A new genus and species of a submarine cave crab of the family Plagusiidae Dana, 1851 (Crustacea: Brachyura: Grapsoidea) from Okinawa Island, Ryukyu Islands, southwestern Japan.

Caligoplagusia okinawa n. gen. & n. sp., assigned to the brachyuran family Plagusiidae Dana, 1851 is described on the basis of a male and a female specimens collected from a semi-submerged marine cave on the limestone shore of Okinawa Island, Ryukyu Islands, southwestern Japan. The new monotypic genus is most similar to Euchirograpsus H. Milne Edwards, 1853 and Miersiograpsus Trkay, 1978 in that the frontal margin lacks a deep sublateral cleft adjacent to the orbit, but differs significantly by its subhexagonal carapace shape, the anterolateral margin of the carapace with three teeth including the external orbital tooth, the anterior margin of ambulatory meri each armed with a row of large teeth, and the greatly reduced eyes. The pale body colour, reduced eyes, the very elongate antennal flagellum, and long ambulatory legs are all typical brachyuran adaptations to living in cave environments. This is the first cave-dwelling species of the family Plagusiidae.

A new species of the genus Trichopagurus de Saint Laurent, 1968 (Crustacea: Decapoda: Anomura: Paguridae) from a semi-submerged marine cave in Okinawa Island, southwestern Japan.

A new hermit crab species of Paguridae, Trichopagurus spinibrachium n. sp., is described on the basis of a single male specimen collected from the anchialine environment of a semi-submerged marine cave in Okinawa Island, Ryukyu Islands, southwestern Japan. It is morphologically similar to T. macrochela Komai & Osawa, 2005 and T. tenuidactylus Komai, 2013, but differs in the shape and armature of the ocular, antennular and antennal peduncles, chelipeds, and ambulatory legs. The new species may be distinguished from all known congeners by the stronger armature of the carpi and meri of both chelipeds. Trichopagurus spinibrachium n. sp. is the third species of the genus recorded from submarine caves, although it may also occur on nearby coral reefs as does T. macrochela and T. trichophthalmus (Forest, 1954).

Diagnostic Ultrasound: On-Site Diagnosis of Type B Aortic Dissection During Cataract Surgery.

We report a case of aortic dissection occurring during cataract surgery under local anesthesia, which was diagnosed on-site by point-of-care ultrasound. Intimal flaps were detected in the abdominal aorta, whereas the parasternal view showed no abnormalities in the aortic root or left ventricular function. According to these ultrasound findings, a Stanford type B aortic dissection was more likely than a type A aortic dissection, and imminent death was unlikely. Therefore, we decided to resume and complete the surgery. Subsequent computed tomography (CT) confirmed the point-of-care diagnosis. The patient was transferred to a tertiary hospital for medical treatment.

New lithistid sponge of the genus Sollasipelta (Porifera, Demospongiae,Tetractinellida, Neopeltidae) from submarine caves of the Ryukyu Islands,southwestern Japan, with redescription of S. sollasi.

A new species of 'lithistid' (rock sponge) Sollasipelta subterranea sp. nov. is described from near-shore submarine caves of Okinawa and Shimoji Islands, the Ryukyu Islands, southwestern Japan. This new species is characterized by the smooth dentate ectosomal pseudophyllotriaenes, slender choanosomal oxea/style/subtylostyles and two types of amphiasters, one of which is in two size classes. Sollasipelta subterranea sp. nov. is morphologically closest to Sollasipelta sollasi (Lévi & Lévi, 1989), known from the Philippines deep sea, and our examination of the type specimen of S. sollasi revealed that the pseudophyllotriaenes and desmas are substantially different between the two species, and both species possess two types of amphiasters, one of which has two size classes. Sollasipelta cavernicola (Vacelet & Vasseur, 1965) and S. punctata (Lévi & Lévi, 1983) are transferred to the genus Daedalopelta Sollas, 1888, based on possession of one type of amphiastes as microscleres. Sollasipelta mixta (Vacelet, Vasseur and Lévi, 1976) is formally transferred to the genus Neopelta Schmidt, 1880, based on the morphological characters. A key to species of the genus Sollasipelta Van Soest & Hooper, 2020 is also provided. Sollasipelta subterranea sp. nov. represents the first 'lithistid' sponge from submarine caves of the Western Pacific and the first species of sponge inhabiting anchialine cave environments in the Indo-West Pacific. This is also a new record of the family Neopeltidae from Japanese waters.

