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Meiofauna samples were collected using the multicorer during three FS POLARSTERN research expeditions to the Southern Ocean between 2013 and 2019. The samples yielded, among other representatives of the CopepodaHarpacticoida, 11 individuals of a previously unknown species of the Ancorabolidae Sars. The six males and five females could be assigned to the genus Breviconia Conroy-Dalton & Huys, within which they form a separate species. Breviconia acuminata sp. nov. differs from the two already known species B. australis (George) from the Beagle Channel (Chile) and B. andrei Garlitska, George & Chertoprud from the Barents Sea (Russia) in the following autapomorphies: (i) the female antennule has only nine setae on the last segment instead of ten, (ii) the inner apical seta on P2enp2 is strongly shortened and only reaches half the length of the outer apical seta. In addition to the detailed description of the new species, a morphologically based comparison with the taxa Arthropsyllus Sars and Uptionyx Conroy-Dalton & Huys confirmed the monophyletic status of Breviconia. A key to the Breviconia species is also provided. Breviconia acuminata sp. nov. has a very limited distribution range. To date, it has only been found on the continental shelf at the northernmost tip of the Antarctic Peninsula and on the continental slope in Bransfield Strait, at depths between 420 and 750 metres. The sediments at the stations where the new species was found were characterised by low bottom temperatures, a high silt and clay content (84-89%), and high pigment content, indicating a high food availability.

Two species belonging to the family Laophontidae Scott T., 1905 were identified among harpacticoid copepods collected from marine plastic debris (MPD) stranded along the Korean coastline. These species were assigned to the genera Pseudonychocamptus Lang, 1944 and Heterolaophonte Lang, 1948. Pseudonychocamptus setadefectus sp. nov. conforms to the generic diagnosis, displaying sexual dimorphism in the armature of the swimming legs. It is distinguished from its six congeners by possessing only two endites on the maxillary syncoxa, notably lacking the proximal endite bearing the seta that is present in all other known species within the genus. Although most morphologically similar to P. colomboi Ceccherelli, 1988, the new species differs in several key characteristics, including the number of setae on the maxillary endopod, the relative length ratios of setae on the female P5 exopod, the presence of an inner seta on the male P5 exopod, and the asymmetry of the male P6. The second species, Heterolaophonte discophora (Willey, 1929), was previously reported from the Atlantic coast of Canada and the Pacific coasts of the USA and Japan. The Korean specimens closely correspond to these previous records, yet exhibit intraspecific variation, particularly in the setal count on the female P3 enp-2. Additional morphological differences were also observed, including variations in the segmentation of the male P3 endopod and in the number of setae on the maxillary endopod. Based on the sexually dimorphic traits observed in males, we propose the subdivision of the genus Heterolaophonte into four distinct species groups. The discovery of P. setadefectus sp. nov. and H. discophora on anthropogenic MPD underscores the potential role of such substrates as microhabitats for benthic harpacticoid copepods.

The discovery and description of a new representative of the Ceratonotus group (Copepoda, Harpacticoida, Cletodidae T. Scott) in the Grussaí Canyon off the coast of Brazil opened up the possibility of clarifying the relationship between Echinopsyllus Sars and Pseudechinopsyllus George. Pseudechinopsyllus andrei sp. nov. is characterised by several autapomorphies, including (a) the extensive development of long spinules on the second and third segment of the female antennule, and the strong respectively extreme elongation of (b) the exopod and (c) the setophore on the female P5. Synapomorphies shared with P. sindemarkae include (d) the formation of long spinules at the bases of P2-P4 as well as (e) on exp1 of the P2, and (f) the strong elongation of a tube pore on P2 exp2. Furthermore, the sister group relationship of Pseudechinopsyllus and Echinopsyllus could be substantiated by eleven synapomorphies, among them (g) the large body size, (h) the development of long, rigid cephalothoracic ventrolateral anterior and posterior processes and (i) the loss of the syncoxal seta on the maxilliped. The present study represents a further step towards clarifying the systematic relationships within the Ceratonotus group. A key to the species is provided.

