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A new genus and species of Parabathynellidae (Crustacea: Bathynellacea), Megabathynella totemensis Camacho & Abrams gen. et sp. nov., is described from the Northern Territory, Australia. This species is the first to be described from an Australian cave. It is a new giant species (4 to 6 mm). The new species displays several unique morphological character states within Parabathynellidae and is the only known species with: more than 12 articles on antennules, with a short, curved barbed seta on each article from the fifth; eight setae on the last article of antennae; more than three setae on the mandibular palp; up to 17 articles on the exopod of the thoracopods, without ctenidia but with a strong spine on each article at the base of the external seta; strong row of pair of spines on latero-external side of second article of endopod in all thoracopods; the male thoracopod VIII is different from all those known; more than 50 spines on the sympod of the uropod and more than 35 spines on the furcal rami. Specimens of the new species are morphologically different from all known species, but more closely resemble some giant species of the genera Kampucheabathynella (Asia), and Billibathynella and Brevisomabathynella (Australia).
Samples of Crustacea and Annelida (Polychaeta, Sipuncula, and Hirudinea) were collected in the Bering Sea and the northwestern Pacific Ocean during scientific cruise SO-249 BERING in 2016. Biological samples were collected from 32 locations by the team on-board RV Sonne using a chain bag dredge at depths ranging between 330–5,070 m, and preserved in 96% ethanol. Specimens were morphologically identified to the lowest taxonomic level possible using a Leica M60 stereomicroscope. The generated data here comprise taxonomic information as well as annotated bathymetric and biogeographic information from a total of 78 samples (26 Crustacea, 47 Polychaeta, 4 Sipuncula, and 1 Hirudinea). The dataset was prepared following Darwin Core Biodiversity standards for FAIR data sharing based on Ocean Biodiversity Information System (OBIS) and Global Biodiversity Facility (GBIF) guidelines. The standardised digitised data were then mobilised to both OBIS and GBIF under CC BY 4.0 licence to publicly share and adopt the data. As records of these important marine taxa from bathyal and abyssal depths are sparse, especially from the deep Bering Sea, the herein generated and digitised data aid in filling existing knowledge gaps on their diversity and distribution in that region. As part of the “Biogeography of the NW Pacific deep-sea fauna and their possible future invasions into the Arctic Ocean” (BENEFICIAL) project, this dataset thus not only increases our knowledge in re-assessing and uncovering the deep-sea diversity of these taxa, but also serves policy and management sectors by providing first-hand data for global report assessments.
A new species of the gecarcinucid freshwater crab genus, Spiralothelphusa Bott, 1968, is described from the Andhra Pradesh State of South India, with supporting data from mitochondrial cytochrome c oxidase subunit I. This brings the number of known species of Spiralothelphusa to seven, five from India and two from Sri Lanka. The identity of S. wuellerstorfi (Heller, 1862) has remained uncertain because the former lectotype designation was not clear. Bott (1968), while designating a male lectotype of S. wuellerstorfi from the Naturhistorisches Museum Wien, Vienna, Austria, had neither stated the catalogue number nor the size of the specimen. It is now difficult to trace the particular lectotype among several paralectotypes of the depository. A new lectotype is, therefore, designated herein for S. wuellerstorfi, and the species is redescribed. The new species, S. andhra sp. nov., has morphological affinities with S. wuellerstorfi, but can be distinguished from the latter species by the shape of the male telson and outer margin of the non-twisted portion of the male first gonopod. Phylogenetic analyses of the molecular data also corroborate their separation. An illustrated identification key is provided for the species of Spiralothelphusa.
This paper describes new or little known Amphipoda collected from Hydrozoa, Bryozoa, Porifera or kelp along the Chilean fjord region. The following species have been found and most of them were redescribed and illustrated: Sunamphitoe femorata (Krøyer, 1845); Caprella cf. equilibra Say, 1818; Haplocheira barbimana robusta K.H. Barnard, 1932; Epimeria (Metepimeria) acanthurus (Schellenberg, 1931); Labriphimedia vespuccii K.H. Barnard, 1931; Leucothoe kawesqari Esquete & Aldea, 2015; Podocerus cf. danae (Stebbing, 1888); Ligulodactylus macrocheir (Schellenberg, 1926) and Torometopa cf. crassicornis (Schellenberg, 1931). One species in this contribution is new to science: Liouvillea rocagloria sp. nov.
A new genus and new species of potamid crab, Gurumon gurumayum gen. et sp. nov., are described from the Arunachal Pradesh State of northeastern India. Gurumon gen. nov. has affinities with Abormon Mitra, Pati & Ng, 2021, Pararanguna Dai & Chen, 1985, and some species of Potamiscus Alcock, 1909, but the new genus can easily be differentiated from them mainly by its low external orbital angle, the relatively stouter exopod of the third maxilliped, and the relatively broader male pleonal somite 6. Their male first gonopods are also different from each other. Counting Gurumon gurumayum gen. et sp. nov., India is currently known for ten genera and 24 species of potamiscine freshwater crabs, and Arunachal Pradesh for eight genera and 11 species of these crabs. The current nomenclatural problems with Potamiscus are also discussed.
