Analysis of the diet of the long‐snouted seahorse H ippocampus guttulatus by 18 S r DNA amplification of prey in faeces

Abstract Breeding in captivity for research or exhibition (e.g. in aquaria) can replace the capture of wild specimens of endangered species and allow controlled reinforcement of wild populations. With this aim, diet analysis and establishing the adequate prey are determinant factors for breeding success. However, non‐invasive approaches such as faecal DNA analysis are advisable for analysing the diet of these species. Therefore, the aim of the present study was to demonstrate the usefulness of faecal DNA analysis by specific PCR amplification of prey DNA for assessing the diet of the seahorse H ippocampus guttulatus . In a comparison of the suitability of different genes ( COI , 18Sr RNA and 28Sr RNA ), 18Sr RNA was found to be the most suitable for designing specific primers for the prey types fed to seahorses ( A rtemia , P alaemonetes and M ysidae). The technique was assessed in feeding experiments in which prey ingestion was recorded daily, and faeces were collected for DNA extraction and presence/absence PCR analysis. Amplification of the prey DNA in faeces was consistent with the sequence of prey supplied (prey eaten the day before was always detected). Differences in the time between feeding and detection in faeces suggested prey‐specific gut passage times, which were shorter for P alaemonetes than for M ysidae. This fact highlights the importance of feeding trials to avoid overestimating the consumption of prey with long gut retention when PCR ‐based methods are used. This molecular technique is thus applicable for studying the feeding behaviour of captive seahorses and could be adapted for use in other marine species.