Abstract
During general field surveys carried out recently to collect benthopelagic copepods from near the substrate of the shallow waters off Jeju Island, Korea, a few specimens of three new species of Stephos Scott, 1892, were collected. The new species are placed in the genus Stephos because of the following combination of features: absence of seta on the basal exite of maxillule, and male right leg 5 ending in an unarmed claw-like and/or mitten-like segment. Stephos jejuensissp. nov. can be distinguished from its congeners by body length 0.92 mm, left side of the female genital double-somite with protruding lobes, antennule that extends beyond the distal area of the genital double-somite, and the male leg 5 terminal complex. Stephos concavussp. nov. can be distinguished from its congeners by the genital double-somite with protruding lobes on both sides, and the presence of larger spinules on the distomedial margin of leg 5. Stephos fortipessp. nov. can be distinguished from its congeners by its longer body length, 1.12 mm long in the female, antennules that extend to the end of the genital double-somite, and the presence of a covered row of minute spinules on the ventral surface of the genital operculum in the female. Until now, 35 species of stephids were known worldwide.
Highlights
Benthopelagic copepods are of low abundance and high diversity in the benthic boundary layer (Bradford-Grieve 2004)
There have been a total of eleven species from the Australia-Western Pacific region, as follows: S. pentacanthos Chen & Zhang, 1965; S. morii Greenwood, 1978; S. tropicus Mori, 1942; S. tsuyazakiensis Tanaka, 1967, S. pacificus Ohtsuka & Hiromi, 1987; S. angulatus Bradford-Grieve, 1999; S. robustus Ohtsuka & Hiromi, 1987; S. kurilensis Kos, 1972; S. hastatus Bradford-Grieve, 1999; S. geojinensis Moon, Youn & Venmathi Maran, 2015; and S. projectus Moon, Youn & Venmathi Maran, 2015
Species of Stephos show many similarities to species of its confamilial genera but differs as follows: the male right fifth leg is 4-segmented; and the male right fifth leg ends in an unarmed claw-like and/or mitten-like segment (Boxshall and Halsey 2004)
Summary
Benthopelagic copepods are of low abundance and high diversity in the benthic boundary layer (Bradford-Grieve 2004). The benthopelagic calanoid family Stephidae Sars, 1902, consists of four valid genera by: Stephos Scott, 1892; Parastephos Sars, 1902; Miostephos Bowman, 1976 and Parastephos Sars, 1902; Speleohvarella Kršinić, 2005 Their species are generally smaller in body size, and include hyperbenthic forms living in anchialine and marine coastal habitats (Boxshall and Halsey 2004; Jaume et al 2008; Kršinic 2012, 2015; Moon et al 2015; Suárez-Morales et al 2017). During a survey of the copepod fauna of the southern coasts of Jeju Island, the largest island in Korea, a few specimens of stephids were collected from near-bottom shallow waters by vertical tows of 0.1-mm mesh conical nets at high tide in dusk hours One of these samples contained representatives of several Stephos not known to the benthopelagic environment. This paper reports on three undescribed species of the genus Stephos that are described in full and compared with their known congeners around the world
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