Mermithid (nematoa: mermithidae) infections of black flies (Diptera: Simuliidae) : seasonal variation and developmental characteristics /

Mermithid nematodes (Nematoda: Mermithidae) parasitize larval, pupal and adult black flies (Diptera: Simuliidae), oftentimes resulting in partial or complete host feminization. This study was designed to characterize parasite-host seasonal variation and to estabUsh the developmental life stage at which feminization is initiated. Data indicate that the total adult population of black flies collected from Algonquin Provincial Park throughout the spring of 2004 was comprised of 31.8% female, 67.8% male and 0.4% intersex individuals. Of the total population, 0.6% was infected by mermithid nematodes (69.0% female, 3.5% male and 27.6% intersex). Seasonal infection trends established over a 12-month period revealed that black flies with different life histories host the same mermithid subfamilies, while black flies with similar life histories host mermithids from different subfamilies. If a simuliid species simultaneously hosts two mermithid species, these parasites are from different subfamilies. Molecular mermithid identification revealed two mermithid subfamilies, Me.somermithinae and Gastromermithinae, present in the simuliid hosts. Mermithid colour variation was not found to be a reliable species indicator. The developmental stage at which feminization is initiated was determined by examining gonad morphology and meiotic chromosomal condition. Results indicate that mermithid-infected black flies exhibit feminization prior to larval histoblast formation. Larvae can be morphologically male (testes present) or female (ovaries present), with morphological males exhibiting either male (achiasmate) or female (chiasmate) meiotic chromosomes; morphological females were only genetically female. Additionally, mermithid infection inhibits simuliid gonad development.

Parasitismo por Mermithidae (Nematoda) em larvas do gênero Chironomus gr. decorus (Diptera: Chironomidae) no Rio dos Peixes, Dois Córregos, SP, Brasil

Registramos a incidência de parasitismo por vermes Mermithidae em larvas de Chironomus gr. decorus (Diptera: Chironomidae), no Rio dos Peixes, Dois Córregos, região centro-oeste do Estado de São Paulo, Brasil. Neste estudo, de um total de 791 larvas amostradas, 205 (25,9%) estavam infectadas por mermitídeos, indicando que larvas de Chironomidae são comumente parasitadas por vermes mermitídeos.

两索线虫属Amphimermis和复索线虫属Complexomermis在索科线虫中分类位置的探讨

<正> 索科线虫Mermithidae���线虫纲中的一个特殊的科。其幼虫主要寄生于昆虫体内,能使其宿主产生一系列病理变化,最后导致死亡,它们就在自然界中有控制昆虫种群数量的作用,引起科学工作者高度重视。近二十年来在国外已成为生物防治害虫的材料,在应用于控制蚊类、蝗虫、金龟子等方面,都取得了显著的效果,并已经在生产上推广应用。 近年来,我国许多单位开展了这方面的研究工作,但有关的研究报道还不多;特别是

室内培养两索线虫幼虫为成虫的方法

<正> 索科线虫(Mermithidae)的幼虫主要寄生在昆虫体内,发育到一定时期,离开宿主到土壤中发育为成虫.过去从宿主体内取出的索科线虫幼虫,往往不能正确鉴定种类,因此解决寄生幼虫培养为成虫的方法问题,对线虫的分类学、生态学、离体培养及利用索科线虫进行生物防治等,都有重要意义. 我们在1977年至1979年于室内进行两批两索线虫(Amphimermis sp.)的培养试验均获成功.