Intra- and interspecific genetic diversity of New Zealand hairworms (Nematomorpha).

Hairworms (Nematomorpha) are a little-known group of parasites, and despite having been represented in the taxonomic literature for over a century, the implementation of molecular genetics in studies of hairworm ecology and evolution lags behind that of other parasitic taxa. In this study, we characterize the genetic diversity of the New Zealand nematomorph fauna and test for genetic structure within the most widespread species found. We provide new mitochondrial and nuclear ribosomal sequence data for three previously described species from New Zealand: Gordius paranensis, Parachordodes diblastus and Euchordodes nigromaculatus. We also present genetic data on a previously reported but undescribed Gordius sp., as well as data from specimens of a new Gordionus sp., a genus new for New Zealand. Phylogenetic analyses of CO1 and nuclear rDNA regions correspond with morphological classification based on scanning electron microscopy, and demonstrate paraphyly of the genus Gordionus and the potential for cryptic species within G. paranensis. Population-level analyses of E. nigromaculatus showed no genetic differentiation among sampling locations across the study area, in contrast to previously observed patterns in known and likely definitive hosts. Taken together, this raises the possibility that factors such as definitive host specificity, intermediate host movement, and passive dispersal of eggs and larvae may influence host-parasite population co-structure in hairworms.

Cryptic species of hairworm parasites revealed by molecular data and crowdsourcing of specimen collections.

Recognizing cryptic species promotes a better understanding of biodiversity, systematics, evolutionary biology, and biogeography. When cryptic species are disease-causing organisms, such as parasites, their correct recognition has important implications for the study of epidemiology, disease ecology, and host-parasite relationships. Freshwater nematomorphs (Nematomorpha: Gordiida) or hairworms, are an enigmatic yet fascinating group of parasites that are known to manipulate host behavior to aid transition from the parasitic phase, within terrestrial insects, to the free-living aquatic stage. Hairworm taxonomy has been hampered by a paucity of informative diagnostic characters and it has long been suspected that this group contains numerous cryptic species. Study of single hairworm species over large geographical areas has been difficult due to extremely rare encounters and unreliable methods of collecting adult worms. Here we report that by using crowdsourcing, citizen scientists have collected and submitted samples of Gordius cf. robustus from throughout its range in North America making its genetic study possible. Combined with our own collections, we examined samples from 28 localities within the USA; despite the collection of numerous hairworms from Canada and Mexico, G. cf. robustus were not collected outside of the contiguous United States. Mitochondrial CO1 genetic distances revealed that specimens grouped into 8 clades separated by 8-24.3%. In addition, molecular evidence from mitochondrial (CO1 and cytB) and nuclear (partial 28S, ITS1, 5.8S and ITS2) DNA suggests that these 8 clades are distinct species and that this group of species is paraphyletic, since the North American species G. attoni and the European species G. aquaticus and G. balticus group among the G. robustus lineages. Furthermore, there was a significant correlation between genetic (CO1) and geographic distance between the 8 Gordius species. This study demonstrates the value of involving the general public in biodiversity studies and highlights the feasibility of using the mitochondrial CO1 gene as a taxonomic marker for genetic barcoding and species identification within the phylum Nematomorpha.

Broad phylogenomic sampling improves resolution of the animal tree of life.

Long-held ideas regarding the evolutionary relationships among animals have recently been upended by sometimes controversial hypotheses based largely on insights from molecular data. These new hypotheses include a clade of moulting animals (Ecdysozoa) and the close relationship of the lophophorates to molluscs and annelids (Lophotrochozoa). Many relationships remain disputed, including those that are required to polarize key features of character evolution, and support for deep nodes is often low. Phylogenomic approaches, which use data from many genes, have shown promise for resolving deep animal relationships, but are hindered by a lack of data from many important groups. Here we report a total of 39.9 Mb of expressed sequence tags from 29 animals belonging to 21 phyla, including 11 phyla previously lacking genomic or expressed-sequence-tag data. Analysed in combination with existing sequences, our data reinforce several previously identified clades that split deeply in the animal tree (including Protostomia, Ecdysozoa and Lophotrochozoa), unambiguously resolve multiple long-standing issues for which there was strong conflicting support in earlier studies with less data (such as velvet worms rather than tardigrades as the sister group of arthropods), and provide molecular support for the monophyly of molluscs, a group long recognized by morphologists. In addition, we find strong support for several new hypotheses. These include a clade that unites annelids (including sipunculans and echiurans) with nemerteans, phoronids and brachiopods, molluscs as sister to that assemblage, and the placement of ctenophores as the earliest diverging extant multicellular animals. A single origin of spiral cleavage (with subsequent losses) is inferred from well-supported nodes. Many relationships between a stable subset of taxa find strong support, and a diminishing number of lineages remain recalcitrant to placement on the tree.

