The Bathyal Holothurians of the New Zealand Region
Composition of the Bathyal Fauna
Composition of the Bathyal Fauna
Bathyal holothurians now known from the New Zealand region comprise 21 genera and 24 species. Elasipodida (nine genera, nine species) and Molpadida (four genera and seven, perhaps eight species) are particularly well represented, while the number of synallactid aspidochirotes (two genera and two species) is surprisingly small.
page 3Dell (1956) has demonstrated that for the New Zealand Mollusca there is always some interrelationship between typically shelf and typically archibenthal (bathyal) species, and he notes further that the interrelationship becomes particularly marked where the change from shelf to bathyal conditions takes place suddenly, and the continental shelf is steep. Three shelf holothurian species have been taken from the bathyal zone in Cook Strait (Pawson, 1963). However apart from the presence in the fauna of such strays, the bathyal holothurian fauna as it is known at present bears no close relationship to that of the shelf, although two molpadid species Paracaudina chilensis (bathymetric range 0–990 metres) and Heteromolpadia marenzelleri (bathymetric range 25–1,260 metres) are common both on the shelf and in bathyal depths.
Further sampling of the deep bathyal and abyssal zones is needed before the vertical distribution of the New Zealand holothurians can be properly evaluated.