Diversity and distribution of deep-sea Pseudotanaidae (Tanaidacea, Peracarida)

Abstract

A large collection of Pseudotanaidae was obtained during three international expeditions. Samples were taken from shelf areas down to the slope (213−2750 m) and from the abyss (4093–5780 m). In North Atlantic waters, six areas off Iceland (Irminger Basin, Iceland Basin, Norwegian Sea, Denmark Strait, Iceland-Faroe Ridge, and Norwegian Channel) were investigated. In this sampling collection, Pseudotanaidae was the most numerous Tanaidacea family. Morphological identification revealed five species, for which the descriptions are given in Chapter 2. A large group of indistinguishable specimens, from a wide depth range and different areas was discriminated using morphometric methods. This allowed me to distinguish variation within one species (P. svavarssoni and complex cryptic species of P. svavarssoni). Another 13 new species were described from Central Pacific waters (Chapter 3). All the new taxa present restricted distributions and where found on a few closest stations. The high heterogeneity in the area reduced the spatial distribution of each taxa, but an increasing number of available niches has triggered diversity levels. The integrative taxonomy approach applied on the third studied area, the abyss of the Kurile-Kamchatka Trench, has allowed us to identify six new species. The homogeneity of the abyss in KKT provides a wide distribution of pseudotanaids, and the examined taxa of the KKT did not show limited distributions.