Genetic variation of the Nile soft-shelled turtle (Trionyx triunguis)

Structural Variation of the Turtle Mitochondrial Control Region

The present study describes the most comprehensive comparison of turtle mtD-loop regions to date. The primary structure was compared from DNA sequences accessed from GenBank from 48 species in 13 families of extant turtles, and secondary structures of the mtD-loop region were inferred from thermal stabilities, using the program Mfold, for each superfamiliy of turtles. Both primary and secondary structures were found to be highly variable across the order. The Cryptodira showed conservation in the primary structure at conserved sequence blocks (CSBs), but the Pleurodira displayed limited conservation of primary structural characters, other than the coreTAS, a binding site for the helicase TWINKLE, which was highly conserved in the Central and Right Domains across the order. No secondary structure was associated with a TAS, but an AT-rich fold (secondary structure) near the 3' terminus of the mtD-loop region was detected in all turtle superfamilies. Mapping of character states of structural features of the mtD-loop region revealed that most character states were autapomorphies and inferred a number of homoplasies. The Left Domain of turtles, containing no highly conserved structural elements, likely does not serve a functional role; therefore, the Central Domain in turtles is likely equivalent to the Left Domain of mammals. The AT-rich secondary structural element near the 3' terminus of the mtD-loop region may be conserved across turtles because of a functional role, perhaps containing the Light Strand Promotor, or perhaps interacting with the TWINKLE-coreTAS complex in the Central and Right Domains to regulate mtDNA replication and transcription.

Development and characterization of new polymorphic microsatellite loci for Trionyx triunguis (Testudines: Trionychidae) in the Mediterranean Basin

The Mediterranean subpopulation of T. triunguis has been listed by IUCN as critically endangered (European Reptile and Amphibian Specialist Group 1996, category CR C2A). There are very few studies for determination of distribution and population genetics of this species in the world. A total of 13 polymorphic microsatellite loci were isolated from 42 samples of T. triunguis by using biotinylated (GT)10, (CT)10, (GATA)5-enriched library. The range of observed heterozygosities was 0.000-0.833 with a mean of 0.274, and the range of expected heterozygosities was 0.081-0.607 with a mean of 0.374. It was found that four loci deviated significantly from Hardy-Weinberg equilibrium after Bonferroni correction analysis. There was no evidence for large allele dropout. Null alleles may be present at ttmed-6, ttmed-8, and ttmed-9 loci, as suggested by the general excess of homozygote for most allele size classes. Designed microsatellite loci could provide a powerful tool for the population structure and conservation genetics studies of the Nile soft-shelled turtle and for captive breeding programs or to detect species illegal trade.