Global estimates for species numbers and diversity in Mysidacea

So far, 1050 species of Mysidacea (Peracarida, Crustacea) were described and classified. The main number, about 90\%, is marine (mainly coastal) species, the rest belongs to brackish, freshwater and subterranean forms. The number of known pelagic species showed a roughly linear increment since 1860. Descriptions of benthopelagic and benthic species are still increasing an a logarithmic scales. Due to this exponential growth form, no prediction an the final number of living species can be made from the time-series of descriptions, except that the final number will be large compared with the actual one. As in most living forms, there is a strong latitudinal decrease of species numbers and diversity from the equator towards higher latitudes. At present, about twice the number of species is known from the northern hemisphere compared to the southern one. This may be indicative of a strong bias in the degree of exploration. The number of known benthopelagic and benthic species is about four times that of pelagic species, a relation which increases year by year. Pelagic species are efficiently sampled and further species may be expected mainly in deep waters. New types of epibenthic sledges recently strongly increased the efficiency of benthopelagic catches, and resulted in a great number of new species. Sampling methods for benthic species are still at the beginning of development; with the use of traps, examination of molluscs shells, sponges and corals, and with night sampling of diurnally emergent species. Most sea areas of the globe were poorly explored for mysid species. Best known are the faunas of Japan waters, Caribbean, North AtIantic, Black Sea, and Mediterranean. Projections of species diversity and numbers in well known areas suggest that the globe may be populated by a reasonable minimum of about 4000 living species. Plausibility rather than reason supports a maximum estimate of about 10.000 mysid species.