In this study, the meiofaunal diversity in Lake Varano (southern Italy) is investigated in detail. Using a statistical approach, these data were coupled with the physicochemical parameters of the bottom water and the sediment characteristics in order to understand the factors influencing meiofaunal biodiversity distribution. The lake is selectively influenced by different factors, namely: organic matter and grain-size, as well as water salinity. Although these assemblages appear to be poorly diversified, the diversity index values are similar to those generally reported in other transitional environments. Relatively higher values of both meiofaunal and benthic foraminiferal diversity were found in front of the Capoiale channel and in the inner part of the lake. The meiofaunal assemblages are mainly dominated by nematodes, copepods, and turbellarians. The benthic foraminiferal assemblages comprise 18 taxa and are mainly represented by calcareous forms, suggesting a relatively low degree of confinement and, consequently, moderately restricted conditions. These assemblages are comparable to the Ammonia assemblages with Haynesina germanica that are characteristic of lagoons along the Mediterranean coasts. On the basis of these findings, coupled with the biotic data, the lake can be regarded as an oligo-mesotrophic environment.

In this study, biodiversity patterns of free-living marine nematode communities were assessed in the Yangtze River estuary and its adjacent waters by certain diversity measures. The studied area exhibited spatial variation in nematode biodiversity patterns. According to habitat heterogeneity, two station groups, shallow water near shore area and shallow water continental shelf area, were observed in the Yangtze River estuary and its adjacent waters. In general, nematode abundance and species diversity in the near shore area were significantly lower than the continental shelf area. Salinity, sediment Chlorophyll-a (Chl-a) and Phaeophytin-a (Phaeo-a) concentrations were responsible for the discrimination of species diversity measures. They reflect the reverin influence to nematode species diversity. By contrast, our results showed that the average taxonomic distinctness with presence/absence data (Δ ), and the variation in taxonomic distinctness (Λ ) were not influenced by natural environmental variability, nor pollutant and anthropogenic disturbances. The funnel plots for Δ and Λ also indicate none of the studied stations were subjected to environmental stress and perturbation. Possibly because of nematodes' strong resistance to environmental stress, the taxonomic indices did not discriminate perturbed from unperturbed conditions in the present study. We should be cautious to regard the taxonomic distinctness indices as surrogates for other traditional indices such as the number of species or Shannon diversity.

Biodiversity estimations, in particular in tropical regions, are a useful tool in research focused on the knowledge and conservation of ecosystems. Inferences on the biogeography of marine nematodes are often difficult due to the poor knowledge of the species distribution. In particular, limited information on the composition of the free-living marine nematodes is available from the Indian Ocean and Maldivian Archipelago. This study aims at providing a checklist of the free-living marine nematodes associated with coral sediments of the Maldives. Forty-six species, in 28 genera and 10 families, are newly recorded for the Archipelago, increasing the number of known nematode species to 111, in 79 genera, and 25 families. The distribution range of the species is updated, and a noticeable faunistic richness is recorded for the southern archipelago. The presence of six species described first in Maldives by Gerlach and still known only for this region is confirmed. The present synthesis of the faunistic and taxonomic data available so far for the Maldives Islands integrates the global information on the distribution of this phylum and provides information for future interesting comparisons from a zoogeographical perspective.

Meiofauna were sampled from the NOAA ship Gordon Gunter during Fall 2012 off the coast of Louisiana. At five locations near the Deepwater Horizon drilling site (located 54–115 km away) box core samples and Shipek® grab samples were collected for subsurface meiofauna and sediment analysis. The goals of this study were to: 1) perform a taxonomic analysis of the meiofauna groups Nematoda and Copepoda, 2) perform statistical analyses of animal densities and sediment characteristics, and 3) compare sampling results using two different collection devices. Nematodes were the most abundant animals recovered, ranging from 88–791 animals per 10 cm² area. Nematodes were represented by 60 genera in 23 families. The nematode community was dominated by one genus at the deepest location. Cluster analysis showed that there were two major groups for the five sites; nematodes from two shallow sites 81 and 84, and those from two shallow sites 85 and 86 along with deep site 82. Copepods were represented by 35 species from six families, with no animals identified at the deepest location (site 82). Cluster analysis also demonstrated two major groups similar to the two nematode groups but without site 82 present. Spearman correlation analysis revealed positive correlations among nematode, copepod, polychaete, and kinorhynch densities, and no correlations among the meiofauna densities and sediment chemistry values (metals and polycyclic aromatic hydrocarbon [PAH] concentrations). Nickel concentrations varied from 3.1–30.0 mg/kg, vanadium from 5.5–71.6 mg/kg, and PAHs from 94–395 ppb. Statistical comparison (Mann-Whitney U-test) of the box corer and Shipek® sampling equipment, using animal abundance, heavy metal analysis, and PAH data, revealed no difference between the two samplers.

