Search Results (71)

During a survey of marine biodiversity in the deep sea off northeastern Guam, two marine desmoscolecid nematodes belonging to the subgenus Tricoma were discovered. Tricoma (Tricoma) disparseta sp. nov. was described based on specimens collected from sponge and starfish habitats on a seamount at depths ranging from 1300 to 1500 m. Tricoma (Tricoma) disparseta sp. nov. is distinguished by having 59 to 62 main rings, 9 to 10 subdorsal setae, and 14 to 18 subventral setae on each side. Notable features include the differentiation in length and insertion between the subdorsal and subventral setae, as well as the amphid extending to the second or third main ring. Additionally, the spicules have a relatively small capitulum at the proximal end, while the gubernaculum is bent into a hooked shape. The specimen of T. (T.) longirostris observed in this study closely resembles previously reported specimens, characterized by 78 main rings, a long and narrow head shape, eight to nine subdorsal setae, 14 to 15 subventral setae, and a gubernaculum with a knobbed apophysis. Two Tricoma species from the Northwest Pacific Ocean are described in detail, and pictorial keys and comparative tables for species identification are provided for groups with 50 to 64 main rings. Full article

Human influence on Antarctic marine ecosystems is a growing concern, despite limited information being available. This study investigated the coastal meiofauna and environmental parameters of 10 locations, 4 of which served as reference points (OB1, OB2, OB3, and McGrady) and 6 which were impacted by different levels of human activity in the past and present (Wharf, Wilkes, BBIN, BBMID, BBOUT, and Shannon) in East Antarctica. Environmental variables such as metals, total petroleum hydrocarbons (TPHs), polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), grain size, organic matter content, and nutrients were measured for analysis. Locations close to human activities showed higher concentrations of pollutants (metals, TPHs, PBDEs, PCBs) and greater variations in meiofauna diversity compared to the reference sites (OB1, OB2, OB3, and McGrady). In the area impacted by the Casey Station waste dump (Brown Bay), the meiofauna community at the location furthest from the pollution (BBOUT) source exhibited greater diversity compared to the closest location (BBIN). In addition to metals and TPHs, particle size was also correlated with community patterns, with finer sediments associated with more impacted sites, facilitating the accumulation of toxic compounds. These results contribute to the understanding of the role and impact of pollutants on meiofauna biodiversity in Antarctic coastal ecosystems. Full article

Baiyangdian Lake, the largest freshwater shallow lake on the North China Plain, plays a pivotal role in maintaining the regional ecological balance and biodiversity. Meiofauna are integral components of Baiyangdian Lake; however, their community characteristics and relationship with environmental factors have not yet been studied. The aim of the following study was to evaluate the density, spatiotemporal patterns, and habitat response dynamics of meiofauna in Baiyangdian Lake. A field investigation was conducted at 33 sites spanning various habitats, including aquatic plant-dominant, trench, and pelagic areas, across the spring, summer, and autumn seasons of 2021. The results revealed that the meiofauna in Baiyangdian Lake primarily comprise freshwater nematodes (91.78%), ostracods, and copepods, with a mean abundance of 69.40 ± 35.20 ind. 10 cm⁻², peaking in the spring, followed by summer and autumn. The mean biomass was 164.95 ± 99.39 dwt. 10 cm⁻², with that of ostracods being the most substantial and that of copepods being the least, with both of them exhibiting seasonal fluctuations. Notably, in the summer, the abundance of meiofauna was positively correlated with the water depth and negatively correlated with ammonia nitrogen levels (R² = 0.13 and R² = 0.24, respectively; p < 0.05 and p < 0.01; n = 33). The results of our study indicate that the distribution and abundance of meiofauna are significantly affected by environmental factors, with the water depth and ammonia nitrogen levels being potential key determinants. The results of the present study are conducive to evaluating the health status of the Baiyangdian ecosystem, protecting biodiversity, and studying the impacts of anthropogenic activities and environmental changes on the lake, and can also provide scientific support for its ecological restoration and governance as well as the assessment of ecological service functions. Full article

