Pygmy Seahorse, Hippocampus bargibanti Whitley 1970

Tropical West Pacific, including Indonesia, the Philippines, Japan, New Caledonia, Papua New Guinea, Solomon Islands and the Great Barrier Reef, Queensland, Australia. Inhabits coral reefs and reef slopes at 16-60 m, usually on gorgonian corals of the genus Muricella.

Meristic features: D 13-15; A absent in adults; P 10; trunk rings 11-12; tail rings 31-34; subdorsal rings obscured.

Head and body extremely fleshy without recognisable bony rings; spines or tubercles not visible, becoming overgrown with soft tissue, forming large bulbous or wart-like lumps in adults; snout extremely short, tip bulbous; head angled at 90° to the trunk.

A single prominent rounded fleshy bulbous spine is present above each eye and on each cheek; spines otherwise absent. Body ornamentation is in the form of irregular prominent bulbous tubercles on the body and tail.

Coronet rounded, knob-like, spines absent.
Dorsal fin very short-based, wholly on trunk; anal fin absent in adults.

A tiny species, reaching a maximum height of about 24 mm; mimimum height at maturity 13 mm.

Colour is variable depending on the host gorgonian species. Individuals living on the gorgonian, Muricella plectana, are pale striated grey or purple with pink or red tubercles to match the gorgonian. Individuals living on M. paraplectana are yellow with orange/yellow tubercles. The tail is striped with dorsolateral circular markings.

Presumably feeds on tiny crustaceans and may also feed on tissue of gorgonian corals, or on tiny zooplankton trapped in the polyps or slime.

The sexes are separate, and the males give birth to tiny independent young. The female uses an ovipositor to transfer her eggs into an elaborate enclosed pouch under the abdomen of the male. The male not only fertilizes the eggs inside the pouch and provides physical protection for the developing embryos, he also osmoregulates and aerates the embryos and may provide some nourishment until the offfspring are born. 

The breeding season extends from March to November and the Pygmy Seahorse seems to prefer the red polyp Muricella spp in depths over 20 m during breeding. Adult males and females are usually found in pairs or clusters of pairs (up to 28 on a single gorgonian) and may be monogamous.
Males brood the eggs in an enclosed pouch on the underside of the trunk. Brood size about 35 eggs.
Larvae are Pelagic. Larvae are born after a gestation period of 2 weeks and are about 2 mm long at birth; larvae morphologically similar to adults; post-pelagic young have the enlarged tubercles and distinctive colour pattern of the adults and settle on various gorgonian hosts.

There is no known trade in this species for the aquarium industry. Pygmy Seahorses are reliant on their gorgonian hosts and would be very difficult to keep in home aquaria.

CITES: Listed under Appendix II of the Convention on the International Trade in Endangered Species of Wild Flora and Fauna  (CITES).

IUCN: Listed as Data Deficient on the 2010 IUCN Red List of Threatened species (International Union for Conservation of Nature).

EPBC Act 1999: Marine Listed under the Federal Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act 1999)

Part of the gorgonian coral appears to live symbiotically in the skin of the Pygmy Seahorse and reacts into wart-like growths around the short spines on the head and body. The resulting camoflauge is so effective that the species was only discovered after a pair of individuals was found attached to a gorgonian seafan collected by Georges Bargibant for the Nouméa Aquarium in New Caledonia.

H. bargibanti most closely resembles H. denise Lourie & Randall 2003, and H. satomiae Lourie & Kuiter 2008, both of which are not found in Australian waters. Although somewhat similar, the very rare H. minotaur, found in relatively deep waters off southeastern Australia, has no obvious tubercles on the body.

Hippocampus is from the Greek, ippos = horse and kampe = curvature. The species is named for Georges Bargibant who collected the gorgonian sea fan on which H. bargibanti was discovered.

Hippocampus bargibanti Whitley 1970, Proc. Linn. Soc. N. S. W. 94(3): 294, New Caledonia.

Dianne J. Bray & Vanessa J. Thompson