Biodiversity patterns of marine crustaceans are still unknown in many locations or might have been overlooked due to our knowledge gaps, despite increasing sampling and data sharing efforts during the last decades. By analysing big data extracted from open portals such as Ocean Biodiversity Information System (OBIS) and Global Biodiversity Information System (GBIF), we aim to revisit the distribution and biodiversity patterns of the highly speciose and abundant Crustacea in the Northwest Pacific (NWP) from shallowest depths to the deep sea. This study focussed on selected benthic and pelagic crustacean (sub) classes and their species richness, sampling effort, and expected species richness (ES50) using equal/sized hexagonal cells, 5° latitudinal bands, 500 m depth intervals were analyzed. Crustacean species richness was highest in the tropical Philippines as well as around the Japanese islands. Pelagic crustacean species richness peaked at 30° latitude and declined beyond that. Benthic taxa; however, depicted high levels of species richness across most of the latitudinal gradient, reaching its highest point at 45° latitude. Due to the prevalence of certain crustacean orders in the deep sea, benthic species richness showed a distribution pattern with two distinct peaks across bathymetric gradients; with highest species richness recorded at shallow-water depths and also at abyssal depths. The most important environmental drivers of benthic and pelagic crustacean species richness were primary productivity (positive correlation) and salinity (negative correlation). Our study provides first insights into biodiversity patterns of the highly diverse Crustacea in the NWP and highlights strong differences between benthic and pelagic taxa. The results presented here could help us to better understand whether benthic or pelagic taxa might respond differently to climate changes in the NWP based on their distinct physiological and biological characteristics. This information is crucial in establishing species management strategies and ecosystem restorations in both shallow water and deep-sea environments.
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.
Three leptostracan species (Crustacea: Phyllocarida) are reported from mud volcanoes at the Moroccan margin of the Gulf of Cadiz (NE Atlantic). Nebalia strausi Risso, 1826 and N. abyssicola Fage, 1929 were found in experimentally deployed organic substrates in Mercator, Meknès and Darwin mud volcanoes; N. abyssicola was also found among bathymodiolin bivalves and is recorded for the first time in the Atlantic Ocean. The third species was collected from the Gemini mud volcanoes and is described herein as Sarsinebalia ledoyeri sp. nov. The new species is characterised by having the eyes provided with ommatidia and lacking pigment, the ventral margin of the eye is concave along distal half, the antennular scale is more than twice as long as wide, the second article of the mandibular palp bears one seta on lateral surface about 0.5 times as long as the article and one subterminal seta longer than the third article, the distal article of the maxilla II endopod is about 1.8 times as long as the proximal article, the maxilla II exopod is clearly longer than the endopod proximal article, the lateral margin of the pleopod I exopod lacks setae and the posterodorsal border of pleonites VI–VII is provided with rounded to pointed denticles.
The extent of male mate choosiness is driven by a trade-off between various environmental factors associated with the costs of mate acquisition, quality assessment and opportunity costs. Our knowledge about natural variation in male mate choosiness across different populations of the same species, however, remains limited. In this study, we compared male mate choosiness across 10 natural populations of the freshwater amphipod Gammarus roeselii (Gervais 1835), a species with overall high male mating investments, and evaluated the relative influence of population density and sex ratio (both affecting mate availability) on male mate choosiness. We investigated amplexus establishment after separating mating pairs and presenting focal males with a novel, size-matched female from the same population. Our analysis revealed considerable effects of sex ratio and (to a lesser extent) population density on time until amplexus establishment (choosiness). Male amphipods are able to perceive variable social conditions (e.g., sex ratio) and modify their mating strategy accordingly: We found choosiness to be reduced in increasingly male-biased populations, whereas selectivity increases when sex ratio becomes female biased. With this, our study expands our limited knowledge on natural variations in male mate choosiness and illustrates the importance of sex ratio (i.e., level of competition) for male mating decisions in natural environments. Accounting for variation in sex ratios, therefore, allows envisioning a distinctive variation of choosiness in natural populations and highlights the importance of considering social background information in future behavioral studies.
The ingestion of microplastics (MPs) is well documented for various animals and spherical MPs (beads) in many studies. However, the retention time and egestion of MPs have been examined less, especially for irregular MPs (fragments) which are predominantly found in the environment. Furthermore, the accumulation of such particles in the gastrointestinal tract is likely to determine whether adverse effects are induced. To address this, we investigated if the ingestion and egestion of beads are different to those of fragments in the freshwater shrimp Neocaridina palmata. Therefore, organisms were exposed to 20–20,000 particles L−1 of either polyethylene (PE) beads (41 μm and 87 μm) or polyvinyl chloride (PVC) fragments (<63 μm). Moreover, shrimps were exposed to 20,000 particles L−1 of either 41 μm PE and 11 μm polystyrene (PS) beads or the PVC fragments for 24 h, followed by a post-exposure period of 4 h to analyze the excretion of particles. To simulate natural conditions, an additional fragment ingestion study was performed in the presence of food. After each treatment, the shrimps were analyzed for retained or excreted particles. Our results demonstrate that the ingestion of beads and fragments were concentration-dependent. Shrimps egested 59% of beads and 18% of fragments within 4 h. Particle shape did not significantly affect MP ingestion or egestion, but size was a relevant factor. Medium- and small-sized beads were frequently ingested. Furthermore, fragment uptake decreased slightly when co-exposed to food, but was not significantly different to the treatments without food. Finally, the investigations highlight that the assessment of ingestion and egestion rates can help to clarify whether MPs remain in specific organisms and, thereby, become a potential health threat.