Biodiversity & Conservation

MarLIN Glossary

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U

Ultra-sheltered
Of wave exposure - fully enclosed coasts with a fetch measured in tens or at most a few hundred metres (from Hiscock 1990).

Umbo
In the shell valve of bivalve molluscs (e.g. cockles, mussels or clams), the strongly curving dorsal region following the beak (Stachowitsch, 1992).

Umbones
Plural of 'umbo'.

Understorey
Organisms occurring under the main canopy of algae, especially of kelps (from Hawkins & Jones, 1992).

Uniramous
Composed of a single branch, see biramous (Hayward & Ryland, 1995).

Upper Shore
An informal physical term for the area of the shore around the high tide level.

Urchin
Rounded and covered in spines, resembling a hedgehog. Cf. sea urchin.

Uropod
Sixth abdominal appendages in malacostracan crustaceans (Ruppert & Barnes, 1994). In decapod crustaceans the paired uropods may be flattened and, together with the telson, form a characteristic 'tail-fan' (adapted from Stachowitsch, 1992).

Uropods
Plural of 'uropod'.

Utricle
A swollen, vesicular part of the thallus of macroalgae (Hoek van den et al., 1995).

Utricles
Plural of 'utricle'.

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Glossary references