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The Mermithidae are primarily simple parasitoids of insects. In this study, we report the first observation of hyperparasitism by mermithid nematodes. Two Mermithidae individuals emerged from a specimen of the parasitoid wasp Coleocentrus incertus collected in Hokkaido, Japan. Although the nematodes were in the juvenile stage and many morphological characteristics were underdeveloped, we were able to observe cross fibre layers on the cuticles. A molecular sequence analysis of the 18S ribosomal DNA suggested that the nematode belonged to the genus Hexamermis, which was supported by the presence of the cross fibre layers. The phylogenetic analysis also suggested a close relationship between our specimens and ‘Mermithidae sp. NM1’, a taxon found in bumblebees, as differences between the sequences of the two taxa were minimal; however, further research is required to confirm the species’ identity. Hyperparasitism by nematodes is rare and is typically unsuccessful in non-host species, yet the nematodes in this study successfully parasitised a parasitoid wasp. Our study is the first to demonstrate that mermithid nematodes can exhibit hyperparasitism in addition to their known parasitic behaviour. The parasitic strategies of Mermithidae nematodes appear to be more flexible than previously assumed, indicating a high degree of adaptability as parasites. [ABSTRACT FROM AUTHOR]

Mermithidae is a family of nematodes that parasitize a wide range of invertebrates worldwide. Herein, we report nematodes that were unexpectedly found in three of 486 adult stable flies (Stomoxys calcitrans) captured from three farms (F1, F2, and F3) in different regions of Gifu Prefecture, Japan. We aimed to characterize these nematodes both at the morphological and molecular level. Morphological studies revealed that the nematodes were juveniles of Mermithidae. Phylogenetic analysis based on 18S and 28S rDNA indicated that the mermithids from farms F1 and F2 could be categorized into the same cluster as Ovomermis sinensis and Hexamermis sp., whereas the mermithid from farm F3 clustered with Amphimermis sp. Additionally, these mermithids could be categorized within the same clusters as related mermithids detected in Japan that parasitize various arthropod orders. Our findings suggest that these stable flies may have been parasitized by mermithids already present in the region and that genetically distinct species of mermithids occur across Japan. To the best of our knowledge, this is the first report of mermithids parasitizing adult stable flies in Japan.

Mermithid parasitoids are well known to infect spiders; however, their impact on hosts and their taxonomic identity are still poorly analyzed. We present the first record of a mermithid nematode infection in the spider genera Piratula (Lycosidae) and Coelotes (Agelenidae), and in the species Alopecosa pulverulenta and Pardosa paludicola (Lycosidae). We describe the maldevelopment of the spiders' female genitalia induced by the parasitoid and summarize data on the impact of nematode parasitoids on spider development and behaviour. Phylogenetic analysis, based on the 18S rDNA, showed that spider parasitoidism arose independently in different branches of the phylogenetic tree of the family Mermithidae. [ABSTRACT FROM AUTHOR]

Medically, the most dangerous genera are Anopheles, Aedes and Culex due to their ability to transmit mosquito-borne human diseases, such as malaria, yellow fever, chikungunya, lymphatic filariasis, dengue fever, hemorrhagic fever and encephalitis. Mosquito control is a prerequisite work for fighting the increasing mosquito populations and mosquito-borne diseases. Generally, chemical insecticides have been widely used to suppress mosquito populations but these chemicals were evidenced to be less-than-perfect solutions for the long-lasting control of mosquitoes due to the development of insecticide resistance in all mosquito species and different hazards all over the world. Therefore, the search for alternative agents is urgent to avoid or minimize the insecticidal hazards on ecosystem components. One of the potential alternatives is biological control which received great research attention in the world. One of these biocontrol agents is Entomopathogenic Nematodes (EPNs). Therefore, the objective of the present article was primarily to review the current knowledge focusing on the use of EPNs for controlling mosquito vectors. It highlighted the global attention to EPN application as a novel strategy for combating mosquito vectors. Also, this review discussed the pathogenic efficiencies of three EPNs, Mermithidae, Steinernematidae and Heterorhabditidae. Other important issues had been reviewed, such as diverse susceptibility of mosquito larvae and variation of EPN virulence, Key parameters and environmental conditions affecting the virulence of EPNs against mosquito larvae, EPN-symbiotic bacteria and their potential role for the control of mosquito vectors and Suppressive activity of EPN/symbiotic bacteria complex against innate immune defences of mosquito larvae. This review provided, also, some future prospects for the EPN application for controlling mosquito vectors. In conclusion, EPNs can be equal to chemical pesticides against human-disease-transmitting mosquitoes if they are applied in critical concentration under suitable environmental conditions and precautions for application. [ABSTRACT FROM AUTHOR]

Mermithid parasitoids are well known to infect spiders; however, their impact on hosts and their taxonomic identity are still poorly analyzed. We present the first record of a mermithid nematode infection in the spider genera Piratula (Lycosidae) and Coelotes (Agelenidae), and in the species Alopecosa pulverulenta and Pardosa paludicola (Lycosidae). We describe the maldevelopment of the spiders’ female genitalia induced by the parasitoid and summarize data on the impact of nematode parasitoids on spider development and behaviour. Phylogenetic analysis, based on the 18S rDNA, showed that spider parasitoidism arose independently in different branches of the phylogenetic tree of the family Mermithidae.