Despite the recognized ecological significance of hyporheic zones, biological investigations into their ecology, especially concerning functional diversity, remain limited. This is particularly true for copepod assemblages, abundant in the transitional zone between groundwater and surface waters, requiring more thorough exploration. To bridge this knowledge gap, our study extensively monitored a hyporheic zone within a mountain creek and examined nine functional traits across twelve copepod species found in this environment. Through the application of RLQ and fourth-corner analysis, as well as functional diversity indices including functional richness, evenness, divergence, and dispersion, we aimed to establish links between functional traits and environmental factors. Our findings revealed relationships between environmental features—specifically electrical conductivity, pH, and ammonium concentration—and the trait composition of copepod assemblages, which were influenced by species abundances. Considering the intimate connection between functional traits and ecosystem services, assessing functional diversity within hyporheic zones offers valuable insights into its functionality in terms of services rendered. This study emphasizes the importance of understanding and managing functional diversity in hyporheic zone dynamics to ensure the health and stability of ecotones and, by extension, riverine and groundwater ecosystems. Full article

Cryptofaunal nematodes, those living on the hard substrate of the coral reefs, are largely unknown in terms of diversity and assemblage structure. We described nematode assemblages at seven sites spanning about 200 km along Jardines de La Reina, a well-preserved reef system in the Greater Antilles. We identified about 3000 nematodes, mostly of the families Desmodoridae and Chromadoridae; the most abundant species were Croconema cinctum, Desmodora communis, and Euchromadora vulgaris. The regional richness was moderate with 70 observed species (0.95 confidence interval: 65–75 species) and 75 extrapolated species (0.95 CI: 68–83 species). This richness was lower than in other reef biotopes, maybe reflecting evolutionary constraints due to interactions with stony corals. The local expected richness at 100 individuals was similar among sites, with a median of 26 species (0.95 CI: 20–34 species), and likely caused by diversification rate and evolutionary time acting at the same pace on populations. The taxonomic β-diversity was high and without differences among sites (median: 0.85; 0.95 CI: 0.33–1), probably due to significant substrate heterogeneity at 10-cm scale. The prevalence of replacement over richness difference suggests that local processes (e.g., environmental filtering and competition) contribute more to β-diversity than niche availability, which would be largely similar across the reef terraces. Contrary to our expectations, no gradient of assemblage structure occurred, nor significant effect of benthic cover on nematodes. However, nematode functional structure showed a conservative set of biological traits reflecting adaptations to hydrodynamic regime: armed oral cavity/intermediate colonizing capability/ornamented cuticles/conical tail. Our results provide insights about the taxonomic and functional diversity of nematodes and highlight the vast knowledge gaps about the processes ruling the meiofauna community structure in coral reefs. Full article

A new species of the genus Eupelte Claus, 1860, was obtained from the algal bed bottom in Dokdo Island, East Sea of Korea, using a light trap. Specimens of both sexes of the Korean new species are described in detail and compared with its congeners. The present species, Eupelte dokdoensis sp. nov., is closely similar to E. aurulenta Wells and Rao, 1987, found in algal sands from the Andaman and Nicobar Islands, and E. setacauda Monk, 1941, collected from seaweeds in the Californian coast of the USA. These species share the body length (0.5–07 mm), the nine-segmented A1, the setation of the first and second endopodal segments of P1 (one and four setae), P4 exp-3 with three inner setae, and enp-3 of P2–P4 with five setae in both sexes. The new species can be readily discernable from the previous two species by the short rostrum with a serrate distal margin, the shape of the maxillipedal basis, the setation and surface ornamentation of P1 enp-2 (covered with long setules), the exp-3 of P3 and P4 with thicker middle inner seta, and the setation of female and male P5 exopod and baseoendopod (six and six, four and two setae, respectively). In addition, the zoogeography of the valid species of the genus Eupelte is briefly discussed, and a diagnostic key to the females of the species is provided. Eupelte dokdoensis sp. nov. described herein is the first report of the genus from Korean waters and is the fourteenth member of the genus. Full article