Bioaccumulation and metabolism of polybrominated diphenyl ethers (PBDEs) in coenobitid hermit crabs from marine litter-polluted beaches in remote islands.

Plastic litter containing additives is potentially a major source of chemical contamination in remote areas. We investigated polybrominated diphenyl ethers (PBDEs) and microplastics in crustaceans and sand from beaches with high and low litter volumes on remote islands that were relatively free of other anthropogenic contaminants. Significant numbers of microplastics in the digestive tracts, and sporadically higher concentrations of rare congeners of PBDEs in the hepatopancreases were observed in coenobitid hermit crabs from the polluted beaches than in those from the control beaches. PBDEs and microplastics were detected in high amounts in one contaminated beach sand sample, but not in other beaches. Using BDE209 exposure experiments, similar debrominated products of BDE209 in field samples were detected in the hermit crabs. The results showed that when hermit crabs ingest microplastics containing BDE209, BDE209 leaches out and migrates to other tissues where it is metabolized.

A new shrimp of the genus Odontozona Holthuis, 1946 (Decapoda: Stenopodidea: Stenopodidae) from a submarine cave of the Ryukyu Islands, Indo-West Pacific.

A new species of the stenopodid shrimp genus Odontozona Holthuis, 1946 is described and illustrated on the basis of single specimen recently collected from a submarine cave at Shimoji-jima Island, Miyako Island Group, Ryukyu Islands, southwestern Japan. Odontozona ganzu sp. nov. appears to be unique within the genus Odontozona by lacking transverse row of posterior small spines on sixth pleuron. General morphology of the new species is also similar to O. stigmatica Saito, Okuno Anker, 2017 described from Ishigaki-jima Island, Ryukyu Islands, West Pacific, but differs from it by a combination of morphological characters, viz., lacking the cincture of small spines on the posterior margin of the carapace, the distinct transverse carina on the third pleuron, as well as the lateral teeth of the uropodal endopod. This study increases the total number of the described species in the genus Odontozona to 23, 11 of which occur the Indo-West Pacific.

A new species of the genus Eutrichopagurus Komai, 2015 (Crustacea: Decapoda: Anomura: Paguridae) from a submarine cave in the Ryukyu Islands, southwestern Japan.

A new hermit crab species of the family Paguridae is described on the basis of two male specimens from Hedo Dome, a submarine cave located on the north coast of Okinawa Island, Ryukyu Islands, southwestern Japan. The assignment of the new species to the genus Eutrichopagurus Komai, 2015 is based on the structure of the gills and right male sexual tube, the article 3 of the antennular peduncle with a prominent tuft of setae on the dorsodistal margin, and the posterior lateral margins of the telson each bearing a prominent tuft of setae. Among two known congeners, Eutrichopagurus crassoculus n. sp. may be closer to the type species of the genus, E. shirakawai Komai, 2015, in having greatly reduced corneas, basally bearing sparse setae, and no small corneous spines or spiniform setae on the dorsal surface of the meri of the ambulatory legs, but is distinguishable by the morphology of the ocular peduncles, ocular acicle, antennular peduncle, and chelipeds.

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.

Heteromysoides taramensis, a new species of mysid (Mysida: Mysidae) from an anchialine cave on Tarama Island, Ryukyu Islands, southwestern Japan.

