Seborgia cavernicola sp. nov. from a submarine cave on Okinawa Island, Ryukyu Islands, southwestern Japan (Crustacea, Amphipoda, Seborgiidae)

A new seborgiid, Seborgia cavernicola sp. nov. is described from a submarine cave in Okinawa Island, Ryukyu Islands as the first record of the family from Japan. This species differs from its congeners by the following combination of characters: body without microspinules; eyes fainted, without ommatidia; epimeral plates with posterodistal angle produced into pointed process; main flagellum of antennule 4-articulate; article 2 of main flagellum of antennule longest; propodus of gnathopod 2 as long as wide; gland cone of antenna directed anteriorly; maxilla bilobed; uropod 3 biramous; and telson without setae and setules. A key to species of the genus is provided.

Malacofauna from soft bottoms in the Cerro Gordo marine cave (Alboran Sea): biodiversity and spatial distribution

The molluscan fauna of Cerro Gordo submarine cave, in the Spanish part of the Alboran Sea, is studied for the first time. The cave bottom spans from 16 m deep at its entrance to the sea level at its innermost section. Replicate soft bottom samples were collected from three different stations, along the horizontal gradient of the cave. Additional samples were collected on photophilous hard bottoms next to the cave entrance, in order to assess the origin of cave bioclasts. The cave sediments contained 158 species of molluscs (23 collected alive and 155 recorded only as shells), more than in Mediterranean cave sediments elsewhere. Species richness and abundance of molluscs decreased from the outermost to the innermost part of the cave. No cave-exclusive species were found, possibly due to the scarcity of caves in the Alboran Sea, but many of the recorded species are known from other Mediterranean caves. The lack of adult individuals for most of the living species inside the cave suggests that these do not constitute self-maintaining populations. Finally, our results suggest that bioclasts found in the sediment do not derive from the outside of the cave nor from the sediment itself, but mostly from the communities inhabiting the walls and ceiling of the cave.

The More You Search, the More You Find: A New Mediterranean Endemism of the Genus Ocenebra Gray, 1847 (Mollusca: Gastropoda: Muricidae) from a Submarine Cave of the Messina Strait Area (Italy)

Three hundred years of study on the Mediterranean molluscan fauna led the scientific community to consider it as the best ever known. However, the rate at which new taxa are discovered and described every year is still remarkably high, even in key predators such as Muricidae Rafinesque, 1815. Within this family, the genus Ocenebra Gray, 1847 comprises species widely distributed in the northeastern Atlantic and the Mediterranean Sea that were already the target of a decadal nomenclatural, morphological, and molecular combined research. Notwithstanding, we hereby describe an additional ocenebrid endemism from the Mediterranean Sea, whose distribution appears to be restricted to a circalittoral submarine cave of the Messina Strait area (Italy). The new species Ocenebra vazzanai is compared with the recent Atlanto-Mediterranean congeneric taxa on the basis of the known type materials, and a table summarizing the main diagnostic features of the species is offered to facilitate future identifications. The high biodiversity highlighted in the genus Ocenebra reveals a wide adaptive radiation and suggests the necessity of further studies aiming to tackle biodiversity issues even in popular groups, such as molluscs, and in widely studied biogeographic areas, such as Italy, and the Mediterranean basin in general.

Three new meiobenthic species from a submarine cave in Japan: Echinoderes gama, E. kajiharai and E. uozumii (Kinorhyncha: Cyclorhagida)

