Agamermis sp. (Nematoda: Mermithidae) parasitizing Armadillidium vulgare (Crustacea: Isopoda) in Argentina.

The Mermithidae is a family of nematodes parasitic in many kinds of insects, spiders, leeches, crustaceans and other invertebrates throughout the world. While conducting an assay with entomopathogenic nematodes, we found Armadillidium vulgare (Crustacea: Isopoda) individuals to be infected with Agamermis sp., marking the fourth known discovery of a mermithid infection in the order Isopoda. In this work, we contribute with an 18S rDNA sequence of the isolated nematode and the morphological and morphometrical characterization of the juveniles.

Dive into the sea: first molecular phylogenetic evidence of host expansion from terrestrial/freshwater to marine organisms in Mermithidae (Nematoda: Mermithida).

We report the first mermithid nematode found to be parasitic in a marine tanaidacean crustacean. Ten host tanaidaceans were collected from a depth of 52 m in Otsuchi Bay, Iwate, Japan, north-western Pacific, and identified as a species in the tanaidid genus Zeuxo Templeton, 1840. Nematodes occurred in the host's body cavity; in one case, at least two individuals inhabited a single host. We provide a brief description and illustrations of the morphology of the nematode. In a phylogenetic reconstruction based on the 18S ribosomal RNA gene, the nematode nested in a clade otherwise containing mermithids from terrestrial or freshwater hosts, showing an expansion in host utilization in Mermithidae Braun, 1883 from terrestrial/freshwater hosts to a marine organism.

First Record of A Species of Mermithidae Braun, 1883 Infecting a Decapod, Palaemon paludosus (Palaemonidae).

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.

Morphological and molecular characterization of Mermis nigrescens Dujardin, (Nematoda: Mermithidae) parasitizing the introduced European earwig (Dermaptera: Forficulidae) in New Zealand.

Parasitic nematodes of the family Mermithidae were found to be infecting the introduced European earwig Forficula auricularia (Dermaptera: Forficulidae) in Dunedin, South Island, New Zealand. Adult females were later collected from various garden plants while depositing eggs. These mermithid specimens were identified morphologically as Mermis nigrescens Dujardin, 1842. A genetic distance of 0.7% between these specimens and a M. nigrescens isolate from Canada (18S rRNA gene), suggests that they have diverged genetically, but there are currently no available comparable sequences for the European M. nigrescens. Two additional nuclear fragments were also amplified, the 28S rRNA and the ribosomal DNA first internal transcribed spacer (ITS1), providing a basis for future studies. Bearing in mind the morphological similarity with other reported M. nigrescens and the lack of sequence data from other parts of the world, we retain the name M. nigrescens, and suggest that the species may be found to represent a complex of cryptic species when more worldwide data are available. Herein, we present a brief description of the post-parasitic worms and adult females, along with an inferred phylogeny using 18S rRNA gene sequences.

Effects of insect growth regulators on the mosquito-parasitic nematode Romanomermis iyengari.

Pyriproxyfen, a juvenile hormone analogue, diflubenzuron, a chitin synthesis inhibitor, and azadirachtin, an ecdysone agonist, are three insect growth regulators (IGRs) considered as selective and effective insecticides for mosquitoes. Romanomermis iyengari (Welch) is a mosquito-parasitic mermithid that can provide biological control against many medically important mosquito species. The compatibility of these two control tactics was tested by evaluating the sublethal effects of exposure to IGR on nematode developmental stages (preparasitic, parasitic, and preparasitic + parasitic) using Culex pipiens larvae as the host. Sublethal concentrations of IGRs were 90 % emergence inhibition of host mosquito. Preparasitic exposure to pyriproxyfen, azadirachtin, and diflurbenzuron had no effect on infectivity, parasite load, sex ratio, or male size but reduced nematode female length and increased male sex ratio at one parasite/larva. When IGRs treatments were made against the parasitic and preparasitic + parasitic stages, pyriproxyfen and azadirachtin reduced R. iyengari infectivity, parasite load, and male nematode length, whereas pyriproxyfen exposure increased male sex ratio and reduced the female R. iyengari length. Thus, IGRs have significant negative impacts on different stages of mosquito mermithid that can destabilize the balance of host-parasite population interaction. Therefore, IGRs should be used with caution in mosquito habitats where these parasites have established.

Effect of temperature, photoperiod, flooding, and drying on the hatching pattern of the eggs of Strelkovimermis spiculatus (Nematoda: Mermithidae).

