Carcharhinus sorrah (Mülle and Henle, 1839) is a coastal pelagic shark of the tropical and subtropical Indo-West Pacific, reaching 1.6 m total length. The species is widely harvested in line, net, and trawl fisheries over tropical continental shelves. We investigated mtDNA genetic differentiation in C. sorrah across the majority of the species' range, and examined the importance of six major historical and contemporary biogeographic features in shaping population genetic structure in this species. The present study includes dense sampling for a shark species across the Indo-West Pacific, with 349 specimens sampled from 21 collection locations from the northwestern Indian Ocean, southeast Asia, New caledonia, and to southerly distribution limits in Australia. based on 469 base pairs of the control region, we found extensive genetic population structure, with allopatric lineages confined to Australia, New caledonia, and the remaining surveyed area. significant genetic subdivisions were observed over stretches of deep water dividing shelf habitat, particularly the Indonesian Throughflow-timor Passage and coral sea, consistent with strong shelf habitat associated dispersal. Male length at maturity was consistent with a larger size throughout southeast Asia and the Arabian sea than known from Australia. Carcharhinus sorrah currently is assessed range-wide on the IUcN red List (Near Threatened) based largely on Australian demographic data, which may under-represent overharvest risk in other parts of the species' range. The present study highlights the need for independent risk assessment and management for C. sorrah in Australia, southeast Asia and the northwestern Indian Ocean, and New caledonia.
Transposable elements (TEs) are nearly ubiquitous in eukaryotes. The increase in genomic data, as well as progress in genome annotation and molecular biology techniques, have revealed the vast number of ways mobile elements have impacted the evolution of eukaryotes. In addition to being the main cause of difference in haploid genome size, TEs have affected the overall organization of genomes by accumulating preferentially in some genomic regions, by causing structural rearrangements or by modifying the recombination rate. Although the vast majority of insertions is neutral or deleterious, TEs have been an important source of evolutionary novelties and have played a determinant role in the evolution of fundamental biological processes. TEs have been recruited in the regulation of host genes and are implicated in the evolution of regulatory networks. They have also served as a source of protein-coding sequences or even entire genes. The impact of TEs on eukaryotic evolution is only now being fully appreciated and the role they may play in a number of biological processes, such as speciation and adaptation, remains to be deciphered.
New biological data relevant to the conservation of the rare and threatened shark Carcharhinus leiodon are presented, based on specimens sampled in fish markets in Kuwait, the UAE and Yemen. The maximum size of this species is extended to 1648 mm total length (TL); females are mature by at least 1312 mm TL and demonstrate placental viviparity with litters of 4–6 embryos. In the north-western Persian Gulf there is evidence that parturition occurs in spring when embryos are ~350–515 mm TL, with at least some neonate individuals probably remaining in the area through the summer. Further records of C. leiodon from the western Arabian Sea indicate that adults are present in this region throughout the year. Landings of C. leiodon apparently caught in the eastern Persian Gulf may extend the highly fragmented known distribution of this species. Contrary to an earlier study, the first detailed examination of dissected adult C. leiodon jaws revealed that fine serrations are present on upper teeth, and characters are provided to separate the dentition and jaws of C. leiodon from congeners. The stomach of an adult C. leiodon contained bentho-demersal fish, and an individual with fin abnormalities is noted.
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