Abstract:One thousand three hundred seventy three fish specimens of eight different species from the vicinity of Kyiv, Ukraine, were examined for the presence of trypanosomes and 921 individuals were found to be infected. The prevalence of infection ranged from 24% in freshwater bream, Abramis brama (Linnaeus), to 100 % in spined loach, Cobitis 'taenia' Linnaeus. The level of parasitaemia also varied significantly between generally mild infections in pikeperch, Sander lucioperca (Linnaeus), and heavy ones in C. 'taenia'. In most cases the infections with trypanosomes were asymptomatic. Cases of co-infection with species of Trypanoplasma Laveran et Mesnil, 1901 were documented for five out of eight examined host species. Molecular analysis of the 18S rDNA sequences revealed that four hosts, namely northern pike, Esox lucius Linnaeus, freshwater bream, spined loach and European perch, Perca fluviatilis Linnaeus, were simultaneously infected with two different trypanosome species. Our findings advocate the view that to avoid the risk posed by mixed infections, subsequent molecular taxonomic studies should be performed on clonal lines derived from laboratory cultures of fish trypanosomes.
BackgroundAmphibian trypanosomes were the first ever described trypanosomatids. Nevertheless, their taxonomy remains entangled because of pleomorphism and high prevalence of mixed infections. Despite the fact that the first species in this group were described in Europe, virtually none of the trypanosomes from European anurans was analyzed using modern molecular methods.MethodsIn this study, we explored the diversity and phylogeny of trypanosomes in true frogs from Europe using light microscopy and molecular methods.ResultsA comparison of observed morphotypes with previous descriptions allowed us to reliably identify three Trypanosoma spp., whereas the remaining two strains were considered to represent novel taxa. In all cases, more than one morphotype per blood sample was observed, indicating mixed infections. One hundred and thirty obtained 18S rRNA gene sequences were unambiguously subdivided into five groups, correspondent to the previously recognized or novel taxa of anuran trypanosomes.ConclusionsIn this work we studied European frog trypanosomes. Even with a relatively moderate number of isolates, we were able to find not only three well-known species, but also two apparently new ones. We revealed that previous assignments of multiple isolates from distant geographical localities to one species based on superficial resemblance were unjustified. Our work also demonstrated a high prevalence of mixed trypanosome infections in frogs and proposed a plausible scenario of evolution of the genus Trypanosoma.
This work summarizes the results of the 8-year study focused on Trypanoplasma sp. parasitizing freshwater fishes in the vicinity of Kyiv, Ukraine. Out of 570 fish specimens of 2 different species analyzed, 440 individuals were found to be infected. The prevalence of infection ranged from 24 % in Abramis brama Linnaeus (freshwater bream) to 100 % in Cobitis taenia Linnaeus (spined loach). The level of parasitemia also varied between moderate in freshwater bream and very high in spined loach. Interestingly, no clinical manifestations of trypanoplasmosis were observed even in extremely heavily infected C. taenia. We hypothesize that different species may differ in evolutionary timing allowing for reciprocal adaptation of the members of the "host-parasite" system. Molecular analysis of the 18S rRNA sequences revealed that several specimens were simultaneously infected with at least two different trypanoplasm species. To the best of our knowledge, this is the first report of the mixed infection with fish trypanoplasms.
Ответ на вопрос о причинах эволюционного замещения клонового способа воспроизводства половым размножением, связанным с мейозом и рекомбинацией, до сих пор не получен. Считается, что причинами эволюционного ухода от клоновости и приобретения генетической уникальности является способность амфимиктических организмов достигать более высокой приспособленности за счет удачного комбинирования генов [1]. Однако этот довод вызывает большие сомнения. Ведь период существования исключительно апомиктических организмов является самым длительным в истории жизни на Земле. Именно тогда произошли главные ароморфозы (образование эукариот, многоклеточность, фотосинтез и половой процесс), а значит клоновое размножение никак нельзя считать ненадежным и эволюционно бесперспективным. К тому же существует множество примеров того, что организмы, утратившие способность к амфимиксису и перешедшие на партеногенез, достигают биологического прогресса. Часто они многочисленнее амфимиктических анцесторов и име-doi: https://doi.
Жизненные потенциалы амфимиктических и апомиктических щиповок (Cypriniformes, Cobitidae, Cobitis): сравнение по зараженности трипаносомами и числу ядерных фрагментацийПредставлено членом-корреспондентом НАН Украины И.А. Акимовым Сравнительный анализ диплоидных и инвазионных полиплоидных щиповок рода Cobitis двух рек бассейна Среднего Днепра показал, что эти формы по степени устойчивости к инвазии кровяным паразитом Trypanosoma cobitis не отличаются, хотя доля фрагментированных ядер эритроцитов однозначно выше у полиплоидных форм (особенно тетраплоидных), чем у диплоидов. Тем не менее это негативное обстоятельство никак не сказывается на общей приспособленности триплоидных и тетраплоидных особей, представленность которых в водоемах Днепровского бассейна гораздо выше, чем диплоидов, и обусловлена экспансией, имевшей место в 1960-х гг. Исследованные показатели подвержены сезонной динамике. Максимальная зараженность достигается в первой декаде августа, а наибольшее число фрагментированных ядер эритроцитов приходится на сентябрь.Ключевые слова: Cobitis, диплоидно-полиплоидные формы, кровяные паразиты, микроядра.
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