Heteromysoides taramensis, a new species of the family Mysidae (Mysida) is described from an anchialine cave on Tarama Island, Ryukyu Islands, southwestern Japan. This species differs from its congeners by the following combination of characters: eyes subrectangular in dorsal aspect without process; cornea developed; telson distally rounded, 1.3 times as long as maximum width, with 5 or 6 pairs of simple spines distolaterally, 1 pair of long simple spines subapically and 1 pair of short simple spines apically; antennal scale elongated elliptical, extending to distal margin of antennular peduncle; antennal sympod with distomesial corner produced into blunt tooth; and endopod of third thoracopod with simple, not subchelate, termination.

Two new species of Fauveliopsidae (Annelida, Sedentaria) from submarine caves and deep sea, Japan.

Two new species of fauveliopsid annelids, Fauveliopsis antri sp. nov. and Laubieriopsis soyoae sp. nov., are described based on specimens collected from Japanese waters. Fauveliopsis antri sp. nov. inhabits submarine caves and can be discriminated from the other congeners by the following features: i) 32 chaetigers, ii) chaetigers 1-3 with stout hooks, iii) minute body (about 1 mm in length), iv) all parapodia with same number of chaetae (2 notochaetae; 2 neurochaetae), and v) presence of dorsal and ventral papillae. Laubieriopsis soyoae sp. nov. inhabits deep water sediments and can be distinguished from the other congeners by: i) 24 chaetigers, ii) chaetigers 1-3 without annulations, and iii) acicular chaetae with tips entire, without denticles.

Extensive gene flow among populations of the cavernicolous shrimp at the northernmost distribution margin in the Ryukyu Islands, Japan.

Marine cave habitats in the Ryukyu Islands, Indo-West Pacific, are located at the northern edge of the distribution of many cave-dwelling species. At distribution margins, gene flow is often more restricted than that among core populations due to the smaller effective population size. Here, we used high-throughput sequencing technology to investigate the gene flow pattern among three sampling sites of a marine cave-dwelling species at the margin of its distribution range. We collected individuals of the barbouriid shrimp Parhippolyte misticia from three marine caves in the Ryukyu Islands and performed population genetic analyses by means of multiplexed inter-simple sequence repeat genotyping by sequencing. Based on 62 single-nucleotide polymorphism markers, no clear population structure or directional gene flow pattern was found among the three sites. These results were unexpected because previous studies of other stygobitic shrimps in this region did find significant population genetic structures and northward directional gene flow patterns. Together, these inconsistent findings imply that marine cave-dwelling species in the region have different mechanisms of larval dispersal. Future studies on larval ecology and the biotic and abiotic factors influencing gene flow patterns are needed to clarify the mechanisms underlying the population dynamics of marine cave-dwelling species.

Redescription of the poorly known ghost shrimp species, Scallasis amboinae Bate, 1888, review of the genus, and description of a new species from the Ryukyu Islands, Japan (Decapoda: Axiidea: Callianassidae).

A poorly known callianassid ghost shrimp species, Scallasis amboinae Bate, 1888, is redescribed and illustrated on the basis of the holotype and new material from Papua New Guinea. A new species, S. inermis, is described from the Ryukyu Islands, Japan. Callianassa (Cheramus) pygmaea De Man 1928 is synonymised with S. amboinae. All seven species of Scallasis are diagnosed and compared.

Computational Characteristics of the Striatal Dopamine System Described by Reinforcement Learning With Fast Generalization.

