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Abdominal Flap: In decapod crabs, the abdominal flap folds back under the carapace. Underneath are the reproductive organs and swimmerets. It is here that the female crab keeps the fertilised eggs while they develop before hatching into larvae.

Abdominal Plate: The bottom plate of an echinoderm. Contains the mouth, reproductive and excretory organs. Abdominal relates to the belly, or digestive area.

Acontia: Threadlike filaments armed with nematocysts. Found in jellyfish and anemones

Adductor Muscles: Transverse (across) that draw valves together. In bivalves.

Alimentary: To do with the digestive system. Between the stomach and the anus.

Ambulacra: Areas of a body surface in which tube feet are situated. In sea urchins and sea stars.

Annelids: The group of worms that contains the segmented worms, such as the earthworm, and the leeches, as well as a number of marine species.

Antennae: Appendages, in pairs, often jointed, extending from the head. One group of antennae are tactile for touch, while the other group are chemosensory, for taste.

Anterior: Situated forward, towards the head end. As opposed to Posterior at the tail end. See Gastropod shell parts.

Anus: Excretory opening of the digestive system.

Aperture: A hole, slit, crack, gap or other opening.

Apex: Initial end of the shell of a gastropod. This is also the protoconch, or oldest part of a shell, right at the tip.

Appendages: An accessory structure. Used for some activity such as walking, feeding, chemoreception, touch or swimming. Term often used with arthropods.

Aragonite: A form of calcium carbonate.

Arthropod: Animal within the Phylum Arthropoda, which contains the insects, spiders, ticks and mites, crustaceans. Arthro = jointed; pod = foot.

Ascidian: Solitary or colonial sea squirt of the phylum Chordata. Enclosed in a soft, gelatinous test.

Asexual: Without sex. Having no sexual or reproductive organs. Reproduces by division, or splitting parts off the parent body.

Atrial Siphon: Exhalent (outgoing) siphon, expelling water. In an ascidian.

Autotomy: Ability to cast off a body part, usually at a plan of weakness. Usually the part can be regrown. Sea stars, Brittle stars and crabs can regrow body parts. Crabs do so in a process called moulting.

Axial: Along the univalve mollusc shell axis, around which the whorls turn.

Axial Sculpture: Parallel to the axis. The imaginary line through the apex around which a shell is coiled.

Bacteria: A class of microscopic unicellular or filamentous organisms, without chlorophyll or a well defined nucleus. Break down organic remains. Other bacteria cause disease.

Basal Disk: Disk at the bottom or base of an echinoderm. Contains the feeding, reproductive and excretory organs.

Biconical: Conical at each end. Usually relates to univalve molluscs.

Benthos: Animals and plants found at the bottom of the ocean or lake, either living on to of, or within the substrate.

Bladders: Anything inflated or hollow. Inflated hollow structure called a vesicle in an algae, often filled with air, to aid floating.

Body Whorl: Largest whorl of a gastropod mollusc.

Branchial: Like branches. Relates to mollusc gills, for gathering oxygen and releasing carbon dioxide.

Branchial cavity: Channel between foot and girdle where gills are located. In molluscs.

Brooded: The female crustacean looks after the eggs while they develop, usually under an abdominal flap.

Byssus: Strong filaments, for attachment. Secreted by the foot gland. In bivalve molluscs.

Calcareous, or calcite: Limy or shelly matter (calcium carbonate).

Calloused: Hardened area of the skin.

Callus: Thickened part of the skin or soft tissue.

Carapace: Chitinous shield covering head and thorax of a crab.

Carnivorous, Carnivore: Flesh-eating. See feeding.

Carpus: Wrist or region between forearm and metacarpus in crabs.

Chelae: The pinching claw of a crustacean, including false crabs and crabs, with a moveable and an immovable finger.

Cheliped: Claw-bearing appendage, terminating in a chelae or a pincer. See crabs.

Chemosensory: Sensitive to chemical stimuli. Often associated with antennae.

Chiton, Chitinous: Organic substance forming the horny covering of a crustacean, including prawns, false crabs and crabs.

Chordate, Chordata: The phylum of backboned animals.

Cilia: Hair-like projections that create currents by rhythmic waving in unison. See sponges.

Circulatory: The fluid system where nutrients and oxygen are taken too, and toxic by-products are taken from all cells in an organism. In higher animals referred to as blood.

Cirri: Feeding "baskets" of the barnacles.

Cirripeds: The individual feeding arms of a barnacle.

Cloaca: The single excretory cavity in some animals.

Cnidaria: Soft bodied animals, such as hydrozoans, corals, jellyfish and anemones, which have stinging cells (nematocysts). Once grouped with Ctenophora, or 'comb jellies' within the old phylum Coelenterata.

