First report on Mermithidae (Mermithida) infection in Ligidium sp. (Isopoda,Ligiidae)

Specimens of Ligidium sp. (Crustacea, Isopoda, Oniscidea) collected from Kanagawa Prefecture in Japan were found to be infected with parasitic nematodes. We have obtained two Mermithidae (Nematoda) by dissecting the fresh specimen and from the dead specimen of Ligidium, which marks the second known discovery of a mermithid infection in the order Isopoda. Herein, a report on the nuclear 28S rDNA and 18S rDNA sequence of the isolated Mermithidae nematodes and on the morphology of the juveniles is provided.     

Heydenius araneus n.sp. (Nematoda: Mermithidae), a parasite of a fossil spider, with an examination of helminths from extant spiders (Arachnida: Araneae)

Abstract. A mermithid, a parasite of a spider (Araneae: Thomisidae) in Baltic amber (40 mya), is described as Heydenius araneus n.sp. (Nematoda: Mermithidae) and represents the first fossil record of a nematode parasite of an arachnid. After a critical examination of reports of naturally occurring helminths of extant spiders, I conclude that although mermithid parasitism is well established in this host group, previous reports of hairworm parasites of spiders are "nomina dubia," putative records, or refer to mermithid nematodes.     

A molecular revision of the taxonomic status of mermithid parasites of black flies from Quebec (Canada)

The four currently recognized mermithid (Nematoda) species parasitizing black flies (Diptera: Simuliidae) from Northeast America were distinguished using discriminatory PCR primers aimed at COI and 18S rDNA. Isomermis wisconsinensis, Gastromermis viridis and Mesomermis camdenensis were easily differentiated using either genomic target, even for juvenile mermithids damaged beyond morphological recognition. However, specimens from Mesomermis flumenalis being identical in external morphology and producing a unique-sized PCR product were classified by sequence data into four clearly distinguished molecular variants. This quartet was made of two winter and two summer ‘physiological variants’, including one which also belonged to, but diverged early from the rest of the Mesomermis genus. Combining the multiplex PCR and sequencing approaches allowed for the characterization of a multiple parasitism which simultaneously implicated I. wisconsinensis and two M. flumenalis variants. With another instance where parasites were identified by morphology only, this is the first report of black fly parasitism by multiple mermithid species. A phylogenetic tree built by combining our sequences to previous GenBank entries likely indicates a monophyletic origin for the mermithid family, but also suggests that differentiation between parasite genera sometimes occurred before the evolutionary emergence of the actual host group.     

Thaumamermis cosgrovei n. gen., n. sp. (Mermithidae: Nematoda) parasitizing terrestrial isopods (Isopoda: Oniscoidea)

Summary A new mermithid nematode, Thaumamermis cosgrovei n. gen., n. sp. (Mermithidae: Nematoda) was found parasitizing two terrestrial isopods (Isopoda: Oniscoidea) in California. The hosts, Armadillidium vulgare (Latr.) (a pillbug) and Porcellio scaber (Latr.) (a sowbug) represent the first cases of isopods attacked by mermithid nematodes. The genus Thaumamermis can be distinguished from all previously described mermithids by the extremely dimorphic spicules, one being short and broad and the other long and filiform. It has been discovered that the nematodes are infected with an iridiovirus which commonly destroys the isopod hosts. ac]19800917     

Strelkovimermis spiculatus n. sp. (Mermithidae: Nematoda) Parasitizing Aedes albifasciatus Mac. (Culicidae: Diptera) in Argentina

Strelkovimermis spiculatus n. sp. (Mermithidae: Nematoda), a parasite of the mosquito Aedes albifasciatus Mac. in Argentina, is described. Diagnostic characters of this species include a ventrally shifted mouth opening and spicules fused at the tips. The mermithid has been reared on Culex pipiens L. larvae in the laboratory.     

A new mermithid nematode from Ablabesmyia monilis (L.) (Diptera: Chironomidae) in northern Minnesota

Limnomermis steineri n. sp. (Nematoda: Mermithidae) is described from the hemocoel of male, female, and intersex imagos of Ablabesmyia (s. str.) monilis (L.) eclosing from Lake Ozawindib and Lake Alice Bog in northern Minnesota during summers 2000-2005. The species is distinguished from other described members of the genus. Paramermis rosea is returned to Limnomermis. A review of adequately described members of the genus is included. One species of the genus has been reported previously from the Nearctic Realm. Emphasis is placed on the need for host identification, larger number of specimens of both mermithid sexes, and information on the intensity of infections to enable more precise range comparisons in mermithid biometrics.     

