Abdomen Hind section on an invertebrate’s body.
Acute Sharply pointed.
Alien Introduced by Man from another part of the world.
Annelid A segmented worm, phylum Annelida.
Antennae Slender, paired sensory organs on the head of an invertebrate.
Barbel Fleshy filament growing from the head or mouth of a fish.
Brackish Mixed fresh and sea water.
Bryozoan Belonging to the phylum Bryozoa.
Calcareous Chalky, composed of calcium carbonate.
Carapace Hard upper surface of a crustacean’s shell.
Cardinal teeth Projections from the middle of a bivalve mollusc’s shell hinge.
Carpus Crustacean leg segment basal to the propodus.
Caudal Relating to the tail.
Cephalothorax Fused head and thorax found in some invertebrates.
Cerata Dorsal projections in some sea slugs, containing branches of the digestive tract; they are often armed with stinging cells.
Chaeta (plural Chaetae) Chitinous bristle.
Chela Crustacean appendage whose terminal segment is movable against an immovable one on the propodus (hence, chelate).
Cirri Hair-like filaments used during feeding (e.g. in barnacles).
Colonial Organisms that remain together, having been produced asexually.
Compound eye Eye structure comprising numerous cells and lenses, not a single lens.
Coralline Calcareous and coral-like (as in certain seaweeds).
Coxa Ventral projections from thoracic segments in amphipod crustaceans.
Crenulate With a finely notched edge.
Dactylus Movable finger of decapod crustacean claws.
Dentate Toothed.
Dorsal Upper surface.
Epibiotic Growing on the surface of another organism.
Epiphytic Growing on the surface of a living plant.
Gnathopod Leg-like crustacean appendage, modified to serve as a jaw.
Holdfast Root-like structure that anchors seaweeds to rocks.
Hydranth Feeding polyp of a hydroid colony, with stinging tentacles and a mouth.
Hydroid General term embracing members of the cnidarian class Hydrozoa.
Intertidal Zone between highest and lowest tides.
Invertebrate An animal without a backbone.
Juvenile Stage in the life cycle between larva and adult, typically unable to reproduce.
Lamella Thin plate.
Larva Pre-adult growing stage in the life cycle of certain species, differing in morphology from juveniles and adults.
Lateral teeth Projections from the shell hinge of bivalve molluscs, both in front of and behind cardinal teeth.
Littoral zone Shore zone exposed to influences of tides and waves, and with alternating exposure to air and sea water, including spray.
Lower shore Shore zone around low-tide level.
Moult Process seen in birds during which old feathers are lost and replaced by new ones; also applies to certain invertebrates that shed their skins.
Ocelli Eye-like markings.
Operculum Plate found in some invertebrates (e.g. some tubeworms and molluscs) used to seal off entrance to shell.
Opposite Arising in opposite pairs on a stem.
Pallial line Line inside a bivalve mollusc’s shell marking the extent of attachment of mantle.
Papillae Tiny nipple-like protuberances.
Parapodia Leg-like lateral appendages on segments in annelids, each parapodium comprising a dorsal notopodium and ventral neuropodium.
Parasite Organism that obtains food and shelter in or on another living organism, the host, which does not benefit.
Pedunculate Borne on a stalk.
Pelagic Favouring the open sea.
Pereopod Forked limb of Malacostraca crustaceans, used for walking and feeding.
Pinnate Branched like a feather.
Plankton Organisms that drift in the water column.
Pleopod Abdominal limb in crustaceans.
Propodus Decapod crustacean leg segment immediately below claw.
Reticulate With a netted pattern.
Rhinophores Paired sensory tentacles seen in sea slugs, posterior to oral tentacles of opisthobranch molluscs.
Salinity Measure of dissolved salt concentration in sea water.
Sedentary Attached to a substrate but capable of movement.
Sessile Permanently attached to a substrate.
Spicule Tiny spine, present in the body and skin of sponges and echinoderms.
Sub-littoral zone Shore zone below the low-tide mark.
Telson Tail-like last segment in a crustacean’s body; often flattened and used in movement.
Thorax Middle section of the body of some invertebrates.
Tubercle Small rounded projection.
Umbo Strongly curved dorsal section of bivalve mollusc shells.
Uropod Abdominal appendage in certain crustaceans; in decapods, uropods are paired and adjacent to the telson, forming the ‘tail fan’.
Ventral Relating to the belly or lower surface of an animal.
Wingspan The distance from one wingtip to the other in birds.