In this work, we investigated parasites of the firebug Pyrrhocoris apterus in Austria and demonstrated that in addition to the extensively studied Leptomonas pyrrhocoris, it can also be infected by Blastocrithidia sp. and by a mermithid, which for the first time has been characterized using molecular methods. This diversity can be explained by the gregarious lifestyle, as well as the coprophagous and cannibalistic behavior of the insect hosts that makes them susceptible to various parasites. In addition, we showed no tight association of the L. pyrrhocoris haplotypes and geographical locations (at least, considering the relatively small scale of locations in Austria) implying that the natural populations of L. pyrrhocoris are mixed due to the mobility of their firebug hosts. [ABSTRACT FROM AUTHOR]

Heleidomermis magnapapula parasitizes the blood-feeding midge Culicoides sonorensis. Most (84%) single mermithid infective second stage juveniles (J2) developed into adult females, while parasitism by multiple J2 yielded 97% male adults. Nematodes emerged from the midge larval host as adults and mated immediately; females were ovoviviparous. Host larvae were exposed to nematode J2 and examined intact microscopically to score initial parasite load. Midge hosts were reared individually. Premature midge death, nematode survival within the host, and emerging adult nematode sex ratio and size as a function of load and host size were all tracked. Higher nematode loads produced smaller adult nematode males. The higher loads also increased and accelerated premature host death. Emergence of > 7–9 adult nematode males was rare, but up to 19 tiny males emerged from a single host. Larger midges supported higher parasite loads and a larger total volume of emerged nematode biomass. Virgin adult nematode males then were paired with females of variable, known sizes (volume) and held to determine size effects on fertility (egg hatch), and male survival (longevity). Tested adult males ranged in size from 0.0025 – 0.0334 mm3 and females from 0.0121 – 0.1110 mm3. Logistic regression indicated female nematode fertility was positively influenced by male nematode size, while nematode load and female nematode size had no significant effect. While fertility was reduced statistically in smaller males, even some of the smallest male and female individuals could be fertile. Findings are related to field studies in this system.

Los nematodos mermítidos juveniles parasitan diferentes grupos de invertebrados, entre los que se encuentran las hormigas, en las que suelen inducir cambios morfológicos. Los registros de parasitación de hormigas por estos nematodos son relativamente escasos a escala global, con pocos datos referentes a la península ibérica. En este trabajo se cita por primera vez su presencia como parásito de la casta obrera de Lasius flavus y en obreras y pupas de Tetramorium grupo caespitum por primera vez en el género. Se comparan la morfología y biometría de los especímenes infestados con las de los sanos de las mismas especies.

This document provides information on the role of mermithid nematodes in controlling insect pests. It discusses the advantages of using mermithids as a biological control alternative to chemical pesticides, such as their non-polluting nature and selectivity. However, there are also constraints to their use, such as vulnerability to environmental factors and incompatibility with agrochemicals. The document suggests that biological control should be adopted by farmers and residents to control pests, and references various studies on the efficacy of mermithid nematodes in controlling specific insect pests. Additionally, the document includes references to scientific articles on the parasitism of mermithid nematodes on various insect species, providing valuable information for researchers. [Extracted from the article]

Almost every animal trait is strongly associated with parasitic infection or the potential exposure to parasites. Despite this importance, one of the greatest challenges that researchers still face is to accurately determine the status and severity of the endoparasitic infection without killing and dissecting the host. Thus, the precise detection of infection with minimal handling of the individual will improve experimental designs in live animal research. Here, we quantified extracellular DNA from two species of endoparasitic worm that grow within the host body cavity, hairworms (phylum Nematomorpha) and mermithids (phylum Nematoda), from the frass of their insect host, a cave wētā (Orthoptera: Rhaphidophoridae) and an earwig (Dermaptera: Forficulidae), respectively. Frass collection was done at two successive time periods, to test if parasitic growth correlated with relative DNA quantity in the frass. We developed and optimized two highly specific TaqMan assays, one for each parasite‐specific DNA amplification. We were able to detect infection prevalence with 100% accuracy in individuals identified as infected through post‐study dissections. An additional infection in earwigs was detected with the TaqMan assay alone, probably because some worms were either too small or degraded to observe during dissection. No difference in DNA quantity was detected between sampling periods, although future protocols could be refined to support such a trend. This study demonstrates that a noninvasive and minimally stressful method can be used to detect endoparasitic infection with greater accuracy than dissection alone, helping improve protocols for live animal studies. [ABSTRACT FROM AUTHOR]