Coelenteron: The body cavity of a cnidaria and ctenophore, which is used as a stomach, an excretory organ and as a primitive vascular system. Cnidaria included the jellyfish, corals and anemones

Coelenterate: The Phyla Cnidaria and Ctenophores were once grouped together as Coelenterates.


Colonial, Colony: Group of organisms which prefer to live together.

Columella: The central pillar or axis of coiling in gastropod molluscs. See gastropod shell parts.

Column: The body of a sea anemone.

Commensal: One organism lives with another, but is not parasitic. The word refers to the practice of "eating at the same table".

Concave: Surface, bending slightly inwards. See convex.

Concentric: Circles or ovals having a common centre.

Conical: Cone shaped.

Convex: Surface, bending slightly outwards. See concave.

Crenulated, crenulations: Finely notched. Used to describe the margin or edge of a shell.

Crustacean: A large group of aquatic arthropods with hardened shells. Includes the prawns, shrimp, lobsters, yabbies, isopods and amphipods, barnacles, crabs, etc.

Ctenophores: The Phylum which contains the Sea Gooseberries or Comb Jellies.

Cuvier's Organs: Long, white, poisonous sticky threads which are ejected through the cloaca by a holothurian when molested.

Cylindrical: A long, roller-shaped body with circles at the two ends, with straight sides between.

Cyprid, Cypris: One of the planktonic larval stages of crustaceans, especially barnacles. Called cyprid because it resembles an ostracod, which is one of the crustacean groups.

Dentate, Denticulate, Denticles: Toothed, small teeth or raised points. See carapace and decapod crabs.

Deposit Feeders: Animals that feed on detritus which lies as an ooze on the ocean floor, or left on a shore after the tide has gone out. Also includes huge numbers of bacteria which is breaking down the organic remains. The Deposit Feeders eat both the remains and the bacteria.

Detritus: The ooze lying on the sea floor and left on shores after the tide has recede. It consists of the broken down remains of dead plants and animals, as well as the living bacteria which are living in and eating it. This is a major food source for intertidal and marine animals.

Disk, Disc: Central part or hub from which arms radiate, See echinoderms.

Dorsal: Top. See ventral.

Echinoderms: Animals having a spiny skin. Member of the Phylum Echinodermata, including sea stars, sea urchins and holothurians.

Elytra: overlapping scales which resemble small wings. In worms, and especially the Scaled Worm, Lepidonotus melanogrammus.

Endemic: Native to a country or a specific region.

Epidermis: In invertebrates, cuticle, the outer chitinous part of a shell or covering.

Eversible: Able to be turned inside out, like the finger of a glove.

Excreta: Waste products discharged from a body.

Excretory: Organ which discharges waste products from the body.

Extrovert: body part which can be turned inside out, like the finger of a glove.

Extroverted: Turned outward.

Felted: Having a dense covering of short fine hair. Found on limbs of crabs.

Fingers: The 'nippers' of the chelae, in crabs.

Flagellum: Lash-like slender appendage or limb. Found in sponges.

Foot: The body-part of a mollusc which is used for contact with the surface, and on which to glide along.

Fusiform: Spindle-shaped, relating to the shape of a mollusc's shell.

Frond: The "leaf" part of an algae. Not only does the frond take up and release gasses like the leaves of land plants, it also takes in nutrients from the surrounding water.

Gametes: Mature sex cell which unites with another in sexual reproduction.

Gastrodermis: The cell layer which lines the coelenteron of the cnidarians and ctenophores.

Gastropod: A member of the Class Gastropoda, a group of asymmetrical molluscs in which the foot is broad and flat, the mantle undivided, the shell in one piece, usually conical. Includes the limpets, whelks, and other snail-like molluscs.

Gastrovascular: The digestive - excretory system of a cnidarian and ctenophore.

Gelatinous: Like jelly, or gelatin.

Gill: The respiratory organ in animals that obtains oxygen from the water and releases carbon dioxide. Most groups of marine animals have gills, including molluscs, crustaceans and Fish.

Girdle: The outer part of a mantle, not covered with shell plates, as found in chitons.

Globose, Globular: Rounded like a globe, sphere or ball.

Granules, Granulose, Granular: Covered with grains or tiny elevations, finely rough.

Gregarious: Prefers to live together in groups. Often close together.

Habitat: A place where an organism lives, including all the biological and environmental factors.

Herbivore, Herbivorous: Plant eating. In the intertidal and marine environment, this is the algae eating animals, including many molluscs.

