Dr. Éva Murai szerk.: Miscellanea Zoologica Hungarica 3. 1985 (Budapest, 1985)
Sulgostowska, T.; Giziewicz, J.: Influence of material extracted from Diploposthe laevis (Bloch) and D. bifaria (Siebold in Creplin) (Cestoda) on tapeworm Hymenolepis diminuta (Rudolphi) in rats
ileum; 2) in all experiments, rejection of the posterior segments of strobila, which were found in the caeca, rectum and faeces; 3) distinct lowering of tapeworm viability; 4) in many cases the tapeworms were compactly curled up, whereas in untreated rats they rested loosely along the jejunum; 5) in some cases the oncospheres originating from the rejected segments optically appeared to be damaged. Essential changes in the behaviour of H. diminuta took place during the first 2-3 hrs after the administration of the studied materials. Experiments on characterization of the active substance (s) from isolated D. laevis and D. bifaria showed the presence of activity in AEO; a lack of activity in WE and the absence of activity in the aqueous phase after chloroform extraction of AEO. AEO from other tapeworm species, parasites of the duck genus Anas showed, very slight toxic activity. No activity was found in WE extracted from other tapeworms. These results testify to the non-polar lipophylic nature of the substance (s) obtained from D. laevis and D. bifaria which are active against H. diminuta . DISCUSSION So far no conclusive concept interpreting the interrelations between parasites in hosts has been put forward. Some authors emphasise the importance of ecological factors and consider the problem from the standpoint of population structure; other s stress the role of chemical factors, and yet others confine themselve to the presentation of the experimental results, without interpreting the underlying mechanisms. In the literature some data concerning the reactions of one parasite species to other parasites are reported. For example, LARSH and DONALDSON (1964) have studied the interspecific relationship in the populations of the nematode Nippostrongylus brasiliensi s (Travassos, 1914) = N. muris (Yokogawa, 1920) and the tapeworm Hymenolepis nana (Siebold, 1882). According to these authors, the nematodes adversely affect the development of tapeworms, because in the case of a mixed invasion only less than one half of the tapeworms remained in the intestine, as compared with a single-species invasion. PAWLOWSKIJ and GNIEZDILOW (1950) have found that in dogs infected with the nematode Toxocara canis (Werner, 1782) fewer plerocercoides of the tapeworm Diphyllobothrium latum (L., 1758) remained alive; mean body weight and length of the tapeworms were much smaller as compared with tapeworms in dogs free from nematodes. In studies on interspecific relationships in populations of the nematodes Trichuris muris (Schrank, 1788) and Aspiculuris tetraptera (Nitzsch, 1821), KEELING (1961) has demonstrated the occurrence of an antagonism between these parasite species; the antagonism was shown by a reduction of the number of parasites of both species during a mixed invasion. The latter author has also found that the sequence of introduction of the parasite species influenced the number of settled individuals of the second parasite; in these studies T. muris proved to be more sensitive to the presence of A. tetraptera invasion. In our study we have found that D. laevis and D. bifaria contain substances which can exert a toxic effect on other Cestoda species. They are extracted by acetons or chloroform which indicates their lipid nature. The present results suggest that the secretion of active chemical substances by parasites may regulate the numbers of other parasites in the host. The action of these compounds could explain for instance the exclusive occurrence of either D. laevis or D. bifaria - in a number of only 1-2 individuals - in the duck genus Aythya. Moreover, the results of studies on the effectiveness of the material from tapeworms parasitizing ducks against tapeworms occurring in rats seem to suggest that the toxic action of the investigated materials is nonspecific. REFERENCES KEELING, J.E.D. (1961): Experimental Trichuriasis. I. Antagonism between Trichuris muris and Aspiculuris tetraptera in the albino mouse. - Journal of Parasitology, 47; 641-646. LARS, J.E. & DONALDSON, A.W. (1944): The effect of concurrent infection with Nippostrongylus on the development of Hymenolepis nana in mice. - Journal of Parasitology, 30^/2: 18-20.
