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The subgenus Hystricochaetonotus Schwank, 1990 is one of the most species-rich subgenera of Chaetonotus Ehrenberg, 1830. It has a worldwide distribution and encompasses 37 species predominantly living in the benthos and periphyton of limnetic habitats. We have discovered further nine new species in running and stagnant waters in Slovakia (Central Europe): Ch. (H.) arcanus sp. nov., Ch. (H.) avarus sp. nov., Ch. (H.) gulosus sp. nov., Ch. (H.) iratus sp. nov., Ch. (H.) luxus sp. nov., Ch. (H.) mirabilis sp. nov., Ch. (H.) optabilis sp. nov., Ch. (H.) slavicus sp. nov., and Ch. (H.) superbus sp. nov. Their morphology was studied using differential interference contrast microscopy and subsequent morphometric analyses were carried out. In addition, the primary and secondary structures of their 18S, ITS2, and 28S rRNA molecules as well as their barcoding mitochondrial gene encoding for cytochrome c oxidase (COI) were analyzed. Species boundaries were tested also using the compensatory base change analysis. The new species could be well separated both morphologically and molecularly. The present barcoding analyses revealed that the nuclear ITS2 sequences represent a powerful DNA barcode in addition to the mitochondrial COI gene. According to the multi-gene phylogenetic analyses, the lineage leading to the last common ancestor of the ‘Hystricochaetonotus’ clade is the longest internal branch within the family Chaetonotidae Gosse, 1864. Since members of the subgenus Hystricochaetonotus are morphologically highly heterogeneous, parallel evolution of Chaetonotus-like and/or Hystricochaetonotus-like characters of scales and spines occurred during its radiation.
Thirteen species of Echinoderes with nearly identical spine/tube patterns, and apparently similar tergal extensions were re-examined and compared. Based on this, redescriptions and/or emended species diagnoses are provided for Echinoderes aureus, E. dujardinii, E. gerardi, E. imperforatus, E. pacificus, E. pilosus, E. sensibilis, E. sublicarum and E. worthingi, and new details about cuticular structures are added for E. kozloffi and E. gizoensis. The new information derived from the redescriptions, and the subsequent comparative studies revealed that: 1) the holotype of Echinoderes lanceolatus is identical with the types of Echinoderes aureus, and E. lanceolatus is thus a junior synonym of E. aureus; other potentially synonymous species that should be addressed further in the future include: E. dujardinii + E. gerardi; E. imperforatus + E. sensibilis, and E. pacificus + E. sublicarum; 2) the paratypes of E. lanceolatus represented a different yet undescribed species, here described as E. songae Sørensen & Chang sp. nov.; 3) a comparison with literature information about E. ehlersi showed that the species is so insufficiently described that a redescription of topotype material is required before the species should be considered for taxonomic comparison; 4) specimens from the Andaman Islands, India, that previously have been reported as Echinoderes cf. ehlersi represent two different undescribed species, of which one is described as E. chandrasekharai Sørensen & Chatterjee sp. nov. and the other is left undescribed due to the limited material available; 5) out of a total of fifteen addressed species, it is proposed that eleven represent a putatively monophyletic group that is named the Echinoderes dujardinii group. The group includes following species: E. dujardinii, E. ehlersi, E. gerardi, E. imperforatus, E. kozloffi, E. sensibilis, E. pacificus, E. sublicarum, E. songae Sørensen & Chang sp. nov., E. chandrasekharai Sørensen & Chatterjee sp. nov., and Echinoderes sp. from the Andaman Islands, and is supported by a similar spine/tube pattern (except for variation regarding the presence of lateral accessory tubes on segment 8); generally short middorsal spines, especially on segments 4 to 6; glandular cell outlets type 1 always present in middorsal positions on segments 1 to 3, and in subdorsal positions on segments 4 to 9; glandular cell outlets type 2 always present in laterodorsal or midlateral positions on segment 8, and sometimes in same positions on segment 9 but never at any other segments or positions; female papillae always present on sternal plates of segments 7 and 8, and occasionally also on segment 6; tergal extensions well-spaced, triangular, gradually tapered cones, and pectinate fringes of sternal extensions are differentiated into seta-like tufts. The comparisons furthermore showed potential taxonomic significance of two echinoderid character traits that previously have been slightly neglected as diagnostic traits, namely the presence and appearance of female papillae, and the dorsal pattern of glandular cell outlets type 1. Female papillae may occur on the sternal plates of segments 6 to 8, but the positions may differ from ventrolateral to ventromedial, and the morphology of the intracuticular substructure also differ at species level. Information about position and morphology of female papillae proved helpful for species recognition, but it might also provide information of phylogenetic importance. Analyses of glandular cell outlet type 1 patterns on the dorsal sides of segments 1 to 9 in species of Echinoderidae, revealed several apparently unique or rare patterns, but also three distinct patterns that applied to larger groups of species. One pattern is the one present in all species of the E. dujardinii group, whereas the other two common patterns included 1) middorsal outlets on segments 1 to 3, and paradorsal outlets on segments 4 to 9 (found in 27 species), and 2) middorsal outlets on segments 1 to 3, 5 and 7, and paradorsal outlets on segments 4, 6 and 8 to 9 (found in 27 species).
