A new species of Psammonitocrella Huys, 2009 (Copepoda, Harpacticoida, Ameiridae) from California (USA), with a discussion of the relationship between Psammonitocrella and Parastenocarididae

The freshwater harpacticoid Psammonitocrella kumeyaayisp. nov. from the Nearctic Region (California; USA) is proposed. The position of the genus within Harpacticoida and its relationship with the Parastenocarididae is discussed. The new species can be included within Psammonitocrella on account of a) the cylindrical furca, longer than the telson, b) the unmodified inner spine on the basis of the male first leg, c) loss of the outer spine on the second exopodal segment of the first leg, d) loss of the outer spine of the third exopodal segment of the second, third, and fourth legs, e) loss of the inner apical seta on the third exopodal segment of the second and third legs, f) transformation of the inner apical seta of the third exopodal segment of the fourth leg into a spine, and g) loss of the endopodite of the fourth leg. The new species differs remarkably from P. boultoni, and P. longifurcata in the loss of the outer spine of the second exopodal segment of the fourth leg, in the presence of a one-segmented fifth leg exopodite, and in the presence of an outer seta on the basis of the first and second legs. Both Psammonitocrella and the known species of Parastenocarididae have a one-segmented endopod on the fourth leg, and the endopods of the second and third legs are reduced to one or two segments. Psammonitocrella is currently allocated into the Ameiridae, and evidence suggesting a sister-group relationship with Parastenocarididae—both share the loss of the inner seta on the first endopodal segment of the first leg—indicates that the Parastenocarididae should be included into the Ameiridae. In an evolutionary context, Parastenocarididae could have evolved from a lineage of freshwater ameirids that became interstitial in continental waters and colonized aquifers and groundwaters.

On some new species of Stenheliinae Brady, 1880 (Copepoda, Harpacticoida, Miraciidae) from north-western Mexico, with the proposal of Lonchoeidestenhelia gen. nov.

Quarterly sampling campaigns during 2019 to study the diversity of meiofauna in a polluted estuary in northwestern Mexico revealed the subfamily Stenheliinae Brady, 1880 as one of the most important contributors to the diversity of benthic harpacticoids. Two new stenheliin species are described here. One of them was assigned to the, so far, monotypic genus Lonchoeidestenheliagen. nov. defined by the autapomorphic modified proximal outer spinules on the sigmoid process of the male P2ENP2. The other species was assigned to Willenstenhelia Karanovic and Kim, 2014. Lonchoeidestenheliagen. nov. shares the armature formula of the P1 EXP2 with Stenhelia, Anisostenhelia, and Beatricella, but seems to bear a sister-group relationship with the former two genera by the loss of one inner seta on the P2–P3 EXP3, the presence of two outer spine-like elements on the male P5EXP, and the displacement of the outer spine and medial and inner distal setae of P2ENP3, to an apical and subapical inner position, respectively, but is more closely related to Anisostenhelia by the overall shape of the male P2ENP2. Willenstenhelia reductasp. nov. is attributed to a group of species composed of Wi. minuta, Wi. urania, and Wi. terpsichore characterized by the strongly reduced inner seta of the female P5 baseoendopod, but differs in the discrete female P5 baseoendopods and in the presence of one outer seta only on that segment. Willenstenhelia reductasp. nov. is defined here by the autapomorphic loss of the outermost seta of the female P5 baseoendopod.

A New Species of the Genus Halectinosoma Vervoort, 1962 (Copepoda: Harpacticoida: Ectinosomatidae) from the East Coast of Korea, with a Key to Species of the Curticorne-Group

A new species of genus Halectinosoma Vervoort, 1962 was collected from the east coast of Korea. The genus Halectinosoma comprises about 70 species, but only three species have previously been reported in East Asia. Halectinosoma munmui sp. nov. is morphologically most closely related to H. langi Wells 1967 from Inhaca Island, Mozambique, and H. oblongum (Kunz, 1949) from Heligoland island, Germany, however clearly distinguishable from it based on the following morphological characteristics: 5-segmented and elongated female antennule, mandible gnathobase without seta, about 5.6 times as long as the greatest width of the basis of the maxilliped, and outer seta of the P5 endopodal lobe longer than the inner seta. A key to species of the curticorne-group of Halectinosoma is provided.