Beach meiofauna in brackish waters has received very little attention compared to fauna in fully marine and fresh water habitats. This study explores for the first time the species composition and seasonal dynamics of zoopsammon communities in the Gulf of Finland, the brackish Baltic Sea, and relates the observed patterns to the key environmental variables. The study communities consisted of rotifers, nematodes, ciliates, testaceans, tardigrades, oligochaetes, polychaetes, small crustaceans, gastrotrichs, turbellarians, and insect larvae. Regardless of environmental conditions, ciliates, nematodes, and rotifers were the most abundant taxa in all sampling sites. The total population densities varied largely within site, among sites, and seasons with different sites showing different seasonal patterns. The BRT models reproduced reasonably well the spatial patterns and seasonal dynamics of psammon communities and identified environmental variables that affected the psammon seasonality (temperature, sand organic content, human trampling) and spatial patterns (sediment characteristics, porewater, and pH). Our study also shows that the majority of psammon taxa had species-specific responses to their environment. This provides a strong conceptual argument for enhancing expertise in the taxonomy of psammon, especially when constructing predictive models of psammon in the brackish-water habitats.

The effects of the most important factors (food quality and quantity, temperature, and salinity) on the production of the harpacticoid copepod Amphiascoides atopus Lotufo & Fleeger, originally described from a mass culture system at the Department of Zoology and Physiology of the Louisiana State University at Baton Rouge, were evaluated to ascertain potential yields. For aquacultural purposes, it is important to assess these factors for laboratory-controlled conditions. Feeding treatments were not significantly different between monospecific (Chaetoceros muelleri, Isochrysis sp., and Nannochloropsis oculata) and mixed diets (all three of the mentioned diets in ratios of 1:1:1) (527.2 ± 68.3 to 404.4 ± 160.6 organisms L⁻¹). Copepods fed diets of 320 cells μL⁻¹ (539.6 ± 115.8 organisms L⁻¹) showed the highest mean egg production. Our results demonstrate that a temperature of less than 20°C (15 ± 3.5 organisms L⁻¹) significantly affected the final mean population counts. No statistical differences were observed at 24, 28, and 32°C with productions varying between 330 ± 67.4 to 527 ± 101.3 organisms L⁻¹. Of all the salinity levels tested, the highest population densities were recorded at 32 psu (983.0 ± 78.8 organisms L⁻¹). Identifying the correct copepod species as live prey for larviculture is also considered important so that the appropriate size and characteristics of the food can be administered. These findings suggest that the copepod A. atopus can serve as a good potential live feed for larviculture.

The damaging effect of mid-ultraviolet (UVB, 280–315 nm) radiation on a marine copepod, Tigriopus japonicus sensu lato was investigated. Copepods were collected from tidal pools on rocky shores, Yeosu, on the south coast of Korea, and were cultured under constant conditions (temperature: 20°C, salinity: 20 psu, L : D = 12 : 12 h) in the laboratory. Each stage of nauplius (N1–N6) and copepodite (CI–CVI) was harvested from the culture and exposed to one of eight irradiation doses (1, 5, 10, 15, 20, 25, 30, and 35 kJ m⁻²) of UVB. No deleterious effect was induced by UVA or PAR. Extensive morphological deformities were observed, i.e., shrunken body (in groups 5 kJ m⁻² at N4; 1 and 15 kJ m⁻² at CI), in the urosome and caudal rami (5 and 15 kJ m⁻² at N6; 10 kJ m⁻² at CI), in the swimming legs (5, 10, and 15 kJ m⁻² at CI; 10 kJ m⁻² CIV), and in the antennule (5 kJ m⁻² at CIII; 1 kJ m⁻² at CIV). The types of deformity observed depended on the developmental stages of copepods that were exposed to UVB radiation. UVB radiation had a damaging effect on the morphology of T. japonicus s. l. Exposure of earlier larval stages to mid-ultraviolet affected the shape of the entire body, and the prosome shape was abnormal. Exposure of later larval stages to mid-ultraviolet resulted in abnormalities at the appendage level, i.e., in the antennules and swimming legs.

