MarLIN

information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

MarLIN Glossary

vadill

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

vagile

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

vagility

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

vagrant

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).

veliger

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).

velum

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

venerid

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).

ventral

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

vermiform

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).

viability

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

viable

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

viviparous

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

voe

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

vomer

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

vulnerability

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'.

vulnerable

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').