We assessed the number of Strelkovimermis spiculatus preparasites obtained from a known initial number of nematode eggs and the effect of abiotic conditions (temperature, photoperiod, flooding-drying) on the number of emerged preparasites. Two egg groups were maintained: one continuously flooded, another with flooding-drying cycles (every 15, 30, 60 days). Each egg group was studied at 25°C and 14:10 (L:D) and 16°C and 12:12 (L:D). The flooded eggs contained a higher overall percentage of S. spiculatus preparasites compared to the wet-dry-cycle eggs. The conditions of continuous flooding at 16°C and 12:12 (L:D) produced the maximum percent of emerged J2s (30±15%). Preparasites were recorded by 7 (25°C) and 14 (16°C) days, suggesting this period as the minimum time for embryonic development. The preparasite-emergence time observed from the same flooded-egg batch (98 and 112 days at 25°C and 16°C, respectively) suggested a nonsynchronous hatching, possibly through nonuniform egg embryonation. The time of exposure to drought in the assays did not significantly affect the total average percentage of J2s obtained at 25°C and 14:10 (L:D), whereas at 16°C the number of emerged J2s diminished with a prolongation of the drying period. The oviposition period was also recorded only at 16°C and 12:12 (L:D): S. spiculatus eggs were detected at 12.6 days after postparasite emergence, and oviposition was complete at 51days under those conditions. We propose a flooding schedule to optimize the mass-rearing of S. spiculatus.

Hexamermis eurygasteri n. sp. (Nematoda: Mermithidae) parasitising the sunn pest Eurygaster integriceps Puton (Hemiptera: Scutelleridae) in Turkey.

A new species of mermithid nematode, Hexamermis eurygasteri n. sp. (Nematoda: Mermithidae) is described as a parasite of the sunn pest Eurygaster integriceps Puton (Hemiptera: Scutelleridae) in Turkey. The combination of the following characters separate H. eurygasteri from other members of Hexamermis Steiner, 1924, as defined by Artyukhovsky (1990) and Kaiser (1991): amphidial pouch integrated into lateral cephalic papillae; amphidial openings minute; well-developed cuticular vulval cone; small vulval lips; vagina straight or slightly curved at tip, without reverse bend; spicules shorter in length than body diameter at cloaca; spicules straight, except occasionally for short bend at base; spicule tips bluntly rounded; and two double rows of genital papillae. This is the first description of a nematode parasite of a member of the Scutelleridae and the first description of a mermithid nematode from Turkey. This mermithid has potential as a biological control agent in an integrated control programme of the sunn pest.

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.

A new genus and species of mermithid (Nematoda) emerging from chironomid imagos eclosing from the Mississippi River headwaters area in northern Minnesota.

Fibromermis roarki n. gen., n. sp. (Nematoda: Mermithidae) is described from the hemocoel of chironomid imagos of Ablabesmyia monilis (L.) eclosing from the headwaters of the Mississippi River at Gulsvig Landing in northern Minnesota in the summer of 2007. The new genus is described, distinguished from the most closely related tetrapapillate aquatic mermithid genus, and the new species described. Intensity and sex specificity of infection are recorded from 28 host adult chironomids of a single cohort. The new species represents the fourth tetrapapillate mermithid species described from the area and the third tetrapapillate genus.

A new mermithid nematode in imagos of Cladopelma collator (Townes) (Diptera: Chironomidae) eclosing from waterways in northern Minnesota.

Octomyomermis connellyi n. sp. (Nematoda: Mermithidae) is described from the hemocoel of male and female imagos of Cladopelma collator (Townes) eclosing from Lake Ozawindib and from Gulsvig Landing in the upper Mississippi River in northern Minnesota. The species is distinguished from the other species in the genus. Included is a list of the other 9 adequately described members of the genus Octomyomermis that have been reported from the United States (California and Minnesota), Argentina, Russia, and Zambia. Bionomics and anomalies of the new species are addressed.

Mermithids (Nematoda: Mermithidae) of biting midges (Diptera: Ceratopogonidae): Heleidomermis cataloniensis n. sp. from Culicoides circumscriptus Kieffer in Spain and a species of Cretacimermis Poinar, 2001 from a ceratopogonid in Burmese amber.

Heleidomermis cataloniensis n. sp. (Nematoda: Mermithidae) is described from Culicoides circumscriptus Kieffer (Diptera: Ceratopogonidae) in Spain. Diagnostic characters include prominant elevations with multiple genital papillae on either side of the cloacal opening, only one row of genital papillae on the lateral surface of the tail, the tapering tip of the spicule and a reduced vagina. A male intersex of C. circumscriptus parasitised by H. cataloniensis n. sp. has mouthparts resembling those of the female. Two 100 million year-old fossil specimens of an un-named species of Cretacimermis Poinar, 2001, from an Early Cretaceous Burmese amber biting midge of the genus Leptoconops Skuse, show the antiquity of ceratopogonid-mermithid associations.

A new species of mermithid (Nematoda) in chironomids eclosing from a northern Minnesota bog.

Hydromermis haggardi n. sp. (Nematoda: Mermithidae) is described from the hemocoel of chironomid imagos eclosing from Lake Alice Bog in northern Minnesota in June and July 2007. The species is distinguished from the other 27 described members of the genus by the subventral mouth, tulip shape to anterior end of esophagus, colorless vesicular trophosome, single nonbifurcated spicule, short body lengths of both males and females, structure of the S-shaped vagina, decrease in body width at vulva, brevity of postparasitic stage, and the greater development of a posterior ventral protractor muscle in the males. An anomalous adult male bearing large oval structures in the posterior testis is reported. Evidence is presented for the developmental interaction of the new species with Lanceimermis palustris Johnson and Kleve, 2004.

