Diversity of Tanaidacea (Crustacea: Peracarida) in the World's Oceans – How Far Have We Come?

Tanaidaceans are small peracarid crustaceans which occur in all marine habitats, over the full range of depths, and rarely into fresh waters. Yet they have no obligate dispersive phase in their life-cycle. Populations are thus inevitably isolated, and allopatric speciation and high regional diversity are inevitable; cosmopolitan distributions are considered to be unlikely or non-existent. Options for passive dispersion are discussed. Tanaidaceans appear to have first evolved in shallow waters, the region of greatest diversification of the Apseudomorpha and some tanaidomorph families, while in deeper waters the apseudomorphs have subsequently evolved two or three distinct phyletic lines. The Neotanaidomorpha has evolved separately and diversified globally in deep waters, and the Tanaidomorpha has undergone the greatest evolution, diversification and adaptation, to the point where some of the deep-water taxa are recolonizing shallow waters. Analysis of their geographic distribution shows some level of regional isolation, but suffers from inclusion of polyphyletic taxa and a general lack of data, particularly for deep waters. It is concluded that the diversity of the tanaidomorphs in deeper waters and in certain ocean regions remains to be discovered; that the smaller taxa are largely understudied; and that numerous cryptic species remain to be distinguished. Thus the number of species currently recognized is likely to be an order of magnitude too low, and globally the Tanaidacea potentially rival the Amphipoda and Isopoda in diversity

Diversity of hard-bottom fauna relative to environmental gradients in Kongsfjorden, Svalbard

A baseline study of hard-bottom zoobenthos in relation to environmental gradients in Kongsfjorden, a glacial fjord in Svalbard, is presented, based on collections from 1996 to 1998. The total species richness in 62 samples from 0 to 30 m depth along five transects was 403 species. Because 32 taxa could not be identified to species level and because 11 species are probably new to science, the total number of identified species was 360. Of these, 47 species are new for Svalbard waters. Bryozoa was the most diverse group. Biogeographic composition revealed features of both Arctic and sub-Arctic properties of the fauna. Species richness, frequency of species occurrence, mean abundance and biomass generally decreased towards the tidal glaciers in inner Kongsfjorden. Among eight environmental factors, depth was most important for explaining variance in the composition of the zoobenthos. The diversity was consistently low at shallow depths, whereas the non-linear patterns of species composition of deeper samples indicated a transitional zone between surface and deeper water masses at 15–20 m depth. Groups of “colonial” and “non-colonial” species differed in diversity, biogeographic composition and distribution by location and depth as well as in relation to other environmental factors. “Non-colonial” species made a greater contribution than “colonial” species to total species richness, total occurrence and biomass in samples, and were more influenced by the depth gradient. Biogeographic composition was sensitive to variation of zoobenthic characteristics over the studied depth range. A list of recorded species and a description of sampling sites are presented

The Magnitude of Global Marine Species Diversity

Background: The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered. Results: There are ∼226,000 eukaryotic marine species described. More species were described in the past decade (∼20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are ∼170,000 synonyms, that 58,000–72,000 species are collected but not yet described, and that 482,000–741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7–1.0 million marine species. Past rates of description of new species indicate there may be 0.5 ± 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science. Conclusions: Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century

Observations on Cumacea (Malacostraca: Peracarida) from Antarctic and Subantarctic Waters. I. \u3ci\u3eEkleptostylis debroyeri\u3c/i\u3e (Diastylidae), a New Species from Waters off the Antarctic Peninsula

Eighteen species of diastylid cumaceans have been described from Antarctic and subantarctic waters. A nineteenth species, Ekleptostylis ebroyeri, n. sp., was collected in depths of 83 to 530 m off the Antarctic Peninsula. The new species appears to be closely allied to Ekleptostylis heardi McLelland & Meyer, 1998; E. inornata (Hale, 1937), n. comb.; E. pseltdoi-nornata (Ledoyer, 1977); and E. vemae (B (a) over circle cescu-Mester, 1967), all of which are known from subantarctic and Antarctic waters. Ekleptostylis debroyeri is distinguished from these species by a combination of characters including the size of the anterior-most pair of lateral spiniform setae of the telson and the proximal article of the uropodal endopod subequal to the combined length of the two distal most articles. The genera Diastylis Say, 1818, Ekleptostylis Stebbing, 1912, and Leptostylis G. O. Sars, 1869 have morphological features that appear to be transitional, especially among the subadults and females. The generic status of many species within these genera can only be determined with certainty by the morphology (length of antenna, structure of the second pereopod, ornamentation of telson) of the terminal male stage. Although the mature male of E. debroyeri is unknown, it is tentatively placed in Ekleptostylis based on the similarity of the female to other known species of the genus

Observations On Cumacea (Malacostraca : Peracarida) From Antarctic And Subantarctic Waters. I. Ekleptostylis Debroyeri (Diastylidae), A New Species From Waters Off The Antarctic Peninsula

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Tanaidacean (Crustacea : Peracarida) fauna from chemically reduced habitats - the lucky strike hydrothermal vent system, mid-atlantic ridge

The tanaidacean fauna from the hydrothermal vents in the Lucky Strike Field on the Mid-Atlantic Ridge is examined. The material reveals species belonging to the genera Agathotanais, Apseudes, Leviapseudes, Sphyrapus, Armaturatanais, Leptognathiella, Mesotanais, Pseudotanais and Typhlotanais. One new typhlotanaid genus, Obesutanais, and five new species, Armaturatanais atlanticus, Obesutanais sigridae, Mesotanais styxis, Leptognathiella fragilis, and Typhlotanais incognitus, are described.KBN-000000/PO4/2005Training Through Research Program, IOC-UNESC

Are there widespread peracarid species in the deep sea (Crustacea: Malacostraca)?

The global zoogeographic distribution of the most widespread peracarid species occurring in three or more ocean basins below 2000 m is analysed. Basing on the published data we investigated 45 peracarid species, which have a most widespread distribution and most likely are cosmopolitan. Thirty-three species have a wide distribution in the Northern Hemisphere. Most species occur in the North Atlantic, however, 16 of these species occur also in the North Pacific, a more limited number of species occurs in the South Atlantic or South Pacific The Southern Ocean displays some special zoogeographic features and 22 widespread species occur there below 2000 m, including highly eurybathic ones. In total, 11 of the analysed species occur in all oceans. Eucopia australis (Lophogastrida), Munneurycope murrayi (Isopoda) and Eurythenes gryllus (Amphipoda) are the species with the widest distributions. Other peracarids occurring in all oceans are: the isopods Paramunnopsis oceanica and Eurycope sarsi, the mysid Caesaromysis hispida the lophogastrid Eucopia unguiculata, the amphipod Mesopleustes abyssorum and the tanaids Exspina typica, Paranarthura insignis and Pseudotanais nordenskioldi. No cumacean species has been reported with an ocean-wide distribution but Campylaspis glabra occurs in the Atlantic, Indian and Pacific oceans. Among plenty of rare species in each order there are only few species with wide distribution records. There is evidence from molecular genetic studies that some of the widespread peracarids represent several cryptic species, however, some, e. g. Eucopia australis, seem to be truly cosmopolitan species. Geography of sampling is biasing our view of biogeography. The history and quality of taxonomic work as well as the reliability of geographic records (quality control of large databases) limits our investigations of widespread or cosmopolitan species as much as the limited knowledge of variation within most species causes difficulties in defining morpho-species with certainty