Hermaphrodyte, Hermaphrodytic: Animal which combines the characteristics of both sexes, having both male and female sex organs.

High Water Neap: High Water Spring: Every lunar month (28 days) there is one spring very high tide and corresponding spring very low tide. A fortnight later there is a not so high neap tide and a not so low neap tide. High water neap is the same as high neap tide. See tides.

Hirsute: Covered with hairs or bristles.

Holdfast: The outgrowths at the base of an algae which hold the plan to the substrate.

Holothurian: A Sea Cucumber of the Phylum Echinodermata. Long, soft and worm-like.

Horny: Made of a horn-like material. Horn is made up of compacted and matted hairs.

Hydraulic, Hydraulically: Working by the pressure of fluid pumped along an enclosed "pipe".

Interambulacra: Areas of the test (shell) between ambulaca (walking spines). Found in sea-urchins.

Interior Valve: In a bivalve where one shell lies inside the edge of the other.

Intestine: The lower part of the alimentary canal from the end of the stomach to the anus.

Intra-specific: Intra = within; specific = relating to the same species.

Introverted: Turned inside out, like the pushed-in finger of a glove.

Invertebrates: Animals without a backbone, including worms, sponges. arthropods, spiders, cnidarians, crustaceans, molluscs, echinoderms, etc.

Iridescence: Showing brilliant colours like these in a rainbow and changes colour with position. These optical illusion colours are created by the special structure of the light reflecting surface.

Jugium: Longitudinal rib of the intermediate valve (middle shell plate) in a chiton.

Keel: Flattened ridge.

Lamellae, laminate: Thin plates or scales.

Larva (singular), Larvae (plural): Self-contained embryo before it changes into the adult form. For some species, there many be a number of quite different larval stages during development.

Lateral: Side

Lateral Plates: The side plates between the carina and rostrum in barnacles.

Laterals: Raised fan-like area on the side of chiton valves.

Lattice: Very fine crisscross sculpture pattern on mollusc shells.

Leeches: A group of bloodsucking segmented worms. There are both freshwater and marine leeches.

Lobes: Rounded and flattish, or hanging part often divided by a gap.

Longitudinal: Running lengthwise, along the length.

Low Water Neap: Low Water Spring: Every lunar month (28 days) there is one spring very high tide and corresponding spring very low tide. A fortnight later there is a not so high neap tide and a not so low neap tide. Low water neap is the same as low neap tide. See tides.

Mandible: Paired mouth appendages, as in arthropods such as insects and crustaceans, etc.

Mantle: Flesh outer layer of the body. The mantle secretes and protects the shell. Found in molluscs.

Mantle Cavity: Respiratory space between the mantle and the body. Found in molluscs.

Medusa: The free-swimming "jellyfish" stage in a cnidarians life cycle. The other stage is the sedentary "polyp" stage.

Merus: The fourth segment of a crab's walking leg, which is attached to the carpus.

Mesoglea: The jelly substance of a cnidarian or ctenophore (coelenterate).

Microhabitat: A small section of habitat. In a small area.

Molluscs: A very large Phylum with about 100,000 species worldwide. Australia has a very rich mollusc fauna. Molluscs usually have a shell, but not always. Most have a fleshy foot, all have gills. They include the chitons, gastropods, bivalves, and octopods.

Monerans: Bacteria and cyanobacteria.

Moult, Moulting: Where all arthropods, including crustaceans, spiders, insects and others, shed their outer covering (epidermis) periodically as the body inside grows in size.

Nacreous, nacre: Having a pearly sheen. Found in molluscs.

Nauplius, Naupli: One of the early planktonic stages of a crustacean.

Neap Tide: Every lunar month (28 days) there is one spring very high tide and corresponding spring very low tide. A fortnight later there is a not so high neap tide and a not so low neap tide. Low neap water is the same as low neap tide. See tides.

see High-water Neap and Low-water Neap.

Nematocyst: Cnidarian stinging cell. As found in Anemones and Jellyfish.

Nocturnal: Active at night.

Nodule, nodules, nodulose, nodular: Small lump, knob or knot, rough to touch (nodule is singular; others are plural).

Nekton: Free-swimming animals which are capable of moving where they want to. They are different to plankton.

Nodules: Small rounded bumps, which are part of a mollusc's shell sculpture.

Non-sexual: Able to reproduce without two sexes coming together. "Juveniles" bud off the parent body. In anemones.

Notochord: Rod-like primitive backbone. Found in Ascidians.

Nudibranch: A group of often beautifully-coloured molluscs which have lost their shell. They usually have feather-like gills.

Oblique: At a side angle, at 45 degrees.

