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The vertical behavior of planktonic larvae has been increasingly recognized as an important factor in their transport. However, little is known about the roles ofthis behavior in open-ocean migration ofteleplanic larvae. Using Japanese spiny lobster Panulirus japonicus in the western North Pacific and adjacent waters as a model species, we aimed to clarify (1) the effect of vertical behavior of larvae on transport success, (2) migration pathways of larvae, and (3) mechanisms that enable larvae to approach adult habitats before metamorphosing into competent swimmers (pueruli). Larval transport was simulated using an individual-based model with 10 different vertical behavior types (VBTs) and mortality caused by exposure to water temperatures outside the range (19-30[degrees]C) at which wild larvae appear. The VBTs that started transport at a shallow depth (1 m) had significantly higher transport success than those that started at greater depths (> or =25 m). Of the successful VBTs, those with ontogenetic vertical migration (OVM) showed greater detrainment of particles from the Kuroshio Extension (KE) and facilitated southwestward transport of particles in the recirculation region. Furthermore, the results indicate that phyllosoma larvae are transported by the Kuroshio, KE, and Kuroshio Countercurrent. Our study suggested that (1) detrainment of phyllosoma larvae from the KE to the recirculation region is facilitated by OVM and cross-frontal exchange at the meander trough, and (2) southwestward transport to adult habitats and avoidance of the low-temperature water shifting southward in winter are facilitated by OVM and the beta spiral. These findings highlightthe importance of vertical behavior in open-ocean migration ofteleplanic larvae.

An ultimate benefit of marine protected areas (MPAs) is to reverse trophic cascades caused by human-driven collapse of critical ecological interactions. Here we demonstrate that, despite a small scale (0.28 km²) and not being fully protected, an MPA with strict fishing management and habitat enhancement by artificial reefs (ARs) in southwest Japan can lead to well-established macroalgal communities on widespread sea urchin barrens through cascading effects of predator recovery. Areas with low urchin densities occurred in and around daytime lobster (Panulirus japonicus) shelters primarily formed by quarry-rock ARs inside the MPA. We confirmed in the laboratory that lobsters preyed on two dominant sea urchins (Echinometra sp. A and Heliocidaris crassispina), with size- and species-dependent predation. The area with few urchins extended farther (~65 m) from an AR with numerous lobsters than from a natural shelter (patch reef) with far fewer lobsters. Causation of this pattern was confirmed by a tethering experiment showing that predation on urchins was similarly high at and near lobster shelters but decreased at ~100 m from the AR to a similar level as at an unprotected site. Time-lapse photography revealed that predation on tethered urchins was due mostly to the largest size class of lobsters (>100 mm carapace length), which comprised only 7% of the population, highlighting the importance of large-sized lobsters in controlling urchin abundance in localized areas adjacent to urchin-dominated barrens. Despite an ongoing once-a-year fishing event permitted within the MPA, lobster populations were persistent, demonstrating that the cascading effect of the lobsters on urchins and ultimately macroalgae was robust to temporary reductions in predator population size. Erect macroalgal cover was not simply accounted for by snapshot urchin density or biomass, suggesting a hysteresis effect of the phase shifts between macroalgal dominance and urchin barren states.

Here we utilize a combination of genetic data, oceanographic data, and local ecological knowledge to assess connectivity patterns of the ornate spiny lobster Panulirus ornatus (Fabricius, 1798) in the South-East Asian archipelago from Vietnam to Australia. Partial mitochondrial DNA control region and 10 polymorphic microsatellites did not detect genetic structure of 216 wild P. ornatus samples from Australia, Indonesia and Vietnam. Analyses show no evidence for genetic differentiation among populations (mtDNA control region sequences ΦST = -0.008; microsatellite loci FST = 0.003). A lack of evidence for regional or localized mtDNA haplotype clusters, or geographic clusters of microsatellite genotypes, reveals a pattern of high gene flow in P. ornatus throughout the South-East Asian Archipelago. This lack of genetic structure may be due to the oceanography-driven connectivity of the pelagic lobster larvae between spawning grounds in Papua New Guinea, the Philippines and, possibly, Indonesia. The connectivity cycle necessitates three generations. The lack of genetic structure of P. ornatus population in the South-East Asian archipelago has important implications for the sustainable management of this lobster in that the species within the region needs to be managed as one genetic stock.