Generalization is the ability to apply past experience to similar but non-identical situations. It not only affects stimulus-outcome relationships, as observed in conditioning experiments, but may also be essential for adaptive behaviors, which involve the interaction between individuals and their environment. Computational modeling could potentially clarify the effect of generalization on adaptive behaviors and how this effect emerges from the underlying computation. Recent neurobiological observation indicated that the striatal dopamine system achieves generalization and subsequent discrimination by updating the corticostriatal synaptic connections in differential response to reward and punishment. In this study, we analyzed how computational characteristics in this neurobiological system affects adaptive behaviors. We proposed a novel reinforcement learning model with multilayer neural networks in which the synaptic weights of only the last layer are updated according to the prediction error. We set fixed connections between the input and hidden layers to maintain the similarity of inputs in the hidden-layer representation. This network enabled fast generalization of reward and punishment learning, and thereby facilitated safe and efficient exploration of spatial navigation tasks. Notably, it demonstrated a quick reward approach and efficient punishment aversion in the early learning phase, compared to algorithms that do not show generalization. However, disturbance of the network that causes noisy generalization and impaired discrimination induced maladaptive valuation. These results suggested the advantage and potential drawback of computation by the striatal dopamine system with regard to adaptive behaviors.

It was not a fall, but fainting: A case report of pulmonary embolism.

We encountered a case of pulmonary thromboembolism, in which an 84-year-old woman (body weight 62 kg, height 150 cm) fell in the ward eight days after upper arm surgery. In this event, she had fractured her ankle and hit her head, with transient loss of consciousness. She needed surgery for the ankle fracture under general anesthesia. Her anesthesia course was unstable, with heart rate varying between 95 and 140 bpm, systolic blood pressure between 70 and 110 mmHg, and oxygen saturation between 92 and 98%. Immediately after reversing anesthesia, we performed bedside ultrasound and diagnosed acute pulmonary embolism in the operating room. We assume that the event was not a simple fall, but pulmonary embolism-related fainting (syncope). This case and recent reports provide two lessons: (1) cases of syncope among postoperative patients may be reported as simple falls in the safety surveillance of hospitals, and (2) ultrasonography at the bedside plays a pivotal role in the diagnosis of pulmonary embolism in perioperative settings.

Evaluating the effect of overharvesting on genetic diversity and genetic population structure of the coconut crab.

Birgus latro (coconut crab) is an edible crustacean that has experienced serious overharvesting throughout its whole habitat range; however, the negative effects of overharvesting on the genetic diversity within B. latro populations have not been elucidated. Here, we report sex ratio, body size, and genetic diversity in populations of B. latro in the Ryukyu Islands where large-male-biased overharvesting of B. latro has continued. In 2 of the study populations, the sex ratio was significantly skewed toward females, and in all of the study populations large males were rare, which we attributed to sex- and size-biased overharvesting. We found no differences in genetic diversity between small and large individuals, suggesting that genetic diversity, even among the large (i.e., old) individuals, may have had already been negatively affected by overharvesting. Continued monitoring of sex ratio, body size and genetic diversity are needed for effective management of the study populations.

Cuff Failure of Spiral-Filled Polyvinyl Chloride Endotracheal Tube Immediately after Tracheal Intubation Using a Channeled Videolaryngoscope (Pentax Airway Scope).

We report on a case of mechanical damage to the spiral-filled polyvinyl chloride endotracheal tube that occurred shortly after tracheal intubation using a channeled videolaryngoscope (Pentax airway scope). We also found this problem in two other cases among 350 neurosurgery patients over the past 5 years. Prior to intubation, we did not observe any defect in the cuff. However, the cuff could not be filled with air immediately after the intubation. Anesthesiologists should be aware that, during tracheal intubation using an airway scope, friction between the endotracheal tube and inner surface of the introducer might result in sudden rupture of the cuff.

Disparate responses to salinity across species and organizational levels in anchialine shrimps.