An account of previous lists and descriptions of marine and freshwater harpacticoid copepods of Mexico yielded, by year 2010, 71 marine and 21 freshwater species from a variety of habitats. Sediment samples from the littoral zone to more than 2000 m depth along the Mexican Pacific coast, from the west coast of the Baja California peninsula, from the Gulf of Mexico, and from anchialine caves and cenotes from Yucatan, were taken during the last 15 yr as a continued effort to improve our knowledge of the diversity of the harpacticoid fauna from Mexico. This study shows that, at present, 151 species/subspecies distributed in 85 genera and 31 families are known from Mexican marine and freshwater systems. Additionally, a number of species belonging to 78 genera and 25 families are yet to be described. The checklist contains information on the locality, geographic coordinates, habitat, and source of the recorded taxa. There is a better knowledge of the harpacticoids from Sinaloa (northwestern Mexico). However, the number of species from Mexico is expected to grow rapidly in the forthcoming years.

Both sexes of a new species of Nitokra Boeck, 1865 were collected from a brown alga, Padina australis at Bangsaen sandy Beach in Chon Buri province, Thailand. Nitokra karanovici, sp. nov., is similar to many species of the genus in having a slender and cylindrical body shape, eight-segmented antennules in female and nine-segmented in male, exopod of female P5 with 5 setae; the new species shares the same armature formula of the swimming legs with the following six congeners: N. balli Rouch, 1972 from Long Island, Papua New Guinea; N. evergladensis Bruno, Reid & Perry, 2002 from Florida, U.S.A.; N. minor Willey, 1930 from Bermuda; N. minor mozambicae Wells, 1967 from Inhaca Island, Mozambique; N. platypus bakeri Chappuis, 1930 from the Philippines and Japan; and N. uenoi Miura, 1962 from Ryukyu Islands, Pacific. However, the new species can easily be distinguished from N. balli and N. uenoi by the number of setae on the female P5 Enp, and from N. evergladensis, N. minor and N. platypus bakeri by the much longer P1 Enp-1. Nitokra karanovici is most closely related to N. minor mozambicae, but it can be distinguished by the number of spinules on the anal operculum (6–7 in N. minor mozambicae and 11 in N. karanovici), and relative length of the P1 Enp-1 (slightly shorter in the new species). Therefore, we conclude that N. karanovici most resembles N. minor mozambicae as mentioned above.

Tigriopus kingsejongensis, new species, is described from tidal pools near the King Sejong Station on King George Island, Antarctica. The new species is closely related to Tigriopus kerguelenensis from Kerguelen Island. Both species share several characters, including the presence of an abexopodal seta on the allobasis of the antenna in the male, the setal formula of the swimming legs, and the shape of the P5 exopod in the female. However, the new species is distinguishable from its congeners by the combined characters of a relatively well-developed abexopodal seta on the antennary allobasis, and a knob-like structure in the middle of the lateral margin of the second endopodal segment of the P2 in the male. The new species belongs to the ‘Austral islands group' within the genus. The mtCOI gene sequence is provided as a DNA barcode for the new species, and a phylogenetic tree based on the DNA sequences is also suggested.

The complete larval development of Romaleon gibbosulum, comparing five zoeal stages and one megalopal stage, and the first zoea of Metacarcinus magister are described and illustrated. The zoeal morphologies of the two species are compared with those known for other Cancridae species. Based on the zoeal mouthparts, R. gibbosulum shows more affinity to species of Glebocarcinus than its congeners. Metacarcinus magister is different from its congeners and coincides well with Cancer productus. These results may indicate that a re-examination of their generic classification is necessary.

A new species of Normanellidae is described from Gwangyang Bay, Korea. This species is placed in the genus Normanella Brady, 1880 based on the following morphological characteristics: 1) 5-segmented female antennule, 2) antennary exopod with four setae, 3) mandible with discrete endopod and two setae on basis, 4) maxillule with two basal endites, 5) maxilla with allobasis accompanied by two setae and a spine, and 6) the sixth leg of the male with three setae.

Normanella spinosa, new species, is closely related to Normanella bifida Lee & Huys, 1999. However, the new species is clearly distinguished by the characteristic processes on the dorsal surface, especially well-developed, large spiny-form processes on the urosome. In addition, N. spinosa has a sharply pointed rostrum, and the P1 enp-1 with a smaller inner seta than that of N. bifida. Normanella spinosa also displays substantial abnormalities of the reduced setal number in the swimming legs. This is the first report of the family Normanellidae from Korea.