The extensive use of chemical insecticides to control mosquitoes led to the development of insecticide resistance and environmental health hazards. This caused a surge in interest in eco-friendly biocontrol agents. The present study aimed to explore the susceptibility of different instar larvae of the common mosquito, Culex pipiens Linnaeus, 1758, to the mermithid nematode, Romanomermis iyengari Welch, 1964. Moreover, the effects of R. iyengari on the mosquito pupal developmental time, adult emergence, longevity, female fecundity, as well as egg-hatching rate were determined after larval treatment with an LC50 quantity of the nematode pre-parasites. Different instars of Cx. pipiens (1st–4th) were exposed separately to R. iyengari at concentrations of 1–6 pre-parasites/mosquito larva. Mortality rates of mosquito larvae were observed and the LC50 values were calculated. The estimated LC50 values for the 1st–4th larval instars were 3.18, 2.73, 3.79 and 4 pre-parasites/larva, respectively. Mean percent mortality of the 1st–4th larval instars ranged from 10–94%, 16–100%, 4–100% and 0–52%, respectively. The results indicated that exposure of 4th larval instar to the LC50 of R. iyengari pre-parasites significantly prolonged the duration of pupal development, reduced the percentage of emerged adults and reduced mosquito female fecundity compared with the control. In contrast, adult longevity and the egg-hatching rate did not differ between the control and the exposed group. In conclusion, this isolate of R. iyengari could be a promising biocontrol agent for Egyptian Cx. pipiens. Other trials are required to assess the biocontrol potential of this parasite in field conditions. [ABSTRACT FROM AUTHOR]

Aedine mosquitoes go through unfavorable periods as dormant eggs. However, extended dormancy times lead to a depletion of egg reserves, which might be partially compensated by changes in larval-feeding behavior. Changes in larval behavior may also be induced by parasitism by mermithids probably as a strategy to reduce the impact of the parasite on the host. The most abundant floodwater mosquito in southern South America is Aedes albifasciatus (Diptera: Culicidae), a species naturally parasitized by Strelkovimermis spiculatus (Nematoda: Mermithidae). This study aimed to evaluate the behavior of fourth-instar larvae of Ae. albifasciatus from eggs with 2, 4, and 6 months of dormancy, parasitized or not by S. spiculatus. To achieve this, eight categories of behavior were defined, and then, each individual was observed for 5 min, and its behaviors and their duration were recorded. The behaviors with the highest percentage of observation time were still (50.1%) and wriggle swimming (33.6%), while those with the lowest percentage of observation time were those involving active foraging (less than 8%). A great variability in the behaviors was observed among individuals within the same treatment. The type and duration of each behavior did not vary in relation to egg dormancy time or parasitism, but parasitism affected the level of larval activity. Parasitized larvae performed, on average, fewer behaviors than non-parasitized larvae. This result supports the hypothesis that S. spiculatus parasitism affects the behavior of Ae. albifasciatus larvae by reducing their level of activity. [ABSTRACT FROM AUTHOR]

Juvenile mermithid nematodes were found to parasitize winged females (sexuparae) of Eriosoma auratum and Tetraneura radicicola. The morphological characteristics of mermithid nematodes are briefly described. The 18S rDNA and 28S rDNA obtained from one nematode were sequenced and used to construct a Bayesian phylogenetic tree, on which the host ranges of mermithid nematodes were represented. Our study indicated that mermithid parasitism of sexuparae led to fewer and smaller sexual female embryos. This is the first record of a mermithid in relation to eriosomatine aphids and the fourth record with respect to Aphididae. [ABSTRACT FROM AUTHOR]

Many spiders are parasitized by mermithid nematodes today, but their fossil record is very scarce. Previously, only two examples were reported, from the Eocene Baltic amber and the Miocene Dominican amber, respectively. In this study, we report the earliest fossil record of a mermithid nematode–spider association from mid-Cretaceous Kachin amber of northern Myanmar. The mermithid nematode, Cretacimermis dolor sp. nov., was observed emerging from a spider of Haplogynae clade. This discovery indicates that parasitic relationships between spiders and nematodes were already established during the Cretaceous. [ABSTRACT FROM AUTHOR]

Nematodes of the family Mermithidae were found parasitizing adults and nymphs of the species Hortensia similis (Auchenorryncha: Cicadellidae). The host specimens were collected from weeds associated to citrus orchards located in Corrientes, Argentinean province, during a biodiversity study in 2015. As far as we know, this is the first South American example of leafhoppers parasitized by mermithids.