 A new species of the harpacticoid copepod genus Esola is described from specimens collected in Rodadero Beach, on Gaira Bay, on the Caribbean coast of Colombia. The species, E. wellsi sp. nov. , is described, illustrated, and com­pared with its congeners. Esola wellsi sp. nov. differs from its known congeners in details of the armature of legs 1-4. It most closely resembles E. bulbifera (Norman, 1911) in the armature formula of P1-P5 but differs from the latter in several respects, including the female antennule segmentation (7-segmented in E. bulbifera but distinctly 6-segmented in E. wellsi sp. nov. ) and in the shape and size of the male P3ENP2 apophysis, among other characters. This is the second species of the genus known from the Caribbean and the second record of Esola in the Northwestern Tropical Atlantic. The genus now contains eight species. A key to the known species of the genus is also included. Keywords: Benthic copepods, Caribbean, crustaceans, harpacticoids, taxonomy

Brady, 1880 is considered to be distributed worldwide and is the type species of Brady, 1880 that, in turn, is the type genus of the family Nannopodidae Brady, 1880. However, its original description and subsequent amendments are discrepant and is insufficiently detailed, giving rise to considerable taxonomic confusion thus hampering species delimitation, further revisions, and other taxonomical acts. This paper presents a detailed morphological redescription of both sexes of with the designation of a neotype from material recently collected from the type locality. We compared key characteristics of the newly collected specimens of with those of other species of . Morphological and molecular analyses, including 18S rDNA, support the subdivision of the genus into two species groups as proposed by Sciberras et al. (2021). Specimens from several distant populations, previously identified as were reexamined. Specimens from the Westerschelde estuary (SW Netherlands) and Small Adzhalyk Estuary (NW Black Sea) were found to be identical to those from the type locality and were attributed to . Specimens from the White Sea, however, turned out to be conspecific with Fiers & Kotwicki, 2013. Specimens from the Vellar estuary (Bay of Bengal) and Lake Hinuma (Japan) likely represent distinct, yet undescribed species of . An updated generic diagnosis is provided, offering a clearer framework for future taxonomic studies.

Species of Balaenophilus are the only harpacticoid copepods that exhibit a widespread, obligate association with vertebrates, i.e., B. unisetus with whales and B. manatorum with marine turtles and manatees. In the western Mediterranean, juveniles of the loggerhead sea turtle, Caretta caretta are the only available hosts for B. manatorum, which has been found occurring at high prevalence (>80%) on them. A key question is how these epibionts are transmitted from host to host. We investigated this issue based on experiments with live specimens of B. manatorum that were cultured with turtle skin. Specimens were obtained from head-started hatchlings of C. caretta from the western Mediterranean. Hatched nauplii crawled only on rough substrates and lacked the ability to swim. Only copepodites IV and V, and adults, were able to perform directional swimming. Legs 2, 3 and 4 played a major role in swimming and were only well-developed in these stages. Nauplii reared in wells with turtle skin readily fed on this item. Late copepodites and adults also fed on turtle skin but did not consume other potential food items such as fish skin, baleen plates or planktonic algae. Evidences suggest that the transmission of B. manatorum should rely on hosts' bodily contacts and/or swimming of late developmental stages between spatially close hosts. The possibility of long-ranged dispersal is unlikely for two reasons. First, all developmental stages seem to depend on turtle skin as a food resource. Second, the average clutch size of ovigerous females was small (< 70 eggs) for free-living phases to successfully contact turtles that occur at very low densities (< 0.6 turtles·km.sup.-2) in the western Mediterranean. The high prevalence of B. manatorum in loggerhead turtles in this area raises the question whether these turtles have contacts, or tend to closely aggregate, more than is currently believed.

