Trophic flexibility and prey selection of the wild long-snouted seahorse Hippocampus guttulatus Cuvier, 1829 in three coastal habitats

The present study examined the dietary composition of long-snouted seahorse H. guttulatus Cuvier, 1829 in Mar Piccolo of Taranto (Apulia, Italy) using a non-destructive flushing method. To assess differences in the selection of prey among different habitats, adult specimens were collected from both highly complex (Cladophora prolifera and Corallina elongata) and low complex (unvegetated Sandy bottom) habitats. Additionally, samples of benthic fauna were collected from the same habitats and were used to investigate the local availability of potential preys. Results showed significant differences in the diet composition among three studied habitats. Consistently with the results of faunal analysis, gut contents of specimens sampled on C. elongata had higher prey abundance and diversity compared to the other two habitats. Dietary composition of seahorses found in the vegetated habitats was similar, and it was mainly based on Amphipoda and Copepoda. However, small prey (< 1 mm) was more consumed on C. elongate than on C. prolifera. On the sandy bottom, H. guttulatus preyed mainly on small crustaceans, but actively selected larger prey (i.e. Galathoidea and Paguroidea). Nematodes were also highly preyed in all habitats, although the high consumption could be possibly attributed to the high abundance and availability of these organisms at the investigated site. H. guttulatus showed a great ability to exploit available resources in the best possible manner among different habitats, acting as a specialist predator. With an aim to understand the use of food resources that are available in the environment, the results of this study could help to propose initiatives directed to the seahorse conservation. Since prey availability does not seem to be a limiting factor in the understanding of variability and consistency of H. guttulatus populations, further studies on other environmental and biological aspects could be useful in the assessment of the conservation status of long-snouted seahorses.