Ecology determines appearance: a new taxonomic solution for the soft bottom dwelling spider crab Pisoides bidentatus (A. Milne-Edwards, 1873) from the Sea of Japan, with remarks on Pisoides ortmanni (Balss, 1924) and the northwestern Pacific Pugettia Dana, 1851 (Majoidea: Epialtidae).

The northwestern Pacific soft bottom dwelling spider crab, Pisoides bidentatus (A. Milne-Edwards, 1873) (Brachyura: Majoidea: Epialtidae), is re-described using an integrative approach. As a result, it is transferred to the genus Scyra Dana, 1851 (Epialtidae) based on morphological and molecular data, as well as already described larval morphology, which certainly better reflects the phylogenetic relationships of the species. Japanese Pisoides ortmanni (Balss, 1924), for which morphology and ecology are very similar to P. bidentatus as well as Pugettia quadridens (De Haan, 1839) and the closely related Pugettia ferox Ohtsuchi & Kawamura, 2019, are also transferred to Scyra. The "reduced" morphology of both species is very different from the related northwestern Pacific Scyra spp. and Pugettia spp., which are mostly decorating algae-dwellers. We associate the relatively long ambulatory legs, a smooth tear-drop shaped carapace with a reduced dorsal armature and slightly pronounced pseudorostral spines, characteristic of P. bidentatus and P. ortmanni with their open soft (mainly sand) bottom habitats, where it is difficult to find a foothold or shelter, but it is necessary to resist constant currents. Such morphology is also characteristic of spider crabs of the genera Libinia Leach, 1815 and Doclea Leach, 1815 (Epialtidae: Pisinae), which are also living in similar habitats/conditions and represent a convergent morphological appearance.

Terrestrial crustaceans (Arthropoda, Crustacea): taxonomic diversity, terrestrial adaptations, and ecological functions.

Terrestrial crustaceans are represented by approximately 4,900 species from six main lineages. The diversity of terrestrial taxa ranges from a few genera in Cladocera and Ostracoda to about a third of the known species in Isopoda. Crustaceans are among the smallest as well as the largest terrestrial arthropods. Tiny microcrustaceans (Branchiopoda, Ostracoda, Copepoda) are always associated with water films, while adult stages of macrocrustaceans (Isopoda, Amphipoda, Decapoda) spend most of their lives in terrestrial habitats, being independent of liquid water. Various adaptations in morphology, physiology, reproduction, and behavior allow them to thrive in virtually all geographic areas, including extremely arid habitats. The most derived terrestrial crustaceans have acquired highly developed visual and olfactory systems. The density of soil copepods is sometimes comparable to that of mites and springtails, while the total biomass of decapods on tropical islands can exceed that of mammals in tropical rainforests. During migrations, land crabs create record-breaking aggregations and biomass flows for terrestrial invertebrates. The ecological role of terrestrial microcrustaceans remains poorly studied, while omnivorous macrocrustaceans are important litter transformers and soil bioturbators, occasionally occupying the position of the top predators. Notably, crustaceans are the only group among terrestrial saprotrophic animals widely used by humans as food. Despite the great diversity and ecological impact, terrestrial crustaceans, except for woodlice, are often neglected by terrestrial ecologists. This review aims to narrow this gap discussing the diversity, abundance, adaptations to terrestrial lifestyle, trophic relationships and ecological functions, as well as the main methods used for sampling terrestrial crustaceans.

Two new species of the genus Victoriopisa Karaman amp; Barnard, 1979 (Crustacea: Amphipoda: Eriopisidae) from mangrove communities of Vietnam with a review of previous records.

Two new mud-dwelling amphipod species of the genus Victoriopisa Karaman Barnard, 1979 (Crustacea: Amphipoda: Eriopisidae) are described from the mangrove habitats of the Cn Gi Mangrove Biosphere Reserve and the estuary of the Be River, Vietnam. Both species are characterized by an anteroventral margin of the head being entire, the presence of eyes, the absence of deep excavation on propodus (palm) and well-marked excavation on dactylus of gnathopod 2, relatively long and slender distal segment of uropod 3. The combination of these features clearly separate the newly discovered species from Victoriopisa ovata (Dang Le, 2005) described from Hi Phng, North Vietnam, and other congeneric species. Victoriopisa nhatrangensis sp. nov. from the mouth of the B River (Nha Trang) can be clearly separated from Victoriopisa cangio sp. nov. from the Cn Gi Mangrove Biosphere Reserve by the absence of a tuft of setae on the distodorsal margin of article 2 of antenna 1, not anteriorly expanded distoventral margin of propodus (palm) of gnathopod 2, different shape and armature epimeral plates and telson, proportion and armature of uropods 23. The article also discusses the previous records of the genus Victoriopisa from the coastal waters of Vietnam, and as the result Victoriopisa chilkensis (Chilton, 1921) and Eriopisa elongata (Bruzelius, 1859) are excluded from the fauna of Vietnam.