Limited data are available for the kinorhynch fauna from the Southern Hemisphere, with little or no data from New Zealand. Here, we provide a first comprehensive overview of the diversity of mud dragons, with an emphasis on species of Echinoderes from the continental slope of New Zealand, from a variety of habitats such as slopes, canyons and seamounts located in the Hikurangi Margin region. The study revealed fifteen species of Echinoderes. Of these, ten are described as new to science: E. aragorni sp. nov., E. blazeji sp. nov., E. dalzottoi sp. nov., E. frodoi sp. nov., E. galadrielae sp. nov., E. gandalfi sp. nov., E. landersi sp. nov., E. leduci sp. nov., E. legolasi sp. nov. and E. samwisei sp. nov. Moreover, Echinoderes juliae Sørensen et al., 2018, Echinoderes sp. aff. E. balerioni, Echinoderes sp. aff. E. galadrielae/beringiensis, Echinoderes sp. aff. E. lupherorum and Echinoderes sp. aff. E. unispinosus are reported in the investigated region. The most abundant among all was E. gandalfi sp. nov., but it was found only in canyons. Interestingly, the second most common species was E. juliae that was found at several stations in canyons, seamount and on the slope. This species is one of the deep-sea species originally found on the abyssal plain off Oregon and along the continental rise off California, Northeast Pacific, recorded in polymetallic nodules in the tropical eastern Pacific, and recently found on the abyssal plains off Chile, east of the Atacama Trench. These findings, together with records of Echinoderes sp. aff. E. lupherorum and Echinoderes sp. aff. E. unispinosus indicate that, despite their low dispersal abilities, kinorhynchs, similar to other meiofaunal species, may exhibit a wider distribution pattern than previously assumed. The number of recorded species and numerous new species show that New Zealand sediments not only are inhabited by a diverse kinorhynch fauna, but Echinoderes, the most speciose genus, still holds much to discover.
A new species of echinoderid kinorhynchs, Echinoderes xiphophorus sp. nov. collected from oxidized brown silt at the deepest depression in the Sea of Japan, North-West Pacific, is described and illustrated using light and electron microscopy. This new representative of the most speciose kinorhynch genus is characterized by the unique set of spines and tubes and can easily be distinguished from most of its congeners. The second trunk segment bears three pairs of tubes in subdorsal, midlateral and ventrolateral position in both sexes; one pair of tubes on trunk segment 5 in lateroventral position and on trunk segment 8 in sublateral position; aciculate lateroventral spines on trunk segments 6–9; aciculate middorsal spines on trunk segments 4, 6, 8. This species is well recognized by very long tergal extensions of the posteriormost segment, some of the longest within the family Echinoderidae. Males of Echinoderes xiphophorus sp. nov. are well distinguished from all the congeners by extremely long sword-like appendages dorsally to three pairs of penile spines. The species constitutes the first deep-sea representative of the Echinoderidae in the Sea of Japan and the deepest representative of the Kinorhyncha in this sea.
In the framework of an ongoing extensive phylogenetic evaluation of the Ceratonotus group (Copepoda, Harpacticoida, Cletodidae), Poropsyllus menzelae gen. et sp. nov. from the sublittoral of south-western Cyprus (eastern Mediterranean Sea) and Paratouphapleura aaroni gen. et sp. nov. from the western Weddell Sea (Antarctica) are described. Both new species fit the autapomorphies of the Ceratonotus group but cannot be assigned to any of the genera so far known. Instead, each new species presents a set of derived characters that justify their placement in new genera, Poropsyllus gen. nov. and Paratouphapleura gen. nov., respectively. Furthermore, a comparison of the species placed in Ceratonotus Sars revealed that because of exclusive morphological deviations, Ceratonotus concavus Conroy-Dalton, C. steiningeri George, C. tauroides George, and C. vareschii George should be excluded from Ceratonotus and transferred to a new monophylum, Tauroceratus gen. nov. Likewise, Polyascophorus monoceratus George, Wandeness & Santos is characterized by several apomorphies that justify its transfer from Polyascophorus to a new taxon, Pseudopolyascophorus gen. nov. The Ceratonotus group is therefore increased to 31 species assigned to 13 genera. The systematic modifications conducted and resulting phylogenetic consequences are discussed in detail.
The fauna of Loricifera along a north-south longitudinal transect following the Atacama Trench was explored. Whereas no loriciferans were collected from the actual trench, the continental slope and surrounding abyssal plains yielded two species of Rugiloricus and two of Pliciloricus. All four species are considered as new to science, but only one of them could be formally described. The new species, Pliciloricus ukupachaensis sp. nov., is closely related with the North Atlantic Pliciloricus leocaudatus, and the two species share different morphological traits, including an enlarged anal field with conspicuous pentagonal and hexagonal fields formed by strong, cuticular ridges. Among other peculiar traits, the new species is characterised by having strongly reduced trichoscalid plates and no double trichoscalids. Comparison with previously published, unidentified specimens suggests that the new species’ distributional range might reach as far as Oregon off the US west coast.
In the Pacific Ocean, the taxonomy of the family Zosimeidae Seifried, 2003 is poorly understood and to date only five species of the genus Zosime Boeck, 1873 are known. During oceanographic cruises exploring the species diversity of harpacticoids, two undescribed zosimeid copepods were sampled from shallow Korean waters and the deep northwestern Pacific. A detailed morphological examination has led us to propose two new genera, Heterozosime gen. nov. for the Korean zosimeid H. tenuis gen. et sp. nov. and Acritozosime gen. nov. for the deep-sea zosimeid A. spinesco gen. et sp. nov. Both new genera exhibit a distinctive feature in that the first thoracic leg has a two-segmented exopod, in contrast to the three-segmented exopod of this leg in all known zosimeid genera. Furthermore, Acritozosime gen. nov. can also be discriminated from other genera by the two-segmented endopod in second to fourth thoracic legs and the reduced setal armatures of the second exopodal segment of antenna, the first endopodal segment of first to third thoracic legs and the third exopodal segment in second to fourth thoracic legs. A comparison of the fundamental structures of appendages suggests that A. spinesco gen. et sp. nov. experienced a unique evolutionary history within the Zosimeidae.