Eccentric – off centre.

Ecdysis – moulting.

Echinoderm – invertebrate with penta-radial symmetry, often covered by a hard or spiny skin, including sea urchins and sea cucumbers of the phylum Echinoderma.

Echolocation – the detection of an object by means of reflected sound.  The animal emits a sound, usually at a very high frequency, which bounces off an object and returns as an echo.  Interpreting the echo and the time taken for it to return allows the animal to determine the position, distance, and size of the object, and so helps it to orientate, navigate, and find food.

Echo-sounding – depth measurement using bouced sound waves.

Ecosystem – an interdependent community of organisms and the environment in which they live.

Ectoparasite – a parasite living on the exterior of its host.

Ecotourism – travel that focuses on avoiding harm to wilderness areas and wildlife and wherever possible, actively contributes to their preservation.

Elver – a developmental stage in the eel, Anguilla life cycle between leptocephali and adult, in which a resemblance to adult occurs, as well as an upriver migration.

Embenthic – occurring in (penetrating) the substrate and submerged objects.

Endangered species – in the system of categories developed by IUCN, it is a species that is considered to be in imminent danger of extinction unless the factors threatening its survival are removed.

Endemic species – a species that is restricted to a certain geographic region and is thought to have originated there.

Endopsammon – the microscopic fauna of sand and mud.

Endoskeleton – a skeleton produced within the flesh of an animal and typically remaining embedded there.

Endostyle – a glandular ciliated groove along the ventral side of the pharynx in Urochordata, Cephalochorda, and lamprey larvae.

Entomostraca – a collective term for all the lower subclasses of Crustacea, most of which are of small size and hatch from the egg as nauplius larvae.

Ephyra – the earliest free-swimming stage of scyphozoan medusae that have been released from the polp, or scyphistoma. Also ephyrula.

Epibenthic – occurring on, but not penetrating, the substrate and submerged objects (=Aufwuchs).

Epicone – in dinoflagellates, the portion of the cell above or anterior to the horizontal groove, or cingulum.

Epidermis – thin membranous outer layer or covering.

Epifauna – animals living on the surface of the bottom.

Epipelagic – uppermost (normally photic) layer of the ocean at 0-200 m depth.

Epiphyte – plant growing on another plant.

Epiplankton – plankton occurring near the surface, in the upper 200 meters.

Epipodite – a laterally directed extension from one of the basal segments of an arthropod limb.

Epitheca – the upper or large half of the frustule of a diatom, or the plates above the cingulum in peridinian dinoflagellates.

Epizoan – animal attached to another organism.

Eretmocaris stage – postlarval stage in certain decapod Crustacea, characterized by possession of long eyestalks.

Erichthus larva – the second larval stage in Stomatopoda.

Estuary – place where fresh and sea waters mix.

Euhalabous – plankton, especially phytoplankton living in water of 30 to 40 0/00 salinity

Euphausiid – small, usually luminescent malacostran crustaceans resembling shrimps.

Euphotic zone – upper layer of ocean where photosynthesis takes place. photic zone.

Euplankton – organisms that spend most or all of their lives as plankton.

Eurybathic – tolerating a wide range of depth.

Euryhaline – tolerating a wide range of salinity.

Eurythermal – tolerating a wide range of temperature.

Eutrophic – aquatic habitats of high productivity.

Exogenous plankton – plankton originating in some other locality than in which it was found.

Exopodite – in Crustacea, the outer branch, or ramus, of a biramous appendage.  Also exopod.

Exoskeleton – in Arthropods, the hardened cuticular covering of the body serving for protection of soft parts and as sites for muscle attachments.

Exotic – introduced.

Exumbrella – the top, or convex outer surface, of medusae. The aboral surface.

Exuviae – the cast skin of an arthropod (including insects).

Facultative – capable of living under varied conditions; common in both clean and polluted waters.

Filiform – thread shaped.

Filter feeding – feeding by taking sea water into the mouth then forcing it out through the matted, sieve-like bristles of the baleen plates.  Food suspended in the water, such as small schooling fish and plankton, is trapped inside the mouth cavity as the water exists.

Fjord – narrow deep, steep sided inlet of sea.

Flagellum – whiplike structure.

Flaking – falling off piecemeal.

Flora – plants.

Flukes – in cetaceans, the horizontally flattened tail fin.

Fluvial – pertaining to rivers.

Food chain – is the sequence in which each organism is the food of the next member in the chain.  Green plants are at the beginning of the chain, followed by herbivores, smaller carnivores, and finally larger carnivores.

Fossa – reef attached directly to land.

Foramen – hole or opening.

Foraminifer – large, chiefly marine rhizopod protozoans usually having calcareous shells often perforated with minute holes for protrusion of slender pseudopodia; of the order Foraminifera.

Free-living – nonparasitic.

Fringing reef – reef attached directly to land.

Frustule – the siliceous shell of a diatom.

Fucoxanthin – brownish, xanthin pigment of algae.

Fusiform – tapering at both ends.

Gametogenesis – the production of sperm and egg cells.

Gammarid – a species from the family Gammaridae, order Amphipoda.

Gape – opening between closed valves, usually posterior, through which the siphons or end of body protudes.

Gastropod – snails with spiral or simple shells of the class Gastropoda.

Gill net – a curtain-like net suspended vertically in coastal waters to tangle or snare fish.

Gill rakers - comblike extensions from the inner surfaces of gill arches of plankton feeding fish.

Girdle – outer rim or leathery border of chitons.

Glabrous – smooth.

Gorgonian – colonial anthozoans with a usually horny and branching axial skeleton of the order Gorgonacea.

Granulated – roughened as by small grains or granules.

Great whales – refers to the larger whales.  All the baleen whales and sperm whale are called the great whales.

Gross productivity - rate of total production including respiration and net production.

Growth line – concentric line marking a stationary or slow period of shell growth.

Gular length – the distance from the anterior-most point of the labial plate directly posterior to the occipital margin.

Habitat – the type of environment in which a species is found naturally, providing the biological and physical conditions it requires to sustain life.

Hadal – deepest parts of ocean, over 6000 m.

Hair – a slender flexible filament of equal diameter throughout.

Hair pencil – a cluster of simple (unbranched) hairs or setae.

Herbivore – plant eater.

Hermatypic – reef building corals with zooxanthellae.

Heterotrophic – requiring ready formed organic food.

Hinge – upper rim on which the valves of a clam move or rotate.

Holdfast – attachment organ or macro-algae.

Holophytic – photosynthetic.

Holoplankton – permanent plankton.

Holozoic – heterotrophic nutrition.

Home range – is the area in which an animal normally lives; usually a restricted part of its total range, although occasionally it may be identical to it.

Hydotheca – cuplike exoskeleton structure around hydroid polyp.

Hydrophone – an underwater microphone.

Hydrozoan – simple and compound polys and jellyfishes including stinging corals and Portuguese man of war; of the class Hydrozoa.

Hypersaline – seawater with salinity above 35%.