The hidden diversity of the genus Lyurella Derzhavin, 1939 (Crustacea: Amphipoda: Crangonyctidae): four new species from the subterranean habitats of the northwestern Caucasus, Russia.

Four new species of the Palaearctic crangonyctid amphipod genus Lyurella Derzhavin, 1939 (Crustacea: Amphipoda: Crangonyctidae), L. mikhailovi sp. n., L. fanagorica sp. n., L. fontinalis sp. n. and L. asheensis sp. n., are described based on an integrative approach from the subterranean habitats of the southwestern foothills of the Greater Caucasian Ridge (the north-eastern Black Sea coast). Despite the relative proximity of the habitats, the interspecific genetic divergence (by COI mtDNA gene marker) between the newly outlined Caucasian species of the genus varied from 11 to 21%, demonstrating a long-term isolation and lack of gene flow for at least 37Mya, starting from the Pliocene. The lowest genetic divergence between L. shepsiensis Sidorov, 2015 and L. asheensis sp. n., estimated as 4%, is also considered species-specific due to the presence of distinct morphological differences. We discuss the phylogeny, morphology, and distribution and provide a key for all known species of Lyurella. DNA barcoding data for all species, including the type species of the genus, Lyurella hyrcana Derzhavin, 1939, are presented for the first time.

A New Species of the Aberrant Majid Crab Genus Planotergum Balss, 1935 (Crustacea: Brachyura, Majidae, Planoterginae) from the Southern Red Sea.

A new species of the aberrant monotypic genus Planotergum Balss, 1935 (Brachyura: Majidae: Planoterginae) is described from the southern part of the Red Sea, based on a single female recently found in the collection of the Zoological Museum of Moscow State University. The new species is clearly distinguished from Planotergum mirabile Balss, 1935 in the form of carapace, antennal article and third maxilliped, as well as morphology of the ambulatory legs. The record extends the known range of Planotergum, previously known only from the eastern Indian Ocean and Western Pacific, by more than 7000 km.

Cryptic diversity of the rocky crab genus Glebocarcinus Nations, 1975 (Crustacea: Decapoda: Cancridae): description of a new species from Russian coastal waters of the Sea of Japan based on morphology, DNA and distribution.

A new cancrid crab species Glebocarcinus kashini sp. nov. (Decapoda: Brachyura: Cancridae) is described from Russian coastal waters of the Sea of Japan. The new species can be clearly separated from relative and sibling, Glebocarcinus amphioetus (Rathbun, 1898), by a less prominent and granulated dorsal surface of the carapace and dorsal surface of the cheliped propodus, less prominent sculpture of the carapace front and bluntly triangular anterolateral teeth of the carapace. Comparison of COI gene sequences supports the subdivision of these two species and shows their clear genetic separation from a related species, the American pygmy rock crab, G. oregonensis (Dana, 1852). Along the mainland coast of the Sea of Japan, G. kashini and G. amphioetus possibly overlap only in Posyet Bay and adjacent areas; the new species is distributed to the north from the bay while G. amphioetus is distributed to the south. Previous and new records of G. amphioetus from the area are discussed.

Redescription of Alpheus vladivostokiensis (Vinogradov, 1950), a large and conspicuous snapping shrimp from the northern Sea of Japan (Decapoda: Caridea: Alpheidae).

The poorly described Alpheus vladivostokiensis (Vinogradov, 1950) comb. nov., originally assigned to the genus Betaeus Stimpson, 1860 and hitherto considered as a nomen dubium, is redescribed based on material recently collected in Troitza Bay in the Russian Far East and Hakodate Bay in southern Hokkaido, Japan, as well as older material deposited in the Zoological Museum of the Moscow State University. Since Vinogradov's material is considered as non-extant, a neotype of A. vladivostokiensis is designated. Alpheus vladivostokiensis is closely related to A. japonicus Miers, 1879, a species occurring in deeper waters of Japan, Korea, China and Taiwan. All previous records of A. japonicus from the Russian Far East are reassigned to A. vladivostokiensis.

A new echiuran-associated snapping shrimp (Crustacea: Decapoda: Alpheidae) from the Indo-West Pacific.

Alpheus echiurophilus sp. nov. (Crustacea: Decapoda: Caridea: Alpheidae) is described based on material from Japan (Ryukyu Islands) and Vietnam (Nha Trang Bay); an additional, morphologically slightly different specimen from Madagascar (Nosy-Bé) is preliminarily referred to A. cf. echiurophilus sp. nov., awaiting collection of additional material and/or genetic comparison. All specimens of the new species were collected from burrows of thalassematid echiurans, either on intertidal and shallow subtidal sand-mud flats or in the mixed sand-gravel-rock intertidal. Alpheus echiurophilus sp. nov. belongs to the A. leviusculus species group, being morphologically closest to the Indo-West Pacific A. leviusculus Dana, 1852, A. hululensis Coutière, 1905, A. ladronis Banner, 1956, and the western Atlantic A. zimmermani Anker, 2007. The new species can be separated from all of them by a combination of morphological characters and also appears to have a diagnostic colouration.