Oceanic islands and seamounts as staging posts for Copepoda Harpacticoida (Crustacea) - Shallow-water Paramesochridae Lang, 1944 from the North-East Atlantic Ocean, including the (re-)description of three species and one subspecies from the Madeiran Arc

- First evidence for the role of seamounts as staging posts for Harpacticoida.
- Comprehensive inventory of paramesochrid species of the Madeiran Archipelago.
- Description of new species/subspecies of Paramesochridae.

Despite the apparent restriction in their dispersal potential due to their holobenthic lifestyle and associated morphological adaptations, several species of Paramesochridae (Copepoda, Harpacticoida) occur at multiple shallow-water locations separated by 1000s of kilometres, a phenomenon known as the “meiofauna paradox”. In this context it is thought that seamounts located within a critical dispersion distance from a shallow-water habitat play an important role as staging posts, supporting meiobenthic steady-state dispersion, assuming they provide similar environmental conditions to the coastal habitats. To achieve a more complete understanding of the distribution of meiofaunal assemblages, a thorough investigation of the meiofauna of adjacent seamounts, islands, continental coastlines and surrounding deep-sea areas is necessary. A comprehensive investigation of the harpacticoid fauna of seamounts and islands in the northeast Atlantic Ocean was therefore undertaken, the Portuguese islands Madeira and Porto Santo were studied quantitatively and the material was compared with that from the seamounts Seine, Sedlo and Great Meteor.Fourteen species of Paramesochridae were recorded from the Madeiran Archipelago, of which five were already known to science and two were assumed to be new subspecies of already known species. The remaining seven species (50%) are as yet unknown. A comparison of the Paramesochridae from the Madeiran Archipelago with those of the seamounts Seine, Sedlo and Great Meteor revealed several species which occurred at multiple locations.Our review of the geographical distribution of the paramesochrid species revealed that five species had been previously reported from shallow-water regions in Europe, the Mediterranean, and even from the western coast of South and Central America (Pacific Ocean). Thus the presence of these taxa on the Atlantic seamounts and islands seems to link their formerly disjunct distribution. We conclude that the data presented here provide evidence for the hypothetical role of seamounts and oceanic islands as staging posts for at least some harpacticoid species.In addition, we describe two new species of Paramesochridae, Apodopsyllus seixalensis sp. nov. and Apodopsyllus puetzorum sp. nov., and one subspecies, Apodopsyllus africanus madeirensis ssp. nov., and redescribe Emertonia miguelensis.