Oligiochaetes: A group of worms, which contains the earthworms.

Omnivore: Generalist feeder, both herbivore and carnivore.

Opercular: Having something to do with the operculum lid.

Operculum: A covering or lid which closes an aperture, in molluscs and barnacles.

Oral Disk: Areas surrounding the mouth. Found in anemones.

Orbital Angle: The angle at the junction of the eye orbit (hollow) and the lateral(side) margin. In the anterior (front) edge of a crab carapace.

Orbital Tooth: A small bump at the junction of the eye orbit (hollow) and the lateral(side) margin. In the anterior (front) edge of a crab carapace.

Orifice: An opening.

Ova, Ovum: Female sexual cells in animals. Usually an egg in marine invertebrates, capable of developing into a new individual when fertilised by male sperm.

Ovoviviparous: Producing fully formed eggs that hatch inside the maternal (mother's) body and are released later as live offspring.

Pallial: related to the mantle. Found in molluscs.

Palps: Segmented sense organ at the mouth of an arthropod.

Parapodia: Lateral (side) extensions of the foot. Found in opisthobranch (nudibranch) molluscs.

Parasite: One organism which feeds from another. May be plant or animal.

Parasitised: An organism upon which another is living and feeding from.

Parasitism: The process of one organism living on, and feeding from another.

Pectinate: Shaped like a comb.

Pedicellariae: The pincer-like structure on seastars and sea-urchins.

Penis: Male sexual organ.

Pentagonal: Having five sides or angles. Most echinoderms have a five-sided body plan.

Periostracum: Thin coat of horny material found on molluscs.

Pharynx: The cavity behind the mouth.

Phytoplankton: Single-celled plant plankton. See zooplankton.

Pinnate: Divided in a feathery manner.

Plankton: Algae and animals drifting with surrounding water.

Pleopods: Small abdominal limbs adapted for swimming and carrying eggs. In crustaceans.

Pneumatic: Operated by hydraulic (liquid) pressure along tubes.

Polychaetes: A major group of worms which have reached great diversity in the marine and intertidal environment.

Polynoid: Having many nodules or knots.

Polyp: A single zooid (individual) in a colony, and one of the life stages in cnidarians.

Porcellaneous: Translucent, porcelain-like. Found in mollusc shells.

Pores: Small holes in a surface which allow fluid to seep through.

Porous: Allows water to seep through.

Posterior: The rear, at the end.

Predator, Predatory, Predated: When one animal hunts down another for food. Predator is the hunter; predated means the prey.

Primary Spines: Longer spines, in sea urchins.

Proboscis: Long, retractable head extension with a mouth at the end. Found in worms.

Prostomium: Part of a worm's head in front of the mouth.

Protochordates: An animal, such as an ascidian, which has several features which link them to the higher backboned (chordate) animals.

Protoconch: The first, smallest whorls, which are the preserved larval shell, in gastropod molluscs.

Punctate: Surface sculptured with small depressions. In molluscs.

Pustule: Blister-like shape.

Pyriform: Pear-shaped.

Radial: Arranged like rays around a central point.

Radial symmetry: Equal proportion around a central point.

Radula: Tooth ribbon, for scraping algae off rocks, or slicing up flesh. Found in molluscs. See also feeding.

Ramuli: Fine, branched outgrowths. Smallest "branches".

Regenerate: Regrow, renew or restore portion of body, usually over a series of moults. In crustaceans.

Reproductive glands: Glands in male and female animals to reproduce further members of the same species.

Respiration: The process of taking in oxygen and removing carbon dioxide, usually using gills in marine animals, and lungs in land animals.

Reticulate: Network pattern or formation.

Rhinophores: Tentacles that can detect chemicals. In molluscs.

Rhizoids, Rhizoidal: A single- or few-celled structure which attach an algae to the substrate.

Ribs: Raised lines in sculpture or ornamentation.

Rostrum: Beak-like projection of crab carapace between the eyes.

Scalloped: Edged with semicircular lobes. Relates to mollusc shell edges.

Sculpture: The pattern on a mollusc shell surface.

Secondary Spines: Shorter spines in sea urchins. See primary spines.

Sedentary: Rarely moving, not strictly confined to one place.

Sediments: Fine particled part of the substrate which has been deposited such as silt, mud or sand.

Segmentation: Every arthropod has segments which allow its encased body or limbs to flex and bend.

Septa walls: Partitions or walls inside the column of an anemone, or cnidarian polyp.

Sessile: Attached to the substrate.

Setae: Stiff, bristle-like structures in worms. Like a hair.

Sexual: Fusion of male and female gametes to create offspring.