Gastrotricha are microscopic benthic animals found in almost all water bodies. To date, over 890 species distributed in 71 genera, 18 families, and two orders are known. There are 376 freshwater species, and several are also found in Italy; however, a compendium of the studies carried out so far, and a georeferenced distribution of the species, still need to be provided. This project summarizes information about the diversity and geographic distribution of Italian gastrotrichs. Diversity data, acquired over 239 years, were reviewed and corrected based on taxonomic and nomenclatural updates and, in addition to distribution information, were organized into a data matrix valuable for statistical analysis. The data were fed into geographic information system software to understand the overall figures more easily. The results indicated that Italy is one of the best-known countries regarding freshwater gastrotrichs. With 92 species in 17 genera and three families from 61 investigated localities, Italy counts 17 type localities and 19 endemic species. Despite this high biodiversity, many Italian regions still need to be investigated, and should, therefore, be the focus of future research. The implementation of a web-mapping plugin enabled the creation of interactive maps for an easy and modern method for sharing the work done, and the information acquired. Full article

Periphytic rotifer assemblages from lentic habitats are understudied. To improve knowledge on the principal environmental determinants of their structure and composition, we examined summer periphyton from 184 freshwater bodies from a taxonomic and multi-trait-based perspective. Only the latter allowed consideration of all bdelloids. Alpha diversity decreased with electrolyte and aluminium concentration but increased with macrophyte richness, pointing at salinization, metal toxicity and loss of structural niche heterogeneity as potential threats for rotifer diversity. Replacement was the prominent component of beta diversity, with acidified sites showing the highest local contributions. Variation partitioning indicated that local conditions explained variation in species composition best, but general setting (soil type, land cover, connectivity) and spatial context were also not insignificant. Redundancy analysis related species composition more particularly to gradients of pH and trophic status, whereas the representation of functional groups was structured mainly by phytoplankton productivity. Mirroring shifts observed in the plankton, high phytoplankton productivity associated with larger size and more detritibacterivory. Dominance of collectors constrained variation in guild ratios, underlining the need for more refined functional approaches. To aid the use of periphytic rotifers in regional water quality assessment, we identified indicators and community thresholds for pH and trophic variables and determined optima and tolerances for individual taxa. Full article

During expedition EMB-238 of RV EM BORGESE to the Fehmarn Belt (Baltic Sea, Germany) in 2020, specimens of a new species of the Rhizothrichidae Por (Crustacea, Copepoda, Harpacticoida) were found. Currently, Rhizothrichidae enclose two genera: Rhizothrix Sars and Tryphoema Monard. The assignment of the new species is based on the following commonly derived characters: the formation of a strong spinulose (sub)apical element on the last segment of the female A1, and the formation of a long brush seta on the last exopodal and endopodal segments of the P1. The new species could not be assigned to either Rhizothrix or Tryphoema because it lacks their autapomorphies but presents exclusive derived characters, including the absence of the abexopodal seta on the A2 allobasis, the possession of only one seta on the endopods of P2–P4, and the fusion of the female P5 exopod and baseoendopod. Therefore, it is assigned to a new genus. Besides the species description, its phylogenetic position in the Rhizothrichidae as well as its possible relationship with Rhizothrix and Tryphoema are discussed. Furthermore, the affiliation of the Rhizothrichidae with the Cletodoidea is justified on the basis of 17 apomorphies. A key to the rhizothrichid genera is provided. Full article

