Hippocampus colemani, Kuiter, 2003

Kuiter, Rudie H., 2003, A New Pygmy Seahorse (Pisces: Syngnathidae: Hippocampus) from Lord Howe Island, Records of the Australian Museum 55 (2), pp. 113-116 : 113-116

Hippocampus colemani n.sp.

Figs. 1 , 2

Coleman’s Pygmy Seahorse

Type material. HOLOTYPE: AMS I41181-001, height 22.1 mm, female, near Erscott’s Hole, lagoon, Lord Howe Island , New South Wales (approximately 32°32.950'S 159°05.080'E), depth 5 m, collected by hand, Neville Coleman, January, 2002 . PARATYPE: AMS I41181-002, height 21.4 mm, female, same data as holotype .

Diagnosis. Dorsal-fin rays 12–13; pectoral-fin rays 10; anal fin absent; trunk rings 11; tail rings 27–29; nose ridge well developed in front of eye; a single gill opening on the neck ridge, directly behind the head; base of dorsal fin greatly elevated posteriorly, forming a triangular hump on the back.

Description. Head small, c. 50% of trunk length and strongly angled down onto trunk; snout short, length about equal to eye diameter; trunk very deep, c. 60% of its length; tail thin, 1.3 times eye diameter, its greatest depth and width anteriorly, and its length 58% in height (overall, see fig. 3, Kuiter, 2001); dorsal fin with 12 rays (13 in paratype), its base greatly elevated posteriorly so that fin rays almost parallel with trunk axis, height of fin base at posterior end almost equal to its length; pectoral-fin rays 10; anal fin absent; trunk rings 11, obscured and smooth dorsally; tail rings 29 (27 in paratype); trunk and tail ridges poorly developed, mostly indistinguishable and only evident on lower two-thirds of trunk, as ventral and inferior ridges; all spines reduced to tubercles, those on back at 4th, 7th and 11th rings enlarged and most notable, largest below dorsalfin base, and on head as lateral head spines, some with dermal appendages; coronet low and rounded with tentacle like dermal appendage anteriorly (also in paratype); nose spine present as well-developed ridge in front of eye; single relatively large gill opening, slightly raised by skin, and situated mid-dorsally on neck ridge, immediately behind head. Colour in life (paratype): body mostly pale goldenyellow; trunk with white circular or elliptical markings, each outlined with thin red lines, largest around tubercles on 4th and 7th rings; shoulder-ring tubercles white; head white on nape above eyes, extending over snout to tip of mouth, highlighting several dusky brown bands radiating from eye; tail slightly more brown with red markings, some expressed as elongate spots on same ring, suggesting a band. Colour in alcohol: pale brownish all over, some thin dark lines near tubercles on body and dusky bands radiating from eye.

Distribution and ecology. Only known from the types and two additional specimens photographed ( Figs. 3 , 4 ), but not collected at Lord Howe Island, off the New South Wales coast. All were found in the same general area at a depth of 5 m. The habitat is comprised of coarse sand with sparse Zostera and Halophila plants that have fine filamentous algae on their leaves. The same algae are present on the body of the seahorses, attached to their skin.

Remarks. This species is named colemani after Mr Neville Coleman, who discovered and photographed the species at Lord Howe Island, and then returned specifically to collect the type material. Only 4 specimens have been observed, the largest was collected and measured at 22.1 mm in height. Judging by its shape, it appears to be fully grown and would unlikely get much larger. At this stage it is the smallest known seahorse. Despite its small size, it is surprising that it has gone unnoticed until now. Several extensive fish surveys have been undertaken at Lord Howe Island, the largest and most comprehensive led by the opening is arrowed. Photo by Neville Coleman.

Australian Museum in 1973. At the time, a team of 15 collectors, 8 of whom were ichthyologists, collected constantly for one month ( Allen et al., 1976), and did not find this seahorse.

The closest relative of Hippocampus colemani in Australian waters is H. bargibanti Whitley , a tropical species that lives on gorgonian corals. It has similar meristic values and shares the greatly elevated dorsal-fin base, but is quite different in its fleshy and lumpy appearance, and has a longer tail. From a global perspective, most similar in its morphology is a pygmy species from Japan (sp. 7, Kuiter, 2000) that is nearly identical in shape and has an almost identically formed nose ridge. Kuiter’s Hippocampus sp. 7, however, has small but distinctive spines along the trunk and tail ridges. A further similar species that appears to be closely related (sp. 6, Kuiter, 2000) occurs on gorgonians in Papua New Guinea, but is only known from photographs. All share the unusually elevated dorsal-fin base that forms a large hump on their back. The feature of a single gill opening (see Figs. 2 , 3 ) appears to be the same in the Japanese and the Papua New Guinea species (not clear in photographs). It is likely that the three species form a natural group, but until the relationship of all seahorses are understood the species will be retained together in the single genus Hippocampus .

ACKNOWLEDGMENTS. Martin Gomon, Museum Victoria provided the radiographs and commented on the manuscript. I thank Mr Geoff Kelly , Manager of the Lord Howe Island Marine Park , and Mr Patrick Tully , NSW Fisheries , for providing the collecting permit so quickly. I am most grateful to Neville Coleman who made a special trip and spent many long hours underwater just to find and collect the types plus taking the photographs in situ, and thanks to the Prodive-crew for their patience assisting Neville .

Figures

Fig. 1. Hippocampus colemani, holotype AMS I41181-001 (left) and paratype AMS I41181-002 (right), both female.

Fig. 2. Hippocampus colemani, paratype AMS I41181-002, in situ. Photo by Neville Coleman.

Fig. 3. Hippocampus colemani, this specimen not collected, sex not determined. The single gill

Fig. 4. Hippocampus colemani, this specimen not collected.A probable male as it appears to have a pouch.Photo by Neville Coleman.