Thirty-one nominal species of the benthic harpacticoid family Zosimeidae Seifried, 2003 are known from several coastal systems less than 200 m depth and the deep sea. Several copepods of the family Zosimeidae were found in deep-sea sediment samples from the Gulf of Mexico and the Gulf of California (Mexico). The Mexican material represents new species of the genera Zosime Boeck, 1873, Peresime Dinet, 1974, Heterozosime Kim and Lee, 2021, and Acritozosime Kim and Lee, 2021. Standardized and complete descriptions for these new species are provided. Previous studies have shown that the genus Zosime can be subdivided into two species groups. We performed phylogenetic analyses (88 characters and 42 taxa) to test the naturalness of such subdivision, to subdivide these groupings further, and to shed some light on the phylogenetic relationships among the zosimeid genera and their species. Our results confirmed (i) the monophyly of previous subdivisions of the genus Zosime, and (ii) that the genus Zosime can be further subdivided into two major subgroups composed of several subordinate clades. Additionally, some comments on the phylogenetic hypotheses amongst the species of each genus reported here, are provided.

The taxonomic concept of the genus Stenocaris Sars, 1909 is uncertain because none of the synapomorphies for the species of Stenocaris are defined. Detailed comparison of previous records of Stenocaris minor (T. Scott, 1892) from different localities reveals that this species represents a species complex composed of two species, S. minor s. str. and S. minor sensu Cottarelli & Venanzetti, 1989. Because the latter species has fundamental differences in the nature of the fifth leg in females and the sexual dimorphism of the second leg in males, we propose a new species for S. minor sensu Cottarelli & Venanzetti, 1989, S. figaroloensis sp. nov. We also suggest that S. minor sensu Apostolov, 1971, S. minor sensu Marinov, 1971, and S. minor sensu Apostolov & Marinov, 1988 from the Black Sea and S. minor sensu Wilson, 1932 from North America should be relegated to species inquirenda in the genus. Taxonomic review of the morphology of all Stenocaris species indicated that the generic concept must be restricted to accommodate S. minor s. str., S. gracilis Sars, 1909, S. intermedia Itô, 1972, S. figaroloensis sp. nov., and the South Korean new species, S. marcida sp. nov., based on the synapomorphic condition of the confluent fifth leg in males. As a result of our analysis, two Stenocaris species, S. baltica Arlt, 1983 and S. pygmaea Noodt, 1955, are transferred to the genus Vermicaris Kornev & Chertoprud, 2008 as V. baltica (Arlt, 1983) comb. nov. and V. pygmaea (Noodt, 1955) comb. nov. based on the synapomorphic characters of a reduced condition of the second and fifth legs. Additionally, S. arenicola Wilson, 1932 and S. kliei (Kunz, 1938) are allocated to a new genus, Huysicaris gen. nov., mainly characterized by obvious caudal rami with a recurved dorsal spinous process and convex inner margins, as H. arenicola (Wilson, 1932) comb. nov. and H. kliei (Kunz, 1938) comb. nov. A marine interstitial harpacticoid collected from the subtidal substrate off Dok-do Island in the East Sea of South Korea is proposed as S. marcida sp. nov. and the distribution of S. intermedia, originally known from its type locality in Japanese waters only, is extended to the East Sea of Korea and Russia. We provide their detailed descriptions and illustrations and discuss the morphological characters supporting their identities.

A new species, Robertgurneya jejuensis sp. nov., was described from sandy sediment samples collected at a depth of 25 m on Mun Island, Jeju, in June 2018. The new species is morphologically similar to Robertgurneya similis similis (Scott A., 1896) and Robertgurneya donghaensis Bang, 2021; this is the second record of the genus Robertgurneya in South Korea. The morphological characteristics of the similis group within the genus Robertgurneya, to which the new species is ascribed, are summarized here. Furthermore, an identification key is provided based on the summary. Molecular identification of the collected specimens, based on the nuclear 18S ribosomal RNA (18S rRNA) and the mitochondrial cytochrome oxidase subunit I fragment, was obtained. Finally, a phylogenetic tree was constructed to present the position of Robertgurneya within the Miraciidae family based on 18S rRNA sequences which is relatively conserved. As a result, the relationship with sister genera morphologically similar to Robertgurneya was also molecularly confirmed.