This study aimed to evaluate the effects of egg dormancy times on susceptibility of larvae of the floodwater mosquito Aedes albifasciatus (Diptera: Culicidae) to parasitism by their natural enemy Strelkovimermis spiculatus (Nematoda: Mermithidae) and on their life history traits. Aedes albifasciatus eggs stored for 2, 4, 6, 8 and 10 months were hatched, and the larvae either exposed to S. spiculatus (treatment group) or not exposed (control group). Egg dormancy time had a negative effect on the retention of parasites, but no effect on the prevalence and intensity of parasitism or the melanization of nematodes. The survival to adulthood of control individuals decreased as dormancy time increased, whereas that of exposed individuals that remained uninfected was constant and low. A trend towards increasing development times with longer dormancy times was detected in the control group, but not in the exposed noninfected group. The results suggest nonconsumptive effects of parasites in exposed but not infected larvae from eggs with short dormancy times. In contrast, the relatively low fitness of larvae from eggs with long dormancy times regardless of their contact with the nematodes may be the result of the nutritional deprivation during the egg stage. [ABSTRACT FROM AUTHOR]

A juvenile specimen of a mermithid (Nematoda) was found parasitizing a third instar nymph of Triatoma sordida from Mato Grosso, Brazil. This is the first record of mermithid parasitism in a triatomine species. The Mermithidae represents a family of nematodes that are specialized insect parasites. Entomonematodes are one of the highly influential agents regulating the population dynamics of insects. This report introduces the opportunity to think about mermithids as a possible candidate for use as triatomine biological control. [ABSTRACT FROM AUTHOR]

Amyna axis (Lepidoptera: Erebidae), Chrysodeixis spp. (C. acuta and C. eriosoma) and Spodoptera spp. (S. exigua and S. litura) (Lepidoptera: Noctuidae) are important polyphagous insect-pests of leguminous crops. A mermithid (Nematoda: Mermithidae) nematode was found parasitizing the larval stages of these insects in the western Indian state of Rajasthan. Morphological and molecular analysis suggests that the nematode might be a species of the genus Hexamermis. The average length of post-parasitic nematode juveniles was 15 cm, and the average greatest body width was 1.5 mm. The vulva was median (V% = 48) without vulval flap. Approximately 100-125 μm long caudal appendages were present on tail. The cross-section revealed the presence of six hypodermal chords at the mid body region, and stichosome was present. The 18S rDNA sequence showed 99% similarity to mermithid nematode. A phylogenetic analysis of 18S rDNA sequences of mermithids resulted in identification of a new clade “Lineage 3” which included representatives of Mermis sp., Isomermis sp., Limnomermis sp., and Pheromermis sp. This is the first report of natural mermithid parasitism of A. axis and Chrysodeixis spp. along with its molecular characterization. [ABSTRACT FROM AUTHOR]

The hemocoel of 26 of 30 (86%) eastern grass shrimps, Palaemon paludosus (Gibbes, 1850) (Decapoda: Palaemonidae), captured during June 2017 from several freshwater lakes near Leesburg and Lake Kissimmee, Florida, was infected by juveniles of a nematode species (Mermithidae sp.). Some infected eastern grass shrimps were preserved whole for histopathology, whereas others were dissected to excise parasitic juvenile nematodes, and still others were kept alive in glass aquaria such that post-parasitic (emerged) juvenile nematodes could be opportunistically observed alive and ultimately preserved. Parasitic and post-parasitic juvenile nematodes had cuticle cross-fibers, cephalic papillae, cup-shaped amphids, a horn-shaped vagina, a trophosome, and a caudal appendage, which collectively diagnosed them as Mermithidae sp. They differed from those of nematomorphs (Nematomorpha) by lacking 4 giant cells anteriorly, tegumental bristles, scale or plate-like areoles, a bifurcate or trifurcate posterior end, and an anus. A phylogenetic analysis of the small subunit rDNA (18S) that included all of the available mermithid sequences corresponding to morphologically diagnosed specimens recovered Mermithidae sp. within the clade of mermithids and sister to Ovomermis sinensis Chen, Jian, and Ren, 1991 . This is the first record of a mermithid infection in a decapod and first report of a mermithid infection in an aquatic crustacean from North America (another mermithid infects a terrestrial isopod there). The high prevalence of infection and the multiple geographic localities harboring infected eastern grass shrimps indicated that these infections were not spurious. Because no other decapod is confirmed as a mermithid host, we suspect that these specimens likely represent a new species with a life cycle worth studying, since none for a mermithid involving a decapod nor a crustacean has been elucidated to date. We also provide a table of all mermithid and nematomorph infections in crustaceans. [ABSTRACT FROM AUTHOR]

