Project description:Damselfishes (Family: Pomacentridae) are a group of ecologically important, primarily coral reef fishes that include over 400 species. Damselfishes have been used as model organisms to study recruitment (anemonefishes), the effects of ocean acidification (spiny damselfish), population structure, and speciation (Dascyllus). The genus Dascyllus includes a group of small-bodied species, and a complex of relatively larger bodied species, the Dascyllus trimaculatus species complex that is comprised of several species including D. trimaculatus itself. The three-spot damselfish, D. trimaculatus, is a widespread and common coral reef fish species found across the tropical Indo-Pacific. Here, we present the first-genome assembly of this species. This assembly contains 910 Mb, 90% of the bases are in 24 chromosome-scale scaffolds, and the Benchmarking Universal Single-Copy Orthologs score of the assembly is 97.9%. Our findings confirm previous reports of a karyotype of 2n = 47 in D. trimaculatus in which one parent contributes 24 chromosomes and the other 23. We find evidence that this karyotype is the result of a heterozygous Robertsonian fusion. We also find that the D. trimaculatus chromosomes are each homologous with single chromosomes of the closely related clownfish species, Amphiprion percula. This assembly will be a valuable resource in the population genomics and conservation of Damselfishes, and continued studies of the karyotypic diversity in this clade.
| S-EPMC10085752 | biostudies-literature
Project description:Dascyllus trimaculatus RADSeq data
Project description:Damselfishes (family Pomacentridae) comprise approximately 400 species that play an important ecological role in temperate and coral reefs. Here, for the first time, we assemble and annotate the mitochondrial genome of Dascyllus trimaculatus, the three-spot dascyllus, a planktivorous damselfish that primarily recruits in anemones. The circular genome of D. trimaculatus is 16,967 bp in length and contains 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes, and a control region. Gene arrangement and codon usage is similar to reported mitochondrial genomes of other damselfish genera, and a phylogenetic analysis of a set of damselfish representatives is consistent with known evolutionary analyses.
Project description:Many animals possess high-contrast body patterns. When moving, these patterns may create confusing or conflicting visual cues that affect a predator's ability to visually target or capture them, a phenomenon called motion dazzle. The dazzle patterns may generate different forms of optical illusion that can mislead observers about the shape, speed, trajectory and range of the animal. Moreover, it is possible that the disruptive visual effects of the high contrast body patterns can be enhanced when moving against a high contrast background. In this study, we used the humbug damselfish (Dascyllus aruanus) to model the apparent motion cues of its high contrast body stripes against high contrast background gratings of different widths and orientations, from the perspective of a predator. We found with higher frequency gratings, when the background is indiscriminable to a viewer, that the humbugs may rely on the confusing motion cues created by internal stripes. With lower frequency gratings, where the background is likely perceivable by a viewer, the humbugs can rely more on confusing motion cues induced by disruption of edges from both the background and body patterning. We also assessed whether humbugs altered their behaviour in response to different backgrounds. Humbugs remained closer and moved less overall in response to backgrounds with a spatial structure similar to their own striped body pattern, possibly to stay camouflaged against the background and thus avoid revealing themselves to potential predators. At backgrounds with higher frequency gratings, humbugs moved more which may represent a greater reliance on the internal contrast of the fish's striped body pattern to generate motion dazzle. It is possible that the humbug stripes provide multiple protective strategies depending on the context and that the fish may alter their behaviour depending on the background to maximise their protection.
| S-EPMC11438442 | biostudies-literature
Project description:Hybridization across a suture zone (Dascyllus trimaculatus)
Project description:Hybrid zones are natural laboratories for investigating the dynamics of gene flow, reproductive isolation, and speciation. A predominant marine hybrid (or suture) zone encompasses Christmas Island (CHR) and Cocos (Keeling) Islands (CKE), where 15 different instances of interbreeding between closely related species from Indian and Pacific Oceans have been documented. Here, we report a case of hybridization between genetically differentiated Pacific and Indian Ocean lineages of the three-spot dascyllus, Dascyllus trimaculatus (Rüppell, 1829). Field observations indicate there are subtle color differences between Pacific and Indian Ocean lineages. Most importantly, population densities of color morphs and genetic analyses (mitochondrial DNA and SNPs obtained via RADSeq) suggest that the pattern of hybridization within the suture zone is not homogeneous. At CHR, both color morphs were present, mitochondrial haplotypes of both lineages were observed, and SNP analyses revealed both pure and hybrid genotypes. Meanwhile, in CKE, the Indian Ocean color morphs were prevalent, only Indian Ocean mitochondrial haplotypes were observed, and SNP analysis showed hybrid individuals with a large proportion (~80%) of their genotypes assigning to the Indian Ocean lineage. We conclude that CHR populations are currently receiving an influx of individuals from both ocean basins, with a greater influence from the Pacific Ocean. In contrast, geographically isolated CKE populations appear to be self-recruiting and with more influx of individuals from the Indian Ocean. Our research highlights how patterns of hybridization can be different at scales of hundreds of kilometers, due to geographic isolation and the history of interbreeding between lineages.