Two new pygmy seahorses (Teleostei: Syngnathidae: Hippocampus) from the Indo-West Pacific

Transcription

1 aqua, International Journal of Ichthyology Two new pygmy seahorses (Teleostei: Syngnathidae: Hippocampus) from the Indo-West Pacific Martin F. Gomon and Rudie H. Kuiter Ichthyology, Museum Victoria, GPO Box 666, Melbourne, Victoria 3001, Australia. Received: 12 December 2008 Accepted: 02 January 2009 Abstract Two new pygmy species of the syngnathid genus Hippocampus are described, each from a single specimen. An apparent Red Sea endemic, H. debelius n. sp., the larger of the two, is easily separated from other pygmy seahorses by the long spine-like processes on its head, trunk and tail, separate gill openings and the presence of an external tail pouch in males for brooding the young. The second, H. waleananus n. sp., known only from Sulawesi, has a more rounded trunk, at least in one of the sexes, similar to that of H. colemani Kuiter, 2003, H. pontohi Lourie & Kuiter, 2008, H. severnsi Lourie & Kuiter, 2008 and H. satomi, Lourie & Kuiter 2008, and like those species, has short, often tubercular spines, where present. It differs from H. bargibanti Whitley, 1970 in having 12 dorsal fin rays (versus 14) and nine pectoral fin rays (versus 10 or 11) and from the others in having a long tail with 32 rings (versus 26-31). Zusammenfassung Two new pygmy species of the syngnathid genus Hippocampus are described, each from a single specimen. An apparent Red Sea endemic, H. debelius n. sp., the larger of the two, is easily separated from other pygmy seahorses by the long spine-like processes on its head, trunk and tail, separate gill openings and the presence of an external tail pouch in males for brooding the young. The second, H. waleananus n. sp., known only from Sulawesi, has a more rounded trunk, at least in one of the sexes, similar to that of H. colemani Kuiter, 2003, H. pontohi Lourie & Kuiter, 2008, H. severnsi Lourie & Kuiter, 2008 and H. satomi, Lourie & Kuiter 2008, and like those species, has short, often tubercular spines, where present. It differs from H. bargibanti Whitley, 1970 in having 12 dorsal fin rays (versus 14) and nine pectoral fin rays (versus 10 or 11) and from the others in having a long tail with 32 rings (versus 26-31). Résumé Deux nouvelle espèces du genre Syngnathidé Hippocampus sont décrites, chacune sur base d un seul spécimen. Le plus grand des deux, H. debelius n. sp., apparemment endémique de la Mer Rouge, se distingue aisément des autres hippocampes nains par de longs filaments spiniformes sur la tête, le tronc et la queue, par des ouvertures d ouïes séparées et par la présence d une poche caudale externe chez les mâles pour couver les jeunes. La seconde espèce, H. waleananus n. sp., signalée seulement à Sulawesi, a un tronc plus arrondi, au moins pour un des sexes, semblable à celui de H. colemani Kuiter, 2003, de H. pontomi, Lourie & Kuiter, 2008, H. severnsi Lourie & Kuiter, 2008 et H. satomi, Lourie & Kuiter 2008, et, comme ces espèces, a de courtes épines, souvent tuberculées. Elle diffère de H. bargibanti Whitley, 1970, par la présence de 12 rayons à la dorsale (contre 14) et 9 rayons à la pectorale (contre 10 ou 11), et des autres, par la présence d une longue queue de 32 anneaux (contre 24-31). Sommario Due nuove specie di cavallucci marini pigmei del genere Hippocampus sono descritti sulla base di un singolo esemplare. Hippocampus debelius n. sp., il più grande dei due è endemico del Mar Rosso ed è facilmente distinguibile dalle altre specie pigmee per la presenza sul capo, sul tronco e sulla coda di lunghi processi simili a spine, per avere fessure branchiali separate e per una tasca incubatrice caudale esterna nei maschi. La seconda specie, H. waleananus n. sp., nota solo da Sulawesi, ha un tronco più arrotondato, almeno in uno dei due sessi, simile a quello di H. colemani Kuiter, 2003, H. pontohi Lourie & Kuiter, 2008, H. severnsi Lourie & Kuiter, 2008 e H. satomi, Lourie & Kuiter 2008 e come queste specie possiede spine brevi generalmente tubercolari. Differisce da H. bargibanti Whitley, 1970 per avere 12 raggi dorsali (versus 14) e nove raggi pettorali (versus 10 o 11) e dalle altre per avere una coda più lunga con 32 anelli (versus 26-31). INTRODUCTION As pointed out by Lourie & Kuiter (2008), pygmy syngnathid species are being discovered and described at a remarkable rate and those currently known perhaps represent only a subset of the world s diminutive species. Despite the hiatus 37

