Squalomix: shark and ray genome analysis consortium and its data sharing platform.

The taxon Elasmobranchii (sharks and rays) contains one of the long-established evolutionary lineages of vertebrates with a tantalizing collection of species occupying critical aquatic habitats. To overcome the current limitation in molecular resources, we launched the Squalomix Consortium in 2020 to promote a genome-wide array of molecular approaches, specifically targeting shark and ray species. Among the various bottlenecks in working with elasmobranchs are their elusiveness and low fecundity as well as the large and highly repetitive genomes. Their peculiar body fluid composition has also hindered the establishment of methods to perform routine cell culturing required for their karyotyping. In the Squalomix consortium, these obstacles are expected to be solved through a combination of in-house cytological techniques including karyotyping of cultured cells, chromatin preparation for Hi-C data acquisition, and high fidelity long-read sequencing. The resources and products obtained in this consortium, including genome and transcriptome sequences, a genome browser powered by JBrowse2 to visualize sequence alignments, and comprehensive matrices of gene expression profiles for selected species are accessible through https://github.com/Squalomix/info.

Temporal and Spatial Site Sharing during Spawning in Snappers Symphorichthys spilurus and Lutjanus bohar (Pisces: Perciformes: Lutjanidae) in Waters around Peleliu Island, Palau.

Jiro Sakaue, Hiroshi Akino, Manabu Endo, Hitoshi Ida, and Takashi Asahida (2016) Two species of Lutjanidae, Symphorichthys spilurus and Lutjanus bohar, form spawning aggregation, a large school specifically formed for reproduction. Although they share the same spawning site at the southernmost reef in Peleliu Island, Palau, timing of spawning and their behaviors in the spawning and resting sites differ. Although the spawning behaviors have reported previously, long term and integrated observations documenting the size of the aggregation, exact spawning duration and timing, detailed behavioral profiles, as well as oceanic conditions upon spawning have never been reported. Here, we conducted a comparative study for these species and found behavioral and environmental cues that might be key to differentiate their ecological characteristics. S. spilurus begun to aggregate at full moon. Aggregations of L. bohar on the other hand, started from four days before full moon. Size of the aggregation was > 50,000 in S. spilurus, but about 7,000 in L. bohar. Both species migrated from the resting area to the spawning site in a diel rhythm. S. spilurus started spawning every half- moon, between the full moon and the new moon, while L. bohar spawns on every full moon. The first spawning took place at around dawn but the time shifted. S. spilurus spawned only when the current directs toward the southeast (offshore flow), while L. bohar spawns only when the current directs toward the southwest (tidal flow). Characteristic swimming behavior was observed for S. spilurus, in that, one or few males that could successfully chase the quick-swimming female fish could fertilize the eggs. In contrast, the behavior of L. bohar, was in a manner typical of several other lutjanid fish. The comparative and long-term field observation conducted over 10 years identified clear differences in the spawning behaviors of S. spilurus and L. bohar. Key behavioral and environmental factors found here might be key determinants for the ecology of these species.

A 'living fossil' eel (Anguilliformes: Protanguillidae, fam. nov.) from an undersea cave in Palau.

We report the discovery of an enigmatic, small eel-like fish from a 35 m-deep fringing-reef cave in the western Pacific Ocean Republic of Palau that exhibits an unusual suite of morphological characters. Many of these uniquely characterize the Recent members of the 19 families comprising the elopomorph order Anguilliformes, the true eels. Others are found among anguilliforms only in the Cretaceous fossils, and still others are primitive with respect to both Recent and fossil eels. Thus, morphological evidence explicitly places it as the most basal lineage (i.e. the sister group of extant anguilliforms). Phylogenetic analysis and divergence time estimation based on whole mitogenome sequences from various actinopterygians, including representatives of all eel families, demonstrate that this fish represents one of the most basal, independent lineages of the true eels, with a long evolutionary history comparable to that of the entire Anguilliformes (approx. 200 Myr). Such a long, independent evolutionary history dating back to the early Mesozoic and a retention of primitive morphological features (e.g. the presence of a premaxilla, metapterygoid, free symplectic, gill rakers, pseudobranch and distinct caudal fin rays) warrant recognition of this species as a 'living fossil' of the true eels, herein described as Protanguilla palau genus et species nov. in the new family Protanguillidae.

Inhibiting roles of melanin-concentrating hormone for skin pigment dispersion in barfin flounder, Verasper moseri.

Barfin flounders change their surface color pattern to match their background. We have reported evidence of the association between hormones and body color changes in this fish. First, bolus intraperitoneal injection with melanin-concentrating hormone (MCH) immediately turned the skin color pale, while injection with melanocyte-stimulating hormone (MSH) did not change the skin color. Second, gene expression levels of MCH change in response to background color, while those of MSH do not. We also reported the expression of an MCH receptor gene (Mch-r2) in the skin of this fish. In this study, we aimed to further evaluate the roles of MCH in skin color change. First, long-term adaptation of adult barfin flounder to black or white background colors induced significantly different pigment migration patterns in both melanophores and xanthophores (P<0.05). However, continuous intraperitoneal injection with MCH did not influence chromatophore proliferation. Then, using in vitro experiments, we found that MCH aggregates both melanophores and xanthophores, and inhibits the pigment-dispersing activity of MSH in a similar manner. Finally, we identified transcripts of Mch-r2 in cells isolated from both melanophores and xanthophores. Taken together, the evidence suggests that MCH aggregates pigments via MCH-R2 in concert with the nervous system by overcoming the melanin-dispersing activities of MSH in barfin flounder.