Исследована фауна гельминтов пищеварительного тракта Perca fluviatilis (Perciformes) водоемов национального парка «Самарская Лука» (Россия) в период 1990-2016 гг. В начале 1990-х гг. у P. fluviatilis зарегистрировано девять видов кишечных гельминтов. Жизненные циклы 78% из них были связаны с организмами зоопланктона. Обнаружены корреляционные связи между зараженностью рыб отдельными видами гельминтов и численностью организмов зоопланктона. К 2012-2016 гг. доля паразитов, ассоциированных с зоопланктоном, уменьшилась до 67%. Из состава гельминтов, обнаруженных у P. fluviatilis в период 1990-1992 гг., к настоящему времени сохранилось семь видов. С 1996 г. обнаружено 12 новых паразитов, в том числе два чужеродных. Установлена двукратная смена вида-доминанта в 1990-х гг. В настоящее время к исторически сложившемуся набору факторов добавился новый. Это вселение, натурализация и включение чужеродных видов гидробионтов в трофические цепи ихтиоценоза и паразитарные системы исследованных водных объектов. Состав гельминтов окуня адекватно отображает особенности экологии хозяина и изменения, произошедшие в водоемах за 30-летний период времени. Определены тенденции структурно-функциональной перестройки экосистемы, обусловленной вселением чужеродных видов и сопряженной с этим коррекцией трофических связей рыб. Прогнозируется изменение стратегии поведения рыб, наращивание численности и более активное участие видов-вселенцев (рыбы, моллюски, паразиты) в трофических цепях водоемов национального парка «Самарская Лука», связанных с водохранилищем, расширение круга потребителей/хозяев чужеродных паразитов.
Studied the dynamics of infection of the European perch Perca fluviatilis (Peciformes) by the helminths of the digestive system and their invasion of 13 native and 2 alien fish species in the water bodies of the National Park “Samarskaya Luka”. The similarity of the composition of the fauna of helminths of the digestive system of the European perch and other fish species has been analyzed for the period of 1990-2016. Peculiarities of the distribution of Perca fluviatilis parasites along the trophic chains of the fish community at different stages of ecosystem succession were revealed. Human activity promoted the penetration of alien species of aquatic organisms into the water bodies, their incorporation into the trophic chains and parasitic sub-systems “fish – helminths of the digestive system”. The historically established trophic relations of carnivorous fish with Perca fluviatilis are nowadays weakened; usual food objects are replaced by the invasive fish species. Invasive species participae actively in the formation of trophic chains of the ecosystem; in some cases, it leads to an increase in the invasion rates of indigenous hosts by alien parasites.
The fauna of the multicellular parasites of European perch Perca fluviatilis (Peciformes) of the Usinsky Bay of the Kuibyshev Reservoir was studied in 2019–2020; nine taxa of helminths were found. The parasite prevalence of most of the intestinal helminth species, associated with the zooplankton community, did not exceed 12–25%. In the fish with a body length of 117–200 mm, fish juveniles and benthos organisms played a significant role in the parasite transmission. The Usinsky Bay was a buffer zone at the margin of the “river-reservoir” system and had a specific hydrological regime. This promoted favorable conditions for the spreading of alien species of aquatic organisms in the ecosystem of the reservoir; in some cases this led to an increase in the invasion of indigenous fish (European perch) by invader parasites. As a result of this process, the invasive species of trematode Apophallus muehlingi became dominant in the helminth fauna of the European perch. High degree of infestation of European perch by this parasite indicated wide distribution of its first intermediate host, the alien mollusk Lithoglyphus naticoides, in the Usinsky Bay. Other species of parasites, associated with this invader, were not found in Perca fluviatilis. Helminths of the European perch can be used as biological markers to identify migratory activity, the vector of the invasion of some alien species, the range of their hosts, the population abundance, and indirect infection by alien hosts in different water bodies of the Volga River basin.
The results of the study of the features of polymorphism of green toad populations in the conditions of the Trans-Urals of the Republic of Bashkortostan are presented. It was found that among the green toads in the urbanized territories of the Trans-Urals, individuals with the color type M3 ("light background, merged spots") and M4 ("dark background, merged spots") prevail. There was a decrease in the diversity index in the conditions of low-rise buildings (m=1.995), as well as industrial (m=2.843) and green zones (m=2.986) relative to the control areas (3.286<m<3.99).
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