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In this study, we sampled aquatic snails for the presence of hairworm cysts from 46 streams in Payne County, Oklahoma. Gordiid cysts were found at 70 % (32/46) of sites examined. Based on cyst morphology, we were able to identify three morphological types of gordiid cysts, including Paragordius, Gordius, and Chordodes/Neochordodes. Using our gordiid cyst presence data in conjunction with environmental variables, we developed an ecological niche model using Maxent to identify areas suitable for snail infections with gordiids. The model successfully predicted all presence localities of gordiid cysts in snails over a geographic area of 1,810 km2. We used this information, along with arthropod host infections and crowdsourcing, citizen scientists sampling for adult free-living worms during peak emergent times in areas predicted suitable by the model, to document Paragordius varius, Chordodes morgani, and a new species of gordiid (Gordius n. sp.). To our knowledge, this is the first ecological niche model attempted on such a narrow geographic scale (county level) that recovered known locations successfully. We provide new scanning electron micrographs and molecular data for these species. Our field data and ecological niche model clearly indicate that gordiid cysts are easy to detect in the environment and together these sampling techniques can be useful in discovering new species of gordiids, even in relatively well sampled areas for these cryptic parasites.

A new marine gastrotrich species of the genus Cephalodasys is described from shallow sublittoral coralline sand sampled between Lee Stocking Island and Norman’s Pond Cay (Exuma Cays), Bahamas. Cephalodasys interinsularis n. sp. reaches a body length of 471 µm and is characterized by a new combination of characters including six total anterior adhesive tubes and five pairs of ventrolateral adhesive tubes. The new species is morphologically similar to C. swedmarki but can be distinguished by the different number of anterior adhesive tubes, the spatial arrangement of the ventrolateral adhesive tubes, and a shorter pharynx. We provide an updated diagnosis of the genus and a determination key to all known species of Cephalodasys . C. interinsularis n. sp. is the third known species of Cephalodasys from the Caribbean marine province.

The currently known diversity of horsehair worms (Nematomorpha) from India is only 17 species. We report here two female specimens found on two occasions on a terrace paddy field in Tsupo, Viswema, Kohima, Nagaland, India. Although found at the same location, both species differ in their cuticular structures. One is determined as Chordodes moutoni , a species known from China, Malaysia and India. The other specimen shows a new type of cuticular structure, the areoles, which combines characters of both simple areoles and tubercle areoles. This specimen is described as a new species, C . combiareolatus. Both specimens show arrangements on the cuticle, in which a circle of areoles surrounds a region of “naked” cuticle. We interpret these regions as artifacts caused by the breaking off of the central crowned areoles, leaving only the circumcluster areoles behind.

We reinvestigate five African species of the genus Chordodes in order to certify the taxonomic descriptions and verify the species status. By scanning electron microscopy, we demonstrate characteristic cuticular patterns for the species Chordodes africanus, C. hawkeri, C. sandoensis and C. schoutedeni. The fifth species, C. butensis, is synonymized with C. africanus, because no differences were detected.

Freshwater hairworms infect terrestrial arthropods as larvae but are free-living in aquatic habitats as adults. Estimates suggest that only 18% of hairworm species have been described globally and biodiversity studies on this group have been hindered by unreliable ways of collecting adult free living worms over large geographical areas. However, recent work indicates that non-adult cyst stages of hairworms may be the most commonly encountered stages of gordiids in the environment, and can be used for discovering the hidden diversity of this group. Unfortunately, little information is available on the morphological characteristics of non-adult stages of hairworms. To address this problem, we describe and compare morphological characteristics of non-adult stages for nine species of African and North American gordiids from four genera ( Chordodes , Gordius , Paragordius , and Neochordodes ). Observations were made on the oviposition behavior of adult worms and morphological characteristics were recorded for egg strings, larvae and cysts using light and differential interference contrast microscopy and/or scanning electron microscopy. Our study indicates that three distinct types of oviposition behaviors and three distinct morphological types of egg string, larva, and cysts were present among the four genera of gordiids. Although species identification based on cyst characteristics was not always possible among different species of gordiids, cyst morphology was conserved among some genera and all clades of gordiids. More importantly, our work indicates that gordiid larval morphology can be used for predicting cyst morphology among other gordiid genera. The capability to identify and predict gordiid genera and/or clades based on cyst morphology will be useful for culturing gordiids in the laboratory from field collected cysts and these new techniques will undoubtedly allow others to discover new species of gordiids from around the world.

We review recent advances in the use of non-adult gordiid cyst stages to locate gordiids over large geographical regions and new culturing techniques which can help overcome current difficulties in nematomorph biodiversity studies. Using these techniques, we collected a new species of gordiid as cysts in aquatic snails (Biomphalaria pfeifferi) from the Lake Victoria Basin, western Kenya, Africa and cultured them in the laboratory. We describe the adult free-living male and female worms using morphological (light and scanning electron microscopy) and molecular data as well as the life cycle, mating and oviposition behavior, egg strings, eggs, larvae, and cysts of this new species. Chordodes kenyaensis n. sp. belongs to a large group of African Chordodes in which simple areoles are smooth or superficially structured less so than "blackberry" areoles but contain filamentous projections. Present among the simple areoles are clusters of bulging areoles, crowned and circurmcluster areoles along with thorn and tubercle areoles. In the laboratory, worms developed and emerged within 53-78 days from three, species of laboratory-reared crickets exposed to cysts of this species. Adult male and female C. kenyaensis n. sp. initiated typical Gordian knots within hours to days of being placed together and males deposited masses of sperm on the cloacal region of females. Females began oviposition within a week of copulating and attached egg strings in a continuous zigzag pattern on small branches or air-hoses but never free in the water column. Larvae hatched within two to three weeks, and cysts developed in laboratory-reared and exposed snails within 14-24 days. Morphological characteristics of egg strings, eggs, larvae and cysts of C. kenyaensis were most similar to other gordiids in the genus Chordodes but differed morphologically from other gordiid genera for which similar information is available.

Fifteen species of freshwater Nematomorpha have been described from India, five of which belong to the genus Chordodes . This paper describes one new species of horsehair worms (Nematomorpha): Chordodes lasuboni and a new record, C. moutoni from North-East India, which raises the total number of described species from India to 17. Chordodes lasuboni is characterized by a novel cuticular pattern in the head region and by the presence of slender, hooked thorn areoles on the body cuticle. Compared to the large size and ecological diversity of India, the nematomorph fauna is regarded as under-sampled and several new species are to be expected.

Specimens belonging to the genus Gordius (horsehair worms, Nematomorpha) are comparatively poor in diagnostic characters and determination of species is difficult. The characters important for determination (coloration, size, shape of anterior and posterior end, structures in the male posterior end, cuticular structure) are discussed. From the 119 species of the genus, 40 are regarded as invalid. The remaining 79 species and their characters are summarized in a table. The species Gordius aquaticus is the best known name among nematomorphs, but its diagnostic characters are critically reviewed. Recent methods such as SEM reveal characters such as the presence of fine bristles in the posterior end or different fine structures of the cuticular surface. Such characters were not included in older descriptions and their value for taxonomy will become apparent as more data is available. Despite such problems some specimens show unique and new characters or character combinations and the following seven species are described as new: G. balcanicus sp. nov. from Serbia, G. digitatus sp. nov. from Croatia, G. helveticus sp. nov. from Swizerland, G. karwendeli sp. nov. from Germany, G. pesici sp. nov. from Montenegro, G. serratus sp. nov. from Papua New Guinea and G. zwicki sp. nov. from Russia.