Denise’s pygmy seahorse can often be observed during the daytime swimming across the surface of the sea fan on which it lives, and is generally more active than the pygmy seahorse (4).
Very little is known about the reproductive behaviour of this species, although pregnant individuals have been found in February, May and October, indicating that breeding may occur year-round. Unusually, it is males and not females which brood the young in seahorses. However, while in most species the fertilised eggs develop in a fully enclosed pouch on the underside of the tail, in Denise’s pygmy seahorse and pygmy seahorse males, embryos are housed within the trunk region, without a separate pouch structure. Sexual maturity in Denise’s pygmy seahorse occurs at just 13.3 millimetres in length (4).