Quantitative Analysis of Ultrasonography for de Quervain's Disease: Comparison of the Affected Side With the Asymptomatic Side.

OBJECTIVES: The pathology of de Quervain's disease affects the tenosynovium and rarely the tendons. The ultrasonographic features of de Quervain's disease unresponsive to conservative treatment are unknown. The purpose of this study was to describe and compare the morphological differences between patients with de Quervain's disease that is refractory to conservative treatment and patients who respond to conservative treatment. METHODS: de Quervain's disease unresponsive to conservative treatment was evaluated in 51 patients. The bilateral wrists underwent preoperative ultrasonographic assessments. The asymptomatic side was presumed to be the patient's anatomical baseline and was used for comparison. We measured the diameter and cross-sectional area of the tendons of the abductor pollicis longus (APL) and extensor pollicis brevis (EPB), and the thickness of the tendon sheath and the intercompartmental septum, if present. The affected side and asymptomatic side were compared. RESULTS: The APL and EPB cross-sectional area was significantly larger on the affected side than on the asymptomatic side (APL: 13 mm2 versus 8.3 mm2 ; P < .0001; EPB: 5.4 mm2 versus 3.9 mm2 ; P = .031). The tendon sheath was significantly thicker on the affected side (1.5 mm) than on the asymptomatic side (0.95 mm) (P < .0001). The intercompartmental septum was significantly thicker on the affected side (1.1 mm) than on the asymptomatic side (0.72 mm) (P = .0004). Operative findings revealed 41 (80%) patients had an intercompartmental septum. CONCLUSIONS: The ultrasonographic features of de Quervain's disease requiring surgical treatment were a significantly thickened tendon sheath, an intercompartmental septum, and increased cross-sectional area of the APL and EPB.

Fourth Dorsal Interosseous Muscle Transfer to Treat an Abducted Little Finger.

A patient presented with an abducted little finger due to the avulsion of the third volar interosseous muscle. For treatment, we transferred the fourth dorsal interosseous muscle arising from the ulnar side of the fourth metacarpal bone to the lateral band of the little finger.

Sustained Hypoxia Suppresses Joint Destruction in a Rat Model of Rheumatoid Arthritis via Negative Feedback of Hypoxia Inducible Factor-1α.

Hypoxia inducible factor (HIF)-1α has been implicated in the pathogenesis of rheumatoid arthritis (RA). HIF-1α, which is expressed in hypoxia, is reversely suppressed in sustained hypoxia. Here, we investigated the inhibitory effect of hypoxia on arthritis by controlling HIF-1α. Rheumatoid fibroblast-like synoviocyte MH7A cells were cultured in a hypoxic incubator for up to 72 h to evaluate the expression of HIF-1. Furthermore, collagen-induced arthritis (CIA) model rats were maintained under 12% hypoxia in a hypoxic chamber for 28 days to evaluate the effect on arthritis. In MH7A cells, HIF-1α protein level increased at 3 h, peaked at 6 h, and subsequently decreased in a time-dependent manner. The transcription of pro-inflammatory cytokines increased at 1 h; however, they decreased after 3 h (p < 0.05). Deferoxamine-mediated activation of HIF-1α abolished the inhibitory effect of sustained hypoxia on pro-inflammatory cytokines. In the rat CIA model, the onset of joint swelling was delayed and arthritis was suppressed in the hypoxia group compared with the normoxia group (p < 0.05). Histologically, joint destruction was suppressed primarily in the cartilage. Thus, sustained hypoxia may represent a new safe, and potent therapeutic approach for high-risk patients with RA by suppressing HIF-1α expression.

Treadmill Running in Established Phase Arthritis Inhibits Joint Destruction in Rat Rheumatoid Arthritis Models.