Shell: Calcareous covering secreted by mollusc shell. Composed of lime, or Calcium Carbonate.

Shell Plates: In barnacles and chitons, the individual segments of the shell.

Siphon: In molluscs, a tube-like extension of the mantle edge to conduct water current for respiration and/or feeding and for some bivalves, locomotion. Ascidians, including cunjevoi, also have two siphons for respiration and feeding.

Siphonal canal: A channel in the shell in which the siphon lies. In molluscs.

Siphonal groove: A shallow groove in the shell in which the siphon lies.

Skirt: The edge of the body which joins sea star arms.

Spatula: Spoon-shaped. Often refers to the marking left on the undersurface of a limpet shell when the animal has been removed or died.

Sperm: Sexual fluid containing male gametes.

Spherules: Small spheres, or globe-shaped objects.

Spicules, Spiculed: Needle-like shafts. Relates to the spines in some chiton girdles.

Spiral: Shaped like a coil spring.

Spiral Ribs: Continuous raised ridge which runs along the length of the spiral around a molluscs shell.

Spire: The part of a shell (all whorls) above the aperture. In some gastropod Molluscs.

Spores: the reproductive products of algae that are shed into water.

Stolon: A flat-lying or creeping plant structure which lies along the substrate, from which erect branches grow.

Striations: Narrow lines or grooves.

Sublittoral: Below low-tide level, marine.

Substrate: Surface on which an organism lives.

Suture: Line of junction of non-articulating parts. Spiral line marking the junction between whorls in molluscs.

Swimmerets: Small swimming appendages of crustaceans.

Symmetrical: A mirror-image either side of an imaginary middle line.

Tactile: Able to feel objects by touch.

Teeth: Variety of sharp projections or bumps. In crustaceans.

Telson: Hind part of an abdomen, usually a sharp spike.

Tentacles: Flexible organs on the head. Some are used as tactile feelers. Other tentacles are chemoreceptors, able to taste chemicals in the water.

Tentacular: Relating to, or belonging to the tentacles.

Tessellated: Forming little geometric shapes, such as squares, triangles, etc.

Test: Shell or hard outer covering of echinoderms, and ascidians.

Testis: Organ in the male which produces and stores gametes.

Thalus: The simple plant body of a non-vascular plant.

Tooth: A small sharp projection or bump in a crustacean's carapace shaped like a tooth.

Thorax: Body region between the head and abdomen. In arthropods, including insects and crustaceans.

Torsion: Mantle cavity twists in front of body during developmental growth, in molluscs.

Trochophore: A ciliated larval form of a mollusc which is symmetrical and swims by cilia which occur around its middle.

Tube Feet: Flexible tube-like stems used in locomotion, attachment and feeding. Found in echinoderms.

Tubercle: Small rounded elevations on the shell surface.

Tunic: Body wall of tunicates. In ascidians.

Turbinate: Broadly conical spire, turban or top shaped.

Umbilicus: Basal hollow in columella, in gastropod molluscs.

Umbo, Umbone: Point or apex of a bivalves shell above the hinge. It also marks the juvenile shall and sometimes the sculpture.

Univalve: Molluscs with a single-piece shell covering. The shell may be flat like a limpet, or spiraled like a top shell or turban. They are different to bivalves (two shells), or multivalves (chitons).

Valve: Shell segment of a chiton, or half the shell of a bivalve.

Varices: Prominent axial ridges on whorls, marks position of outer lip at successive stages of growth, in some gastropod Molluscs.

Vascular: Made up of pipe-like vessels for conveying body-fluids, such as blood.

Veliger: A larval form of molluscs which has some adult organs and a ciliated lobe called the velum.

Ventral: Lower, or undersurface. See dorsal.

Verrucae: Blister or wart-like swellings on an anemone column.

Vesicle: A floating gas-filled bubble or bladder-like structure. In algae.

Visceral Mass: Internal organs. In molluscs.

Viviparous: Bringing forth young alive. Not hatching by means of an egg.

Whorl: One turn of a spiral shell. In molluscs.

Zoanthids: A group of colonial cnidarians, related to anemones and corals. Zoanthids are like corals without a skeleton. In each colony the individual polyps are joined at their bases.

Zooplankton: Animal plankton, including single-celled animals, juvenile stages of many marine and shore animals, and larger animals such as jellyfish, etc. See phytoplankton.


If you know of any other words which should be included in this Glossary. Please send me an email. Thank you.

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photo of Keith DaveyLife on Australian Seashores
by Keith Davey (C) 2000

Learning Consultant - Media
The University of Newcastle

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Scientific Consultant: Phil Colman
site created 01.01.98 : updated 01.04.2000