Keywords: Agamomermis termitivoratus n. sp.; collective genus; description; Isoptera; Mermithidae; new species; Reticulitermes flavipes; Rhinotermitidae; subterranean termite; taxonomy Susceptibility of damp wood termites and soil and wood dwelling termites to the entomogenous nematode Neoaplectana carpocapsae. Mites and nematodes associated with three subterranean termite species (Isoptera: Rhinotermitidae). Agamomermis termitivoratus n. sp., collective genus, description, Isoptera, Mermithidae, new species, Reticulitermes flavipes, Rhinotermitidae, subterranean termite, taxonomy. [Extracted from the article]

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In this work, we investigated parasites of the firebug Pyrrhocoris apterus in Austria and demonstrated that in addition to the extensively studied Leptomonas pyrrhocoris, it can also be infected by Blastocrithidia sp. and by a mermithid, which for the first time has been characterized using molecular methods. This diversity can be explained by the gregarious lifestyle, as well as the coprophagous and cannibalistic behavior of the insect hosts that makes them susceptible to various parasites. In addition, we showed no tight association of the L. pyrrhocoris haplotypes and geographical locations (at least, considering the relatively small scale of locations in Austria) implying that the natural populations of L. pyrrhocoris are mixed due to the mobility of their firebug hosts., (© 2023. The Author(s).)

A mermithid nematode parasitic to larvae of Conogethes punctiferalis, a serious pest of ginger and turmeric was recorded under field conditions during 2015 at Peruvannamuzhi (Kerala, India). The infection reached epizootic levels during July to September 2015 exceeding 50% mortality in host insect populations and the parasitism ranged from 18.2 to 80.6% and 17.9 to 66.7% in C. punctiferalis collected from ginger and turmeric, respectively. The level of host parasitism by the mermithid was positively correlated with rainfall and negatively influenced by maximum temperature. Molecular analysis of the partial 18S small ribosomal subunit gene region and phylogenetic analysis with other mermithid sequences available in the GenBank indicated that the present nematode clustered with other nematodes belonging to different genera and hence could not be attributed to a specific genus. The pairwise Kimura 2‐parameter (K2P) distance revealed that the closest taxon to the study nematode was an undescribed mermithid species reported to infect slugs with a K2P distance of 0.009. The epizootics caused by this mermithid nematode in the natural populations of C. punctiferalis suggest its potential as a biocontrol agent against a polyphagous pest of international importance. The results of our studies provide a basis for using this nematode as a biocontrol agent for developing integrated pest management strategies against C. punctiferalis. A mermithid nematode parasitic to larvae of Conogethes punctiferalis, a serious pest of ginger and turmeric was recorded under field conditions. The level of host parasitism by the mermithid was positively correlated with rainfall and negatively influenced by maximum temperature. The epizootics caused by this mermithid nematode in the natural populations of C. punctiferalis suggest its potential as a biocontrol agent against a polyphagous pest of international importance. [ABSTRACT FROM AUTHOR]

Planthoppers are serious pests of rice in both tropical and temperate East Asia. In temperate regions, population density has been shown to be largely determined by the rate and timing of immigration from tropical areas. Historical records of planthopper outbreaks in western Japan over 1300 years suggest that the cropping system may influence planthopper populations as the likelihood of an outbreak has increased substantially since the conversion to intensive rice production during the second half of the twentieth century. To investigate this in more detail, planthopper populations were compared in naturally and conventionally farmed paddies in Hiroshima Prefecture. Naturally farmed paddies differed from conventionally farmed ones in the absence of synthetic chemicals and the use of plant compost as the sole source of fertilizer. Paddies farmed naturally for >8 years had less planthopper damage than conventional paddies, slightly lower densities of white-backed planthopper, much lower densities of brown planthopper, and higher rates of planthopper parasitism by the nematodeAgamermis unka. Nematode density and parasitism showed a close correlation with variation in planthopper populations, suggesting that nematodes may control planthoppers in naturally farmed paddies. [ABSTRACT FROM PUBLISHER]

