Mucus: aiding elasmobranch conservation through non-invasive genetic sampling

Abstract

Large-scale genetic sampling by non-invasive methods is of vital importance for the conservation of vulnerable or elusive species. In the marine environment, non-invasive genetic sampling can provide a powerful alternative to conventional biopsies. We designed and implemented mucus swabbing for a free-ranging elasmobranch, thereby demonstrating the utility of this method in the field. We report the first attempt at mucus collection from 30 plankton-feeding basking sharks Cetorhinus maximus from 3 spatially distinct 'hotspots' in Irish waters. C. maximus DNA was successfully extracted and verified using DNA barcoding of the mitochondrial DNA cytochrome c oxidase 1 gene (99% sequence similarity) and basking shark species-specific multiplex PCRs derived from the nuclear ribosomal internal transcribed spacer 2 locus. Mitochondrial control region sequencing (1086 bp) showed that Irish samples were dominated by 2 haplotypes previously found to be globally distributed. Additionally, 1 novel haplotype was defined from western County Kerry. On-going genetic tagging will eventually provide more accurate estimates of global basking shark population structuring, abundance and behavioural ecology.

Use of mucus as a non‐invasive sampling method for DNA barcoding of stingrays and skates (batoid elasmobranchs)

“…Although the DNA quantity ranged from different values, it was enough to amplify coI region from mucus, such as already observed for others organism such as bony fishes, and elasmobranchs (Kashiwagi et al, 2015;Lieber et al, 2013;Mirimin et al, 2011). In times where populations of sharks and rays are declining worldwide, the increasing of studies considering the development of non-lethal methods can improve genetic monitoring and other conservation strategies for elasmobranchs.…”

“…However, the use of this tool is still very dependent on tissue sampling (e.g., muscle, scale and blood), usually obtained from dead animals in fish markets and fishing vessels or from live animals, with many challenges involving the angling and handling processes, such as physical injuries and pathology due to hook removal or retention, and post-release survivorship (Danylchuck et al, 2014). On the other hand, less invasive procedures for DNA extraction has been tested in a wide variety of vertebrates (including large species of elasmobranchs) to assess information on genetic population, forensic identification, sex determination and genetic diversity (Alvarado Bremer et al, 2014;Hilsdorf et al, 1999;Kashiwagi et al, 2015;Lieber et al, 2013;Presti et al, 2013). Such outcomes demonstrated the feasibility of non-destructive approaches to DNA extraction and its use in different analyses, at a low cost and with a high degree of sensitivity and confidence.…”

DNA sampling from mucus in the Nile tilapia,Oreochromis niloticus: minimally invasive sampling for aquaculture-related genetics research

“…). Potential drawbacks of such methods may include sample contamination, low DNA quantity or poor quality DNA (Taberlet, Waits & Luikart ; Lieber, Berrow, Johnston, Hall, Hall, Gubili, Sims, Jones & Noble ).…”

Serendipitous re‐sighting of a basking shark Cetorhinus maximus reveals inter‐annual connectivity between American and European coastal hotspots

“…Given that this was one of the first tracking studies of the species, the authors could only speculate as to how frequently such transatlantic movement might occur. Over recent decades basking shark mark– recapture studies have been conducted widely on both sides of the North Atlantic Ocean (Berrow & Johnston, ; Gore et al ., ; Hoogenboom et al ., ; Kohler et al ., ; Lieber et al ., ). Collectively, these efforts have resulted in >1500 individual sharks being marked for recapture (Visual tags and Photo ID), but further evidence of transatlantic mixing has remained elusive.…”