Quinquelaophonte is a genus of laophontid harpacticoid, including 13 valid species around the world. Many of them are known to possess inter- and/or intra-individual variations in their swimming legs. During a survey of the meiofaunal biodiversity of Jeju Island in Korea, specimens of Quinquelaophonte were collected from an intertidal zone off the west coast of Jeju Island. This study examined the morphological characteristics and amplified partial sequence of four genes (18S rRNA, 28S rRNA, COX1, and CYTB). As with other Quinquelaophonte species, specimens of this new species showed variability in the chaetotaxy of their swimming legs in both sexes. There was a setal arrangement pattern in females that could be considered a standard, whereas male individuals showed two sets of the chaetotaxy on the fourth swimming legs. The molecular data confirmed that individuals belonged to a single species, regardless of morphological variations. The result of the morphological comparison showed that the new Quinquelaohponte species shared some characteristics with congeneric species but included some specific morphological characters different from its congeners. The new species was named Quinquelaophonte sominer sp. nov. and was presented with detailed descriptions, illustrations, and confocal micrographs. Furthermore, phylogenetic analyses were conducted using newly obtained data plus the sequences of other copepods and two Quinquelaophonte species. The result suggested that Q. sominer sp. nov. and two congeners were classified as branched lineages. This discovery brings the total number of species to three in the Northwest Pacific region. Full article

Understanding trait selection factors is vital for decoding the processes shaping species’ assemblages. However, trait-based studies in freshwater crustacean copepod assemblages are scarce, especially in groundwater environments. We explored how environmental filtering influences functional traits in copepod assemblages across four freshwater habitats (an alluvial aquifer, a hyporheic zone, a stream benthic zone and a lake littoral) along a depth gradient. Each habitat had distinct environmental templates based on light, temperature and dissolved oxygen. We analysed 4898 individuals from 43 copepod species and examined 12 morphological and life history traits. The results revealed significant differences in copepod traits among habitats, notably in ovigerous female biomass, egg biomass and ovigerous female percentages. Furthermore, despite some statistical uncertainty, notable differences were also observed in the number of juveniles, male-to-female abundance ratios and overall biomass. No significant differences were observed in juvenile biomass, egg characteristics, body size dimorphism or juvenile-to-adult ratios among habitats. The trait variations offer insights into copepod-mediated ecosystem services, particularly carbon recycling. To gain a deeper understanding of copepod adaptations to environmental features and anthropogenic changes, future research should consider additional functional traits, such as locomotion and feeding habits. Full article

The invasion of Spartina alterniflora is one of the main threats faced by mangrove wetlands in Quanzhou Bay, Fujian. To effectively manage S. alterniflora, mangrove plants (Kandelia obovata, Aegiceras corniculatum, Bruguiera gymnorhiza, Rhizophora stylosa, and Avicennia marina) were used to replace it in 2022 to restore the wetland ecosystem. Samples of meiofauna and marine nematodes were collected four times, including in September 2022 (before the removal of S. alterniflora), October 2022 (after removal), and December 2022 and March 2023 (after planting mangrove plants). This paper investigates changes in the composition, abundance, and biomass of meiofauna in different time periods, with a specific focus on comparing the community structure and biodiversity indices of marine nematodes in S. alterniflora and mangrove habitats. The results indicate that among the five meiofauna groups identified, marine nematodes account for 92.91%, 91.91%, 92.03%, and 85.92% of the total meiofauna abundance in the respective study periods. In the S. alterniflora habitat in September, marine nematodes were identified belonging to 12 families and 20 genera, of which 6 genera were dominant (percentage ≥ 5%). They were Ptycholaimellus, Parodontophora, Terschellingia, Halichoanolaimus, Metachromadora, and Parasphaerolaimus. In the mangrove habitat in December, marine nematodes were identified belonging to 15 families and 23 genera, with 6 genera being dominant, namely Daptonema, Admirandus, Parodontophora, Ptycholaimellus, Terschellingia, and Anoplostoma. Comparing the marine nematode communities in the two habitats, the mangrove habitat exhibits higher diversity than the S. alterniflora habitat. There was a change in the dominant genera, and their dominance has decreased. The dominant genera of marine nematodes found in both habitats are common and widely distributed groups. The changes in the abundance of meiofauna and the community structure of marine nematodes following the restoration of the S. alterniflora habitat by planting mangroves provide valuable insights for ecological monitoring after restoration measures in estuarine wetland conservation areas. Full article