A new species in the genus Acartia Dana, 1846 (Crustacea, Copepoda, Calanoida, Acartiidae) from the South Pacific coastal waters of Nadi Bay, Fiji

A new species in the genus Acartia, Acartia nadiensissp. nov., is described from Fijian coastal waters. This species belongs to the subgenus Odontacartia based on the following morphological features: presence of a rostral filaments, a pointed process on the last prosomite, a serrated terminal spine on female P5, and the absence of a protrusion on the basis of the male right P5. This new species can be differentiated from its congeners by the combination of the absence of a spine on the first segment of the antennules, the short outer seta of female P5, and a medial spine on the exp-2 of the left male P5. Phylogenetic analyses using mitochondrial COI partial sequences show that the new species is distinct from its congeners.

Onychocamptus Daday, 1903 from Thailand, with descriptions of two new species and two new records (Crustacea, Copepoda, Harpacticoida, Laophontidae)

In this paper, two new species ofOnychocamptusDaday, 1903 are described from Thailand:Onychocamptussatunensissp. n.andOnychocamptustratensissp. n.The following features mainly distinguishO.satunensissp. n.from known species: internal sausage-like and internal rounded structures on cephalothorax and one outer seta on the male P5 exopod that is as long as the supporting segment. In contrast, the cephalothorax ofO.tratensissp. n.is smooth but has rounded integumental window-like structures, and the outer seta on the male P5 exopod is two times as long as the supporting segment.Onychocamptusanomalusshows the highest similarity with the two new species, but in contrast to both Thai species, it has only one seta on the exopod of the antenna. In addition, in the present study, two additional species,O.bengalensisandO.vitiospinulosa, are newly recorded in Thailand. Thus, the number ofOnychocamptusspecies recorded in Thailand increases to five species. A key to all known species of this genus in the world is also proposed.

Revision of the Remaneicaris argentina-group (Copepoda, Harpacticoida, Parastenocarididae): supplementary description of species, and description of the first semi-terrestrial Remaneicaris from the tropical forest of Southeast Mexico

Remaneicaris is a species-rich Neotropical monophyletic group, easily recognized by the synapomorphic position of the outer seta of the third exopodite of leg 4, localized at 2/3 of the outer margin. The genus, comprising 35 species in five monophyletic groups, plus R. ignotus and R. meyerabichi, retains an unusual set of plesiomorphic characters. Herein we supplement the descriptions of the species belonging to the Remaneicaris argentina-group, and describe a new species from the tropical forest of Southeast Mexico. The present study extends the geographic distribution of the genus, with the northernmost record until now being from El Salvador. The genus having hitherto been known from interstitial groundwater habitats, this is its first record in epigean semi-terrestrial habitats. Remaneicaris siankaan sp. nov. was found in phytotelmata (bromeliads), leaf litter, moist soil, permanent ponds (known locally as “aguadas”), and temporal and permanent wetlands (savannahs). The new species can be easily characterized by its finely pitted cuticle, the ε (epsilon)-shaped thumb of the male P3 and the bifid accessory spine with distal hyaline inner tip, which precedes the thumb. A new method for the 3D reconstruction of microcrustaceans is described.