2 Two new pygmy seahorses (Teleostei: Syngnathidae: Hippocampus) from the Indo-West Pacific between Whitley s (1970) description of Hippocampus bargibanti, the first of the true pygmy seahorses, and Gomon s (1997) publication of H. minotaur, a recent flurry of descriptions have brought the number of recognised species to seven. The likelihood that they are not a natural grouping was observed by Lourie & Randall (2003). This paper provides names and formal descriptions for two additional miniature species that were first brought to our attention from photographs, before specimens were acquired. Despite their similarly small size, the two species are significantly different from each other anatomically, indicating a more distant relationship. Although it is never desirable to describe species on the basis of single specimens, both have featured in publications or have been prominent on websites and the features present in the holotypes are sufficient to verify that they are unique and undescribed. METHODS Type specimens are deposited in the fish collections of the Indonesian Institute of Sciences (MZB) and Museum Victoria (NMV). Terminology and methodology follow that of Lourie & Randall (2003) and Lourie & Kuiter (2008). Hippocampus waleananus n. sp. Walea pygmy seahorse (Figs 1-3a) Holotype: MZB (17.8 mm SL), Indonesia, Sulawesi Tengah, Togean Archipelago, Walea Island, June/July 2008, collected by M. Pontoh. Diagnosis: Extremely small (height 16.8 mm, standard length 17.8 mm); 12 trunk rings; tail elongate with 32 tail rings; 12 dorsal fin rays; 9 pectoral fin rays; anal fin absent (at least in one sex); eggs apparently brooded within trunk; medium length snout that lacks a bulbous tip; raised, angular coronet; fused gill openings on midline behind coronet supported by raised cleithral girdle; enlarged knob-like structures on head and trunk; paired laterally directed knob-like structures each with short fleshy filament on superior trunk ridge of the fifth trunk ring; last 28 tail rings each with small paired knobs on inferior tail ridge, fifth, ninth and twelfth tail rings with bilaterally paired enlarged knob-like structures on superior tail ridges; pale pinkish to yellowish with red to brown blotches, radiating bands from eye; body protuberances white, appearing as white spots (Fig. 1). Description: In addition to diagnostic characters above: head length 17.7% in SL; head depth 67.9% in HL; snout length 26.8% in HL without bulbous tip; snout depth 95.2% in SnL; orbit diameter 25.4% in HL; post-orbital length 51.5% in HL; coronet as low double mound, anterior mound larger and with short cirrhus at apex; pectoral fin base slightly raised; pectoral fin rays 9; trunk rings 12; trunk length 31.3% in SL; trunk depth just anterior to dorsal fin base 15.0% in SL; dorsal fin base strongly raised posteriorly; dorsal fin base starting immediately posterior to TrR9 and ending posterior to TrR12 (covering 3+0 rings); dorsal fin rays 9; no external pouch visible, young apparently brooded within trunk region; anal fin not visible; first tail ring quadrangular; tail rings 32; tail length 63.4% in SL. Body ornamentation: each eye encircled by about five or six equally spaced small bulbous protuberances at the distal ends of dark lines radiating from lens; head and body with prominent bulbous knob-like features; moderately large knob dorsoposterior to eye; nose spine as low, thick mound on midline in front of eye; large knob laterally on coronet base; large knob ventrally on pectoral-fin base; three rows of large knobs on trunk apparently following superior, lateral and inferior trunk ridges, two in superior series, eight in lateral series and five in inferior series; knob posteriorly on lateral dorsal fin base; broad bilaterally paired wing-like protuberances on superior ridge of TrR2 and TrR6, those on TrR6 larger, each with a short thick fleshy cirrhus; last 28 tail rings each with bilaterally paired, small bulbous protuberance on inferior tail ridge; TaR5, TaR3, TaR12 and TaR15 with prominently enlarged, bilaterally paired knob-like structures on superior tail ridges; maximum height less than 20 mm SL. C o l o u r i n l i f e (Fig. 2): Pale pinkish to yellowish with red to brown blotches, some as radiating bands from eye and one on underside of mouth; body protuberances white, appearing as white spots, entire surface of head and body peppered with tiny white dots. Distribution: Known only from the Togean Islands in Tomini Bay, central Sulawesi, Indonesia, where it occurs at a depth range of about 5 to 20 m. Etymology: waleananus after the type and only confirmed locality Walea Island, Sulawesi, Indonesia, where this species occurs and the Latin nanus for dwarf. This species has become known 38

