Representatives of Ligophorus Euzet et Suriano, 1977 were found on the gills of Mugil liza Valenciennes caught in southern Brazil. They were identified as Ligophorus uruguayense Failla Siquier et Ostrowski de Núñez, 2009 and Ligophorus saladensis Marcotegui et Martorelli, 2009, even though specific identification proved to be difficult due to inconsistencies in some diagnostic features reported for these two species. Therefore, a combined morphological and molecular approach was used to critically review the validity of these species, by means of phase contrast and confocal fluorescence microscopical examination of sclerotised hard parts, and assessing the genetic divergence between L. saladensis, L. uruguayense and their congeners using rDNA sequences. The main morphological differences between the two species relate to the shape of the accessory piece of the penis and the median process of the ventral bar. The accessory piece in L. uruguayense is shorter than in L. saladensis, has a cylindrical, convex upper lobe and straight lower lobe (vs with the distal tip of the lower lobe turning away from the upper lobe in the latter species). The ventral bar has a V-shaped anterior median part in L. uruguayense (vs U-shaped in L. saladensis). The two species are suggested to be part of a species complex together with L. mediterraneus Sarabeev, Balbuena et Euzet, 2005. We recommend to generalise such comparative assessment of species of Ligophorus for a reliable picture of the diversity and diversification mechanisms within the genus, and to make full use of its potential as an additional marker for mullet taxonomy and systematics.
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With only three named species, Antarctica is the continent with the least explored kinorhynch biodiversity. The present contribution provides the most comprehensive study of Antarctic kinorhynchs collected along the coast of the West Antarctic Peninsula. Quantitative samples were collected in three regions along the Peninsula: in Andvord Bay Fjord at the Danco Coast, in the Gerlache Strait, and on the open continental shelf west of the Peninsula. Comparison of the sampling areas suggests that the highest kinorhynch abundance was in the Gerlache Strait, where kinorhynchs were over six times more abundant than in Andvord Bay. Lowest abundance was on the open shelf, where the abundance was four times lower than in Andvord Bay. Among all examined specimens 98% were found in the top 4 cm of the sediment. All adult kinorhynchs were identified, and the study revealed the presence of the known Antarctic species Polacanthoderes shiraseae and at least seven species new to science: Condyloderes notios sp. nov., Polacanthoderes grzelakae sp. nov., Echinoderes ahlfeldae sp. nov., E. nataliae sp. nov., E. kathleenhannae sp. nov., E. antarcticus sp. nov., and E. crux sp. nov. In addition to the five new species of Echinoderes, two potentially known species are reported. Echinoderes aff. angustus shows close resemblance to the Arctic E. angustus, and the specimens only differed by their lack of a midventral fissure in segment 2, present in Arctic specimens of E. angustus only. A detailed examination of the E. angustus type material revealed new diagnostic details for the species, i.e., a complete mapping of sensory spots, presence of a middorsal protuberance between segments 10 and 11, and a tergal division of segment 11. Another unidentified species, Echinoderes aff. beringiensis/romanoi/xalkutaat, showed such close resemblance to three congeners that further studies are needed to identify clear diagnostic characters for the species, or alternatively clarify whether they should be synonymised. The comparisons prompted by the two unidentified species led to the suggestion of a new species group, the Echinoderes remanei species group, including E. remanei, E. angustus, E. beringiensis, E. cernunnos, E. drogoni, E. galadrielae, E. obtuspinosus, E. quasae, E. pennaki, E. romanoi, and E. xalkutaat. In addition, the Echinoderes aragorni species group is proposed, including the New Zealand species E. aragorni and the new species E. crux.
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RBINS Staff Publications 2025
A new gastrotrich species, Musellifer leasiae sp. nov., is described from the west coast of the Antarctic Peninsula. The species is recognised by its considerable size, up to 415 μm, and by its conspicuous three-lobed, keeled head scales. Besides the new species, the genus Musellifer accommodates five additional species known from the Mediterranean Sea, the Black Sea, the Central-West Atlantic, the Northeast Atlantic, and the Northeast Pacific, and from depths ranging from sublittoral to 5.485 m depth. A representative of Musellifer has previously been reported from Antarctica, but M. leasiae sp. nov. represents the first formally described Muselliferidae species from the Southern Hemisphere, and from the polar regions.
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RBINS Staff Publications 2025
