Abstract
Multiple paternity has been documented as a reproductive strategy in both viviparous and ovoviviparous elasmobranchs, leading to the assumption that multiple mating may be ubiquitous in these fishes. However, with the majority of studies conducted on coastal and nearshore elasmobranchs that often form mating aggregations, parallel studies on pelagic, semi-solitary species are lacking. The tiger shark (Galeocerdo cuvier) is a large pelagic shark that has an aplacental viviparous reproductive mode which is unique among the carcharhinids. A total of 112 pups from four pregnant sharks were genotyped at nine microsatellite loci to assess the possibility of multiple paternity or polyandrous behaviour by female tiger sharks. Only a single pup provided evidence of possible multiple paternity, but with only seven of the nine loci amplifying for this individual, results were inconclusive. In summary, it appears that the tiger sharks sampled in this study were genetically monogamous. These findings may have implications for the genetic diversity and future sustainability of this population.
Highlights
Increased human exploitation over the past two decades coupled with increasing habitat modification poses immediate threats to shark populations worldwide [1]
Simulations were performed across the range of litter sizes (16–36) in our study, using allele frequencies estimated from the Australian east coast population (34 adults) and assuming maternity was unknown
Preliminary screening of adult genotypes from selected east coast Australian locations detected no significant deviation from Hardy–Weinberg disequilibrium, and all locus pairs were in linkage equilibrium following sequential Bonferroni correction (p < 0.05)
Summary
Increased human exploitation over the past two decades coupled with increasing habitat modification poses immediate threats to shark populations worldwide [1]. In one of the few studies on oceanic sharks, Corrigan et al [12] reported multiple paternity in the shortfin mako (Isurus oxyrinchus) using just one litter and five microsatellite loci. As with other migratory sharks that employ polyandry as a reproductive strategy (e.g. C_carcharias [17] and I. oxyrinchus [12]), we hypothesize that female tiger sharks will mate with multiple males and produce litters with multiple sires. We examine four litters of G. cuvier pups from northeast Australian waters to investigate the presence of multiple paternity in this species for the first time
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