Pellioditis pelhamensis n. sp. (Nematoda: Rhabditidae) and Pellioditis pellio (Schneider, 1866), earthworm associates from different subclades within Pellioditis (syn. Phasmarhabditis Andrássy, 1976).

Recently, much attention has been focused on a group of rhabditid nematodes called Phasmarhabditis, a junior synonym of Pellioditis, as a promising source of biocontrol agents for invasive slugs. Pellioditis pelhamensis n. sp. was first isolated from earthworms near Pelham Bay Park in Bronx, New York, USA, in 1990 and has been found to be pathogenic to slugs as well as some earthworms. It has also been used in several comparative developmental studies. Here, we provide a description of this species, as well as a redescription of a similar earthworm-associated nematode, Pellioditis pellio Schneider, 1866, re-isolated from the type locality. Although P. pelhamensis n. sp. and P. pellio are morphologically similar, they are reproductively isolated. Molecular phylogenetic analysis places both species in a clade that includes all species previously described as Phasmarhabditis which are associated with gastropods. Phasmarhabditis Andrássy, 1976 is therefore a junior synonym of Pellioditis Dougherty, 1953. Also, Pellioditis bohemica Nermut', Puza, Mekete & Mrácek, 2017, described to be a facultative parasite of slugs, is found to be a junior synonym of Pellioditis pellio (Schneider, 1866), adding to evidence that P. pellio is associated with both slugs and earthworms. The earthworm-associated species P. pelhamensis n. sp. and P. pellio represent different subclades within Pellioditis, suggesting that Pellioditis species in general have a broader host range than just slugs. Because of this, caution is warranted in using these species as biological control agents until more is understood about their ecology.

Comparative genomics of 10 new Caenorhabditis species.

The nematode Caenorhabditis elegans has been central to the understanding of metazoan biology. However, C. elegans is but one species among millions and the significance of this important model organism will only be fully revealed if it is placed in a rich evolutionary context. Global sampling efforts have led to the discovery of over 50 putative species from the genus Caenorhabditis, many of which await formal species description. Here, we present species descriptions for 10 new Caenorhabditis species. We also present draft genome sequences for nine of these new species, along with a transcriptome assembly for one. We exploit these whole-genome data to reconstruct the Caenorhabditis phylogeny and use this phylogenetic tree to dissect the evolution of morphology in the genus. We reveal extensive variation in genome size and investigate the molecular processes that underlie this variation. We show unexpected complexity in the evolutionary history of key developmental pathway genes. These new species and the associated genomic resources will be essential in our attempts to understand the evolutionary origins of the C. elegans model.

Rhabditophanes schneideri (Rhabditida) phoretic on a cave pseudoscorpion.

Information of phoretic nematode-pseudoscorpion associations and cases of parasitism on five European species of pseudoscorpions was summarized by Curcic et al. [Curcic, B.P.M., Dimitrijevic, R.N., Makarov, S.E., Lucic, L.R., Curcic, S.B., 1996. Further report on nematode-pseudoscorpion associations. Acta arachnol. 45, 43-46; Curcic, B.P.M., Sudhaus, W., Dimitrijevic, R.N., Tomic, V.T., Curcic, S.B., 2004. Phoresy of Rhabditophanes schneideri (Bütschli) (Rhabditida: Alloionematidae) on pseudoscorpions (Arachnida: Pseudoscorpiones). Nematology 6 (3), 313-317]. An examination of a sample of the cavernicolous pseudoscorpion Neobisium rajkodimitrijevici (Curcic and Tomic, 2006) (comprising a holotype male and a paratype tritonymph) from a cave in Eastern Serbia revealed this false scorpion to be a nematode carrier; the present paper reports this finding and extends our knowledge of phoresy of Rhabditophanes on pseudoscorpions. This is the first time that the rhabditid R. schneideri (Bütschli, 1873) has been noted in association with a cavernicolous pseudoscorpion. There must be some patchily distributed micro-habitats in caves where saprobiotic nematodes and small arthropods can complete their life-cycles, for example something like deposits of bat guano. The transportation of Rhabditophanes J3 by pseudoscorpions indicate that Neobisium specimens often visit these micro-habitats to find their prey.

Ecology of Caenorhabditis species.

Although several Caenorhabditis species are now studied in laboratories in great detail, the knowledge of the ecology of most Caenorhabditis species is scarce. In this chapter we present data on the habitat, animal associations, and geographical distribution of the eighteen described and five undescribed Caenorhabditis species currently known to science. The habitats of these species are very diverse, ranging from rotting cactus tissue to inflamed auditory canals of zebu cattle. Some species, including C. elegans, have only been isolated from anthropogenic habitats. Consequently, their natural habitat is unknown. All Caenorhabditis species are colonizers of nutrient- and bacteria-rich substrates and none of them is a true soil nematode. Dauer juveniles of many Caenorhabditis species were shown to be associated with terrestrial arthropods or gastropods. An association with invertebrates is also likely for the remaining species. The type of association is either phoresy (for transport to a new habitat) or necromeny (to secure the body of the associated animal as a future food source). There are also some records of Caenorhabditis species associated with vertebrates. The Caenorhabditis stem species was probably a colonizer of nutrient-rich substrates and was phoretic on arthropods. Some evolutionary trends within the taxon are discussed.

How can nematodes mate without spicules? Function of the male gonoduct glands in the roundworm Myolaimus.

Males of roundworms (Nematoda) usually possess cuticular copulatory organs (spicules) that are inserted in the female's vulva to attach the male to the female and to widen the vulva against the inner body pressure for sperm transfer. Among free-living nematodes, the only exception of this rule is Myolaimus where the males lack spicules. Until now there exist no reports on how mating is achieved in Myolaimus. Here we show that sperm transfer in Myolaimus apparently involves at least six different secretions of the male gonoduct that are pumped into a sack-like cuticular protrusion of the female's vulva to form a spermatophore-like capsule. The role of gonoduct glands in male nematodes (even in the model organism Caenorhabditis elegans) is poorly understood. Here we present the first study explaining the role of different vas deferens gland products in nematodes and argue that Myolaimus males lost their spicules as a result of sperm competition.