Nematode (Nematoda: Mermithidae) and hairworm (Nematomorpha: Chordodidae) parasites in Early Cretaceous amber

The present report describes a mermithid nematode (Nematoda: Mermithidae) and a gordiid hairworm (Nematomorpha: Chordodidae) from Early Cretaceous Burmese amber dated at 100-110 million years. The mermithid, Cretacimermis protus sp. n., is emerging from a biting midge (Diptera: Ceratopogonidae) while the hairworm, Cretachordodes burmitis, gen. n., sp. n. had already emerged from its host. These rare specimens represent the first fossil mermithid parasite of a ceratopogonid midge and second oldest described nematode and the earliest known and only Mesozoic fossil of the phylum Nematomorpha. A list of previously described fossil mermithids is included.     

Hexamermis cathetospiculae n. sp. (Mermithidae: Nematoda), a Parasite of the Rice Stemborer,Tryporyza incertulas (Wlk.) (Pyralidae: Lepidoptera) in Malaysia

Hexamermis cathetospiculae n. sp. (Mermithidae: Nematoda), a parasite of the rice stemborer, Tryporyza incertulas (Wlk.), is described. This mermithid was observed to control the stemborer in Malaysia. It is distinguished from other members of the genus by the shape of the vagina, the nearly straight spicules, and the form of the amphids.     

Thaumamermis zealandica n sp (Mermithidae: Nematoda) parasitising the intertidal marine amphipod Talorchestia quoyana (Talitridae: Amphipoda) in New Zealand,with a summary of mermithids infecting amphipods

A new nematode, Thaumamermis zealandica n. sp. (Mermithidae; Nematoda), is described parasitising the intertidal marine amphipod Talorchestia quoyana Milne-Edwards (Talitridae) from the coast of South Island, New Zealand. The new species is characterised by the degree of dimorphism of the spicules, the arrangement of the genital papillae, the shape and length of the vagina and the anteriorly-placed amphids. This is the first known marine host of a member of the family Mermithidae. Published records of mermithid nematodes from amphipods are presented.     

Potentialities of mermithid nematodes for the biocontrol of blackflies (Diptera: Simuliidae)--a review

Mermithids comprise a family of nematodes which invariably kill/sterilize their insect host(s). These nematodes have considerable potential as biocontrol agents of agricultural insect pests and medically important insect vectors. More specifically, mermithid nematodes appear to regulate natural population of blackflies. The taxonomy of the Mermithidae has been only partially evaluated and the taxonomic status of many representatives is uncertain. At least three mermithid genera and species parasitize North American blackflies, although a more varied mermithid fauna probably exists. The host specificity of mermithid parasites of simuliids is variable, but these nematodes do not appear to infect other stream fauna. The sporadic distribution of mermithid parasites of simuliids among potential biotopes may be associated with a relatively inefficient mode of dispersal for such nematodes. Detailed information is lacking concerning stages in the life cycles of these pathogens and their synchronization with the simuliid host. Mermithids cause pathogenic effects upon several blackfly tissues, although no information is available concerning physiological manifestations of mermithid parasitism in blackflies. A brief review of the present state of knowledge of simuliid taxonomy and bionomics is presented. The physiology of blackflies and their mermithid parasites has been largely ignored. The potentialities of mermithid nematodes for the biocontrol of blackflies are assessed and a feasible research programme presented, in relation to the present state of knowledge of mermithid-simuliid interrelationships and related areas of insect nematology.     

Isomermis bipapillatus n. sp. and Gastromermis mesostoma n. sp. (Mermithidae: Nematoda), parasites of Simulium japonicum (Simuliidae: Diptera) in Japan

Summary Two new species of the Mermithidae (Nematoda) are described from the Japanese blackfly Simulium japonicum Matsumura. They are the first representatives of Gastromermis and Isomermis from Japan. Gastromermis mesostoma n. sp. is characterized by a terminal or near terminal mouth, 6 hypodermal cords and the absence of cloacal or vulvar lips. Isomermis bipapillatus n. sp. is characterized by the small size of the spicules, their curved shape and by a pair of terminal hypodermal protuberances in the tail. This work was in part supported by a grant (No. 58570188) from the Japanese Ministry of Education, Science and Culture This work was in part supported by a grant (No. 58570188) from the Japanese Ministry of Education, Science and Culture     

Prevalence of parasitism and adult survival time of Aedes albifasciatus (Diptera: Culicidae) parasitized by Strelkovimermis spiculatus (Nematoda: Mermithidae)

We described the carryover of Strelkovimermis spiculatus (Poinar and Camino) (Nematoda: Mermithidae) from mosquito larvae, the primary site of maturation, to adults. We analyzed the survival time of male and female Aedes albifasciatus (Macquart) (Diptera: Culicidae) parasitized by S. spiculatus, the time of emergence of nematodes from adult mosquitoes, and the state of parasitism in the same mosquito cohorts during the immature stages. Mosquito larvae with single and multiple parasitism (up to 11 parasites) were observed. The mortality of mosquito larvae and adults was produced in all cases where at least one mermithid emerged. The mortality of S. spiculatus showed an increasing trend in mosquito larvae with larger numbers of nematodes and was higher in larvae parasitized by eight or more nematodes. Maximum survival of parasitized adult females of Ae. albifasciatus was 38 days, while non‐parasitized adult males and females survived 39 and 41 days, respectively. Strelkovimermis spiculatus mortality was observed in Ae. albifasciatus larvae with single or multiple parasitisms. The spread of mermithid parasitism in adult mosquito populations is discussed.     