Molecular genetics has proven to be an essential tool for studying the ecology, evolution and epidemiology of parasitic nematodes. However, research effort across nematode taxa has not been equal and biased towards nematodes parasitic in vertebrates. We characterize the evolutionary genetics of the mermithid nematode Thaumamermis zealandica Poinar, 2002 and its host, the sandhopper Bellorchestia quoyana (Milne-Edwards, 1840) (Talitridae: Amphipoda), across sandy beaches of New Zealand's South Island. We test the hypothesis that parasite population genetic structure mirrors that of its host. Sandhoppers and their parasites were sampled at 13 locations along the island's southeastern coast. Sequencing of the mitochondrial gene cytochrome c oxidase subunit 1 (CO1) from B. quoyana reveals a regional pattern of population structure that suggests a northward pattern of dispersal. Surprisingly, no population structure was observed for T. zealandica. In fact, sequencing of three commonly used markers revealed no intraspecific parasite variation. This result suggests that mermithid mtDNA may evolve at an extraordinarily slow pace, perhaps as a result of extensive and frequent changes in gene order and mitochondrial genome length. Furthermore, a mermithid phylogeny based on sequences of the 18S and 28S ribosomal RNA genes suggests that a systematic revision of the family is necessary. [ABSTRACT FROM AUTHOR]

Superparasitism is a common phenomenon in mosquito-parasitic mermithid nematodes. Multiple nematodes are needed in a single host to produce males. Host selection behavior and intraspecific competition among Romanomermis iyengari and Strelkovimermis spiculatus were investigated against their host, Culex pipiens pipiens in laboratory experiments. In a choice assay between previously infected and uninfected host larvae, infectious preparasites of both nematode species could distinguish not only between infected and uninfected hosts, but even between different parasite loads in showing a strong preference for uninfected hosts or hosts with a low parasite load. Host heart rate declined briefly immediately after parasitism. Superparasitism resulted in increased parasite mortality. Scramble competition within mosquito larvae for limited host nutrients, coupled with a skewed sex ratio favoring males, is assumed to lead to parasite population decline and subsequently toward host-parasite population equilibrium. The ability of mermithid preparasites to accurately assess parasite load likely plays an important role in host population dynamics and regulation. [ABSTRACT FROM AUTHOR]

To understand the infection strategies of the mosquito parasitic mermithid nematodes Romanomermis iyengari (Welch, 1964) and Strelkovimermis spiculatus (Poinar and Camino, 1986), we have investigated the foraging behaviors of the pre-parasites of both species. Romanomermis iyengari with body length of 0.99 ± 0.071 mm (twice as S. spiculatus 0.55 ± 0.01 mm) swims faster (2.76 ± 0.13 cm/min) than S. spiculatus (1.61 ± 0.09 cm/min). The nematode pre-parasites of R. iyengari showed negative phototaxis in responding to natural light, which caused them to migrate to shade where mosquito larvae tend to aggregate. This behavior helped the nematode to gain significantly higher parasitism when shade was present (37.7 ± 2.74%) than no shade (11.3 ± 0.95%). In contrast, S. spiculatus pre-parasites had no response to natural light and therefore, shade contributed no parasitism gain to this species. The host searching pattern data indicated that the two species used different strategies for host searching. The pre-parasites of R. iyengari tended to do long range search and responded to host aggregation habitat but slowed down and do more localized search when host present. However, the species of S. spiculatus , tended to do localized movement when hosts were absent regardless shade. Once host larvae present in nearby location, the nematodes responded to the host cue and moved faster toward their hosts. The active foraging behavior of R. iyengari may suggest that the species is more suitable for mosquito control in clear and moving water such as streams. However, the passive stay and wait behavior of S. spiculatus might be more suitable against mosquitoes in small sized water bodies such as temporarily flooded or stagnant ponds. [ABSTRACT FROM AUTHOR]

Adult female individuals of the nematode Mesomermis devii sp. nov. (Nematoda: Mermithidae) have been described. The host organism is not determined. The individuals were isolated from moist guano obtained in the dark zone of Devi Cave (West Georgia). The new species is characterized by the following: rounded and symmetrical apical end of the head; mouth aperture is located in the middle of the head terminus; 6 cephalic papillae are arranged in a single row; each papilla is equipped with 2 or 3 sensilla; stoma has uneven width and the pharyngeal tube is of even width along the whole length; small amphids, with large, slightly oval, roundish holes and large, rounded pouches; pear-shaped vagina. Additionally, the radial holes emerging from the gland situated in the cuticle of the terminal part of the tail differentiate it from the species of the genus Mesomermis. This is the second record of this genus in Georgia. A list of species in the genus Mesomermis distributed in the Palearctic and brief morphological descriptions indicating their hosts and distribution details are provided. [ABSTRACT FROM AUTHOR]

A new species of fossil mermithid, Cretacimermis aphidophilus sp. n. (Nematoda: Mermithidae), is described from the primitive extinct aphid, Caulinus burmitis (Hemiptera: Burmitaphididae), in mid-Cretaceous Myanmar amber. Aphid parasitism by mermithid nematodes is rare today with only two known cases involving root-feeding aphids. Based on the habits of the parasitised extant aphid hosts, it is likely that the fossil aphid was also a root parasite and encountered the infective stage mermithid in the soil. Such fossils provide rare glimpses of nematode-host associations from the distant past and provide minimum dates for the appearance of specific mermithid clades. [ABSTRACT FROM AUTHOR]