3 Martin F. Gomon and Rudie H. Kuiter Fig. 1. Hippocampus waleananus n. sp., holotype, MZB 13599, 17.8 mm SL, Indonesia, Sulawesi Tengah, Togean Archipelago, Walea Island. 39

4 Two new pygmy seahorses (Teleostei: Syngnathidae: Hippocampus) from the Indo-West Pacific Fig. 2. Hippocampus waleananus n. sp., mated pair, Indonesia, Sulawesi Tengah, Togean Islands, Tomini Bay. Photo by Beo Brockhausen. a b c Figs 3 a-c. Radiographs of: a. Hippocampus waleananus n. sp., holotype, MZB b. Hippocampus colemani n. sp., holotype AMS I c. Hippocampus debelius n. sp., holotype, NMV A

5 Martin F. Gomon and Rudie H. Kuiter among underwater photographers as the Walea pygmy seahorse. Remarks: This is another of the very small pygmy seahorses. So far, it has only been found in association with the soft coral Nephtea, but has also been observed swimming lengthy distances from one coral to the next. Some of the first photographs of this species were thought to be of H. satomiae Lourie & Kuiter, Although much of its ornamentation and general body shape resemble the features in H. satomiae and H. severnsi, the tail of H. waleananus is much longer (63.4% SL, versus % SL) with four more tail rings (32 versus 27 or 28). The fine white dots on H. waleananus are occasionally present in H. satomiae and H. severnsi as well, but are not a consistent feature of those species. Hippocampus waleananus has the least number of dorsal fin rays of the tropical species (12 versus 13 or 14). The characteristic knob-like structures on the head and trunk resemble the rather thick, blunt spines on H. severnsi, but are much more similar in form to those of H. bargibanti Whitley, The bulbous structures of H. waleananus and H. bargibanti are therefore probably homologous with the spines in other pygmy species. Although only a single specimen was available for this description, photos of individuals in the wild imply that sexual dimorphism exists. In photos of what are likely to be mated pairs (Fig. 2), one individual is noticeably more slender than the other. It is likely that the more rotund individual is a brooding adult. In their comparison of pygmy species, Lourie & Kuiter (2008) failed to comment on differences in skeletal features that are obvious in the radiographs of their three holotypes (their Fig. 2). Hippocampus pontohi, H. severnsi and H. colemani (Fig. 3b) retain the ring and ridge structure of larger seahorses, although the skeletal support is far more delicate. Gomon (1997) described the ventral portion of the trunk skeleton in H. bargibanti as being incomplete, the inferior trunk ridge and median ventral trunk ridge reduced to star-shaped, embedded, dermal ossifications anterioriorly, ossifications forming structural bases for low fleshy spines.... It does appear that the superior ridge elements are present in this species, but they are extremely delicate. The same condition exists in H. satomiae and one of the sexes of H. denise. The other sex of H. denise, regarded as the female by Lourie & Randall (2003), retains the dorsal elements of the rings and ridges but appears to lack any ossification ventrally. The latter appears to be the only species in this genus that has this degree of difference in the skeleton between sexes. Based on the reduction of the trunk rings ventrally in H. bargibanti, H. denise and H. satomiae, it is likely that the three form a natural group. Attempts to radiograph the holotype of H. waleananus were unsuccessful in revealing details of the skeleton (Fig. 3a). As the specimen was initially preserved in alcohol and has not been subjected to formalin, it is unlikely that decalcification due to acidity is responsible for the apparent absence of ossification. Determination of the condition of osteological development in the trunk region will have to await the collection of additional material. However, the presence of the enlarged knob-like features on the trunk resembling those of H. bargibanti and H. denise imply a relationship with