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Degenerative and constructive features of a phylogeneticcaly young cave form of Poecilia sphenops (Pisces, Poeciliidae).Abstract DARWIN'S statement, that rudimentary parts of organisms are a p t t o be highly variable, is also true for the regressive structures of cavernicolous animals. On the other hand, adaptive traits develop under cave conditions, the variability of which is lowered rather than increased, compared to that of their precursors in the epigean population. These differences in the genetically controlled variability of constructive and degenerative features indicate action and nonaction of natural selection. Inhaltsverzeichnis

The present study considers the important role of bone resorp! tion for bone growth in general\ and aims to clarify if and how bone resorption contributes to the skeletal development of carp\ Cyprinus carpio L[\ a teleost species with {normal| osteocyte! containing "cellular# bone[ To ensure the identi_cation of osteo! clasts and sites of bone resorption independently from the mor! phology of the bony cells\ bones were studied by histological procedures\ and by demonstration of the enzymes which serve as osteoclast markers\ viz[ tartrate resistant acid phosphatase "TRAP#\ ATPase and a vacuolar proton pump[ Two types of bone!resorbing cells were observed in juvenile carp] "0# multi! nucleated giant cells displaying morphological and biochemical attributes which are known from mammalian osteoclasts^and "b#~at cells which lack a visible ru/ed border and for which identi_cation requires the performance of enzyme histo! chemical procedures[ Bone resorption performed by osteoclasts mainly occurs at endosteal bone surfaces[ To a lesser extent\ bone resorption also takes place at periosteal bone surfaces\ but without an apparent connection to bone growth[ The latter observation\ and the occurrence of bone remodelling\ suggest that the endoskeleton of juvenile carp might be involved in mineral metabolism[ Morphological di}erences and bio! chemical similarities to bone resorption in teleosts with acellular bone are discussed[

In flounder Platichthys flesus, ruffe Gyrnnocephalus cernua, and smelt Osmerus eperlanus, caught mainly during 1980 through 1983 in the Lower Elbe, a large number of serious pathological liver conditions were diagnosed. The predominant symptom was a shrinkage of liver cells, which spreads with advancing age and is increasingly accompanied by other degenerative changes, such as dissolution of the well-organized liver structure, blood clots, and tissue necroses. Neoplastic liver nodules were found in 32 % of sexually mature ruffe. Elbe flounders, which mature sexually shortly after migrating to their spawning grounds in the southern North Sea, still showed no signs of such nodules. In contrast, recent investigations of sexually mature flounders off the Dutch coast revealed occurrence rates as high as 10 %. Fishes from the River Eider, in which pollution is minimal, were effectively free from such liver damage. The livers of some 1 yr old flounders from the Lower Elbe, kept for 40d in uncontaminated water and fed on a diet free of harmful substances, showed signs of regeneration along with a decrease in chlorinated hydrocarbon content. Livers of other fishes kept under the same conditions maintained their high chlorinated hydrocarbon concentrations and continued to display the pathological liver symptoms. That the liver damage observed in Elbe fishes is due to high pollution levels receives support from 2 facts: (1) Other authors found similar pathological liver conditions in coastal regions where the pollution level was high; (2) liver conditions of this kind could be induced experimentally in fishes by PCBs in concentrations of the same order of magnitude as those recorded in the Lower Elbe.