Eastern Spiny Seahorse, Hippocampus hendriki Kuiter 2001

Endemic to tropical Queensland, from the Gulf of Carpentaria and waters inside the Great Barrier Reef to about Lindeman Island. Lives on soft bottom habitats near coral reefs at 18-25 m.

Dorsal fin 17-18; Pectoral fin 16-17; trunk rings 11; tail rings 34; subdorsal rings 2 + 1.
Head large, snout moderately long, about equal to postorbital length.
Spines prominent. Nasal spine of moderate length, angular in shape; spine above eye moderately long, shorter than eye diameter; spine behind eye of moderate size, followed by longer lateral head spine; superior trunk ridge spines reduced to tubercles before dorsal fin in males, or entire ridge having irregular rugose parts with small spines on and in between junctions with rings; subdorsal spines 3/0,1,0. Small juveniles have proportionally longer spines and disproportionally enlarged spines featuring dermal flaps near their tips.
Coronet moderately high, sloping back in line with head profile.
Lateral line with pores detectable to about 20^th tail ring.

Pale yellow on snout, lower part of head and front of trunk, darkening to pale orange on top and back with dark saddle-like markings; small saddle below dorsal fin, others on tail on about 4^th and 7^th rings; top of snout with about 10 thin dusky bars; dark blotch on head below gill-opening; eye with brown vertical bar, extending to spine above it; tips of spines black; dorsal fin with thin longitudinal lines. In preservative - pale to dark brown, sometimes with pale saddle-like markings at first and eight trunk rings, as well as on tail, becoming bands posteriorly; snout with thin dark barring.

Like other seahorses, this species presumably feeds by sucking small crustaceans and other planktonic organisms into its mouth.

Sexes separate; males brood the developing embryos in a pouch and 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 offspring are born.

Listed under Appendix II of the Convention on the International Trade in Endangered Species of Wild Flora and Fauna (CITES). As a result, the species is subject to the Convention, http://www.cites.org/.
Marine Listed under the Federal Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act 1999). http://www.environment.gov.au/epbc/species/marine.html

In all specimens examined by Kuiter (2001), the head is positioned at right angles to the body, possibly an adaptation to living on open substrates. The seahorse may orientate itself almost horizontally to feed on epibenthic invertebrates such as small crustaceans moving over the bottom.

H. hendriki has been confused with other species with prominent spines, including H. angustus, H. multispinus, and H. grandiceps. H. angustus has lateral-ridge spines on the 3rd and 5th rings that are absent in H. hendriki. H. multispinus has longer spines above the eyes. H. grandiceps has a longer head which it holds close to the trunk, while H. hendriki holds its head at 90° to the trunk. Males can look superficially similar to H. queenslandicus which has different fin counts and a tail with less spine development, but H. hendriki is readily distinguished from that species by its nasal spine and barring on the snout.

From the Greek ippos = horse and kampe = curvature. The specific name hendriki is for Hendrik Kuiter.

Hippocampus hendriki Kuiter 2001, Rec. Aust. Mus. 53: 333, fig. 48. Type locality: Cape York, Queensland.

Dianne J. Bray