this complex. Hippocampus debelius n. sp. Softcoral seahorse (Figs 3c-5) Hippocampus lichtensteinii non Kaup, 1856: Debelius 1998: 37 38; Lourie et al. 1999: 137; Kuiter 2000: 58. Holotype: NMV A (23.7 mm SL, male) Egypt, Red Sea, Hurghada, Erg Camel, N E, 25 September 2008, collected by S. Kahlbrock. Diagnosis: Very small (height 19.2 mm, standard length 23.7 mm); 10 trunk rings; 28 tail rings; inferior and ventral trunk ridges well ossified (Fig. 3c); 14 dorsal fin rays; pectoral fin rays; 4 anal fin rays; brooding area in males posterior to anal fin; medium length snout without a bulbous tip; low, angular coronet; gill openings separate, midway between pectoral fin base and dorsal midline; prominent, long and slender spines on head, trunk and tail; filaments or cirrhi absent; white background, mostly obscured by numerous closeset, brown lengthwise stripes or striations, tips of many of the spines dark brown to black, anterior trunk spines also with dark band centrally (Fig. 4). Description: In addition to diagnostic characters above: head length 20.0% in SL; head depth 54.8% in HL; snout length 33.6% in HL without bulbous tip; snout depth 46.1% in SnL; orbit 41

6 Two new pygmy seahorses (Teleostei: Syngnathidae: Hippocampus) from the Indo-West Pacific a b Fig. 4 a-b. Hippocampus debelius n. sp., holotype, NMV A , 23.7 mm SL, male, Egypt, Red Sea, Hurghada, Erg Camel, N E. a. Lateral view. b. Ventral view. Photos by Lucy Gibson. 42

7 Martin F. Gomon and Rudie H. Kuiter diameter 23.6% in HL; post-orbital length 44.0% in HL; coronet well-developed, broadly angular; pectoral fin base raised; pectoral fin rays 10-11; trunk rings 10; trunk length 30.8% in SL; trunk depth just anterior to dorsal fin base 12.6% in SL; dorsal fin base moderately raised posteriorly; dorsal fin base starting immediately posterior to TrR8 and ending posterior to TrR10 (covering rings); dorsal fin rays 14; external brooding pouch at anterior end of tail; anal fin rays 4, positioned between anus and pouch opening in males; tail rings quadrangular; tail rings 28; tail length 49.2% in SL. Based on photographs, no pronounced differences in shape were observed between the sexes beyond those associated with pouch development. Body ornamentation: spines on head and body long and slender; eye ringed by spines, double spines dorsally, anterior spine less than half length of posterior spine, additional small spines on posterior and anteroventral margin of orbit; coronet with prominent vertical spine on dorsal midline, just in front of slightly smaller laterally angled bilateral pair; nose spine absent; prominent bifurcate spine on temporal; moderately short cheek (throat) spine below eye; small spine anteroventral to base of pectoral fin; long, slender laterally angled, bilateral pair of spines from superior ridge of TrR1-2 and similar spines curved slightly posteriorly on superior ridge of TrR4-5 and 9-10 and TaR4,8, and 11 with spine rudiment on 14, spines progressively shorter posteriorly; long spines also on lateral ridge of TrR4-5,6-7, and 9-10 and inferior ridge of TrR6-7 and 8-9. Maximum height based on photos was estimated as 35 mm. C o l o u r i n l i f e : white background, mostly obscured by numerous close-set, brown lengthwise stripes or striations, striae on some parts of the head and body converging; dorsal midline of head and body white; snout white except for dark brown around mouth, in patch anteroventral to eye, and on forehead between eyes; spines and bases of spines white, tips of many dark brown to black, anterior trunk spines with dark band centrally (Fig. 5). Distribution: Apparently a Red Sea endemic, recorded from moderate depths of about 15 to 30 m. Etymology: debelius, after Helmut Debelius in recognition of the effort he made in obtaining the type specimen. a b Fig. 5 a-b. Hippocampus debelius n. sp., Egypt, Red Sea, Gulf of Suez, Hurghada. a. Male with distended brood pouch. Photo by Kai Walz. b. Female. Photo by Elke Bojanowski. 43