Three species of the genus Paradoxostoma Fischer, 1855 are reported from the South Korean East Coast: Paradoxostoma flaccidum Schornikov, 1975, P. brunneum Schornikov, 1974, and one new species, P. sokchoensis, new species. The first species was previously reported from the East Sea off the Korean peninsula, with additional Paradoxostoma as part of a species list of an ecological study carried out in South Korea. Paradoxostoma sokchoensis is most closely related to P. depressum Okubo, 1977 and P. assimile Okubo, 1978. Three major differences between the new species and the other two species are: 1) the presence of an unusual group of setulae on the antennule, 2) absence of seta on first segment of L6, and 3) a more slender anterior margin of the carapace.

A new gastrotrich species of the genus Tetranchyroderma, bearing three-pronged cuticular hooks, was discovered in the Pacific, from littoral sandy bottoms of a beach at Joyagdo Island off Wando, south coast of the Korean Peninsula. Tetranchyroderma pinnatum, sp. nov., is characterized by feathered triancres, two pairs of rod-like cephalic tentacles, absence of dorsal and dorsolateral adhesive tubes, a short testis, and a large tube-shaped copulatory organ. Scanning electron microscopy is used to describe the fine details of the species, and a comparison among known species with triancres is provided. We also provide a key to the species of the genus Tetranchyroderma recorded in the northwest Pacific.

We present an annotated checklist of the taxa of Cladocera (Crustacea: Branchiopoda) from inland aquatic habitats of South Korea. The group contains 85 valid species grouped into three orders, nine families, and 36 genera. Knowledge of the cladoceran fauna of Korea has been significantly improved, but such efforts need to be continued. Further studies will likely increase the number of taxa regarded as endemics of the Far East.

We erect Mekongbathynella, new genus, to accommodate two new parabathynellid species, M. sesanensis and M. kryi, collected from subterranean water in Cambodia. The new genus is characterized by: the sexual dimorphism of the second antennular segment in the form of a 2-lobed projection in the male, the mandible with seta-like proximal teeth and a molar process having six dentate spines, including the most distal one being distally wide and bifurcated, the absence of a medial seta on the second maxillary segment, the male thoracopod VIII with massive protopod and basipod, rudimentary epipod, the exopod having dentate distal lobes and setae and endopod pointing backward, the absence of a pleopod and the uropod having two spines. The characters distinguishing the two new species are provided in a table. Mekongbathynella is closely related to Eobathynella yeojuensis Schminke, 2011, because of the similarities in the 6-segmented antennule and antenna, in the feature of the mouthparts and thoracopods I–VII, in the general shape of the male thoracopod VIII, and in the absence of pleopod I. In the context of the affinity, the details of the male thoracopods of the two new species and E. yeojuensis are compared. The status of Eobathynella is briefly discussed.

Two species of Enhydrosoma Boeck, 1873, found in muddy sediments in the sublittoral zone of Gwangyang Bay, represent the first record of this genus in Korea. Enhydrosoma coreana, new species, shares a number of rare morphological features with the type species, E. curticauda Boeck, 1872, such as a bifid rostrum with centrally inserted sensilla, endopodal lobe of P5 with a peduncle, and a characteristic shape of the female genital field. They differ in the armature formula of the mandible, P1 endopod, and P5 exopod, size of the P5 peduncle, and minor details in the ornamentation of several somites. Enhydrosoma intermedia Chislenko, 1978 is redescribed from its holotype, freshly collected Korean material, and freshly collected material from and near its type locality in the Russian Far East. Its male is described for the first time. Minor morphological differences are observed between these two disjunct populations, such as longer caudal rami and sparse hair-like spinules on somites in Korean specimens. However, molecular data from the mtCOI gene suggest them to be conspecific. Detailed morphological comparisons between E. coreana and E. intermedia reveal a number of important differences, and molecular phylogenies suggest only a remote relationship. Their average pairwise maximum likelihood distances are very similar to those between other well-established genera of harpacticoid copepods. Geehyndrosoma, new genus, is erected to accommodate E. intermedia, together with E. brevipodum Gómez, 2004, from the Pacific coast of Mexico.

Sea squirts were collected from shallow waters of 0.5–5.0 m depth at 27 harbors or ports in Korea: 14 harbors in the East Sea, 10 harbors in the Korea Strait, and three harbors in the Yellow Sea. Ciona intestinalis was identified as an introduced alien species and was compared with the Asian native C. savignyi, which was first reported in Korea. Four distinct morphological differences are recognized between these two species: 1) shape of pigment spots on branchial and atrial siphons, 2) flecks of body, 3) color or shape of the tip of the vas deferens, and 4) thickness and transparency of the body wall. Phylogenetic relationships of these species are examined through molecular analysis based on 720 bp of mtCOI gene sequences. Korean C. intestinalis belong to Type A.