Environmentally induced plasticity in gene expression is one of the underlying mechanisms of adaptation to habitats with variable environments. For example, euryhaline crustaceans show predictable changes in the expression of ion-transporter genes during salinity transfers, although studies have typically been limited to specific genes, taxa and ecosystems of interest. Here, we investigated responses to salinity change at multiple organizational levels in five species of shrimp representing at least three independent invasions of the anchialine ecosystem, defined as habitats with marine and freshwater influences with spatial and temporal fluctuations in salinity. Although all five species were generally strong osmoregulators, salinity-induced changes in gill physiology and gene expression were highly species specific. While some species exhibited patterns similar to those of previously studied euryhaline crustaceans, instances of distinct and atypical patterns were recovered from closely related species. Species-specific patterns were found when examining: (1) numbers and identities of differentially expressed genes, (2) salinity-induced expression of genes predicted a priori to play a role in osmoregulation, and (3) salinity-induced expression of orthologs shared among all species. Notably, ion transport genes were unchanged in the atyid Halocaridina rubra while genes normally associated with vision and light perception were among those most highly upregulated. Potential reasons for species-specific patterns are discussed, including variation among anchialine habitats in salinity regimes and divergent evolution in anchialine taxa. Underexplored mechanisms of osmoregulation in crustaceans revealed here by the application of transcriptomic approaches to ecologically and taxonomically understudied systems are also explored.

A comprehensive taxonomic list of brittle stars (Echinodermata: Ophiuroidea) from submarine caves of the Ryukyu Islands, southwestern Japan, with a description of a rare species, Dougaloplus echinatus (Amphiuridae).

The ophiuroid species listed were collected by benthic faunal surveys from 2016 to 2018 in submarine caves of the Ryukyu Islands, southwestern Japan. The material includes 20 species from 8 families, Amphiuridae, Ophiocomidae, Ophiodermatidae, Ophiolepididae, Ophioleucidae, Ophiomyxidae, Ophionereididae and Ophiotrichidae. This is the first comprehensive report of submarine cave-dwelling ophiuroids from Japanese waters. Also provided is a redescription of a rare species, Dougaloplus echinatus (Ljungman, 1867), with a detailed description of its ossicle morphology. The species has previously been reported from Brazil, Australia, Eastern Indian Ocean to Southern China, in 11-118 m depth, and this is the first record of D. echinatus from Japanese waters. A brief discussion of the scarcity of submarine cave systems, and the need for their conservation, is provided.

Submarine cave hermit crabs (Crustacea: Decapoda: Anomura: Paguroidea) from three islands of the Ryukyu Islands, southwestern Japan.

Hermit crab species are reported on the basis of specimens collected by recent faunal surveys in submarine caves of three islands (Ie, Okinawa, and Shimoji Islands) of the Ryukyu Islands, southwestern Japan. The material includes three species in three genera of Diogenidae and 11 species in four genera of Paguridae. Catapaguroides longior Komai, Yamada Shirakawa, 2010 and Pylopaguropsis granulata Asakura, 2000, each previously known only from the holotype, are recorded with intraspecific morphological variation observed in the present specimens. Color and morphological variations of Pagurixus nomurai Komai Asakura, 1995 are also discussed. The present specimens of Catapaguroides foresti McLaughlin, 2002, C. longior, and Pylopaguropsis granulata suggest that the three species prefer the sandy or silty substrate in the deeper inner sites of submarine caves rather than other cryptic habitats in coral or rocky reefs.

A new species of the mud shrimp genus Axianassa Schmitt, 1924 (Decapoda: Gebiidea: Laomediidae) from the Ryukyu Islands, southern Japan.

A new species of the laomediid mud shrimp genus Axianassa Schmitt, 1924, A. planioculus, is described and illustrated on the basis of a single male specimen from intertidal muddy sand flat of Kabira Bay, Ishigaki Island, southern Ryukyu Islands, Japan. Axianassa planioculus n. sp. is morphologically closest to A. mineri Boone, 1931, known from Pacific Panama, among the 11 known congeners, but is readily distinguished from the latter by the eyes being dorsally concealed by the rostrum, the subovate telson, the unarmed carpus of the maxilliped 3 and the unarmed uropodal endopod. The discovery of a new mud-shrimp species in an easily accessible habitat indicates that the shallow-water infaunal decapods are still relatively poorly known. A partial segment of the mitochondrial 16S rRNA gene was sequenced from the holotype for future genetic studies.