Description of two new species of Dorsiceratus Drzycimski, 1967 (Copepoda: Harpacticoida: Ancorabolidae) from Sedlo and Seine Seamounts (Northeastern Atlantic) and remarks on the phylogenetic status of the genus

Two new species of Dorsiceratus Drzycimski, 1967 (Copepoda, Harpacticoida, Ancorabolidae), Dorsiceratus wilhelminae sp. nov. and D. dinah sp. nov. are described from Sedlo and Seine Seamounts, respectively (both northeast Atlantic). These are the first records of Dorsiceratus species from seamount summits. Both new species resemble the described species D. octocornis Drzycimski, 1967, D. triarticulatus Coull, 1973, and D. ursulae George, 2006, with respect to most morphological features. On the other hand, D. wilhelminae sp. nov. has long spinules at the inner margin of the A2 enp, while D. dinah sp. nov. bears two, rather than one, tubepores dorsally on third abdominal somite, and a geniculate first outer seta on P1 exp2. These characters are considered as apomorphic relative to the described Dorsiceratus species. As discussed in the present paper, the maintenance of a genus Dorsiceratus appears to be problematic. Although specimens may be assigned without difficulty to a group “Dorsiceratus”, such assignments are based on diagnostic features only; no clear-cut apomorphies have been detected so far to characterize the monophyly of Dorsiceratus. Just two apomorphic characters appear to be synapomorphies for all of the described Dorsiceratus species: 1) P2 enp2 with one rather than two setae and 2) P4 exp sexually dimorphic. Unfortunately, these features are relatively widespread within the Ceratonotus-group sensu Conroy-Dalton (2001) and therefore of rather low value. The authors decided, however, to retain the genus Dorsiceratus until new insights provide more information to support or disprove that hypothesis.

A new and exceptional species of Bradya Boeck, 1873 (Copepoda: Harpacticoida:Ectinosomatidae) from the abyssal plain of the Angola Basin and the variabilityof deep-sea Harpacticoida

Bradya kurtschminkei sp. nov. is described from deep-sea samples collected from the Angola Basin (Southeast Atlantic) during the DIVA 1 campaign in 2000, the Guinea and Cape Basins (Southeast Atlantic) during the DIVA 2 campaign in 2005, and the Porcupine Abyssal Plain (Northeast Atlantic) during the RRS ‘‘Challenger’’ cruise 111 in 1994. B. kurtschminkei sp. nov. is exceptional because of many characters, hitherto unknown from other Bradya species. B. kurtschminkei sp. nov. can be distinguished from its congeners by its unique habitus as the body is slightly flattened dorso-ventrally and the female cephalothorax is almost as long as the free pedigerous somites and the urosome together. The rostrum’s length is a third of the cephalothorax length and it tapers to a point. The antennule is 5-segmented, the basis of maxillule is fused with exopod and endopod, and the endopod has only four setae. The endopod of maxilla has only one large claw, the exopod of the P5 is short, its distal end reaches to the distal end of the baseoendopod, and the outer seta of the baseoendopod has a double tip. The armature formula of P1–P4 is exceptional as there are in total seven setae less on the endopods than in all other species of Bradya. Like many other deep-sea Harpacticoida, B. kurtschminkei sp. nov. shows compared with shallow waters species a remarkable, as yet unknown morphological variability.

A new species of Eucyclops Claus (Copepoda: Cyclopoida) from Southeast Mexico with a key for the identification of the species recorded in Mexico

Eucyclops torresphilipi sp. nov. is described from samples collected in the state of Chiapas, on the southeastern Pacific coast of Mexico. It belongs to a group of species similar to the presumably cosmopolitan E. agilis (Koch, 1838). The new species is closest to the South American E. delachauxi (Kiefer, 1925); it can be distinguished from its congeners by a combination of characters that include a fifth leg with a particularly slender inner spiniform seta that is as long as the outer seta, the caudal rami has spinules covering up to of the outer margin, caudal rami over 4 times longer than wide, the relative length of the dorsal seta, and the proportion of the terminal spines of the third exopodal segment of the fourth legs. Only nine other nominal species of Eucyclops have been recorded in Mexico; nearly half of them are known also from South America. The new species seems to have a restricted distributional range; however, it could be present also in Guatemala. Its morphological affinity with South American forms confirms the influence of the South American cyclopoid fauna in Mexico. A key for the identification of the species of Eucyclops recorded in Mexico is included.