Diversity and zoogeography of Antarctic deep-sea Munnopsidae (Crustacea, Isopoda, Asellota) from three ANDEEP expeditions

The family Munnopsidae was the most abundant and diverse among 22 isopod families collected by the ANDEEP deep-sea expeditions in 2002 and 2005 in the Atlantic sector of the Southern Ocean. A total of 219 species from 31 genera and eight subfamilies were analysed. Only 20% species were known to science, and 11% of these were reported outside the ANDEEP area mainly from other parts of the SO or the South Atlantic deep sea. One hundred and five species (50%) were rare, occurring at only 1 or 2 stations. Seventy-two percent of all munnopsid specimens belong to the most numerous 25 species with a total abundance of more than 75 specimens; 5 of these species (40% of all specimens) belong to the main genera of the world munnopsid fauna, Eurycope, Disconectes, Betamorpha, and Ilyarachna. About half of all munnopsid specimens and 34% of all species belong to the subfamily Eurycopinae, which is followed in occurrence by the Lipomerinae (19%). Munnopsinae is the poorest represented subfamily (1.5%). The composition of the subfamilies for the munnopsid fauna of the ANDEEP area differs from that of northern faunas. Lipomerinae show a lower percentage (7%) in the North Atlantic and are absent in the Arctic and in the North Pacific. This subfamily is considered as young and having a centre of origin and diversification in the Southern Ocean. The analyses of the taxonomic diversity and the distribution of Antarctic munnopsids and the distribution of the world fauna of all genera of the family revealed that species richness and diversity of the genera are highest in the ANDEEP area. The investigated fauna is characterised also by high percentage of endemic species, the highest richness and diversity of the main munnopsid genera and subfamily Lipomerinae. This supports the hypothesis that the Atlantic sector of SO deep sea may be considered as the main contemporary centre of diversification of the Munnopsidae. It might serve as a diversity pump of species of the Munnopsidae to more northern Atlantic areas via the deep water originating in the Weddell Sea.平扁水虱科（Munnopsidae）是2002年与2005年，由ANDEEP南极深海科考航次在南大洋大西洋扇区采集的22个等足目（Isopoda）科类群中，丰度与多样性最高的类群。本研究共分析了隶属于31属、8亚科的219个物种。其中仅20%的物种为科学界已知，且该已知物种中有11%的分布记录超出ANDEEP研究区域，主要见于南大洋其他海域或南大西洋深海区域。105个物种（占比50%）为稀有种，仅在1或2个采样站位出现。平扁水虱科所有标本中的72%均隶属于物种数量最多的25个物种，其总个体数超过75头；其中5个物种（占所有标本的40%）隶属于全球平扁水虱科动物区系的主要类群：宽额水虱属（Eurycope）、盘肢水虱属（Disconectes）、贝氏水虱属（Betamorpha）以及伊氏水虱属（Ilyarachna）。平扁水虱科约半数标本与34%的物种隶属于宽额水虱亚科（Eurycopinae），其次为脂水虱亚科（Lipomerinae，占比19%）。平扁水虱亚科（Munnopsinae）的物种占比最低，仅为1.5%。ANDEEP研究区域内平扁水虱科的亚科组成与北半球同类区系存在显著差异：脂水虱亚科在北大西洋的占比仅为7%，在北极海域与北太平洋则完全缺失。该亚科被认为是较为年轻的类群，其起源与多样化中心位于南大洋。通过对南极平扁水虱科的分类多样性、分布情况，以及该科所有属的全球区系分布开展分析，结果显示ANDEEP研究区域的物种丰富度与属级多样性均为最高。本次研究的区系还具备极高的特有物种占比，且平扁水虱科主要类群与脂水虱亚科的丰富度与多样性均处于最高水平。上述结果支持了“南大洋大西洋扇区深海可被视为平扁水虱科当前主要的多样化中心”这一假说。该区域或可通过源自威德尔海的深层海水，成为平扁水虱科物种向更北部大西洋海域扩散的多样性泵源。