Abstract
Three new species of Mesacanthion Filipjev, 1927 were found along Patagonian coasts (Argentina). Mesacanthion bifidum sp. nov. is characterized by short labial and cephalic setae, onchia of equal size, spicule arcuate, and gubernaculum with caudal apophysis, ending in two teeth. The species is related to M. virile (Ditlevsen, 1930) De Coninck & Schuurmans Stekhoven, 1933. However, the spicules and gubernaculum of both species are different in shape. Mesacanthion longigubernaculum sp. nov. is characterized by its long and slender body, striated cuticle, relatively long cephalic and cervical setae, onchia of different sizes, amphidial fovea lentil-shaped, spicule arcuate, gubernaculum surrounding the spicule, and tail conical-cylindrical with terminal setae. Mesacanthion sanantoniensis sp. nov. is characterized by its long and stout body, striated cuticle, long cephalic setae, onchia of different sizes, amphidial fovea pouch-shaped, spicule arcuate, gubernaculum with dorsal apophysis, and tail conical without terminal setae. Following the key of Jeong et al. (2019), the last two species are related to M. pali Wieser, 1959 and M. longissimesetosum Wieser, 1953, so we provide a key to differentiate the four species.
Highlights
Since the middle of the 1970s, the free-living marine nematodes have been studied uninterruptedly in the Argentine coasts, the southernmost continental region of South America
Considering the similarities between M. longigubernaculum sp. nov., M. sanantoniensis sp. nov., M. longissimesetosum and M. pali, we provide a small key for an easy differentiation
With the new species described in this study, the total number of Mesacanthion species amounts to 42
Summary
Since the middle of the 1970s, the free-living marine nematodes have been studied uninterruptedly in the Argentine coasts, the southernmost continental region of South America. More than 400 species have been distinguished along the coastal area that extends over 4725 km. The purpose of the studies was for ecological investigations but taxonomical. As most of the species found were new to science, intense work has been carried out over the years to try to describe them. To. European Journal of Taxonomy 787: 17–31 (2021). Date, descriptions of 74 species have been published. Some belonging to the genus Mesacanthion Filipjev, 1927 were found
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