Exercise therapy inhibits joint destruction by suppressing pro-inflammatory cytokines. The efficacy of pharmacotherapy for rheumatoid arthritis differs depending on the phase of the disease, but that of exercise therapy for each phase is unknown. We assessed the differences in the efficacy of treadmill running on rheumatoid arthritis at various phases, using rat rheumatoid arthritis models. Rats with collagen-induced arthritis were used as rheumatoid arthritis models, and the phase after immunization was divided as pre-arthritis and established phases. Histologically, the groups with forced treadmill running in the established phase had significantly inhibited joint destruction compared with the other groups. The group with forced treadmill running in only the established phase had significantly better bone morphometry and reduced expression of connexin 43 and tumor necrosis factor α in the synovial membranes compared with the no treadmill group. Furthermore, few cells were positive for cathepsin K immunostaining in the groups with forced treadmill running in the established phase. Our results suggest that the efficacy of exercise therapy may differ depending on rheumatoid arthritis disease activity. Active exercise during phases of decreased disease activity may effectively inhibit arthritis and joint destruction.

Limb saving surgery for Ewing's sarcoma of the distal tibia: a case report.

BACKGROUND: Ewing's sarcoma is a primary malignant tumor of bone occurring mostly in childhood. Few effective reconstruction techniques are available after wide resection of Ewing's sarcoma at the distal end of the tibia. Reconstruction after wide resection is especially difficult in children, as it is necessary to consider the growth and activity of the lower limbs. CASE PRESENTATION: A 12-year-old Japanese boy had presented with right lower leg pain at age 8 years. Imaging examination showed a bone tumor accompanied by a large extra-skeletal mass in the distal part of his tibia. The tumor was histologically diagnosed as Ewing's sarcoma. The patient received chemotherapy, followed by wide resection. Reconstruction consisted of a bone transport method involving external fixation of Taylor Spatial Frame. To prevent infection after surgery, the external fixation pin was coated with iodine. One year after surgery, the patient showed poor consolidation of bone, so iliac bone transplantation was performed on the extended bones and docking site of the distal tibia. After 20 months, tibia formation was good. Three years after surgery, there was no evidence of tumor recurrence or metastases; bone fusion was good, and he was able to run. CONCLUSIONS: The bone transport method is an effective surgical method of reconstruction after wide resection of a bone tumor at the distal end of the tibia, if a pin can be inserted into the distal bone fragment. Coating external fixation pins with iodine may prevent postoperative infection.

Treadmill Running Ameliorates Destruction of Articular Cartilage and Subchondral Bone, Not Only Synovitis, in a Rheumatoid Arthritis Rat Model.

We analyzed the influence of treadmill running on rheumatoid arthritis (RA) joints using a collagen-induced arthritis (CIA) rat model. Eight-week-old male Dark Agouti rats were randomly divided into four groups: The control group, treadmill group (30 min/day for 4 weeks from 10-weeks-old), CIA group (induced CIA at 8-weeks-old), and CIA + treadmill group. Destruction of the ankle joint was evaluated by histological analyses. Morphological changes of subchondral bone were analyzed by µ-CT. CIA treatment-induced synovial membrane invasion, articular cartilage destruction, and bone erosion. Treadmill running improved these changes. The synovial membrane in CIA rats produced a large amount of tumor necrosis factor-α and Connexin 43; production was significantly suppressed by treadmill running. On µ-CT of the talus, bone volume fraction (BV/TV) was significantly decreased in the CIA group. Marrow star volume (MSV), an index of bone loss, was significantly increased. These changes were significantly improved by treadmill running. Bone destruction in the talus was significantly increased with CIA and was suppressed by treadmill running. On tartrate-resistant acid phosphate and alkaline phosphatase (TRAP/ALP) staining, the number of osteoclasts around the pannus was decreased by treadmill running. These findings indicate that treadmill running in CIA rats inhibited synovial hyperplasia and joint destruction.

The outcomes of reconstruction using frozen autograft combined with iodine-coated implants for malignant bone tumors: compared with non-coated implants.

OBJECTIVE: We perform reconstruction using frozen tumor bone treated by liquid nitrogen after excision of malignant bone tumors. To prevent post-operative infection, we use iodine-coated implants that we developed. The purpose of this study is to compare the outcome of reconstruction using frozen autograft with non-coated implants (group N) and iodine-coated implants (group I). METHODS: Sixty-two patients were included in group N. The mean age was 31.9 ± 2.3 years. A total of 20 patients died and two were lost to follow-up, averaging 20.0 ± 2.9 months post-operatively, leaving 40 patients available for an assessment at a mean of 79.1 ± 5.8 months post-operatively. There were 38 patients in group I. The mean age was 29.8 ± 3.9 years. The mean follow-up period was 32.1 ± 3.0 months. All patients were alive at the latest follow-up. Survival of frozen bone was determined by Kaplan-Meier analysis. RESULTS: In group N, survival of frozen bone was 80.7 ± 6.0% and 57.4 ± 10.2% at 5 and 10 years, respectively. Complications were encountered in 31 of 62 patients (50.0%), including deep infection in 10 (16.1%), fracture in 11 (17.7%), local soft-tissue recurrence in 6 (9.7%) and bone absorption in 4 (6.5%). In group I, survival of frozen bone was 86.7 ± 6.3% at 5 years. Complications were encountered in 8 of 38 patients (21.1%), including deep infection in one (2.6%), fracture in four (10.5%), local soft-tissue recurrence in two (5.3%) and bone absorption in one (2.6%). There was a significantly lower infection rate in group I (P = 0.032). CONCLUSION: Reconstruction using frozen autograft combined with iodine-coated implants for patients with malignant bone tumor is very useful method in which good limb function can be gained with minimized risk of infection.

Effect of sulfide, osmotic, and thermal stresses on taurine transporter mRNA levels in the gills of the hydrothermal vent-specific mussel Bathymodiolus septemdierum.

Hydrothermal vent environmental conditions are characterized by high sulfide concentrations, fluctuating osmolality, and irregular temperature elevations caused by vent effluents. These parameters represent potential stressors for organisms that inhabit the area around hydrothermal vents. Here, we aimed to obtain a better understanding of the adaptation mechanisms of marine species to hydrothermal vent environments. Specifically, we examined the effect of sulfide, osmolality, and thermal stress on the expression of taurine transporter (TAUT) mRNA in the gill of the deep-sea mussel Bathymodiolus septemdierum, which is a dominant species around hydrothermal vent sites. We analyzed TAUT mRNA levels by quantitative real-time polymerase chain reaction (PCR) in the gill of mussels exposed to sulfide (0.1 or 1mg/L Na2S·9H2O), hyper- (115% seawater) and hypo- (97.5%, 95.5%, and 85% seawater) osmotic conditions, and thermal stresses (12°C and 20°C) for 24 and 48h. The results showed that mussels exposed to relatively low levels of sulfide (0.1mg/L) and moderate heat stress (12°C) exhibited higher TAUT mRNA levels than the control. Although hyper- and hypo-osmotic stress did not significantly change TAUT mRNA levels, slight induction was observed in mussels exposed to low osmolality. Our results indicate that TAUT is involved in the coping mechanism of mussels to various hydrothermal vent stresses.

Hypoxia Potentiates Anabolic Effects of Exogenous Hyaluronic Acid in Rat Articular Cartilage.

Hyaluronic acid (HA) is used clinically to treat osteoarthritis (OA), but its pharmacological effects under hypoxic conditions remain unclear. Articular chondrocytes in patients with OA are exposed to a hypoxic environment. This study investigated whether hypoxia could potentiate the anabolic effects of exogenous HA in rat articular cartilage and whether these mechanisms involved HA receptors. HA under hypoxic conditions significantly enhanced the expression of extracellular matrix genes and proteins in explant culture, as shown by real-time reverse transcription-polymerase chain reaction (RT-PCR), Western blotting, and dimethylmethylene blue (DMMB) assays. Staining with Safranin-O and immunohistochemical staining with antibody to type II collagen were also enhanced in pellet culture. The expression of CD44 was increased by hypoxia and significantly suppressed by transfection with siRNAs targeting hypoxia-inducible factor 1 alpha (siHIF-1α). These findings indicate that hypoxia potentiates the anabolic effects of exogenous HA by a mechanism in which HIF-1α positively regulates the expression of CD44, enhancing the binding affinity for exogenous HA. The anabolic effects of exogenous HA may increase as OA progresses.

Metastasis of differentiated thyroid cancer in the subchondral bone of the femoral head: a case report.

BACKGROUND: Differentiated thyroid cancer (DTC) is relatively rare and can metastasize to both the lungs and bones. The great majority of bone metastases occur in red marrow regions where blood flow is high. Only one patient has been described with direct DTC metastasis to the subchondral bone of the femoral head. CASE PRESENTATION: The patient was a 68-year-old Japanese female who had presented with left hip joint pain at age 63 years. At age 51 years, she had been diagnosed with DTC and underwent partial excision. X-rays showed partial femoral head collapse, suggesting osteoarthritis or idiopathic necrosis of the left femoral head. Three years later, a (131) I whole-body scan showed accumulation in the left femoral head, resulting in a diagnosis of DTC metastasis to the left femoral head. Bipolar hip arthroplasty was performed. Examination of the excised femoral head resulted in a final diagnosis of metastasis of follicular thyroid cancer, which was limited histopathologically to the subchondral bone of the femoral head. CONCLUSION: Tumor metastasis to the subchondral bone of the femoral head is exceedingly rare. Overall survival of patients with bone metastasis is improved by complete resection. Differential diagnosis of patients with a previous history of DTC who present with femoral head collapse should include bone metastasis of DTC.

Hydrostatic pressure influences HIF-2 alpha expression in chondrocytes.

Hypoxia-inducible factor (HIF)-2α is considered to play a major role in the progression of osteoarthritis. Recently, it was reported that pressure amplitude influences HIF-2α expression in murine endothelial cells. We examined whether hydrostatic pressure is involved in expression of HIF-2α in articular chondrocytes. Chondrocytes were cultured and stimulated by inflammation or hydrostatic pressure of 0, 5, 10, or 50 MPa. After stimulation, heat shock protein (HSP) 70, HIF-2α, nuclear factor kappa B (NF-κB), matrix metalloproteinase (MMP)-13, MMP-3, and vascular endothelial growth factor (VEGF) gene expression were evaluated. The levels of all gene expression were increased by inflammatory stress. When chondrocytes were exposed to a hydrostatic pressure of 5 MPa, HIF-2α, MMP-13, and MMP-3 gene expression increased significantly although those of HSP70 and NF-κB were not significantly different from the control group. In contrast, HIF-2α gene expression did not increase under a hydrostatic pressure of 50 MPa although HSP70 and NF-κB expression increased significantly compared to control. We considered that hydrostatic pressure of 5 MPa could regulate HIF-2α independent of NF-κB, because the level of HIF-2α gene expression increased significantly without upregulation of NF-κB expression at 5 MPa. Hydrostatic pressure may influence cartilage degeneration, inducing MMP-13 and MMP-3 expression through HIF-2α.

When did decapods invade hydrothermal vents? Clues from the Western Pacific and Indian Oceans.

Hydrothermal vents are typically located in midocean ridges and back-arc basins and are usually generated by the movement of tectonic plates. Life thrives in these environments despite the extreme conditions. In addition to chemoautotrophic bacteria, decapod crustaceans are dominant in many of the hydrothermal vents discovered to date. Contrary to the hypothesis that these species are remnants of relic fauna, increasing evidence supports the notion that hydrothermal vent decapods have diversified in more recent times with previous research attributing the origin of alvinocarid shrimps to the Miocene. This study investigated seven representative decapod species from four hydrothermal vents throughout the Western Pacific and Indian Oceans. A partitioned mix-model phylogenomic analysis of mitochondrial DNA produced a consistent phylogenetic topology of these vent-endemic species. Additionally, molecular dating analysis calibrated using multiple fossils suggested that both bythograeid crabs and alvinocarid shrimps originated in the late Mesozoic and early Cenozoic. Although of limited sampling, our estimates support the extinction/repopulation hypothesis, which postulates recent diversification times for most hydrothermal vent species due to their mass extinction by global deep-water anoxic/dysoxic events during the Late Cretaceous and Early Tertiary. The continental-derived property of the West Pacific province is compatible with the possibility that vent decapods diversified from ancestors from shallow-water regions such as cold seeps. Our results move us a step closer toward understanding the evolutionary origin of hydrothermal vent species and their distribution in the Western Pacific-Indian Ocean Region.

Sensing deep extreme environments: the receptor cell types, brain centers, and multi-layer neural packaging of hydrothermal vent endemic worms.

INTRODUCTION: Deep-sea alvinellid worm species endemic to hydrothermal vents, such as Alvinella and Paralvinella, are considered to be among the most thermotolerant animals known with their adaptability to toxic heavy metals, and tolerance of highly reductive and oxidative stressful environments. Despite the number of recent studies focused on their overall transcriptomic, proteomic, and metabolic stabilities, little is known regarding their sensory receptor cells and electrically active neuro-processing centers, and how these can tolerate and function in such harsh conditions. RESULTS: We examined the extra- and intracellular organizations of the epidermal ciliated sensory cells and their higher centers in the central nervous system through immunocytochemical, ultrastructural, and neurotracing analyses. We observed that these cells were rich in mitochondria and possessed many electron-dense granules, and identified specialized glial cells and serial myelin-like repeats in the head sensory systems of Paralvinella hessleri. Additionally, we identified the major epidermal sensory pathways, in which a pair of distinct mushroom bodies-like or small interneuron clusters was observed. These sensory learning and memory systems are commonly found in insects and annelids, but the alvinellid inputs are unlikely derived from the sensory ciliary cells of the dorsal head regions. CONCLUSIONS: Our evidence provides insight into the cellular and system-wide adaptive structure used to sense, process, and combat the deep-sea hydrothermal vent environment. The alvinellid sensory cells exhibit characteristics of annelid ciliary types, and among the most unique features were the head sensory inputs and structure of the neural cell bodies of the brain, which were surrounded by multiple membranes. We speculated that such enhanced protection is required for the production of normal electrical signals, and to avoid the breakdown of the membrane surrounding metabolically fragile neurons from oxidative stress. Such pivotal acquisition is not broadly found in the all body parts, suggesting the head sensory inputs are specific, and these heterogenetic protection mechanisms may be present in alvinellid worms.

Deep-Sea decapod crustaceans (Caridea, Polychelida, Anomura and Brachyura) collected from the Nikko Seamounts, Mariana Arc, using a remotely operated vehicle "Hyper-Dolphin".

Samples and images of deep-water benthic decapod crustaceans were collected from the Nikko Seamounts, Mariana Arc, at depths of 520-680 m, by using the remotely operate vehicle "Hyper-Dolphin", equipped with a high definition camera, digital camera, manipulators and slurp gun (suction sampler). The following seven species were collected, of which three are new to science: Plesionika unicolor n. sp. (Caridea: Pandalidae), Homeryon armarium Galil, 2000 (Polychelida: Polychelidae), Eumunida nikko n. sp. (Anomura: Eumunididae), Michelopagurus limatulus (Henderson, 1888) (Anomura: Paguridae), Galilia petricola n. sp. (Brachyura: Leucosiidae), Cyrtomaia micronesica Richer de Forges & Ng, 2007 (Brachyura: Inachidae), and Progeryon mus Ng & Guinot, 1999 (Brachyura: Progeryonidae). Affinities of these three new species are discussed. All but H. armarium are recorded from the Japanese Exclusive Economic Zone for the first time. Brief notes on ecology and/or behavior are given for each species.

Pins and Rubber Band Traction System Combined with Internal Fixation for Intra-articular Fractures of the Proximal Interphalangeal Joints.

Background: Intra-articular fractures of the proximal interphalangeal joint (PIPJ) can result in poor outcomes if inadequately treated. Dynamic external fixation and internal fixation with plates and/or screws are two treatment options. The role of combining these two methods is unclear. The aim of this study is to determine the outcomes of patients with intra-articular fractures of the PIPJ treated with a combination of dynamic external fixation with a plate and/or screws. Methods: A retrospective review was conducted on 18 consecutive cases of intra-articular fractures of the PIPJ treated with pins and rubber band traction system (PRTS) combined with dorsal internal fixation with plates and/or screws. The patients' average age was 51 years (range: 20-81 years). The fracture patterns were volar-type (n = 2), dorsal-type (n = 4) and pilon-type (n = 12). Data with regard to time to surgery, interphalangeal joint range of motion, grip strength, VAS for pain, Quick DASH score, complications, duration of follow-up and return to work were collected. Results: The levels of articular involvement were stable (n = 1), tenuous (n = 5) and unstable (n = 12). The average time to surgery was 9 days, and the average follow-up period was 15 months. The fracture was fixed with a dorsal plate and screws in 10 patients and with only screws in eight patients. All patients had PRTS. All patients returned to their original occupation and the fractures united in good alignment. The average grip strength was 86% of that of the unaffected side. The average active PIPJ motion was 85° (range: 50°-106°), and the average active distal interphalangeal joint (DIPJ) motion was 48° (range: 10°-90°). Conclusions: Our results show that a combination of PRTS and open reduction and fixation with plate and/or screws achieved a good range of motion and articular reduction. Level of Evidence: Level IV (Therapeutic).

Preserved walking function without postoperative reconstruction for pelvic Ewing's sarcoma: a case report.

BACKGROUND: Ewing's sarcoma is a primary bone tumor predominantly observed in children and adolescents, necessitating a multidisciplinary treatment approach. While localized cases have a 5-year survival rate of 60-70%, the prognosis is significantly worse in pelvic advanced cases with metastasis. Moreover, pelvic Ewing's sarcoma has the unique problem of leading to high rates of postoperative infection. CASE PRESENTATION: We present the case of a Japanese 14-year-old boy with left iliac Ewing's sarcoma and multiple metastases. At the initial visit, imaging revealed a large tumor in the left iliac bone with extraosseous extension and metastasis to multiple sites. Neoadjuvant chemotherapy resulted in significant tumor reduction. Surgical resection was performed without pelvic ring reconstruction to enable early postoperative chemotherapy and minimize postoperative infection risk. Despite complete abductor muscle removal, the patient achieved a stable gait postoperatively by centering the load axis. CONCLUSION: Our case highlights the successful management of a left iliac Ewing's sarcoma with multiple metastases, with a focus on functional preservation and infection risk reduction. Pelvic ring reconstruction was not performed to avoid postoperative complications, emphasizing the importance of early postoperative chemotherapy. The patient achieved a stable gait postoperatively, demonstrating the potential benefits of this approach in similar cases.

Adaptive radiation of chemosymbiotic deep-sea mussels.

Adaptive radiations present fascinating opportunities for studying the evolutionary process. Most cases come from isolated lakes or islands, where unoccupied ecological space is filled through novel adaptations. Here, we describe an unusual example of an adaptive radiation: symbiotic mussels that colonized island-like chemosynthetic environments such as hydrothermal vents, cold seeps and sunken organic substrates on the vast deep-sea floor. Our time-calibrated molecular phylogeny suggests that the group originated and acquired sulfur-oxidizing symbionts in the Late Cretaceous, possibly while inhabiting organic substrates and long before its major radiation in the Middle Eocene to Early Oligocene. The first appearance of intracellular and methanotrophic symbionts was detected only after this major radiation. Thus, contrary to expectations, the major radiation may have not been triggered by the evolution of novel types of symbioses. We hypothesize that environmental factors, such as increased habitat availability and/or increased dispersal capabilities, sparked the radiation. Intracellular and methanotrophic symbionts were acquired in several independent lineages and marked the onset of a second wave of diversification at vents and seeps. Changes in habitat type resulted in adaptive trends in shell lengths (related to the availability of space and energy, and physiological trade-offs) and in the successive colonization of greater water depths.

Munidopsis lauensis Baba & de Saint Laurent, 1992 (Decapoda, Anomura, Munidopsidae), a newly recorded squat lobster from a cold seep in Taiwan.

The squat lobster, Munidopsis lauensis Baba & de Saint Laurent, 1992, is recorded from Taiwan for the first time. This species was previously known only from deep-sea hydrothermal vents in the South-West Pacific but it was now found at a deep-sea cold seep site off southwestern Taiwan. The identity of the Taiwanese material is confirmed by comparison of sequences from the barcoding gene COI. Munidopsis lauensis can be easily separated from other congeners in Taiwanese waters by the eyes bearing a strong mesiodorsal spine and a small mesioventral spine, smooth carapace, fingers of the cheliped distally spooned and fixed finger without a denticulate carina on the distolateral margin. The discovery of this species in Taiwan increases the Munidopsis fauna of the island to 38 species. A color photograph and line drawings illustrating distinctive characters are provided for the Taiwanese material.

Squat lobsters of the superfamily Chirostyloidea (Decapoda: Anomura) from seamounts on the Nishi-Shichito and Mariana ridges, North-West Pacific off Japan, with descriptions of two new species.

A small collection of chirostyloid squat lobsters was studied, collected from seamounts on the Nishi-Shichito, West Mariana, and Central Mariana ridges, which have been collectively designated as marine protected areas (MPAs) of Japan. Specimens were collected using a remotely operated vehicle (ROV). Four species belonging to three families were identified, of which two are new to science: Uroptychus medius n. sp. (Chirostylidae), Eumunida smithii Henderson, 1885, E. treguieri de Saint Laurent & Poupin, 1996 (Eumunididae), and Sternostylus spiniger n. sp. (Sternostylidae). Identities of those species were assessed using an integrative approach based on morphological comparison and genetic analysis of two mitochondrial markers (COI and 16S rRNA genes). The two species of Eumunida represent the first records from Japanese waters.

A new deep-sea palaemonid shrimp assigned to Periclimenes Costa, 1844 (Decapoda: Caridea) from the West Mariana Ridge, northwestern Pacific.

A new palaemonid species, Periclimenes variabilis, is described and illustrated on the basis of four specimens from the Ritto Seamount, West Marina Ridge, northwestern Pacific, at depths of 642-666 m. Specimens of the new species were collected with an unidentified hexacoral of Primnoidae (Cnidaria), an antipatharian octocoral Leiopathes sp. (Cnidaria), and an unidentified crinoid (Echinodermata), suggesting association with those invertebrates. Morphological comparison and molecular phylogenetic analyses using the mitochondrial 16S ribosomal RNA and cytochrome C oxidase subunit I genes indicate that the new species is closest to Periclimenes uniunguiculatus Bruce, 1990 although the possession of more than two spiniform setae on either side of the telson in the new species is consistent with the generic diagnosis of Bathymenes Kou, Li & Bruce, 2016. In reference to the close relationship to the species currently assigned to Periclimenes Costa, 1844 and the unsettled taxonomy of the genus, the new species is provisionally assigned to Periclimenes. Differentiating characters between the new species and closely related taxa are discussed.