The extent of population genetic subdivision differs among four co-distributed shark species in the Indo-Australian archipelago

Background: The territorial fishing zones of Australia and Indonesia are contiguous to the north of Australia in the Timor and Arafura Seas and in the Indian Ocean to the north of Christmas Island. The area surrounding the shared boundary consists of a variety of bio-diverse marine habitats including shallow continental shelf waters, oceanic trenches and numerous offshore islands. Both countries exploit a variety of fisheries species, including whaler (Carcharhinus spp.) and hammerhead sharks (Sphyrna spp.). Despite their differences in social and financial arrangements, the two countries are motivated to develop complementary co-management practices to achieve resource sustainability. An essential starting point is knowledge of the degree of population subdivision, and hence fisheries stock status, in exploited species. Results: Populations of four commercially harvested shark species (Carcharhinus obscurus, Carcharhinus sorrah, Prionace glauca, Sphyrna lewini) were sampled from northern Australia and central Indonesia. Neutral genetic markers (mitochondrial DNA control region sequence and allelic variation at co-dominant microsatellite loci) revealed genetic subdivision between Australian and Indonesian populations of C. sorrah. Further research is needed to address the possibility of genetic subdivision among C. obscurus populations. There was no evidence of genetic subdivision for P. glauca and S. lewini populations, but the sampling represented a relatively small part of their distributional range. For these species, more detailed analyses of population genetic structure is recommended in the future. Conclusion: Cooperative management between Australia and Indonesia is the best option at present for P. glauca and S. lewini, while C. sorrah and C. obscurus should be managed independently. On-going research on these and other exploited shark and ray species is strongly recommended. Biological and ecological similarity between species may not be a predictor of population genetic structure, so species-specific studies are recommended to provide new data to assist with sustainable fisheries management

Research Priorities to Support Effective Manta and Devil Ray Conservation

Manta and devil rays are filter-feeding elasmobranchs that are found circumglobally in tropical and subtropical waters. Although relatively understudied for most of the Twentieth century, public awareness and scientific research on these species has increased dramatically in recent years. Much of this attention has been in response to targeted fisheries, international trade in mobulid products, and a growing concern over the fate of exploited populations. Despite progress in mobulid research, major knowledge gaps still exist, hindering the development of effective management and conservation strategies. We assembled 30 leaders and emerging experts in the fields of mobulid biology, ecology, and conservation to identify pressing knowledge gaps that must be filled to facilitate improved science-based management of these vulnerable species. We highlight focal research topics in the subject areas of taxonomy and diversity, life history, reproduction and nursery areas, population trends, bycatch and fisheries, spatial dynamics and movements, foraging and diving, pollution and contaminants, and sub-lethal impacts. Mobulid rays remain a poorly studied group, and therefore our list of important knowledge gaps is extensive. However, we hope that this identification of high priority knowledge gaps will stimulate and focus future mobulid research

Integrins promote axonal regeneration after injury of the nervous system.

Integrins are cell surface receptors that form the link between extracellular matrix molecules of the cell environment and internal cell signalling and the cytoskeleton. They are involved in several processes, e.g. adhesion and migration during development and repair. This review focuses on the role of integrins in axonal regeneration. Integrins participate in spontaneous axonal regeneration in the peripheral nervous system through binding to various ligands that either inhibit or enhance their activation and signalling. Integrin biology is more complex in the central nervous system. Integrins receptors are transported into growing axons during development, but selective polarised transport of integrins limits the regenerative response in adult neurons. Manipulation of integrins and related molecules to control their activation state and localisation within axons is a promising route towards stimulating effective regeneration in the central nervous system

First photographic records of the giant manta ray Manta birostris off eastern Australia

We present the first photographic evidence of the presence of the giant manta ray Manta birostris in east Australian waters. Two individuals were photographed off Montague Island in New South Wales and off the north east coast of Tasmania, during summer 2012 and 2014, respectively. These sightings confirmprevious unverified reports on the species occurrence and extend the known distribution range of M. birostris to 40°S. We discuss these findings in the context of the species' migratory behaviour, the regional oceanography along the south east Australian coastline and local productivity events.9 page(s