Parasitoid-induced behavioral alterations of Aedes aegypti mosquito larvae infected with mermithid nematodes (Nematoda: Mermithidae).

A wide range of parasites are known to cause behavioral changes in their hosts and parasitized insects are especially amenable to the study of such changes. The majority of studies addressing parasite-induced behavioral alterations have focused on parasites with complex life cycles and the adaptive nature of such changes. Behavioral changes caused by parasitoids, single-host parasites that kill their host upon emergence, have been studied less and the adaptive nature of these changes is likely to be different than those in complex life cycles. I investigated behavioral alterations in Aedes aegypti mosquito larvae infected with parasitoid nematodes (family Mermithidae). I conducted several experiments in which I tested the following hypotheses: 1) Mermithid nematodes induce behavioral changes in mosquito larvae and the changes are density dependent. 2) Different species of mermithid nematodes induce similar changes in mosquito larvae behavior. 3) Behavioral alterations vary with mermithid developmental stage. 4) Mosquito larvae infected with mermithid nematodes behave similarly to uninfected food-deprived mosquito larvae. I found that 4th instar Ae. aegypti infected with Romanomermis culicivorax or Strelkovimermis spiculatus exhibited resting behaviors significantly more often than uninfected controls but that intensity of infection did not affect activity levels. In earlier instars, infected mosquito larvae were more active than uninfected control larvae in some behaviors associated with feeding. There was no significant difference between infected and uninfected food-deprived mosquitoes in nine of the ten behaviors observed. The decrease in activity of late instar Ae. aegypti larvae infected with mermithids may be a parasitoid adaptation that reduces the risk of predation and thus increases host and parasitoid survival. The increase in feeding activity in earlier instars as well as the similarity between uninfected food-deprived and infected Ae. aegypti behavior may indicate that these behaviors are adaptive for the parasitoid, increasing nutritional acquisition for successful parasitoid development.     

A new mermithid species (Nematoda) from chironomid imagos eclosing from Lake Ozawindib in northern Minnesota

Hydromermis biesboeri n. sp. (Nematoda: Mermithidae) is described from the hemocoel of imagos of chironomid host species eclosing from Lake Ozawindib in northern Minnesota in July and August 2008 and 2009. The new species is distinguished from the other 28 described species in the genus by terminal mouth, wide oval (male) and long oval (female) amphids with a dorsal commissure, tapered and rounded posterior ends, split base of the spicule, short protractor muscles in males, and by females having an S-shaped vagina with equal-length terminal limbs. The new species represents the 10th Hydromermis mermithid species described, or reported, from the region and the second from Lake Ozawindib.     

<Emphasis Type="Italic">Allomermis solenopsi</Emphasis> n. sp. (Nematoda: Mermithidae) parasitising the fire ant <Emphasis Type="Italic">Solenopsi s invicta</Emphasis> Buren (Hymenoptera: Formicidae) in Argentina

Allomermis solenopsi n. sp. (Mermithidae: Nematoda) is described from the fire ant Solenopsis invicta Buren (Hymenoptera: Formicidae) in Argentina. Diagnostic characters of the new species include stiff and erect processes on the surface of the mature egg, small female amphids, extension of the latero-medial rows of male genital papillae beyond the middle rows, an obliquely truncate spicule tip and a ventrally swollen male terminus. This is the first record of Allomermis Steiner, 1924 from South America and the first host record for members of this genus. Previous records of mermithids from Solenopsis spp. are summarised. The placement in Allomermis was confirmed by molecular analyses based on nuclear 18S ribosomal DNA sequences, the first such molecular framework for the Mermithidae. The possible life-cycle of the parasite is discussed, with the aim of using A. solenopsi as a biological control agent for fire ants in the United States.     

