Dataset Information

Mitochondrial genomes and genetic structure of the Kemp's ridley sea turtle (Lepidochelys kempii).

ABSTRACT: The Kemp's ridley (Lepidochelys kempii) is the world's most endangered sea turtle species and is primarily distributed in the Gulf of Mexico. In the United States, South Padre Island, Texas serves as a key nesting ground for the species. Genetic studies of the Kemp's ridley have been used to aid in conservation and management practices, with the mitochondrial control region as the most commonly used marker due to its perceived hypervariability and ease of sequencing. However, with the advent of next generation sequencing technology, targeting complete mitochondrial genomes is now feasible. Here, we describe a more complete mitochondrial genome for the Kemp's ridley than has been previously published in literature and demonstrate a cost-effective and efficient method for obtaining complete mitochondrial genomes from sea turtles. We compare the genetic diversity and taxonomic resolution obtained from whole mitochondrial genomes to that obtained from the mitochondrial control region alone. We compare current genetic diversity with previous records. Furthermore, we evaluate the genetic structure between the breeding stock in South Padre Island and that of deceased Kemp's ridleys recovered on the Northern coast of the Gulf of Mexico after the 2010 BP Deepwater Horizon oil spill, and of Kemp's ridleys stranded on the East Coast of the United States. Our results show that complete mitochondrial genomes provide greater resolution than the control region alone. They also show that the genetic diversity of the Kemp's ridley has remained stable, despite large population declines, and that the genetic makeup of deceased turtles stranded after the Deepwater Horizon oil spill is indistinguishable from the breeding stock in South Padre Island, Texas. Open Data Badge:This article has earned an Open Data Badge for making publicly available the digitally-shareable data necessary to reproduce the reported results. The data is available at https://www.ncbi.nlm.nih.gov/genbank/.

SUBMITTER: Frandsen HR

PROVIDER: S-EPMC6972797 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Many juvenile Kemp's ridley (Lepidochelys kempii) and loggerhead (Caretta caretta) turtles strand during fall on the beaches of Cape Cod (MA, USA), with total stranding numbers sometimes exceeding 300 turtles per year. Once rehabilitated, turtles must be released at beaches with appropriate water temperatures, often requiring transportation to southeastern coastal states of the USA. These transportation events (transports) may approach or exceed 24 h in duration. Kemp's ridley turtles are known to exhibit an adrenal stress response during such transports, but the effect of transport duration has been unclear, and no other sea turtle species has been investigated. To assess whether transport duration and/or species affects physiological reactions to transport, we studied pre- and post-transport physiological measures in Kemp's ridley and loggerhead turtles transported by ground for <6, ∼12, ∼18, or ∼24 h, comparing with matched "control events" in which turtles were studied without transport. Blood samples were analyzed for four stress-associated measures (corticosterone, glucose, total white blood cell [WBC] count, and heterophil/lymphocyte ratio [H/L]) and nine measures of clinical status (pH, pO2, pCO2, HCO3, sodium, potassium, ionized calcium, lactate, and hematocrit). In both species, stress-associated measures elevated significantly during transport, while handling without transport had no significant effects. Loggerheads exhibited a greater stress response than Kemp's ridleys across all transport durations. These results indicate that sea turtles do react physiologically to ground transport; therefore, minimizing transport time and streamlining transport logistics (where feasible) may help ensure release of rehabilitated turtles to sea in the best possible condition. Nonetheless, both species remained in good clinical condition even after 24 h transport, indicating that current transport protocols are generally safe for sea turtles from a clinical perspective.

Project description:Endangered species are grouped into genetically discrete populations to direct conservation efforts. Mitochondrial control region (mtCR) haplotypes are used to elucidate deep divergences between populations, as compared to nuclear microsatellites that can detect recent structuring. When prior populations are unknown, it is useful to subject microsatellite data to clustering and/or ordination population inference. Olive ridley sea turtles (Lepidochelys olivacea) are the most abundant sea turtle, yet few studies have characterized olive ridley population structure. Recently, clustering results of olive ridleys in the Eastern Tropical Pacific Ocean suggested weak structuring (F ST = 0.02) between Mexico and Central America. We analyzed mtCR haplotypes, new microsatellite genotypes from Costa Rica, and preexisting microsatellite genotypes from olive ridleys across the Eastern Tropical Pacific, to further explore population structuring in this region. We subjected inferred populations to multiple analyses to explore the mechanisms behind their structuring. We found 10 mtCR haplotypes from 60 turtles nesting at three sites in Costa Rica, but did not detect divergence between Costa Rican sites, or between Central America and Mexico. In Costa Rica, clustering suggested one population with no structuring, but ordination suggested four cryptic clusters with moderate structuring (F ST = 0.08, p < .001). Across the Eastern Tropical Pacific, ordination suggested nine cryptic clusters with moderate structuring (F ST = 0.103, p < .001) that largely corresponded to Mexican and Central American populations. All ordination clusters displayed significant internal relatedness relative to global relatedness (p < .001) and contained numerous sibling pairs. This suggests that broadly dispersed family lineages have proliferated in Eastern Tropical Pacific olive ridleys and corroborates previous work showing basin-wide connectivity and shallow population structure in this region. The existence of broadly dispersed kin in Eastern Tropical Pacific olive ridleys has implications for management of olive ridleys in this region, and adds to our understanding of sea turtle ecology and life history, particularly in light of the natal-homing paradigm.

Dataset Information

Mitochondrial genomes and genetic structure of the Kemp's ridley sea turtle (Lepidochelys kempii).

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