Comparative descriptions of non-adult stages of four genera of Gordiids (Phylum: Nematomorpha).

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.

One new species and a new record of the genus Chordodes (Nematomorpha: Gordiida) from North-East India.

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.

Novel techniques for biodiversity studies of gordiids and description of a new species of Chordodes (Gordiida, Nematomorpha) from Kenya, Africa.

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.

Invertebrate neurophylogeny: suggested terms and definitions for a neuroanatomical glossary.

BACKGROUND: Invertebrate nervous systems are highly disparate between different taxa. This is reflected in the terminology used to describe them, which is very rich and often confusing. Even very general terms such as 'brain', 'nerve', and 'eye' have been used in various ways in the different animal groups, but no consensus on the exact meaning exists. This impedes our understanding of the architecture of the invertebrate nervous system in general and of evolutionary transformations of nervous system characters between different taxa. RESULTS: We provide a glossary of invertebrate neuroanatomical terms with a precise and consistent terminology, taxon-independent and free of homology assumptions. This terminology is intended to form a basis for new morphological descriptions. A total of 47 terms are defined. Each entry consists of a definition, discouraged terms, and a background/comment section. CONCLUSIONS: The use of our revised neuroanatomical terminology in any new descriptions of the anatomy of invertebrate nervous systems will improve the comparability of this organ system and its substructures between the various taxa, and finally even lead to better and more robust homology hypotheses.

Validation of Spadella kappae Schmidt-Rhaesa amp; Vieler, a small benthic chaetognath from Roscoff, France (Chaetognatha).

Schmidt-Rhaesa Vieler (2018) described a new species of benthic chaetognath, Spadella kappae, collected by meiofaunal sampling near Roscoff, France. Although the description and figures presented by Schmidt-Rhaesa Vieler (2018) fully characterize the new species, the journal issue in which the description appeared was published online-only, with no print version, and the article in which the new name appeared did not include a ZooBank registration number for the article (LSID), required for validation of new species names in electronic-only publications (ICZN 2012). As a result, the name Spadella kappae Schmidt-Rhaesa Vieler, 2018, as published in Cahiers de Biologie Marine 59: 257-265, is not available according the International Code of Zoological Nomenclature, hereafter, the Code (ICZN 1999, 2012). Therefore, the present note serves to validate the name Spadella kappae by fulfilling Code conditions for nomenclatural availability. The date and authorship of the specific name, accordingly, are those of this note, not Schmidt-Rhaesa Vieler (2018).

A New Species of Gordionus (Nematomorpha: Gordiida) from the Rocky Mountains of New Mexico.

The 19 genera within the phylum Nematomorpha contain approximately 350 species. The cosmopolitan genus Gordionus Müller, 1926 contains about 58 species, 6 of which occur in the contiguous United States of America. Recently, 2 new Gordionus species were described from high-altitude streams within the southern Rocky Mountains, near Santa Fe, New Mexico. Here we describe another new Gordionus species, from a high-altitude stream in the southern Rocky Mountains, from near Taos, New Mexico. The sites consisted of temporary puddles and a small human-made stream at 3,175-3,250-m altitude in aspen/pine woodland. Gordionus lokeri n. sp. has 1 areole type, which varies in shape and size between and within body regions. Midbody areoles are elongated, polygonal, or triangular, shingled, with the raised side of the areole serrated. The interareolar space is narrow, containing few bristles. The male cloacal opening is surrounded inside and outside by narrow branching bristles that bifurcate or trifurcate deeply; the furcae then subdivide several times terminally. Adhesive warts are lacking. Genetic data, consisting of partial cytochrome c oxidase subunit I (COI) gene sequences, clearly separated G. lokeri n. sp. from other Nearctic species. This is the third Gordionus species described from high-elevation streams in the Rocky Mountains. It appears that this high-altitude habitat represents the preferential niche for numerous species of this genus, and thus future work should focus on describing gordiid diversity in other parts of the Rocky Mountains.