The abyssal Pacific Clarion Clipperton Zone (CCZ) hosts vast, commercially valuable seafloor deposits of polymetallic nodules. Foraminifera (testate protists) dominate benthic communities in this region. Here, we present a taxonomic survey, combining morphological and genetic data and focussing on mainly meiofauna-sized Foraminifera from the eastern CCZ. Sequences obtained from >100 specimens, the majority photographically documented, were analysed phylogenetically. Most were single-chambered Monothalamea (‘monothalamids’), a high percentage of them squatters inhabiting empty tests of mainly multi-chambered Foraminifera. The first sequences for the monothalamid genus Storthosphaera were obtained, while specimens assigned to Gloiogullmia, Hippocrepinella and Vanhoeffenella yielded new sequences. Among multichambered taxa, high-throughput Illumina sequencing (HTS) revealed a second haplotype of the calcareous rotaliid Oridorsalis umbonatus, possibly representing a distinct species. Additional HTS sequences were obtained from the rotaliids Nuttallides umbonifer and Globocassidulina subglobosa, confirming their wide distributions. We also obtained the first sequences for Cribrostomoides subglobosa, showing that it branches separately from other members of this genus. The fact that many sequences did not correspond to known morphospecies reflects the scarcity of reference barcodes for deep-sea Foraminifera, particularly the poorly known but highly diverse monothalamids. We recommend using HTS of single specimens to reveal further unknown species. Despite extensive research, much remains to be learnt about the true scale of foraminiferal biodiversity in the CCZ. Full article

During a survey of the Wando-gun rockpool area in Korea, two species belonging to the family Cyatholaimidae were discovered within a sponge, Hymeniacidon sinapium, and are hereby reported. Despite the monophyletic nature of the family Cyatholaimidae, it has been a topic of discussion among nematologists due to its lack of synapomorphic characteristics and overlapping generic diagnoses. Many genus-defining features consist of a combination of non-unique characters, which may not hold significant taxonomic importance. Consequently, most genera within the family are non-monophyletic according to phylogenetic findings. The absence of molecular data complicates the identification of taxonomically important characteristics that may have been previously overlooked. While the pore complex and the lateral pore-like structure have been suggested as potentially important traits, these insights are lacking in most recorded species, along with molecular data to confirm their significance in topology. Given the considerable amount of work required from the ground up, this study provides both morphological information (including taxonomic description, morphometric measurements, tabular key comparing key features to all valid congeners, illustration, and microscope photographs) and molecular data (partial sequences of three molecular regions, K2P distance comparison, and phylogenetic trees) for the two species discovered in Korea. The study also offers insights on potentially significant traits, such as the pore complex and other pore structures. The Korean specimen of Acanthonchus (Seuratiella) tridentatus resembles the original description regarding aspects such as the number and type of precloacal supplements, as well as the shape of the spicules and gubernaculum. However, variations are observed in the following characteristics: body ratio, nerve ring location, pharynx length, and the presence or absence of the oscelli. Our partial molecular sequences of the specimens also match identically with a single existing entry on NCBI identified as A. (S.) tridentatus. The new species, Paracanthonchus spongius sp. nov., is most similar to P. kamui in terms of the general shape of the body and gubernaculum but can be distinguished by differences in the number of precloacal supplements, amphid position, and gubernaculum ratio. The phylogenetic tree constructed based on the 28S rRNA region shows both species grouped within the monophyletic clade of Cyatholaimidae with high bootstrap support. However, achieving generic resolution of these species will require more molecular sequences of congeners to accumulate in the future. Full article