A new Aporcelinus species (Nematoda, Aporcelaimidae) from Livingston Island - first record of the genus from the Maritime Antarctic

The genus Aporcelinus Andrássy, 2009 was erected to accommodate species with characteristic cuticle and other aporcelaimid features such as the lip region, odontostyle and guiding apparatus structure, which have been previously described under Allodorylaimus/Eudorylaimus. In respect to the cuticle structure, the genus is similar to only two other aporcelaimid genera – Aporcelaimellus Heyns, 1965 and Makatinus Heyns, 1965. The genus Aporcelinus currently contains 27 species and is a wide-spread aporcelaimid taxon (Peña-Santiago and Varela-Benavides 2019), reported to occur in all continents except Australia and Antarctica. Nine specimens  from one unknown species belonging to this genus were recovered from moss communities on Livingston Island, Antarctica and studied by an integrative approach (molecular phylogeny and morphology). Aporelinus sp. is characterised by females with medium body size (1.85–2.12 mm), lip region 18–21 μm wide, set off from the adjoining body by constriction, odontostyle and odontophore 23 μm and 30–33 μm long, respectively, vulva transverse slit (V=50–54%), pars refringens vaginae consisting of (in lateral view) two trapezoid sclerotised pieces, uteri differentiated tri-partite, tail ventrally arcuate with rounded terminus (45–60 μm long, c=33.6–42.6, c'=1.4–1.8). It differs from all other species of the genus by its tri-partite uteri with very long and convoluted middle tubular part. Aporcelinus sp. represents a new geographical record for Antarctica.