Partial mtDNA cytochrome oxidase subunit I (COI) fragments and near entire stretch of 12S rDNA (12S) and control region (Dloop) of the Japanese spiny lobster ( Panulirus japonicus ) (n = 3) were amplified by PCR and used for direct nucleotide sequencing and for clone library-based nucleotide sequence analysis. Nucleotide sequences of a total of 75 clones in COI, 77 in 12S and 92 in Dloop were determined. Haplotypes of the clones matched with those obtained by direct sequencing were determined to be genuine mtDNA sequence of the individual. Phylogenetic analysis revealed several distinct groups of haplotypes in all three regions. Genuine mtDNA sequences were observed to form a group with their closely related variables, and most of these variables may be due to amplification error but a few to be heteroplasmy. Haplotypes determined as nuclear mitochondrial pseudogenes (NUMTs) formed distinct groups. Nucleotide sequence divergence (K2P distance) between genuine haplotypes and NUMTs were substantial (7.169–23.880% for COI, 1.336–23.434% for 12S, and 7.897–71.862% for Dloop). These values were comparable to or smaller than those between species of the genus Panulirus , indicating that integration of mtDNA into the nuclear genome is a continuous and dynamic process throughout pre- and post-speciation events. Double peaks in electropherograms obtained by direct nucleotide sequencing were attributed to common nucleotides shared by multiple NUMTs. Information on the heteroplasmy and NUMTs would be very important for addressing their impact on direct nucleotide sequencing and for quality control of nucleotide sequences obtained.

To date, 19 species of spiny lobsters from the genus Panulirus have been discovered, of which only P. japonicus , P. penicilatus , P. stimpsoni , and P. versicolor have been documented in South Korean waters. In this study, we aimed to identify and update the current list of spiny lobster species that inhabit South Korean waters based on the morphological features and the phylogenetic profile of cytochrome oxidase I (COI) of mitochondrial DNA (mtDNA). Spiny lobsters were collected from the southern and eastern coasts of Jeju Island, South Korea. Phylogenetic analyses were performed using neighbor-joining (NJ), maximum likelihood (ML), and Bayesian inference (BI) methods. The ML tree was used to determine the spiny lobster lineages, thereby clustering the 17 specimens collected in this study into clades A, B, C, and D, which were reciprocally monophyletic with P. japonicus , P. homarus homarus , P. longipes , and P. stimpsoni , respectively. These clades were also supported by morphological examinations. Interestingly, morphological variations, including the connected pleural and transverse groove at the third abdominal somite, were observed in four specimens that were genetically confirmed as P. japonicus . This finding is novel within the P. japonicus taxonomical reports. Additionally, this study updates the documentation of spiny lobsters inhabiting South Korean waters as P. longipes and P. homarus homarus were recorded for the first time in this region.

We used acoustic telemetry to track nine Japanese spiny lobsters Panulirus japonicus (carapace length = 70.5–105.5 mm) in the East China Sea examining their spatiotemporal movement patterns and assessing how environmental factors affect these patterns. Accelerometer-equipped acoustic transmitters were applied to track the lobsters’ fine-scale movements, together with environmental data, over a 58-day period. The individual positions of the lobsters were determined using a hyperbolic positioning system, and their home ranges, calculated via the minimum convex polygon method, showed remarkable variability among individuals. Movement patterns exhibited both “homing” and “nomadic” movements, commonly observed in related lobster species, and the observed variability in home range sizes likely reflects these movement patterns. Analysis of temporal activity patterns, based on standardized detection frequencies and acceleration values, indicated nocturnal activity with fluctuations over time. Generalized linear mixed models showed that lobster activity was negatively associated with moon phase, and positively associated with water temperature, tidal currents, and wind speed. These findings suggest that the catchability of Japanese spiny lobster in gillnet fishing may be affected by both movement patterns and environmental factors.

Molting in exoskeleton-bearing organisms can result in dramatic body shape transformations. While this phenomenon has been well-studied in insects, limited knowledge exists for other animals, including crustaceans. Among crustaceans, achelate lobsters, such as Palinuridae and Scyllaridae, exhibit a unique metamorphic transition from a flattened phyllosoma larva to a three-dimensional puerulus or nisto stage in a single molt. This study investigates the mechanisms underlying this transformation in the Japanese spiny lobster ( Panulirus japonicus ), focusing on carapace deformation through histological analysis, live imaging, and computational modeling. Three-dimensional micro-computed tomography revealed a significant reduction in body length and a shift in mouth position during metamorphosis. Live imaging captured dynamic morphological changes, including epithelial contraction and subsequent reshaping. Furthermore, observation of the transient metamorphosis phase identified a distinctive furrow structure on the carapace surface in a mid-metamorphosis specimen that died during the metamorphosis process, absent in post-metamorphosis puerulus larvae, suggesting a possible role in the transformation process. To explore the formation of this furrow pattern, a computational model was developed based on differential shrinkage rates in vertical and horizontal directions. The model successfully reproduced similar patterns observed in natural specimens, implying that controlled anisotropic contraction could contribute to morphogenesis. Furthermore, three-dimensional shrinkage simulations demonstrated that local contraction with constrained out-of-plane deformation can generate folds, which later expand to form curved structures. This study provides novel insights into the biomechanics of arthropod molting, highlighting a previously unrecognized mechanism of two-dimensional-to-three-dimensional transformation. The findings enhance our understanding of larval development in Achelata and offer broader implications for exoskeletal morphogenesis across arthropods.

