Denise’s pygmy seahorse  (Hippocampus denise)

Denise’s pygmy seahorse is classified as Data Deficient (DD) on the IUCN Red List (1), and listed on Appendix II of CITES (3).

Denise’s pygmy seahorse (Hippocampus denise) is a master of camouflage, its orange colouration and body tubercles exactly matching the stems and polyps of its gorgonian sea fan hosts (4). This relatively delicate seahorse has a thin body, long neck, short snout, a very long, prehensile tail (4), and is one of the smallest of all seahorse species, typically measuring less than two centimetres in height (1). Although similar to the pygmy seahorse (Hippocampus bargibanti), Denise’s pygmy seahorse is more smooth-skinned, showing comparatively fewer and less developed tubercles (2). In addition, males and females show greater differences in body shape than in the pygmy seahorse, with the female having a relatively slender, elongate trunk, while that of the male is noticeably more rounded (4).

Denise’s pygmy seahorse is widespread in the Western Pacific, including in waters around Indonesia, Malaysia, Micronesia, Palau, Papua New Guinea, Philippines, Solomon Islands and Vanutu (1) (5).

Found only on gorgonian sea fans Annella reticulata, Muricella and Echinogorgia, Denise’s pygmy seahorse occurs at depths of between 13 and 90 metres (1).

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).

There is currently insufficient data on the distribution and abundance of Denise’s pygmy seahorse, and major threats to the species remain unknown. However, its small size and attractive colouration make it possible that this seahorse could be collected for the aquarium trade (1).

There are currently no conservation measures targeting Denise’s pygmy seahorse.

View information on this species at the UNEP World Conservation Monitoring Centre.

For more information on this and other seahorse species see:

• Project Seahorse:
  http://seahorse.fisheries.ubc.ca/index.html
• The Seahorse Trust:
  http://theseahorsetrust.co.uk/