Allomermis solenopsi n. sp. (Nematoda: Mermithidae) parasitising the fire ant Solenopsis invicta 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.

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.

Lanceimermis palustris n. sp. and Telomermis palustris n. sp. (Nematoda: Mermithidae) parasites of chironomid (Insecta: Diptera) adults from Lake Alice Bog in northern Minnesota.

In the summer of 2003, chironomid imagoes eclosing from Lake Alice Bog in Minnesota yielded mermithid nematodes of 2 new species. Lanceimermis palustris n. sp. is distinguished from the other 14 species of the genus by the subventral mouth position, thinness of the hook-shaped spicule, body index, and structure of the male tail muscles. Telomermis palustris n. sp. is distinguished from the only other species of the genus by the structure of the amphids, body length, maximum body width, length of the esophagus, and the presence of a minute larval terminal horn. Lanceimermis palustris n. sp. hosts were Chironomus maturus Johannsen and T. palustris n. sp. hosts were Tanytarsus mendax Kieffer, Paratanytarsus nr. dissimilis n. sp., and Micropsectra polita (Malloch). In both mermithid species, the percent of mermithid males per host increased with the intensity of the infection.

Strelkovimermis papillosus n. sp. (Nematoda: Mermithidae), a parasite of chironomid (Insecta: Diptera) adults from the headwaters of the Mississippi River in northern Minnesota.

On 18 August 2002, chironomid imagoes of Rheotanytarsus sp. emerged from the upper Mississippi River in Minnesota and yielded distinctive mermithid nematodes of a new mermithid species. Strelkovimermis papillosus n. sp. is distinguished from the other 14 species of the genus by the presence of unusually large cephalic papillae encircling the mouth and forming a rosette with the mouth in the center and by the absence of a fixator muscle in the males. Additionally, both sexes have very acute posterior ends, long amphids, and a long stoma. Strelkovimermis is revised by eliminating nondiscriminating parameters and accommodating the 15 known species. Intrageneric characteristics useful in separating species of Strelkovimermis are listed. Intensity of infection and intensity of infection versus sex were determined from 41 hosts. Where known, the hosts and geographical distribution are given for all 15 Strelkovimermis species.

Inequalities in size and intensity-dependent growth in a mermithid nematode parasitic in beach hoppers.

Inequality in body sizes is a common feature in populations of helminth parasites, with potential consequences for egg production and population genetics. Inequalities in body lengths and the effects of intraspecific competition on worm length were studied in a species of mermithid nematode parasitic in the crustacean Talorchestia quoyana (Amphipoda: Talitridae). The majority of the 753 worms recovered were relatively small, and an analysis using a Lorenz curve and Gini coefficient suggested that there were no marked inequalities in body lengths among the worms. Total worm length in the 356 infected amphipods (i.e. the sum of the lengths of all the worms in a host) increased steadily as a function of the number of worms per amphipod, whereas the length of the longest worm per amphipod peaked in amphipods harbouring intermediate numbers of worms. This last result was not significantly accounted for by the observed increase in host size with increasing intensity of infection, but resulted from a correlation between worm length and host size. As the number of worms per amphipod increased, the relative sizes of the second-, third-, and fourth-longest worms per host increased markedly. This means that relative inequalities in sizes become less pronounced, i.e. subordinate worms get closer in size to the longest worm, as the number of worms per host increases. The main consequence of this phenomenon is that worm sizes in the mermithid population are more homogeneous than they would be if intraspecific competition had stronger effects on worm growth.

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.

Limnomermis subtropicalis n. sp. (Neumatoda: Mermithidae) a parasite of larvae of Simulium orbitale Lutz (Diptera: Simuliidae) in Argentina

Limnomermis subtropicalis n. sp. (Nematoda: Mermithidae) a parasite of larvae of Simulium orbitale Lutz (Diptera: Simuliidae) found in Argentina is described and illustrated. This species is characterized by having medium sized amphids, pocket-shaped, medium sized vagina, sculptured spicule, and by having 9 preanal, 7 postanal papillae in the ventral row, and 12 papillae in the lateral rows.

Limnomermis subtropicalis n. sp. (Nematoda:Mermithidae) a parasite of larvae of Simulium orbitale Lutz (Diptera:Simuliidae) in Argentina.

Limnomermis subtropicalis n. sp. (Nematoda:Mermithidae) a parasite of Simulium orbitale Lutz (Diptera:Simuliidae) found in Argentina is described and illustrated. This species is characterized by having medium sized amphids, pocket-shaped, medium sized vagina, sculptured spicule, and by having 9 preanal, 7 postanal papillae in the ventral row, and 12 papillae in the lateral rows.