea surface; drifting with currents or winds.
periostracum - The horny outermost layer of gastropod and bivalve shells.
phanerobranch gill - Gills of dorid nudibranchs that cannot be withdrawn into a branchial pocket beneath the notum. They can only be contracted into a tight group above the notum.
pinnate - Bearing side branches; branched as to resemble a feather.
planktotrophic - Relates to the type of development in which larvae actively feed on micro-organisms to nourish themselves while they are in the plankton.
posterior - Towards the rear of the body.
pustule - (= tubercle) A low, conical, rounded or uneven swelling on the notum.
radula - A flexible, cuticularised feeding organ contained within the buccal cavity; bears numerous minute teeth.
reticulum - Network; any reticulated system or structure.
rhinophore - Sensory tentacle on the head, or anterior section of the mantle, of opisthobranchs.
rhinophoral pocket - The cavity into which the rhinophore of a dorid nudibranch can be withdrawn.
rhinophoral sheath - Upstanding flange from the antero-lateral part of the mantle (of dendronotoid nudibranchs) into which the rhinophore can be contracted.
spawn - Mass of eggs embedded in transparent jelly.
spicule A minute rod or star-shaped thickening in the mantle; spicules can be interwoven in a sponge-like fashion to give a protective texture to the mantle.
subapical - Section below the apex or tip.
substrate - The type of sea floor on which a benthic organism lives and grows.
tentacle - Projecting sensory appendage associated with the head or mouth.
tripinnate - With small side branches arising from three sides of the main stem or axis (refers to the gill).
ventral - The underside of the animal.
viscera - The soft interior organs of the body.
|
