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ESR prepress abstract   -  DOI: https://doi.org/10.3354/esr01224

Costs of parthenogenesis on growth and longevity in ex situ zebra sharks Stegostoma tigrinum

Lance Adams*, Kady Lyons, Janet Monday, Elizabeth Larkin, Jennifer Wyffels

*Corresponding author:

ABSTRACT: While popular in aquaria, the zebra shark Stegostoma tigrinum is an endangered species that is known to readily reproduce both sexually and through facultative parthenogenesis while in human care. Artificial insemination trials that took place between 2011 and 2013 resulted in the hatching of 2 sexually produced (herein ‘heterozygotes’) and 10 parthenogenic sharks that allowed for a retrospective comparison of growth, feeding and longevity between offspring produced from 2 distinct reproductive modes. Parthenogenetic offspring were generally smaller at hatch than their heterozygous counterparts and after the first several months post-hatch failed to increase in mass and length at the same rate as heterozygotes. Parthenogenic offspring exhibited non-normal swimming behaviors such as spiraling, spy hopping and head standing, which may have been correlated with a gradual decline in some sharks’ ability to properly suction feed. Median lifespan for parthenotes was 1.05 years (range: 0.27–6.64 years) while one heterozygote lived to 2.37 years of age and the other is alive at present and has reached reproductive maturity. By contrast, the 2 longest surviving parthenotes perished just prior to reaching sexual maturity (~5.5 and ~6.5 years, respectively). Parthenogenesis has been documented among ex situ S. tigrinum maintained in aquaria across the globe, and this study demonstrates substantial negative costs to fitness in parthenogenetic offspring compared with their heterozygous siblings. The reduced fitness of parthenotes has implications for managing populations in human care as well as for in situ conservation efforts.