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<p>Sea snakes are a major component in many coral reef ecosystems, as predators on fishes. <i>Emydocephalus ijimae</i> is a dietary specialist on demersal fish eggs, but it is not well understood how wide a variety of fish species are involved in this unique predator–prey system. To clarify the feeding ecology of <i>E. ijimae</i> on a mid-latitude coral reef, we identified fish eggs taken from the snakes’ stomachs using DNA barcoding. Relative abundances of potential prey species in the snake’s habitat were also estimated by environmental DNA metabarcoding analysis. A total of 209 stomach contents were obtained in monthly field surveys from May 2017 to December 2019, and these consisted of 618 presumptive fish egg clutches of at least 30 species and 14 genera in 5 families. Snake predation peaked in June, with 3.38 clutches/stomach on average, and dropped to 0.04 in December–January. It was estimated that 473 clutches/hectare were consumed at our sites by <i>E. ijimae</i> in June. Pomacentridae (22 species) comprised 93.4% of the total clutches, followed by 4.05% Plesiopidae (2 species), and 1.94% Gobiidae (4 species). The predation frequencies for prey species generally were correlated with their relative abundances in the habitat, suggesting that <i>E. ijimae</i> preys on fish eggs largely in proportion to their availability. Nonetheless, predation frequencies for several pomacentrid species deviated significantly from their abundances in the community, suggesting a certain degree of prey selectivity by <i>E. ijimae</i>. These findings provide an important basis for further studies on this unique system.</p>

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Dietary variation and seasonal changes in the fish egg eating specialist, Emydocephalus ijimae (Squamata: Reptilia) in mid-latitude coral reefs

  • 期刊论文

  • 发表日期：

    2025年1月23日

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  • Takumi Yamamoto,
  • Mamoru Toda

摘要

Sea snakes are a major component in many coral reef ecosystems, as predators on fishes. Emydocephalus ijimae is a dietary specialist on demersal fish eggs, but it is not well understood how wide a variety of fish species are involved in this unique predator–prey system. To clarify the feeding ecology of E. ijimae on a mid-latitude coral reef, we identified fish eggs taken from the snakes’ stomachs using DNA barcoding. Relative abundances of potential prey species in the snake’s habitat were also estimated by environmental DNA metabarcoding analysis. A total of 209 stomach contents were obtained in monthly field surveys from May 2017 to December 2019, and these consisted of 618 presumptive fish egg clutches of at least 30 species and 14 genera in 5 families. Snake predation peaked in June, with 3.38 clutches/stomach on average, and dropped to 0.04 in December–January. It was estimated that 473 clutches/hectare were consumed at our sites by E. ijimae in June. Pomacentridae (22 species) comprised 93.4% of the total clutches, followed by 4.05% Plesiopidae (2 species), and 1.94% Gobiidae (4 species). The predation frequencies for prey species generally were correlated with their relative abundances in the habitat, suggesting that E. ijimae preys on fish eggs largely in proportion to their availability. Nonetheless, predation frequencies for several pomacentrid species deviated significantly from their abundances in the community, suggesting a certain degree of prey selectivity by E. ijimae. These findings provide an important basis for further studies on this unique system.