Management of insecticide resistance in control of the Simulium damnosum complex by the Onchocerciasis Control Programme, West Africa: potential use of negative correlation between organophosphate resistance and pyrethroid susceptibility

1. Resistance of some populations of the Simulium damnosum complex to temephos (100-fold at the LC50 level), with degrees of cross-resistance to chlorphoxim (14-fold) and other organophosphate insecticides, follows intensive larvicidal control of S. damnosum s.l. in West African river systems since 1975 by the WHO Onchocerciasis Control Programme. 2. Larvae of at least three sibling species of the S. damnosum complex have become organophosphate-resistant: these are the forest species S. sanctipauli Vajime & Dunbar and the savanna species S. sirbanum V. & D. and S. damnosum Theobald sensu stricto. 3. Organophosphate-resistant S. damnosum s.l. larvae show increased susceptibility to some organochlorine and pyrethroid insecticides, especially to permethrin (up to 11-fold) and OMS 3002 (up to 17-fold), as compared with organophosphate-susceptible populations. 4. This differential susceptibility is reflected by increased pyrethroid efficacy in operational use for river treatments against organophosphate-resistant field populations of S. damnosum s.l. larvae. Treatment of 100 km of the lower Bandama River in 1985 showed that permethrin at the highly selective dosage of 10 min exposure to 0.01 mg/l caused reversion towards organophosphate-susceptibility of the target population of S. sanctipauli. This effect was less pronounced when the Comoe River was treated at the lower dosage of 0.005 mg/l for 10 min. 5. To overcome temephos-resistance, it is proposed that the most rational usage of currently available larvicides would involve the following annual sequence of treatments: Bacillus thuringiensis serotype H-14 when river discharge is below 75 m3/s; chlorphoxim for about eight weekly treatment cycles after river discharge rises; permethrin (or alternative pyrethroid) for up to six treatment cycles--this should eliminate any incipient selection for chlorphoxim-resistance; resume chlorphoxim (or perhaps carbosulfan) treatments until river discharge falls below 75 m3/s permitting resumed use of B.t. H-14.     

Molecular characterization and physical mapping of two classes of 5S rDNA in the genomes of Gymnotus sylvius and G. inaequilabiatus (Gymnotiformes, Gymnotidae)

The nucleotide sequences of the 5S rRNA multigene family and their distribution across the karyotypes in 2 species of Gymnotiformes, genus Gymnotus (G. sylvius and G. inaequilabiatus) were investigated by means of fluorescence in situ hybridization (FISH). The results showed the existence of 2 distinct classes of 5S rDNA sequences in both species: class I and class II. A high conservative pattern of the codifying region of the 5S rRNA gene was identified, contrasting with significant alterations detected in the nontranscribed spacer (NTS). The presence of TATA-like sequences along the NTS of both species was an expected occurrence, since such sequences have been associated with the regulation of the gene expression. FISH using 5S rDNA class I and class II probes revealed that both gene classes were collocated in the same chromosome pair in the genome of G. sylvius, while in that of G. inaequilabiatus, class II appeared more disperse than class I.     

First extant records of mermithid nematode parasitism of Auchenorrhyncha in Europe

Parasitic nematodes of the family Mermithidae were found within four specimens of Auchenorrhyncha from two families (Cicadellidae and Delphacidae). This appears to be the the first extant example of mermithid parasitism of Auchenorrhyncha in Europe. The insect hosts were collected from agricultural grassland field margins at three locations in Ireland during a farmland biodiversity study in 2007.     

Susceptibility of ten species of mosquito larvae to the parasitic nematode Romanomermis iyengari and its development

Ten species of mosquitoes (Diptera: Culicidae) from five genera were exposed to preparasites of the tropical mermithid nematode species Romanomermis iyengari (Welch) (Nematoda: Mermithidae), a strain isolated in 1978 from Pondicherry. By exposing mosquito larvae during the second instar, nematode infection was invariably lethal, the rate being highest in Culex sitiens Wiedemann (95%) followed by Cx. quinquefasciatus Say (90%), Aedes aegypti (L.) (79%), Anopheles subpictus Grassi (64%), Ae. albopictus (Skuse) and Armigeres subalbatus Coquillett (62%), Cx. tritaeniorhynchus Giles (57%), Mansonia annulifera (Theobald) (46%), An. stephensi Liston (40%) and An. culicifacies Giles (36%). When fourth-instar larvae were exposed, the infection was highest in Ar. subalbatus (66%), followed by An. stephensi (52%), Cx. quinquefasciatus (47%), Ae. aegypti and An. subpictus (42%), Ae. albopictus (30%), An. culicifacies (29%), Cx. sitiens (24%), Cx. tritaeniorhynchus (19%) and Ma. annulifera (8%), with 2-45% of infected culicines surviving to adulthood. The parasitic phase of the nematode lasted 5-7 days in all the host species, yielding 1.1-3.2 parasites per II instar and 1.1-2.5 parasites per IV instar. The overall output of parasites per 100 mosquito larvae (infected + uninfected) was highest for Ae. aegypti when mosquitoes were exposed during II instar (2.53 parasites/larva) and for Ar. subalbatus when mosquitoes were exposed during IV instar (1.65/larva), and lowest for Ma. annulifera exposed during IV instar (0.09/larva). For routine laboratory culture of R. iyengari it is convenient to employ Cx. quinquefasciatus as the host yielding 90-190 parasites/100 larva.