Coloration in fishes plays central roles in communication, defense, and sexual selection, and is mediated by specialized pigment cells (chromatophores). In many species, red and orange hues derive from dietary carotenoids that are metabolically modified and intracellularly transported. The Garibaldi, Hypsypops rubicundus, a long-lived and iconic damselfish endemic to the eastern Pacific, displays a striking carotenoid-based orange-red coloration. To provide genomic resources for studying coloration genes in this species, we generated and assembled a high-quality genome using Oxford Nanopore long reads, yielding a 781.7 Mb assembly with 96% BUSCO completeness. As a proof of concept, we investigated the carotenoid-associated transport gene kif5b, which encodes a kinesin-1 motor protein involved in intracellular pigment mobilization. The kif5b gene in H. rubicundus comprises 25 exons and shows conserved organization relative to other damselfishes, but exhibits a unique amino acid substitution within a conserved nucleotide-binding motif (N3). Specifically, position 238 contains a leucine in H. rubicundus, whereas other damselfishes possess a glutamic acid or serine at this site. This substitution replaces a polar residue with a hydrophobic one, potentially affecting protein conformation or function. Phylogenetic analyses based on mitochondrial genomes and kif5b exons were largely congruent with published relationships. Our results establish the H. rubicundus genome as a valuable resource and identify a candidate molecular change that may contribute to its distinctive carotenoid-based coloration.
Outside the breeding season, small pelagic seabirds are particularly challenging to study due to their large geographic ranges and high mobility. Consequently, their non-breeding distribution and activity patterns are often poorly known. However, the non-breeding period is of critical importance, encompassing both migration and flight feather moult. We combined miniaturised geolocator-immersion loggers (GLS) with carbon and nitrogen bulk and compound-specific stable isotope analyses of rectrix feathers. Using this approach, we investigated the annual phenology, migratory routes, moult locations, non-breeding activity patterns and distribution of two Antarctic storm-petrel species: Wilson's Storm-petrel Oceanites oceanicus and Black-bellied Storm-petrel Fregetta tropica. Stable isotope data revealed a narrower isotopic niche and less intraspecific variation in trophic positions for Black-bellied Storm-petrels (n = 15) compared to Wilson's Storm-petrels (n = 15). GLS data suggested the non-breeding season of Wilson's Storm-petrels to last from around mid-April to end of November. All individuals (n = 7) migrated transequatorial in a clockwise pattern. Three individuals initially stayed at a non-breeding site in the South Atlantic Ocean. The main non-breeding sites of all individuals were in the North Atlantic Ocean, along the eastern coast of Canada and the United States, where flight feather moult took place from July to September, inferred from a period of reduced flight activity (measured by time on water). The foraging activity of Wilson's Storm-petrels was higher at night than during the day. This was not influenced by lunar phase but is likely linked to prey behaviour. The single successfully tracked Black-bellied Storm-petrel also crossed the equator but spent the non-breeding period in the Indian Ocean, mainly in the Arabian Sea. This indicates spatial segregation from Wilson's Storm-petrels. We present the first ever GLS tracking data of Wilson's and Black-bellied Storm-petrels, improving our understanding of their non-breeding behaviour. Future research including more individuals alongside environmental variables will be necessary to examine the drivers of the observed inter- and intraspecific non-breeding spatial and trophic segregation.
Emerging infectious diseases are novel threats to marine ecosystems. Although elucidating the temporal and spatial dynamics of such diseases is critical for managing ecosystems, it is generally challenging because many are invisible and cryptic, making it difficult to conduct long-term surveys at large spatial scales. Here, by analyzing web images on the social network platform X (formerly Twitter), I examined the infection dynamics of the parasitic copepod Lernaeenicus cf. ramosus, which causes pathological impacts on economically important marine fishes. Although previous studies indicated that infections increased after the 2000s in Japanese waters, there is no long-term data. Based on 3390 posts containing images of two host fish species (yellow grouper Epinephelus awoara and grub fish Parapercis sexfasciata) posted from 2012 to 2024, I found the copepods emerged and increased substantially around 2016-2019 in grub fish but declined in yellow grouper. Infection levels tended to be higher in autumn and winter, and methods of fish collection influenced the detectability of parasites. Moreover, I also identified new localities of the copepods, which fall outside of their previously known range, suggesting that their distribution is rapidly expanding north (east) ward. My study showed that analyzing web images sheds important insights into how aquatic diseases emerge and spread.
The endosymbiotic communities of corals are major contributors to the evolutionary success of scleractinian corals as the main reef-building organisms in modern coral reefs. The most studied endosymbiotic taxa associated with scleractinian corals are dinoflagellate family Symbiodiniaceae (previously the genus Symbiodinium), but corals are truly holobionts with a myriad of other microorganisms living together in what is known as the coral microbiome. The goal of this research was to characterize the genetic variability of the microbiome (based on 16S rRNA) and Symbiodiniaceae (based on ITS2) associated with the eurybathic Caribbean sheet coral Agaricia lamarcki along a depth gradient. This plating-crustose coral is found along a wide depth distribution from shallow coastal reefs at approximately 10 m down to mesophotic depths at > 75 m in southwest Puerto Rico. Environmental conditions vary across this gradient, leading us to expect significant differences in zooxanthellae clades and microbiome community composition. We collected fragments of 36 A. lamarcki colonies along a shallow-mesophotic depth gradient from 20 to 70 m at Black Wall in southwest Puerto Rico. PCR and Next-generation sequencing targeting 16S rRNA and ITS2 genes were performed on DNA extracted from coral biomass containing coral tissue and surface mucus layer. Despite no differences in alpha-diversity/richness metrics, our study found significant differences in coral-associated bacterial community composition between shallower reefs (20-30 m) and mesophotic reefs (50-70 m). Contrastingly, we found no significant differences in the Symbiodiniaceae composition of A. lamarcki across the depth gradient, indicating a uniform algal endosymbiont community in this location. Given the increasing loss of shallow water coral reefs, understanding coral adaptation mechanisms to mesophotic environmental conditions becomes ever more important to establish proper management and conservation efforts.
Global climate forcing and anthropogenic pressures are increasingly destabilizing marine ecosystems, pushing high-productivity upwelling zones toward unpredictable ecological tipping points. In the southeastern Caribbean, the eastern Venezuelan coastal region supports one of the world's most significant fisheries for the sardine Sardinella aurita, a species whose population stability is governed by a narrow thermal window (18 degrees C-25 degrees C). Utilizing two decades (2002-2023) of high-resolution MODIS-Aqua satellite data, we applied an early warning signal (EWS) framework based on critical slowing down (CSD) theory to diagnose the loss of resilience in this vital habitat. By contrasting the coastal sardine fishing area (SFA) with the offshore exclusive economic zone (EEZ), we analyzed temporal trends in sea surface temperature (SST) variance (standard deviation) and temporal autocorrelation (AR(1)). Our results reveal a significant divergence in thermal stability: while minimum and mean SSTs show increasing persistence (AR(1)), signaling a classic loss of resilience, the maximum SST in the coastal domain exhibits a sharp increase in volatility (SD) and erratic behavior. These "anti-CSD" signals in maximum SST indicate that extreme thermal events, such as marine heatwaves, are becoming more frequent and intense, frequently trespassing the physiological thresholds of S. aurita. By prioritizing physics-based indicators of habitat stability over confounded fishery-dependent data, this study demonstrates that the coastal sardine habitat is approaching a nonlinear regime shift. These findings provide a robust, proactive diagnostic tool for fisheries management, offering a critical lead time for adaptive strategies before biological collapses become statistically detectable.