Mermithid nematodes are entomophagous parasites and, despite being present in diverse aquatic insects, studies of caddisflies acting as definitive hosts are few and the ecological impacts on host populations are largely unknown. During a four-year study in a stream in southeastern Australia, parasitic mermithid worms were commonly found inside adult caddisflies, but only species of the genusEcnomusMcLachlan, 1864 (Ecnomidae).Ecnomuswere the definitive host and parasite prevalence ranged from <1% to nearly 50% across six species. Species-specific prevalence varied little between years and was typically higher in males than in females. Parasite intensity ranged from 1 to 6 (median = 1), but did not vary between species or sexes. Infected hosts could fly, but were castrated and died when worms emerged. High prevalence and virulence (reproductive failure and death of the host) suggests that these parasites could potentially play a role in the population dynamics of someEcnomusspp. [ABSTRACT FROM AUTHOR]

A new species, Hexamermis paranaense n. sp. (Nematoda, Mermithidae), a parasite of larvae of Diloboderus abderus Sturm, 1826 (Coleoptera, Scarabaeidae) is described and illustrated. This new species is characterized by amphids small, amphidial opening pocket-shaped, the anterior portion of the vagina muscularized and slightly protruding with a descending branch forming a loop before joining the uterus, and three rows of genital papillae: the ventrolateral divided in two rows with eight papillae in the outer row and with six papillae in the inner one; the ventral row with four pairs and one single preanal papillae, and with two pairs, a triplete, one pair, a single and one pair postanal papillae.Una nueva especie, Hexamermis paranaense sp. nov. (Nematoda, Mermithidae), parásito de larvas del gusano blanco, Diloboderus abderus Sturm, 1826 (Coleoptera, Scarabaeidae), se describe e ilustra. Esta nueva especie se caracteriza por poseer anfidos pequeños, con la apertura en forma de bolsillo, parte anterior de la vagina muscular, con una rama que desciende y forma un lazo antes de la conexión al útero, tres hileras de papilas genitales: la hilera de posición ventro-lateral dividida en dos hileras con ocho papilas en la hilera externa y con seis papilas en la interna; la hilera ventral con una papila, seguida de cuatro pares, todas en posición preanal y dos pares, interrumpidos por tres papilas, seguida de un par, una simple, y un par, todas de posición postanal.

Variation among body sizes of adult parasitic worms determines the relative genetic contribution of individuals to the next generation as it affects the effective parasite population size. Here, we investigate inequalities in body size and how they are affected by intensity of infection in Mermis nigrescens (Mermithidae: Nematoda) parasitizing the European earwig Forficula auricularia in New Zealand. Among a population of pre-adult worms prior to their emergence from the host, we observed only modest inequalities in body length; however, among worms sharing the same individual host, inequalities in body sizes decreased with increasing intensity of infection. Thus, the more worms occurred in a host, the more the second-longest, third-longest and even fourth-longest worms approached the longest worm in body length. This pattern, also known from another mermithid species, suggests that worms sharing the same host may have infected it roughly simultaneously, when the host encountered a clump of eggs in the environment. Thus, the life history and mode of infection of the parasite may explain the modest inequalities in the sizes achieved by pre-adult worms, which are lower than those reported for endoparasitic helminths of vertebrates. [ABSTRACT FROM AUTHOR]

Native and invasive stink bugs (Hemiptera: Pentatomidae) and the closely related invasive Megacopta cribraria (Hemiptera: Plataspidae) are agricultural pests in the southeastern United States. Natural enemies, from various phyla, parasitize these pests and contribute to population regulation. We specifically investigated Nematoda infections in pentatomid and plataspid pests in one soybean field in South Carolina in 2015. Nematodes were identified through molecular and morphological methods and assigned to family Mermithidae, genus Agamermis. This study reports mermithid nematode infection in immature M. cribraria for the first time and provides the first mermithid host record for the stink bugs Chinavia hilaris, Euschistus servus, and another Euschistus species, and a grasshopper (Orthoptera: Acrididae) in South Carolina. The same Agamermis species infected all hosts. The broad host range and prevalence suggests that Agamermis may be an important contributor to natural mortality of pentatomid and plataspid pests. Previous mermithid host records for the Pentatomidae and Plataspidae worldwide are summarized. Further work is needed to assess the impact of infection on populations over a broader range of agricultural fields and geographic localities. [ABSTRACT FROM AUTHOR]

