Hippocampus guttulatus diet based on DNA metabarcoding

Seahorses are small sedentary fish considered flagship species of the conservation efforts. They are particularly vulnerable to human pressures because inhabiting threatened coastal ecosystems. Indeed, the worldwide decline of local populations in the last decades led to the inclusion of all seahorse species on the IUCN Red List, where most species, including Hippocampus guttulatus, were classified as ''Data Deficient'' on a global level due to the lack of relative data on several biological and ecological traits. Because of such sensitive conservation status, improvement of the current knowledge on the diet composition of wild animals and its differences among habitats could be of great importance as it could help understanding the way the environment is exploited. In the present study, we used a non-invasive DNA metabarcoding technique to further elucidate long-snouted seahorse diet and expand our understanding of prey choice among different habitats. We identified 24 families, 22 genera and 26 species, and according to the results, most of the seahorse samples contained taxa such as Amphipoda, Decapoda, Isopoda, and Mysida. Several non-native species were discovered in the diet, suggesting their dietary incorporation that could mirror high anthropogenic impacts and habitat modifications. We found significant differences in the diet composition among investigated habitats, thus indicating trophic flexibility of H. guttulatus among diverse habitats, a characteristic that may be essential for the resilience of this iconic yet sensitive species.

Automated summary

Seahorses, as flagship species for conservation efforts, are highly vulnerable to human pressures due to their presence in threatened coastal ecosystems. The decline of seahorse populations globally has resulted in their inclusion on the IUCN Red List, with most species lacking sufficient data on their biology and ecology. In this study, a non-invasive DNA metabarcoding technique was used to study the diet composition of long-snouted seahorses and identify differences in prey choice among habitats. The results revealed a diverse range of prey species, including several non-native species, indicating potential anthropogenic impacts and habitat modifications. Significant differences in diet composition were also found among investigated habitats, highlighting the trophic flexibility of Hippocampus guttulatus and its importance for its resilience as an iconic yet sensitive species.