The mermithid species Isomermis lairdi (Nematoda, Mermithidae), previously only known in Africa, found in Europe

Abstract

The present work contributs to the knowledge on the aquatic mermithids (Nematoda, Mermithidae) occurring in black flies – an insufficiently studied group of parasitic nematodes. Isomermis lairdi Mondet, Poinar & Bernadou, 1977, described from larvae of Simulium damnosum Theobald, 1903 in Western Africa, is reported to occur in Bulgaria. The species was isolated from larvae of Simulium ornatum Meigen, 1818 in a local population of simuliids in a mountain stream near Jeleznitsa Village, Sofia district. Postparasitic juveniles of mermithids were obtained from the hosts and reared to the adult stage. The species was identified by morphological and morphometrical characters of postparasitic juveniles, and of male and female individuals. In the summer of 2012 a relatively high rate of mermithid infection in a local host population was detected (prevalence up to 44.1%). In August of the next year host abundance had considerably declined and other simuliid species, Simulium variegatum Meigen, 1818 and Simulium reptans (Linnaeus, 1758), predominated in the investigated locality. In West Africa, Isomermis lairdi is considered to be a potential biological agent for reducing the population density of the Simulium damnosum complex – the main vector of human onchocerciasis. In Europe, species of the Simulium ornatum complex are among the vectors of onchocerciasis of cattle and deer. The mermithids presumably play a certain role in the epidemiology of these diseases. A brief discussion on the taxonomy of the genus Isomermis Coman, 1953, and of the feasibility of molecular methods in mermithid taxonomy is provided. The species Isomermis lairdi is reported for the first time from Europe.

Nematode endoparasites do not codiversify with their stick insect hosts

“…) while the family as a whole is cosmopolitan and infects a broad range of invertebrates (Poinar ; Mebrahtu ; Kaiser ; Vandergast and Roderick ; Nikdel et al. ; Gradinarov ). Nevertheless, it remains possible that some mermithid species are generalists and use a broad range of hosts.…”

“…Although the ecology and biology of the Timema endoparasites have never been studied specifically, the ecology of a range of mermithid nematode species has been well documented (e.g., Nickle 1972;Poinar 1975;Poinar et al 1976;Platzer 2007). Mermithid species are typically characterized by strong host specificity (Stoffolano 1973;Kennedy 1975;Rohde 1979Rohde , 2002Noble et al 1989;Sasal et al 1998) while the family as a whole is cosmopolitan and infects a broad range of invertebrates (Poinar 1985;Mebrahtu 1987;Kaiser 1991;Vandergast and Roderick 2003;Nikdel et al 2011;Gradinarov 2014). Nevertheless, it remains possible that some mermithid species are generalists and use a broad range of hosts.…”

Rarely reported, widely distributed, and unexpectedly diverse: molecular characterization of mermithid nematodes (Nematoda: Mermithidae) infecting bumble bees (Hymenoptera: Apidae:Bombus) in the USA

“…Of the handful of species that have been well researched, many appear to have wide geographic distributions. For example, Isomermis lairdi , a parasite of black fly (Diptera: Simuliidae) larvae, are found in different simuliid hosts throughout Africa and in Europe, and are morphologically most similar to I. benevolus , I. rossica and I. wisconsinensis , species known from Guatemala (North America), throughout Europe, and the USA (North America), respectively (Gradinarov, 2014). Similarly, M. nigrescens has been recorded from a variety of hosts across Europe, Asia, North America, South America, and, more recently, from Australia and New Zealand, where they were thought to have been anthropogenically introduced (Presswell et al 2015).…”

“…Similarly, M. nigrescens has been recorded from a variety of hosts across Europe, Asia, North America, South America, and, more recently, from Australia and New Zealand, where they were thought to have been anthropogenically introduced (Presswell et al 2015). Efforts to expand our knowledge of the biology, host ranges and distributions of mermithids have been complicated by a troublesome taxonomic treatment of the group (Gradinarov, 2014).…”

Australian Ants Hosting Parasitic Nematodes: Developmental and Physiological Interactions

“…Up to 25% of ant workers can be infected [5], more in other insect taxa, e.g. 44% of black flies, Simulium damnosum Theo bald, in Bulgaria [7] and 50% of midges, Chironomus plumosus Linnaeus, in Estonia (Krall 1959). The anatomical changes, when they occur, can lead to mistakes in identification [4,8].…”