Ovomermis sinensis(Nematoda: Mermithidae) is an entomophilic nematode and a potential biocontrol agent of lepidopteran pests, includingHelicoverpa armigera. The sex ratio of a species can be used to regulate the size of the reproductive population. Parasitic load, parasitic period, host instar, and body size were examined to identify factors affecting theO. sinensissex ratio. We tested the hypothesis that theO. sinensissex ratio is correlated with host nutrient supply and the nutrients absorbed by the nematodes. The results show that the proportion of maleO. sinensisincreased with parasitic load but decreased with host instars and body size. Moreover, the parasitic period of males was significantly shorter than that of females. However, all the factors (host and nematodes) affecting the sex ratio were significantly modified by restricting the host diet, which increased the proportion of males. In turn, juveniles that absorbed fewer nutrients tended to develop into males. Taken together, our findings suggest that factors impacting theO. sinensissex ratio are related to host nutrient status and provide parameters for mass rearing and a release strategy for this natural enemy. [ABSTRACT FROM PUBLISHER]

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El nemátodo mermítido S. spiculatus es un parásito común de culícidos de la Argentina. Presenta características que lo distinguen de otros mermítidos parásitos de culícidos y lo convierten en un promisorio candidato como agente de control biológico de mosquitos. La temperatura es un factor importante en la eficiencia de muchos entomopatógenos y su efecto debe ser determinado previo a la evaluación de campo de los mismos. En este trabajo, se investigó el efecto de la temperatura sobre la longevidad e infectividad de los juveniles preparásitos de S. spiculatus. Se expusieron preparásitos a 4, 10, 20 y 27ºC durante 40 días. Diariamente se cuantificó el número de juveniles preparásitos móviles a cada temperatura y luego se agregaron larvas de segundo estadío de Ae. aegypti para determinar la capacidad infectiva de los preparásitos. La longevidad máxima de los preparásitos fue 35, 30, 25 y 27 días a 4, 10, 20 y 27ºC, respectivamente. A las 48 hr, el porcentaje de preparásitos móviles varió entre 57% y 100% a las temperaturas citadas, disminuyendo entre 21% y 77% al día 5 y entre 9% y 33% al día 10. El porcentaje de parasitismo de los preparásitos fue superior a 70% a las cuatro temperaturas y la intensidad parasitaria varió entre 1 y 4 nemátodos por larva. La prolongada longevidad de los preparásitos, sin disminución de la capacidad infectiva, constituye una característica importante de S. spiculatus como potencial agente de control biológico de numerosas especies de culícidos a temperaturas entre 4 y 27ºCStrelkovimermis spiculatus is a common parasite of culicid species in Argentina. Effect of temperature on longevity and infectivity of juvenile preparasites of S. spiculatus was determined at 4, 10, 20 and 27ºC. Three containers with 100 ml of dechlorinate water and 300 preparasites (12 hour-old), were placed for each day and temperature, during 40 days (total = 480 containers). Survived preparasites were counted on 12 containers per day (three for each temperature). When number of survived preparasites was determined, second instar larvae of Aedes aegypti were added to each container in a 10:1 ratio (preparasites:mosquito) to determine infectivity of daily survived preparasites. Longevity of preparasites decreased at higher temperatures. Maximum longevity of preparasites maintained at 4, 10, 20 and 27ºC were 35, 30, 25 and 27 days, respectively. Survivorship of preparasites, exposed to the same temperatures, varied from 57% to 100% at day two, from 21% to 77% at day five and from 9% to 33% at day ten. Infectivity of preparasites maintained at temperatures from 4 to 27ºC was always higher than 70%. Extended longevity with maintenance of the infectivity capacity of preparasites, are important attributes to consider S. spiculatus an effective mean of controlling a large number of culicid species between 4 and 27ºC

A survey of simulid larval parasites was carried out in different localities of the states of Mato Grosso, Minas Gerais, São Paulo, Paraná, Santa Catarina and Rio Grande do Sul, Brazil, from February 1996 to May 1998. Prevalences for the microsporidian Polydispyrenia simulii Lutz & Splendore, 1908 were found in Morungaba and Leme, São Paulo, ranging from around 0.7 to 66.7%, depending mainly on the host simulid species. Microsporidiosis was registered in localities of São Paulo, Paraná, Santa Catarina and Rio Grande do Sul. Parasitism by Isomermis sp. (Nematoda, Mermithidae) was found in Simulium larvae from Serra do Japi, ranging from 0.8 to 45.8%, depending on the simulid species and the larval microhabitat in the stream, whether a cemented ramp in a lake outlet or the natural stream bed. Parasitism by mermithids was also found in ten localities. Mycoses caused by Coelomycidium sp. were for the first time recorded for larvae of Simulium (Chirostilbia) pertinax Kollar, 1832.