The vertical behavior of planktonic larvae has been increasingly recognized as an important factor in their transport. However, little is known about the roles of this behavior in openocean migration of teleplanic larvae. Using Japanese spiny lobster Panulirus japonicus in the western North Pacific and adjacent waters as a model species, we aimed to clarify (1) the effect of vertical behavior of larvae on transport success, (2) migration pathways of larvae, and (3) mechanisms that enable larvae to approach adult habitats before metamorphosing into competent swimmers (pueruli). Larval transport was simulated using an individual-based model with 10 different vertical behavior types (VBTs) and mortality caused by exposure to water temperatures outside the range (19–30°C) at which wild larvae appear. The VBTs that started transport at a shallow depth (1 m) had significantly higher transport success than those that started at greater depths (≥25 m). Of the successful VBTs, those with ontogenetic vertical migration (OVM) showed greater detrainment of particles from the Kuroshio Extension (KE) and facilitated southwestward transport of particles in the re cir culation region. Furthermore, the results indicate that phyllosoma larvae are transported by the Kuroshio, KE, and Kuroshio Countercurrent. Our study suggested that (1) detrainment of phyllosoma larvae from the KE to the recirculation region is facilitated by OVM and cross-frontal exchange at the meander trough, and (2) southwestward transport to adult habitats and avoidance of the low-temperature water shifting southward in winter are facilitated by OVM and the beta spiral. These findings highlight the importance of vertical behavior in open-ocean migration of teleplanic larvae.

The order Archaeognatha was an ancient group of Hexapoda and was considered as the most primitive of living insects. Two extant families (Meinertellidae and Machilidae) consisted of approximately 500 species. This study determined 3 complete mitochondrial genomes and 2 nearly complete mitochondrial genome sequences of the bristletail. The size of the 5 mitochondrial genome sequences of bristletail were relatively modest, containing 13 protein-coding genes (PCGs), 2 ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes and one control region. The gene orders were identical to that of Drosophila yakuba and most bristletail species suggesting a conserved genome evolution within the Archaeognatha. In order to estimate archaeognathan evolutionary relationships, phylogenetic analyses were conducted using concatenated nucleotide sequences of 13 protein-coding genes, with four different computational algorithms (NJ, MP, ML and BI). Based on the results, the monophyly of the family Machilidae was challenged by both datasets (W12 and G12 datasets). The relationships among archaeognathan subfamilies seemed to be tangled and the subfamily Machilinae was also believed to be a paraphyletic group in our study.

In a search for biomarkers of health in whale sharks and as exploration of metabolomics as a modern tool for understanding animal physiology, the metabolite composition of serum in six whale sharks (Rhincodon typus) from an aquarium collection was explored using (1)H nuclear magnetic resonance (NMR) spectroscopy and direct analysis in real time (DART) mass spectrometry (MS). Principal components analysis (PCA) of spectral data showed that individual animals could be resolved based on the metabolite composition of their serum and that two unhealthy individuals could be discriminated from the remaining healthy animals. The major difference between healthy and unhealthy individuals was the concentration of homarine, here reported for the first time in an elasmobranch, which was present at substantially lower concentrations in unhealthy whale sharks, suggesting that this metabolite may be a useful biomarker of health status in this species. The function(s) of homarine in sharks remain uncertain but it likely plays a significant role as an osmolyte. The presence of trimethylamine oxide (TMAO), another well-known protective osmolyte of elasmobranchs, at 0.1-0.3 mol L(-1) was also confirmed using both NMR and MS. Twenty-three additional potential biomarkers were identified based on significant differences in the frequency of their occurrence between samples from healthy and unhealthy animals, as detected by DART MS. Overall, NMR and MS provided complementary data that showed that metabolomics is a useful approach for biomarker prospecting in poorly studied species like elasmobranchs.