Insights into the nuclear and mitochondrial genome of the Lemon shark Negaprion brevirostris using low-coverage sequencing: Genome size, repetitive elements, mitochondrial genome, and phylogenetic placement.

The Lemon shark Negaprion brevirostris is an important species experiencing conservation issues that is in need of genomic resources. Herein, we conducted a genome survey sequencing in N. brevirostris and determined genome size, explored repetitive elements, assembled and annotated the 45S rRNA DNA operon, and assembled and described in detail the mitochondrial genome. Lastly, the phylogenetic position of N. brevirostris in the family Carcharhinidae was examined using translated protein coding genes. The estimated haploid genome size ranged between 2.29 and 2.58 Gbp using a k-mer analysis, which is slightly below the genome size estimated for other sharks belonging to the family Carcharhinidae. Using a k-mer analysis, approx. 64-71 % of the genome of N. brevirostris was composed of repetitive elements. A relatively large proportion of the 'repeatome' could not be annotated. Taking into account only annotated repetitive elements, Class I - Long Interspersed Nuclear Element (LINE) were the most abundant repetitive elements followed by Class I - Penelope and Satellite DNA. The nuclear ribosomal operon was fully assembled. The AT-rich complete mitochondrial genome was 16,703 bp long and encoded 13 protein coding genes, 2 ribosomal RNA genes, and 22 transfer RNA genes. Negaprion brevirostris is closely related to the genera Carcharhinus, Glyphis and Lamiopsis in the family Carcharinidae. This new genomic resources will aid with the development of conservation plans for this large coastal shark.

The effect of the egg-predator Carcinonemertes conanobrieni on the reproductive performance of the Caribbean spiny lobster Panulirus argus.

BACKGROUND: The Caribbean spiny lobster Panulirus argus is heavily fished throughout its Greater Caribbean and Gulf of Mexico distribution, suggesting a heightened susceptibility to a fisheries collapse. In 2017, a nemertean worm, Carcinonemertes conanobrieni was described from ovigerous females of P. argus in Florida, USA. A year later, the presence of the same egg predator was recorded along the southern Caribbean coast (Colombia). The effect of this egg predator on the reproductive performance, including fecundity, embryo mortality, and reproductive output, of its host is unknown. This study tested whether C. conanobrieni affects embryo mortality, fecundity, and reproductive output in brooding females of P. argus. RESULTS: Artisan fishers caught 90 ovigerous lobsters near Pueblo Viejo, Magdalena, Colombia. Each ovigerous female was examined for the presence/absence of the egg predator. Lobster egg mortality (%), fecundity (nº eggs female-1), and reproductive output (%) were estimated. Prevalence of C. conanobrieni in the studied population was 87.78%. The mean intensity of C. conanobrieni (all life stages) in the population was 11.68 (± 1.98) egg predators per brood mass sample. Infected females brooding late-stage embryos exhibited lower fecundity, lower reproductive performance values, and higher embryo mortality compared to infected females brooding early-stage embryos. Embryo stage and worm infection level negatively impacted fecundity and reproductive output. Worm infection level and the number of adult nemertean worms also negatively affected embryo mortality. CONCLUSIONS: These results demonstrate an adverse effect of C. conanobrieni on the reproductive performance of P. argus. The interactive impact of this egg predator, natural stressors, and anthropogenic stressors on individual P. argus reproductive performance could facilitate losses at large-scale fisheries levels.