Seasonal dynamics of population and age composition of the trematode Gynaecotyla adunca larvae (Linton, 1905) Yamaguti, 1939 in the Black Sea

The purpose of the research is analyzing the seasonal dynamics for the number and the hemipopulation structure of the trematode Gynaecotyla adunca larvae in shrimps of the genus Palaemon Weber, 1795 and determining the dependence of their infection with the metacercariae G. adunca on the host size and the season of the year in the water area of Sevastopol.

Materials and methods. Samples of aquatic organisms were collected monthly during 2012 in two different biotopes, the estuary of the Chernaya River and the Kazachya Bay. We examined a total of 2,445 specimens of the Hydrobia acuta mollusk, 200 specimens of the Palaemon elegans shrimp in the estuary of the Chernaya River, and 2,248 specimens of the H. acuta mollusks and 64 specimens of P. adsepsus in the water area of Kazachya Bay. Shrimps were caught with a 1 × 0.4 m seine with a 6–8 mm mesh. The mollusks were collected with a hand grab sampler with a sampling area of 0.04 m². The mollusks and shrimps were classified in accordance with the World Register of Marine Species. All mollusk and shrimp tissues were examined by the compression method under an MBS-10 binocular microscope. Descriptive statistics was calculated using Statistica 6 for Windows.

Results and discussion. We have found that the parthenita G. adunca is characterized by asynchronous emergence of secondary sporocyst that contain cercariae, while the metacercariae G. adunca hemipopulation is characterized by an overdispersed distribution, which indirectly indicates a low density of the host population and its constant migration. We analyzed seasonal dynamics of the found microfallid larvae population. The metacercariae G. adunca are characterized by one peak of infection with trematodes in summer.

1. Beklemishev V. N. Populations and micropopulations of parasites and nidicols. In: «Biotsenologicheskiye osnovy sravnitel'noy parazitologii» = Collection "Biocoenological Foundations of Comparative Parasitology". Leningrad, Science (Nauka), 1970; 215-225. (In Russ.)

2. Belousova Yu. V. Life cycle of the trematode Gynaecotyla adunca Linton, 1905 Yamaguti, 1939 (Trematoda: Microphallidae) in the Black Sea. Izvestiya Rossiyskoy Akademii nauk = Bulletin of the Russian Academy of Sciences. 2021 (in press).

3. Galaktionov K. V. Seasonal dynamics of development of Microphallus pygmaeus (Trematoda, Microphallidae) in the mollusks Littorina saxatilis and L. obtusata in the Barents and White seas. In: Plankton in coastal waters of the Eastern Murman. Apatity, Publishing house of the Kolsky branch of the USSR Academy of Sciences, 1982; 89-105. (In Russ.)

4. Galaktionov K. V. Life cycles of trematodes in littoral biocenoses. In: Life cycles of parasites in biocenoses of the northern seas. Apatity, Publishing house of the Kolsky branch of the USSR Academy of Sciences, 1987; 5-28. (In Russ.)

5. Galaktionov K. V., Dobrovolsky A. A. Development and reproduction of the maternal generation of the parthenita of the genus Microphallus (Plagiorchiida: Microphallidae). Zoologicheskiy zhurnal = Journal of Zoology. 1985; 64 (10): 1468- 1475. (In Russ.)

6. Galaktionov V. K., Dobrovolskiy A. A. Life cycles of parasites in ecosystems of the northern seas. In: Zhizn' i sreda polyarnykh morey = Life and Environment of the Polar Seas. Leningrad, Science (Nauka), 1989; 199–217. (In Russ.)

7. Dobrovolsky A. A., Galaktionov K. V., Mukhamedov G. K., Sinha B. K., Tikhomirov I. A. Parthenogenetic generations of trematodes. Trudy Leningradskogo obshchestva yestestvoispytateley = Proceedings of the Leningrad Society of Naturalists. 1983; 82 (4): 1–107. (In Russ.)

8. Lozovskiy V. L. On the infection of the Black Sea shrimp Palaemon elegans with the trematode Helicomentra fasciata and Gynaecotyla adunca metacercariae. Sb. nauchnykh statey «Sovremennyye problemy teoreticheskoy i morskoy parazitologii» = Collected scientific papers "Current issues of theoretical and marine parasitology". 2016; 98–99. (In Russ.)

9. Levakin I. A., Nikolaev K. E., Galaktionov K. V. Influence of the host population density on parasite infection – analysis of the model "trematode larvae – second intermediate hosts". Sbornik nauchnykh statey «Sovremennyye problemy teoreticheskoy i morskoy parazitologii» = Collected scientific papers "Current issues of theoretical and marine parasitology". 2016; 96–97. (In Russ.)

10. Mordvinova T. N., Lozovsky V. L. Parasite and commensal organism fauna of some decapods (Decapoda, Reptantia) off the coast of Sevastopol. Ekologiya morya = Marine ecology. 2009; 79: 21– 24. (In Russ.)