Lohmannella (Acari, Halacaridae) from a cold-water coral reef off Norway, description of two new and a list of North Atlantic species.

Cold water coral reefs proved to harbour a diverse halacarid fauna. The fauna extracted from small pieces of corals was dominated by the genus Lohmannella which was represented by three species. Two species, new to science, are described and illustrated, namely Lohmannella njoerdri and Lohmannella sulensis. Of the third species only a single juvenile stage is available, since a reliable identification is not possible. Lohmannella njoerdri is characterized by long, slender claws. Lohmannella sulensis differs from other Lohmannella species by its wide dorsal plates, long and slender gnathosoma and legs and the part of the idiosoma posterior to insertion of leg IV being short.

The genital area of Halacaridae (Acari), life stages and development of morphological characters and implication on the classification.

The genital region of juvenile and adult halacarid genera is described. Larvae are expected to be present in all, protonymphs at least in the majority of the genera. Two of the marine genera have three nymphal instars, in the others one or two nymphal instars are suppressed. Adults of marine species have one, two or three pairs of genital acetabula; intrageneric differences in the number of acetabula are present but rare. Derived from the number of perigenital setae and genital acetabula, in most genera it is the deutonymph which is suppressed, in a few others the tritonymph. Adults of species with two nymphal stages have either two or three pairs of acetabula, those with a single nymphal stage have either one or two pairs of acetabula. Two genera may lack the protonymphal stage, but more material is needed to prove the absence. The present-day classification is outlined and supplemented. Anomalohalacarus and Arenihalacarus are both assigned to the Anomalohalacarinae. The Halixodinae include Agaue, Bradyagaue and Halixodes, the knowledge of Australacarus and Colobocerasides is sparse, but they may have to be incorporated in the Halixodinae. The subfamily Halacarinae includes a single genus, namely Halacarus.

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.

A hydrothermal vent mite (Halacaridae, Acari) with a new Corynophrya species (Suctoria, Ciliophora), description of the suctorian and its distribution on the halacarid mite.

Copidognathus nautilei Bartsch, 1997, from a hydrothermal vent field of the Mid-Atlantic Ridge at about 13 degrees N, 45 degrees W and 4090 m depth, was infested with the suctorian Corynophrya abyssalis n. sp., with up to 58 epizoans per mite. The new suctorian has a sacciform body with seven longitudinal ribs, a compact macronucleus and up to 40 non-retractile tentacles. The budding is exogenous. The systematic position of the new species and the genus Corynophrya is discussed, as well as infestation rates and sites of suctorians on their halacarid hosts.

Geographical and ecological distribution of marine halacarid genera and species (Acari: Halacaridae).

At the end of 2002, the number of marine halacarid species was 1018, that of genera 51. A single genus, Copidognathus contains 33% of all species (336). Eleven genera are monotypic. Geographical provinces with a large number of species are the tropical western Pacific, temperate northeastern Atlantic, temperate southeastern Pacific, and Mediterranean-Black Sea. Most records of halacarid species are from temperate and tropical areas; 10% of species are known from polar zones. On a generic level, 29 genera are recorded from tropical and temperate but not from polar provinces, five genera are restricted to the tropics, and none to polar regions. The majority (920 species or 90%) of all species live in the upper 200 m. Records of genera with exclusively algivorous or brackish/fresh water species are bound to littoral habitats; all the other genera occur in more than one depth zone. Arenicolous genera, though most abundant in the littoral zone, have representatives in the bathyal. Four marine genera (Copidognathus, Halacarellus, Isobactrus, Lohmannella) have representatives in coastal fresh water, and three genera, Acarothrix, Caspihalacarus and Peregrinacarus, are predominantly inhabitants of diluted brackish and fresh water. None of the free-living halacarid genera of the world's oceans appears to be endemic to one geographical province.