8 Two new pygmy seahorses (Teleostei: Syngnathidae: Hippocampus) from the Indo-West Pacific Remarks: Although of similar size to the true pygmy seahorses (sensu Lourie & Randall, 2003, and Lourie & Kuiter, 2008), this soft-coral dwelling species does not appear to belong to that group. As in larger seahorses, the male has an external tail pouch and separate gill-openings. Thick skin hides the ring-detail, but it is obvious in radiographs (Fig. 2c), and spines on the head and back are well ossified and rigid. The skeleton is very similar to the vast majority of external pouch bearing species. A distinct tail pouch also occurs in the similarly small H. minotaur Gomon, 1993, distinguishing it from H. bargibanti, H. denise and their relatives (Lourie & Randall, 2003). Because of the extreme anatomical modifications in H. minotaur, it is not possible to infer a relationship with H. debelius based on morphology alone. Apart from size, there is nothing to suggest a closer relationship between the two, than with other external pouch brooding species. Although known to live at moderate depths, some corals with which H. debelius associates also occur in very shallow shaded areas such as below jetties and it may eventually be found inshore. First photographed in 1993, this seahorse was thought to be H. lichtensteinii Kaup, 1856, a species of uncertain identity and distribution, known only from the original description and type. A photo of the type of this species (Lourie et al., 1999: p. 145) lacks long spines and closely resembles a Japanese species that does not appear to have another name. ACKNOWLEDGEMENTS We are grateful to H. Debelius and S. Motti for arranging the collection of the types; D. Bray (NMV) assisted with collection specimens and provided helpful comments on the manuscript; R. Hadiaty (MZB) also helped with collection management details. Photos of types were taken by K. Walker and L. Gibson (NMV). Underwater photos are by E. Bojanowski, B. Brockhausen and K. Walz. REFERENCES DEBELIUS, H Red Sea Reef Guide. IKAN-Unterwasserarchiv, Frankfurt. 321 pp. GOMON, M. F A remarkable new pygmy seahorse (Syngnathidae: Hippocampus) from southeastern Australia, with a redescription of H. bargibanti Whitley from New Caledonia. Memoirs of the Museum of Victoria 56: KUITER, R. H Seahorses, pipefishes and their relatives. TMC Publishing, Chorleywood, 240 pp. KUITER, R. H A new pygmy seahorse (Syngnathidae: Hippocampus) from Lord Howe Island. Records of the Australian Museum 55: LOURIE, S. A. & KUITER, R. H Three new pygmy seahorse species from Indonesia (Teleostei: Syngnathidae: Hippocampus). Zootaxa 1963: LOURIE, S. A. & RANDALL, J. E A new pygmy seahorse, Hippocampus denise (Teleostei: Syngnathidae) from the Indo-Pacific. Zoological Studies 42: LOURIE, S. A., VINCENT, A. C. J. &HALL, H. J Seahorses. An identification guide to the world s species and their conservation. Project Seahorse. X pp. WHITLEY, G. P In: Abstracts of Proceedings. Proceedings of the Linnean Society of New South Wales 94 (3) No. 421: