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Eviota, known as dwarf gobies, is a diverse genus of marine fishes comprising more than 120 species found throughout the Indo-Pacific Ocean. A previous study has suggested that morphologically similar cryptic species of Eviotamay exist and that the species diversity may be significantly underestimated. This study evaluated the diversity of Eviotaspecies in three habitat types (tidal flats, reef flats, and moats) in the shallow waters (0–1 m in depth at low tide) of Okinawa Islandusing morphological characteristics and molecular phylogenetic analysis. Eleven morphospecies were classified into 17 molecular optical units(MOTUs), and cryptic species for which speciation may have occurred relatively recently were detected in the morphospecies Eviota abax, Eviota japonica, Eviota queenslandica, and Eviota prasina. Most MOTUs exhibited only one habitat use, whereas three MOTUs were found in multiple habitats. Among each cryptic Eviota species, both habitat segregation and habitat overlaps were found. Therefore, speciation in Eviota may occur without habitat segregation, and multiple other factors should be considered regarding speciation in Eviota.

Because adult and juvenile eel gobies usually hide within the burrows of muddy substrates, their diversity and life history have not yet been fully elucidated. We investigated larval specimens of the eel gobies collected on Okinawa Island in southern Japan. The genus Trypauchenopsis was previously thought to consist of only one species, but our larval collection identified two species, Trypauchenopsis limicola and Trypauchenopsis intermedia, distinguished by their species-specific melanophore arrangements and differences in their fin-ray counts. Taenioides kentalleni were previously known from only two specimens worldwide. A third specimen of this species has now been added from the larval collection. In addition to the three species above, Taenioides gracilis and Caragobius urolepis were identified and larval morphologies of the five species were described for the first time. All the larvae collected in the present study were at late postflexion stage. Trypauchenopis limicola, T. intermedia, and T. gracilis were presumably collected in the estuaries and beaches when approaching their adult habitats at the end of pelagic life. They were 8.5–10.3 mm in standard length, and otolith analysis suggests that their pelagic larval durations are a little longer than 1 month (average 34–37 days). The larval occurrence suggested that the spawning season of T. limicola is May–December, when the water temperature is warmer than approximately 20°C. Our work reveals that studying the larval stage can provide new information on the taxonomy and life history of the elusive cryptobenthic fish.

The Longman’s beaked whale (Indopacetus pacificus) is one of the rarest cetaceans worldwide. Since it was first described as its own species in 1926, they have been observed alive at sea on several occasions, and less than 20 strandings have been reported worldwide to date. Thus, basic information regarding this species, such as the maximum size of adult individuals or body length at birth, remains unknown. In this study, the external appearance and DNA analysis of a female Longman’s beaked whale stranded on Miyako Island, Okinawa, Japan, are reported. The external appearance of the specimen matched the features of the Longman’s beaked whale presented in previous studies. The mitochondrial DNA control-region sequences obtained from the specimen also matched the reference sequences of the species deposited in GenBank. Based on these features, the specimen was confirmed as a Longman’s beaked whale. The specimen was estimated to be neonate because of its body length (235 cm) and the clear several fetal folds observed on its body surface. To the best of our knowledge, this is the first report of a confirmed new born neonate of Longman’s beaked whale in the world.

An environmental DNA (eDNA) metabarcoding approach has been widely used for biodiversity monitoring of fishes, although it has rarely been applied to tropical and subtropical aquatic ecosystems, where species diversity is remarkably high. This study examined the extent to which species richness can be estimated in a small coral reef lagoon (1,500 × 900 m) near Okinawa Island, southern Japan, where the surrounding waters are likely to harbor more than 1,500 species of fish. During 2015–2017, a total of 16 capture‐based surveys were conducted to create a faunal list of fish species, followed by eDNA metabarcoding based on seawater samples taken from 11 sites in the lagoon on a day in May 2019. We also tested whether eDNA metabarcoding could detect differences between adjacent fish communities inhabiting the offshore reef edge and shore‐side seagrass beds within the lagoon. A total of 217 fish species were confirmed by the capture‐based samplings, while 291 fish species were detected by eDNA metabarcoding, identifying a total of 410 species distributed across 119 families and 193 genera. Of these 410 species, only 96 (24% of the total) were commonly identified by both methods, indicating that capture‐based surveys failed to collect a number of species detected by eDNA metabarcoding. Interestingly, two different approaches to estimate species richness based on eDNA data yielded values close to the 410 species, including one that suggested an additional three or more eDNA surveys from 11 sites (36 samples) would detect 90% of the 410 species. In addition, nonmetric multidimensional scaling for fish assemblages clearly distinguished between the fish communities of the offshore reef edge and those of the shore‐side seagrass beds. This study demonstrates that an eDNA metabarcoding approach is useful for estimating species richness and detection of habitat segregation even in ecosystems with remarkably high species diversity.

Gobioid larvae collected from the coast of Okinawa Island, southern Japan, were identified on the basis of a combination of morphological characters and a sequence of a hypervariable region of mitochondrial 12S ribosomal RNA (12S rRNA) gene (138–145 base pairs). A short-term formalin fixation technique enabled identification using both morphological and genetic methods. Thirteen of the 21 types of gobioid larvae assessed were identified to the species level. Additionally, we described the morphology of the postflexion larvae of wormfish Paragunnellichthys sp. and shrimp-associated goby Ctenogobiops feroculus, identified for the first time in their respective genera.

An environmental DNA (eDNA) metabarcoding approach has been widely used for biodiversity monitoring of fishes, although it has rarely been applied to tropical and subtropical aquatic ecosystems, where species diversity is remarkably high. This study examined the extent to which species richness can be estimated in a small coral reef lagoon (1500 × 900 m) near Okinawa Island, southern Japan, where the surrounding waters are likely to harbor more than 1500 species of fish. During 2015–2017, a total of 16 capture-based surveys were conducted to create a faunal list of fish species, followed by eDNA metabarcoding based on seawater samples taken from 11 sites in the lagoon on a day in May 2019. We also tested whether eDNA metabarcoding could detect differences between adjacent fish communities inhabiting the offshore reef edge and shore-side seagrass beds within the lagoon. A total of 217 fish species were confirmed by the capture-based samplings, while 291 fish species were detected by eDNA metabarcoding, identifying a total of 410 species distributed across 119 families and 193 genera. Of these 410 species, only 96 (24% of the total) were commonly identified by both methods, indicating that capture-based surveys failed to collect a number of species detected by eDNA metabarcoding. Interestingly, two different approaches to estimate species richness based on eDNA data yielded values close to the 410 species, including one that suggested an additional three or more eDNA surveys from 11 sites (36 samples) would detect 90% of the 410 species. In addition, non-metric multi-dimensional scaling for fish assemblages clearly distinguished between the fish communities of the offshore reef edge and those of the shore-side seagrass beds.

Ram ventilation, which is characterized by the production of a respiratory water current over the gill by locomotory effort, widely occurs among pelagic sharks. However, the process by which the juvenile starts this respiratory mechanism remains largely unknown. The captive birth of a Tiger Shark (Galeocerdo cuvier) at the Okinawa Churaumi Aquarium on 23 March 2017 permitted the examination of the parturition process and behavior of newborn juveniles of this species. Sonographic examination of the pregnant female showed that, unlike adult Tiger Sharks, embryos used buccal pumping, revealing that Tiger Shark shifts its respiratory mechanism from buccal pumping to ram ventilation after birth. Our observation also showed that ram ventilation of the neonate was not continuous, and buccal pumping was also used when the neonate intermittently rested on the bottom of the tank. We speculate that this behavior is the transitional phase in the shift from buccal pumping to ram ventilation in neonates, and continuous ram ventilation may be established after the development of continuous and fast swimming abilities.

During a survey of deep-sea fauna, using a Remotely Operated Vehicle, a single specimen (21.6 mm in standard length) of Larsonella pumilus (Larson & Hoese, 1980) was collected at a depth of 214 m off the coast of Okinawa Island, Japan. It represents the first record of this species from Japan. The collection site was far deeper than previous reports for this species. This suggests that the main habitat of L. pumilus is deeper than previously recognized and it may explain the paucity of records of this species. As the previously available morphological description of L. pumilus was based on only a single specimen (holotype), this new specimen is described herein. Its morphology corresponds closely to the original description of the holotype, except that faint melanophores are arranged radially around the eyes and scattered on the trunk and the fins. Mitochondrial genome sequences of L. pumilus and 19 related species demonstrate close relationships between L. pumilus and the genus Priolepis. These data also indicate that the genus Priolepis is not monophyletic.