First photographic records of the giant manta ray Manta birostris off eastern Australia First photographic records of the giant manta ray Manta birostris off eastern Australia

We present the first photographic evidence of the presence of the giant manta ray Manta birostris in east Australian waters. Two individuals were photographed off Montague Island in New South Wales and off the north east coast of Tasmania, during summer 2012 and 2014, respectively. These sightings confirm previous unverified reports on the species occurrence and extending the range of M. birostris to 40ºS. We discuss these findings in the context of the species' migratory ecology, the regional oceanography along the south eastern Australian coastline and local productivity events. PeerJ PrePrints | http://dx.doi.org/10.7287/peerj.preprints.572v1 | CC-BY 4.0 Open Access

Habitat segregation and mosaic sympatry of the two species of manta ray in the Indian and Pacific Oceans, Manta alfredi and M. birostris

Habitat use of Manta alfredi and M. birostris was assessed at 20 localities in the Indian and Pacific Oceans based upon 3328 photographic observations. Geographical relationships of the two species were scored as either microallopatry, microparapatry or microsympatry at each locality. Our study revealed a mosaic habitat occupancy by the two species within their macrosympatric range

Evaluating manta ray mucus as an alternative DNA source for population genetics study: underwater-sampling, dry-storage and PCR success

Sharks and rays are increasingly being identified as high-risk species for extinction, prompting urgent assessments of their local or regional populations. Advanced genetic analyses can contribute relevant information on effective population size and connectivity among populations although acquiring sufficient regional sample sizes can be challenging. DNA is typically amplified from tissue samples which are collected by hand spears with modified biopsy punch tips. This technique is not always popular due mainly to a perception that invasive sampling might harm the rays, change their behaviour, or have a negative impact on tourism. To explore alternative methods, we evaluated the yields and PCR success of DNA template prepared from the manta ray mucus collected underwater and captured and stored on a Whatman FTA™ Elute card. The pilot study demonstrated that mucus can be effectively collected underwater using toothbrush. DNA stored on cards was found to be reliable for PCR-based population genetics studies. We successfully amplified mtDNA ND5, nuclear DNA RAG1, and microsatellite loci for all samples and confirmed sequences and genotypes being those of target species. As the yields of DNA with the tested method were low, further improvements are desirable for assays that may require larger amounts of DNA, such as population genomic studies using emerging next-gen sequencing

The genetic signature of recent speciation in manta rays (Manta alfredi and M. birostris)

Manta rays have been taxonomically revised as two species, Manta alfredi and M. birostris, on the basis of morphological and meristic data, yet the two species occur in extensive mosaic sympatry. We analysed the genetic signatures of the species boundary using a portion of the nuclear RAG1 (681 base pairs), mitochondrial CO1 (574 bp) and ND5 genes (1188 bp). The assay with CO1 sequences, widely used in DNA barcoding, failed to distinguish the two species. The two species were clearly distinguishable, however, with no shared RAG1 or ND5 haplotypes. The species were reciprocally monophyletic for RAG1, but paraphyletic for ND5 sequences. Qualitative evidence and statistical inferences using the 'Isolation-with-Migration models' indicated that these results were better explained with post-divergence gene flow in the recent past rather than incomplete lineage sorting with zero gene flow since speciation. An estimate of divergence time was less than 0.5 Ma with an upper confidence limit of within 1 Ma. Recent speciation of highly mobile species in the marine environment is of great interest, as it suggests that speciation may have occurred in the absence of long-term physical barriers to gene flow. We propose that the ecologically driven forces such as habitat choice played a significant role in speciation in manta rays. (c) 2012 Elsevier Inc. All rights reserved

Development and characterization of ten microsatellite loci for the reef manta ray Manta alfredi

We isolated and characterised ten microsatellite loci from the reef manta ray, Manta alfredi. Loci were screened for 60 individuals from Japan. The number of alleles per locus ranged from 2 to 10 and observed heterozygosity ranged from 0.033 to 0.867. Cross-species amplification was successful in the sister species M. birostris (9/10 loci) and other mobulids, Mobula japanica (7/10), M. thurstoni (8/10) and M. tarapacana (5/10). These loci provide new tools for assessing population genetic structuring and genetic monitoring