A new species of Gordius (Phylum Nematomorpha) from terrestrial habitats in North America.

Freshwater hairworms (class Gordiida) are members of the phylum Nematomorpha that use terrestrial arthropods as definitive hosts but reside as free-living adult worms in rivers, lakes, or streams. The genus Gordius consists of 90 described species, of which three species were described from freshwater habitats in North America. In this paper we describe a new species of Gordius from terrestrial habitats in Oklahoma, Texas, and Louisiana, United States. Oddly, each year hundreds of adult free-living worms appear after bouts of heavy rain on streets, sidewalks, and lawns during the winter season, when terrestrial arthropod hosts are not active. The new species is described based on morphological characters of adults and non-adult stages including the egg strings, eggs, larvae, and cysts. Adult males have a unique row of bristles on the ventral inner side of each tail lobe and a circular pattern of bristles on the terminal end of each lobe, which distinguishes them from all other described North American species of Gordius. The egg string, larval, and cyst morphology of this new species conform to previous descriptions of non-adult hairworm stages for the genus Gordius. However, the eggs of this new species of hairworm are unique, as they contain an outer shell separated by distinct space from a thick inner membrane. The consistent occurrence of this gordiid in terrestrial habitats, along with its distinct egg morphology, suggests that this new species of hairworm has a terrestrial life cycle.

First report of the Gondwana genus Beatogordius from India, with further records of two Chordodes species (Gordiida, Nematomorpha).

Three horsehair worms (Nematomorpha) are recorded from Nagaland, India. The first species is Chordodes combiareolatus, which was recently described from Nagaland. The second is Chordodes cf. furnessi, earlier reported from Meghalaya, and some new observations are added. The third is a new species, described as Beatogordius nagalandissp. n. This is the first report of the genus Beatogordius in India and this observation fits well into the Gondwana distribution of the genus. The species is quite similar to Beatogordius chinensis, reported from South China.

Nematomorpha from Hong Kong and description of a new species from Malaysia.

We report here for the first time horsehair worms (Nematomorpha) from Hong Kong (China). Most specimens belong to the genus Chordodes, and can be assigned to C. bipilus, C. caledoniensis and to C. cf. moutoni. Two specimens have a cuticular pattern resembling the South American species C. peraccae or C. bouvieri, but for Southeast Asia this pattern is new. These two specimens are reported here as Chordodes sp. Additionally, Gordionus chinensis was found. One new species, Acutogordius koljai, is described from Malaysia. It has a characteristically-structured region posterior to the postcloacal crescent which sets it apart from previously described species in this genus.

Reconstructing the anterior part of the nervous system of Gordius aquaticus (Nematomorpha, cycloneuralia) by a multimethodological approach.

The Nematomorpha (horsehair worms) and Nematoda (round worms) are sister taxa (together Nematoida) and closely related to Scalidophora (Priapulida, Kinorhyncha, Loricifera). To date, all species were assumed to possess a specific brain type, i.e., the "cycloneuralian" brain that forms a ring-shaped neuropil around the pharynx and is composed of anteriorly and posteriorly located somata. However, descriptions of the nematomorph nervous system are rare and somewhat variable, calling in to question the validity of the cycloneuralian condition. To clarify whether there is a typical cycloneuralian pattern in the nematomorph brain, we investigated the anterior end of Gordius aquaticus with different methods: histology, immunohistochemistry and micro-CT analysis. Three-dimensional reconstructions were made from histological serial sections. The brain is composed of a central neuropil and a ring-shaped structure with associated somata. The unpaired ventral nerve cord emerges from the posteroventral part of the brain. A pharynx/esophagus is absent. In addition to the brain, a peripheral nerve plexus was detected. In summary, we interpret the architecture of the brain as potentially derived from a cycloneuralian structure, but being highly modified. The central position of the neuropil is possibly a consequence of the reduction of the anterior intestinal system as a result of the parasitic lifestyle. The ring-shaped arrangement of the somata may be a remnant of a cycloneuralian arrangement, after the two rings of somata (= cycloneuralian condition) either fused or one ring was reduced to form one massive ring-shaped structure in G. aquaticus. J. Morphol. 278:106-118, 2017. ©© 2016 Wiley Periodicals,Inc.

