I have just arrived in Okinawa, Japan for the 9th quadrennial Indo-Pacific Fish Conference. I presented at the last meeting four years ago in Freemantle with my talk ‘First field studies of the obligate gorgonian-associated pygmy seahorses, Hippocampus bargibanti and H. denise‘. This time round I decided to do a poster presentation for a change, on another aspect of my PhD research.
If you happen to be attending, my poster session is on Thursday afternoon so come and say ‘hi’. The poster is about the polygamy that I observed in Denise’s pygmy seahorses. There is a downloadable version of my poster below and the abstract for the poster is as follows:
A wide range of mating systems have been recorded in syngnathids; however, despite some social promiscuity and mate switching, all studies of seahorse reproduction to date have revealed ubiquitous genetic monogamy. Denise’s pygmy seahorse (Hippocampus denise) is among the smallest (maximum standard length 24 mm) and most habitat-specific of all seahorses, with individuals spending their entire adult life isolated in small groups on a single gorgonian coral host. We investigated whether the reproductive strategies and social interactions of this species align with those of its congeners. During 217 thirty-minute observation periods we recorded the reproductive and social behaviour of 18 adult H. denise in four groups of differing sex ratio in a wild population of seahorses in southeast Sulawesi, Indonesia. We found social polygamy and sequential polyandry to feature in the species’ reproductive strategies, although monogamy was dominant. Social and reproductive behaviours were described for the first time and characterised by daily interactions between reproductively active partners at dawn and dusk conducted in a core area. The use of core areas, a term used for protected regions of the gorgonian host shared for the most part by reproductively active individuals, may have been pivotal in enabling a stable polyandry to develop. Conventional sex roles were observed, with males competing for access to females. The ecology of H. denise appears to have favoured the evolution of mating system plasticity and the maximisation of reproductive output, which may be explained by the species’ small size, skewed sex ratios and density of individuals sharing a single host.