SUBJECT: Some Results of Nematode Fauna Investigations.
AUTHOR: Kulakova Irina
DATE: 15th April 2003

Total amount is: 29 samples of fouling and 32 dragger's samples. At present time fauna of the Black Sea nematodes comprises more than 200 species. The most diverse fauna of nematode has been recorded in the Crimea and Caucasus. In the northwestern part of the Black Sea the nematode fauna includes 93 species. The maximal density of nematodes forms at the open regions of the northwestern shelf (average density 530 000 ind·m-2, biomass 1,4 g·m-2), minimal – in a most polluted zone (average density 83 000 ind·m-2, biomass 0,2 g·m-2) (Kulakova, 1989, 2001, 2001a). At present time the fauna of the free-living nematodes in the basin of Odessa port comprises 30 species, belonging to 4 orders. The question about geographical distribution of the free-living marine nematodes until the present time is unclear. In 1920 – 1930s, many specialists considered that nematodes were cosmopolitan organisms. There have been assumptions that the zonal – climatic factors have no influence on their distribution (Steiner, 1915; Kreis, 1934). However this point of view has been contested by Chitwood (Chitwood, 1936a, 1936b, 1937, 1951, 1960) on the basis of differences between the species recorded along American coasts and those along the European coast. Some modern authors (Gerlach, 1955; Meyl, 1956, 1957; Timm, Wieser, 1953) are share this view and consider that the number of cosmopolitan forms among the free-living marine nematodes is much less than it was considered earlier.

It is hard to trace the distribution of the species because of the different level of studies in different regions of the World Ocean. Regarding the marine nematodes this question is still at the stage of investigation. It is of interest to clarify the zoogeographic affiliation of some species. When comparing the fauna of nematodes of the surveyed area with other seas it has been determined that port fauna (including northwestern part) have much more similarities with the fauna of the Mediterranean Sea (number of common species – 73 %) than with the northern seas of Europe (42 %). The nematodes species, that are common for the surveyed basin and for the Atlantic coast, costal zone of Central and South America, tropical seas made up 23 %, for Antarctic and Subantarctic – 1–3 %. This ratio assumes that distribution of the marine nematodes submits in general to same zoogeographical rules, as the distribution of all other marine benthic animals. All species registered in Odessa port are listed by I.N. Filipjev in the register of the nematodes species of the Black Sea (Filipjev, 1918 – 1922). On the basis of determination of the native species, most of the determined species have been ascribed to the native fauna. From the list of nematode species recorded in Odessa port four of them have not been recorded in other regions besides the Black Sea. The frequency of these species is 11 % from the total species frequency at the port; they do not form mass settlements. Five species are typical only for the Black and Mediterranean seas. From them only C. maeoticus was a mass species and was often recorded in Odessa port. Most of the species, recorded in Odessa port, have the vast areal. Besides the Black and Mediterranean seas these species have been recorded in the brackish waters along all European coasts, in the North Atlantic as well as at Arctic seas. Among them the mass species were S. pulchra, O. dujardini, O. ampylocercus. In the port area, 5 organisms of Nematoda were marked as species. Probably these nematodes will be known for the Black Sea. The reason of new species is small investigations but not invasion from the other parts of World Ocean. For predict of fauna changing it is necessary to have long term investigations material for the different regions. The following investigations could determine new species and decide the special ecological and zoogeographic problems.

References:

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A contribution by:

Kulakova Irina
Odessa Branch
Institute of Biology of the Southern Seas
National Academy of Science of Ukraine
65011 Odessa