On the recovery of horsehair worms, Gordius sp. (Nematomorpha: Gordiida) from pork in Shillong, India.

The members of the phylum Nematomorpha, called as horsehair or gordian worms, are the parasites of arthropods and emerge from their host for reproduction and early development in water. There are about 360 species of nematomorphs described till date. Although, horsehair worms are parasites of arthropod species, sporadic cases of their occurrence have also been reported from several other hosts, including man. This paper describes a case history of the occurrence of two nematomorph worms in the meat of a pig in Shillong, India. The worms were reported to have emerged in live condition from pork bought by a consumer from local market in Shillong. One of the recovered specimens was studied by scanning electron microscopy for species determination and identified as Gordius sp., mainly on the basis of flat polygonal areoles and fine bristles on the cuticle.

Head sensory organs of Dactylopodola baltica (Macrodasyida, Gastrotricha): a combination of transmission electron microscopical and immunocytochemical techniques.

The anterior and posterior head sensory organs of Dactylopodola baltica (Macrodasyida, Gastrotricha) were investigated by transmission electron microscopy (TEM). In addition, whole individuals were labeled with phalloidin to mark F-actin and with anti-alpha-tubulin antibodies to mark microtubuli and studied with confocal laser scanning microscopy. Immunocytochemistry reveals that the large number of ciliary processes in the anterior head sensory organ contain F-actin; no signal could be detected for alpha-tubulin. Labeling with anti-alpha-tubulin antibodies revealed that the anterior and posterior head sensory organs are innervated by a common stem of nerves from the lateral nerve cords just anterior of the dorsal brain commissure. TEM studies showed that the anterior head sensory organ is composed of one sheath cell and one sensory cell with a single branching cilium that possesses a basal inflated part and regularly arranged ciliary processes. Each ciliary process contains one central microtubule. The posterior head sensory organ consists of at least one pigmented sheath cell and several probably monociliary sensory cells. Each cilium branches into irregularly arranged ciliary processes. These characters are assumed to belong to the ground pattern of the Gastrotricha.

Gordius gonzalezi, a new species of horsehair worms (Nematomorpha) from Spain.

A new species, Gordius gonzalezi, is described from the Iberian Peninsula, from the Sierra de los Tormantos in Central Spain. Characteristic for the species is the presence of multiple short spines on the cuticle, not present in this form in any other Gordius species. Additionally, two further specimens are reported, which could not be determined to species level. One male of the genus Gordius is close to G. aquaticus and one female with regular areoles could belong either to the genus Gordius or to Gordionus.

Chordodes ferox, a new record of horsehair worms (Nematomorpha, Gordiida) from South Africa.

Three females and one male specimen of a previously unconfirmed species of horsehair worms (Nematomorpha) from South Africa are described using Scanning Electron Microscopy. The females correspond to the description of Chordodes ferox Camerano, 1897, a species previously described from the Democratic Republic of the Congo (Congo-Kinshasa) and an adjacent, not further specified region of the Republic of Congo (Congo-Brazzaville). Characteristic is the presence of enlarged and elevated simple areoles around the base of a thorn areole, in combination with further cuticular characters. This is the latest of a total of six species of horsehair worms reported from South Africa so far. Two species of praying mantids, Polyspilota aeruginosa (Goeze, 1778) and Sphodromantis gastrica Stål, 1858, have been identified as hosts of Chordodes ferox, while its distribution range in the region and the period of adult emergence from the host remain largely unknown.

Nematomorpha from the Philippines, with description of two new species.

With the exception of one species, no horsehair worms (Nematomorpha) were known to date from the Philippines. We report here several records, almost all from Panay Island. Two species, Gordius jorriti and Acutogordius finni, are described as new species. Two species of Chordodes, C. caledoniensis and C. cf. moutoni, were found. In addition, further specimens from the genera Gordius, Acutogordius and Chordodes could not be determined to species level.

New records of Indian Nematomorpha, with the description of a new species from the genus Chordodes.

Chordodes tjorvenae, a new species of horsehair worms is described from Mizoram, Northeast India. The species is distinct from all other known species by a unique combination of cuticular charatcers. In addition, the occurrence of the genus Acutogordius, particularly A. finni, is reported for the first time from India.

Using Gordiid cysts to discover the hidden diversity, potential distribution, and new species of Gordiids (Phylum Nematomorpha).

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.