Three new species of echinoderid kinorhynchs are described from Daidokutsu, a submarine cave in Ryukyu Islands, Japan. Echinoderes gama sp. nov. is characterized by the presence of middorsal acicular spines on segments 4–8; lateroventral acicular spines on segments 7–9; lateroventral tubes on segment 5; sublateral tubes on segment 8; laterodorsal tubes on segment 10; and type-2 gland cell outlets in subdorsal and lateroventral position on segment 2. Echinoderes kajiharai sp. nov. is defined by the presence of middorsal acicular spines on segments 4, 6, 8; lateral accessory acicular spines on segment 9; lateroventral acicular spines on segments 6–8; lateroventral tubes on segments 2 and 5; midlateral tubes on segment 10; and type-2 gland cell outlets in laterodorsal position on segments 2 and 5, and subdorsal position on segments 8 and 9. Echinoderes uozumii sp. nov. is characterized by the presence of middorsal acicular spines on segments 4 and 6; lateroventral acicular spines on segments 6–9; lateroventral tubes on segments 2 and 5; sublateral tubes on segment 8; laterodorsal tubes on segment 10; type-2 gland cell outlets in subdorsal and lateral accessory position on segment 2; and blunt, short pectinate fringe teeth of primary pectinate fringe on segment 1. In addition, the Echinoderes multiporus species group including E. kajiharai sp. nov., and the Echinoderes bispinosus species group including E. uozumii sp. nov. are established. Furthermore, the distribution of the two species groups and the origin of Echinoderes species in Daidokutsu are discussed.

A new marine tardigrade genus and species (Arthrotardigrada, Styraconyxidae) with unique pockets on the legs

A marine heterotardigrade Cyaegharctus kitamuraigen. et sp. nov. (Arthrotardigrada, Styraconyxidae) is described from Daidokutsu, a submarine cave off Iejima island, Okinawa Islands, Ryukyu Archipelago, Japan. It is easily distinguished from all other styraconyxids by its pocket organs (putative sensory structures) on all legs in addition to the usual leg sensory organs. Its combination of other character states, such as the dorso-ventrally flattened body, ovoid primary clavae, conical secondary clavae, large terminal anus, internal digits with proximal pads and peduncles, external digits with developed peduncles and all digits with three-pointed claws in adult female, supports the erection of a new genus and species.

New cave-dwelling Plakina (Plakinidae, Homoscleromorpha, Porifera) from Martinique Island (French Antilles)

Knowledge of homoscleromorph sponge biodiversity has greatly improved during the last decade thanks to the increasing use of integrative taxonomy and extensive exploration of remote ecosystems. Indeed, recently described species have mostly been small sponges living in dark and near-impenetrable habitats. This work integrates morphological, cytological, ecological and molecular data to describe a new species belonging to the Plakina genus. Plakina doudou sp. nov. was found first during close inspection of photographs taken previously in a submarine cave on Martinique Island, where several new species had already been revealed. The new species lives in syntopy with P. arletensis. It is thinly encrusting, whitish in vivo, and its skeleton harbors a unique composition of diods, triods, monolophose triods and monolophose, dilophose and trilophose calthrops. Sequencing of a portion of the mitochondrial gene cox-1 indicates that the new species belongs to a well-supported clade containing the Mediterranean P. crypta and P. trilopha. However, at the time of publication of this work, we have not yet managed to identify synapomorphies that would support the different clades of Plakina. This genus includes a total of 39 species to date, of which 10 have been recorded in the Western Tropical Atlantic, and 4 in Caribbean submarine caves.

Recent thecideide brachiopods from a submarine cave in the Department of Mayotte (France), northern Mozambique Channel

For the first time large numbers of thecideide brachiopods have been collected from the Mozambique Channel, more particularly from the western part of the Comorian Island of Mayotte (France). The moderately diverse brachiopod fauna is from a submarine cave situated on the second barrier reef encircling this island, with three different genera being found: Thecidellina, Ospreyella and Minutella. The last genus is represented by M. cf. minuta (Cooper, 1981), which was first discovered around Madagascar. Ospreyella is represented by a new species (O. mayottensis sp. nov.) as is Thecidellina, which is represented by T. leipnitzae sp. nov. This species is markedly distinct from T. europa Logan et al., 2015 from Europa Island in the southern Mozambique Channel (1,200 km south of Mayotte), providing an example of allopatric speciation in an isolated cryptic habitat.