State of the art of the free-living marine Monhysteridae (Nematoda)

Abstract

The family Monhysteridae is characterized by 17 valid genera, seven of which are known to be free-living, inhabiting marine sediments. In total, 70 valid marine species are ascribed to these seven genera. Overall, the family is characterized by a confused taxonomic history with a large list of synonyms and species inquirendae. The taxonomic problem is not restricted to the old literature, but inconsistencies also appeared in recent studies. The aim of this study is to show the most important diagnostic characters to identify each genus and provide taxonomic tools for species identification. Dichotomous-keys and illustration-guides are attempted for the marine monhysterid species. For the family and each subfamily, tribe and marine genus a brief historical background, diagnosis and a list of valid species is provided. Hereby, we propose to transfer eight species of the genus Thalassomonhystera to the genus Monhystrella.

Description of two free-living nematode species of Halomonhystera disjuncta complex (Nematoda: Monhysterida) from two peculiar habitats in the sea

“…In addition, the morphological and ecological unity of the genus Geomonhystera was restored. This state was also supported in the revision of Monhysteridae made by Fonseca and Decraemer (2008).…”

“…In the recent version of Monhysteridae classification (Jacobs 1987;Fonseca and Decraemer 2008), two subfamilies were established: the Monhysterinae, including species with a funnel-shaped buccal cavity, and Diplolaimellinae, comprising species possessing a double buccal cavity. The subfamily Diplolaimellinae is further divided into two tribes, Diplolaimellini and Geomonhysterini.…”

“…Andrássy (2006) has not discussed the Monhysteridae classification of Jacobs (1987) and not specified the position of Halomonhystera within a tribe or subfamily. Fonseca and Decraemer (2008) have placed Halomonhystera into the tribe Geomonhysterini together with other marine and brackish genera Cryonema Tchesunov and Riemann 1995, Hieminema Tchesunov and Portnova 2005and Monhystrella Cobb 1918. They also provided a list of eleven known species of Halomonhystera and a dichotomous key for their identification.…”

“…The species was considered by de Man (1988) as a possible synonym of M. ambigua and by Gerlach and Riemann (1973) as a synonym of Monhystera disjuncta. However, Andrássy (2006) and then Fonseca and Decraemer (2008) regarded the species as valid. Andrássy (2006) summarized the description of Bütschli (1874) and indicated that H. ambiguoides is similar to H. cameroni in position of the amphideal fovea at a distance of three labial diameters from the anterior end and by relatively long anterior setae (about 1/4 of the labial width, according to Fig.…”

Halomonhystera parasitica n. sp. (Nematoda: Monhysteridae), a parasite of Talorchestia brito (Crustacea: Talitridae) in Portugal

“…Members of the nematode family Monhysteridae De Man, 1876 are typically free-living nematodes occurring in fresh, brackish or salt water as well as terrestrial environments (Fonseca & Decraemer, 2008). External associations with invertebrates include members of Gammarinema Kinne & Gerlach, 1953 on the gills of freshwater crustaceans (crayfish and crabs) (Allen, 1933;Chitwood, 1935;Coomans & Eyualem-Abebe, 2006) and other monhysterids in the gill-chambers of land crabs (Baylis, 1915) and freshwater crustaceans (Schneider, 1932;Osche, 1955;Steiner, 1958).…”