Dataset Information

Newly described nesting sites of the green sea turtle (Chelonia mydas) and the hawksbill sea turtle (Eretmochelys imbricata) in the central Red Sea.

ABSTRACT:

Background

There is relatively little published information about sea turtle nesting distribution and seasonality in the Saudi Arabian Red Sea. Upcoming large-scale developments occurring along the Saudi Arabian Red Sea coast could negatively affect many sea turtle nesting beaches with potential impacts on the survival of local populations.

Methods

In 2019, two coastal beaches and three near-shore islands were surveyed for turtle nesting in the central Red Sea. We recorded all emergences, examined beach morphology, and collected sand samples to determine grain size, moisture content and colour.

Results

Sea turtle nesting was found at all surveyed sites, though emergence counts were often low. The limited occurrence of nesting at several previously undocumented sites suggests that nesting activity may be widespread, but sparsely distributed, in the central Red Sea region. In addition, nesting at novel sites appeared to favour the seaward side of islands, a pattern that was not observed in previously documented areas. The substrate of most surveyed sites was composed of calcium carbonate with Ras Baridi as the only exception; it was composed of dark quartz-rich sediment. This study highlights several important sea turtle rookeries while also demonstrating that low levels of nesting occur throughout the region, although inter-annual nesting patterns still need to be determined. Future developments should be steered away from key nesting areas and the seaward bias in marginal rookeries should be taken into account where possible.

SUBMITTER: Scott K

PROVIDER: S-EPMC9252177 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:After gastrulation, oviductal hypoxia maintains turtle embryos in an arrested state prior to oviposition. Subsequent exposure to atmospheric oxygen upon oviposition initiates recommencement of embryonic development. Arrest can be artificially extended for several days after oviposition by incubation of the egg under hypoxic conditions, with development recommencing in an apparently normal fashion after subsequent exposure to normoxia. To examine the transcriptomic events associated with embryonic arrestAfter gastrulation, oviductal hypoxia maintains turtle embryos in an arrested state prior to oviposition. Subsequent exposure to atmospheric oxygen upon oviposition initiates recommencement of embryonic development. Arrest can be artificially extended for several days after oviposition by incubation of the egg under hypoxic conditions, with development recommencing in an apparently normal fashion after subsequent exposure to normoxia. To examine the transcriptomic events associated with embryonic arrest, RNA-sequencing analysis was performed on embryos from freshly laid eggs and eggs incubated in either normoxia (oxygen tension ~159 mmHg) or hypoxia (<8 mmHg) for 36 hours (h) after oviposition (n = 5 per group). The patterns of gene expression differed markedly among the three experimental groups. Normal embryonic development in normoxia was associated with up-regulation of genes involved in DNA replication, the cell cycle, and mitosis, but these genes were commonly down-regulated after incubation in hypoxia. Many target genes of hypoxia inducible factors, including insulin-like growth factor binding protein 1, were down-regulated by normoxic incubation but upregulated by incubation in hypoxia. Notably, some of the transcriptomic effects of hypoxia in green turtle embryos resembled those reported by others to be associated with hypoxia-induced embryonic arrest in diverse taxa, including budding yeast (Saccharomyces cerevisiae), the annelid Caenorhabditis elegans, and zebrafish (Danio rerio). Thus, while among oviparous species, hypoxia-induced pre-ovipositional embryonic arrest appears to be a unique adaptation of turtles, mechanisms underlying hypoxia-induced embryonic arrest per se may be highly conserved across the diverse taxa in which this mechanism operates. We report the transciptional changes in Chelonia mydas embryos incubated in either normoxia or hypoxia comapred to freshly laid eggs.