Gastrotricha from Raised and Transitional Peat Bogs in Poland

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Language: English with Polish summary

1. In the raised and transitional peat bogs in Poland there were recorded 59 Gastrotricha forms belonging to 58 species and 8 genera. The bulk (54 species) of them belongs to the family Chaetonotidae, the other four being representatives of the family Dasydytidae.  A considerable part of the studied material comprised gastrotrichs never described yet (32% of the recognized forms and 41% of the examined specimens), which testifies to a very poor knowlegde of the animal group under consideration. These are: Chaetanatus oculifer sp. n., Ch. poznaniensis sp. n., Ch. sphagnophilus sp. n., Ch. armatus sp. n., Ch. sp. 1, Ch. sp. 2, Ch. sp. 3, Ch. aff. acanthocephalus, Heterolepidoderma macrops sp. n., H. tenuisquamatum sp. n., H. brevitubulatum sp. n., H. sp., Lepidodermella sp., Aspidiophorus oculifer sp. n., A. polonicus sp. n., A. sp. 1, A. sp. 2, and Ichthydium palustre sp. n. Eight other species (i.e. 15.6% of the recognized forms) were recorded for the first time in Poland, out of which two were never reported from Europe. All these facts imply a need of further studies on Gastrotricha in the area of Poland.

2. From the examined environments a new ecological form is reported which appears to be closely connected with peat bogs; Heterolepidoderma ocellatum f. sphagnophilum was the most numerously occurring Gastrotricha constituting 17.7% of all the determined specimens.

3. The present examinations have revealed that the intraspccific variability of Gastrotricha from the Chaetonotidae family is much greater than it resulted from the hitherto existing data. On the basis of a thorough analysis of this phenomenon a new set of diagnostic criterions has been elaborated, in which metrical and numerable features are of great importance.

4. Numbers of individuals, species composition, and heterogeneity of species are similar in all the lowland peat bogs in Poland. ln montane peat bogs where environmental conditions approximate those in lowland ones, Gastrotricha are much less abundant; the reason of it, however, has not been learned yet.

5. The most important abiotic factor that delimits the occurrence of Gastrotricha in peat bogs is water regime. When it is deteriorating and peat mosses get dried, at first the numbers of Gastrotricha populations are affected, and only after a long time the species diversity is decreased. Only two species: Lepidodermella squamatum Dujardin and Chaetonotus maximus Ehrenberg are able to reconstitute their populations (supposedly from resting eggs) after a long-lasting dry weather period; this ability has probably been acquired when living in environments different from peat bogs.

6. ln the area of Poland three assemblages of Gastrotricha from peat bogs have been recognized. Each of them is connected with at least two types of peat bogs and with several plant associations. In turn, most of plant associations entertains at least two Gastrotricha assemblages. This is an argument for using a direct method of distinguishing any animal assemblage poorly known from the ecological point of view, i. e., to base upon the uniformity of fauna, as opposed to an indirect method that bases on a classification of environments.

7. The most diverse Gastrotricha fauna occurs on transitional peat bogs; there may be found species characteristic of oligotrophic peat bogs, eutrophic waters, and transitional peat bogs. Swampy coniferous forests that follow raised peat bogs in the ecological chain of plant succession are not characterized by any specific Gastrotricha fauna: there occur scarcely representatives of some species characteristic of raised peat bogs, and in spruce forests on peats Gastrotricha are present in extremely small number and compose assemblages dissimilar to any other observed elsewhere.

8. A degree of eutrophication of the environment is an important factor controlling the Gastrotricha occurrence. The most strongly eutrophicated environments are populated by Gastrotricha numerically strongest and most diversified in species composition. The effect of this factor is, however, hardly distinguishable from that of the moisture that plays the most important role among the abiotic factors.

9. At the boundaries between transitional or raised peat bogs and other environments, like valley peat lands of diferent types, and eutrophic or distrophic waters, there occurs a diverse and interesting Gastrotricha fauna that often differs from that living in raised or transitional peat bogs. Hence, it is justifiable to undertake examinations of Gastrotricha in other biocenoses.

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