MarLIN Glossary

Glossary items


(Shetland) A small, sheltered tidal lagoon, generally formed at the head of a voe (q.v.) (from Scott & Palmer, 1987) (cf. 'houb').


Wandering; freely motile, mobile. (cf. 'sessile').


The tendency of an organism or population to change its location or distribution with time; mobility.


Individuals of a species which, by natural means, move from one geographical region to another outside their usual range, or away from usual migratory routes, and which do not establish a self-maintaining, self-regenerating population in the new region (cf. 'alien species'; 'recent colonist').

vas deferens

Tube conveying sperm from testis to the exterior (Abercrombie et al., 1973).


See 'veliger larva'.

veliger larva

Characteristic of marine gastropod and bivalve molluscs. The veliger larva bears a swimming organ termed the velum composed of two large semicircular lobes that bear long cilia. The veliger also bears a larval shell or protoconch.  As development proceeds the larva forms a well developed foot that plays an important role in settlement in many species, at which stage the larva is termed a pedi-veliger (adapted from Ruppert & Barnes, 1994).


A membrane or membranous structure typically bordering a cavity or partly obscuring an opening (particularly for molluscs) (OED, 2008).


The common name for members of the Order Veneroida of bivalve molluscs (Class Bivalvia, Phylum Mollusca). They are characterized by a shell composed of two equal sized valves, with umbones forward of the midline (anterior), and a hinge bearing central (cardinal) and lateral teeth (adapted from Hayward et al., 1996).


Relating to the belly or front of the body (OED, 2005).


Wormlike, long and slender like a worm (Brusca, 1980).

very exposed

Of wave exposure - 1) Open coasts which face into prevailing winds and which receive wind-driven waves and oceanic swell without any offshore obstructions for several hundred kilometres, but where deep water is not close to the shore (50m depth contour further than about 300m). 2) Open coasts adjacent to extremely exposed sites but which face away from prevailing winds. (From Hiscock, 1990).

very sheltered

Of wave exposure - Coasts with a fetch less than about 3 km where they face prevailing winds or about 20 km where they face away from prevailing winds, or which have offshore obstructions such as reefs or a narrow (<30¦) open water window (based on Hiscock, 1990).


The quality or state of being viable; capacity for living; ability to live under certain conditions.


Having the capacity to live, grow, germinate or develop.


A type of reproduction in animals in which the embryo(s) develop within and derive nourishment from the maternal body.


A ria (q.v.) (in Shetland).


The most anterior bone of the roof of the mouth (OED, 2005).


The likelihood that a habitat, community or individual (or individual colony) of a species will be exposed to an external factor to which it is sensitive. See 'Sensitivity'.


1) Open to attack or susceptible to receiving wounds or physical injury (adapted from OED, 1990). 2) IUCN Red List categories - a taxon which is not 'Critically endangered' (q.v.) or 'Endangered' (q.v.) but is facing a high risk of extinction in the wild in the medium term future (International Union for the Conservation of Nature and Natural Resources, 1994) (cf. 'Extinct', 'Critically endangered', 'Endangered').