Biodiversity & Conservation

MarLIN Glossary

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T

Tadpole
Having the body form of a tadpole i.e. consisting of a round head with a tail.

Taxon
(pl. taxa) A taxonomic group of any rank, including all its subordinate groups; may be a single species or a group of related species, e.g. genus, class, order, etc., considered to be sufficiently distinct from other such groups to be treated as a separate unit (based on Lincoln & Boxshall, 1987 and Fitter & Manuel, 1986).

Taxonomy
The branch of biology concerned with the classification of organisms into groups (taxa) based on similarities of structure, origin, etc.

TBT
Tributyl tin (cf 'organotin')

Tellin
The common name for the Family Tellinidae of bivalve molluscs. The tellins (Tellinidae) are bivalves with thin, flattened, oval to subtriangular shells (Hayward et al., 1996). Their shells are often very colourful and they are good burrowers (Tebble, 1976).

Tellins
Plural of 'tellin'.

Telson
Posterior-most segment of the body in crustaceans (Stachowitsch, 1992).

Terete
Cylindrical or slightly tapering and circular in cross section with a surface free of furrows or ridges (OED, 1990).

Terrestrial
Living on, or referring to, land.

Territorial Waters
The seas over which a nation exercises jurisdiction and control, but within which other states have certain rights, notably for innocent passage of vessels. In UK law, the landward limit of UK territorial seas is defined as "the low water line around the coast" (Territorial Waters Order in Council 1964); the seaward limit is 12 nautical miles offshore from the landward limit.

Tetrasporangia
Unicellular thick, sac-like structures present in red seaweeds in which four spores are produced from meiosis (Lincoln et al., 1998).

Tetrasporangial
An intermediate life-cycle phase of marine algae (Lincoln et al., 1998).

Thalli
Plural of 'thallus'.

Thallus
A relatively undifferentiated plant body lacking true leaves, stems and roots (van Hoek et al., 1995). The term 'thallus' can be applied to algae and fungi.

Thermal Pollution
Anthropogenic heat input to natural systems, e.g. the discharge of heated cooling water.

Thermocline
A horizontal boundary layer in the water column in which temperature changes sharply with depth (based on Lincoln & Boxshall, 1987.)

Thixotropic
A sediment containing interstitial water, which becomes liquid as a result of agitation or pressure.

Thoracic
Relating to the upper body region known as the thorax (OED, 2008).

Tidal Race
An exceptionally strong tidal stream, usually caused by the constriction of water passing round a headland, or where tidal streams from different directions converge (Ministry of Defence 1987).

Tidal Range
Generally the difference in water height between Extreme High Water Springs and Extreme Low Water Springs. Daily tidal range is the difference between high tide and the next low tide. Estuarine tidal range is classified in three categories according to average spring tidal range: a) macrotidal: tidal range greater than 4 m; b) mesotidal: tidal range between 2 m and 4 m; c) microtidal: tidal range less than 2 m (Davidson & Buck in prep.).

Tidal Stream
The alternating horizontal movement of water associated with the rise and fall of the tide (from Lincoln & Boxshall, 1987) (cf. 'current').

Tide
The periodic vertical movement of water level with respect to some point on land. See 'astronomical tide'.

Till
Collective term for typically unstratified and unsorted sediments deposited by the direct action of glacial ice without the intervention of water. Boulder clay consists of a clay-dominated matrix containing stones and boulders of varying size (based on Allaby & Allaby, 1990.)

Tombolo
A spit (q.v.) that links an island to the mainland or to another island, formed by deposition when waves are refracted round the island (from Allaby & Allaby 1990).

Tori
Plural of 'torus'.

Torus
In polychaete worms the torus is an outgrowth of small serated plates stacked in the form of parallel swollen lips (Hayward & Ryland, 1995).

Toxicology
The branch of science concerned with poisons, their nature, effects and antidotes (from Makins, 1991). 'Ecotoxicology' is the application of toxicology to the natural environment.

Translucent
That allows light to pass through without being transparent (OED, 2008).

Trawl
Equipment towed behind a vessel for commercial fishing or scientific collecting. Bottom trawls collect demersal species; midwater trawls collect pelagic species. Cf. 'dredge', 'netting'.

Tributyl Tin
(See 'organotin').

Trochophore Larva
A type of larva characterized by a ring or girdle of cilia around the larval body, the prototroch, found in a number of animal groups, including the annelids and molluscs (Ruppert & Barnes, 1994).

Tubercle
A small rounded projection or protuberance (OED, 2005).

Tubercles
Plural of 'tubercle'.

Tuberculate
Bearing tubercles.

Tubeworm
1) General term for a worm living in a tube of its own construction (e.g. composed of mucus, cemented sand grains or a calcareous material) rather than a burrow alone. 2) Common name for members of the Family Serpulidae (Class Polychaeta), which secrete calcareous tubes or Family Spirorbidae (Class Polychaeta), which secrete spiral-shaped calcareous tubes.

Tubeworms
Plural of 'tubeworm'.

Tubicolous
Tube dwelling (Barnes et al., 1993).

Turbinate
Whorled (Brusca, 1980).

Turf
The lowest stratum of erect branching or filiform species.

Turion
A reduced branch with modified leaves and stipules, borne on a leaf axil or at apex of a stem (Preston, 1995).

Typicalness
See 'representativeness'.

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Glossary references