Hippocampus satomiae

Lourie, Sara A. & Kuiter, Rudie H., 2008, Three new pygmy seahorse species from Indonesia (Teleostei: Syngnathidae: Hippocampus), Zootaxa 1963 (1), pp. 54-68 : 64-66

Hippocampus satomiae

Type material. Holotype: NMV A25420–001 (13.8 mm, male), Derawan Island , Kalimantan, Indonesia (02 o 17.690’N, 118 o 15.692’E), 10–18 m depth, on gorgonian Carijoa sp. ? Muller 1867, October 2003, Satomi Onishi. Figures 2C and 3C .

Paratype: NMV A25420–002 (13.4 mm, female), collection details as for holotype .

Diagnosis. Extremely small size (height 11 mm, standard length 14 mm); 12 trunk rings; 27–28 tail rings; reduced ossification of inferior and ventral trunk ridges; 13 dorsal fin rays; 9 pectoral fin rays; small or absent anal fin; brooding area in males anterior to anus; well–developed spine on snout between eyes; distinct raised coronet with laterally expanded anterior and posterior flanges ('H–shaped' when viewed from above); snout without a bulbous tip; single gill opening on midline directly behind coronet supported by raised cleithral bone; large spines above eyes (double), laterally on head, on shoulder (cleithral) ring, bordering throat, and on superior trunk ridge (especially well–developed on TrR1–2,5,8 and 12 and TaR4,8,11,14); spines also present on lateral and ventral angles between trunk ridges and rings; spines on superior ridge of first and second trunk rings appear externally as if they are fused.

Comparison. The spines covering the body of H. satomiae gives it a rough appearance. They contrast with the large rounded tubercles invariably seen in H. bargibanti , occasionally in H. denise , and the scattered, narrower, rounded spines in H. pontohi and H. severnsi . Its colour and pattern contrast with the other species of pygmy seahorses: white–pale brown or greyish–transparent, with dark spot anterior to the eye in H. satomiae vs purple with red tubercles, or grey with yellow/orange tubercles in H. bargibanti , orange in H. denise , white in H. colemani and H. pontohi , and brown in H. severnsi . In addition to differences in body ornamentation and colour H. satomiae can be distinguished from H. pontohi and H. severnsi by shallower head (HD:HL 51.0–52.6% vs 59.3–61.5% or 51.7–62.5%), smaller post-orbital (PO:HL 44.8–45.2% vs 49.0–53.5% or 47.4–51.0%), and fewer pectoral (PF 9 vs 10) and dorsal (DF 13 vs 14) fin rays.

It can be separated from H. colemani by its shallower head (HD:HL 51.0–52.6% vs 61.7–63.6%), larger orbit (OD:HL 23.8–23.9% vs 18.6–18.9%), smaller post-orbital (PO:HL 44.8–45.2% vs 50.1–54.1%), narrower body (TD9:SL 10.7–15.0% vs 18.9–19.5%) and fewer pectoral (PF 9 vs 10) and dorsal (DF 13 vs 14) fin rays.

It can be differentiated from H. bargibanti by its longer, but less deep head (HL:SL 21.7–22.2% vs 14.8–19.5%, HD:HL 51.0–52.6% vs 60.8–70.3%), longer snout (SnL:HL 26.4–27.5% vs 18.5–23.2%), less pronounced coronet ( CH:HL 38.9–41.4% vs 46.1–64.1%), larger orbit (OD:HL 23.8–23.9% vs 14.2–24.0%), smaller post-orbital (PO:HL 44.8–45.2% vs 51.6–63.3%), shorter tail (TaL:SL 46.3–49.7% vs 53.3–57.1%), fewer tail rings (TaR 27–28 vs 31–33), fewer pectoral (PF 9 vs 10–11) and dorsal (DF 13 vs 14) fin rays.

Both sexes of H. satomiae have rounded trunk profiles in comparison to female H. denise’s narrow trunk. From H. denise it can be separated additionally by its shorter snout (SnL:HL 26.4–27.5% vs 27.1–38.7%), and fewer pectoral (PF 9 vs 10–11) and dorsal (DF 13 vs 13–14) fin rays.

Hippocampus satomiae can be differentiated from H. minotaur most clearly on the basis of meristic values: TrR 12 vs 8–9, TaR 27–28 vs 41, PF 9 vs 11 and DF 14 vs 7–9. It also has a significantly shallower head (HD:HL 51.0–52.6 vs 75.1–80.2%), longer trunk (TrL:SL 28.6–31.6 vs 18.4–24.7%), shorter tail (TaL:SL 46.3–49.7 vs 56.0–66.6%) and longer dorsal fin base (DL:SL 7.9–8.2 vs 1.5–2.4%).

Description. In addition to the characters given in the diagnosis: head length 22.3% (21.6%) in SL; head depth 51.0% (52.6%) in HL; snout length 27.5% (26.4%) in HL without bulbous tip; snout depth 88.8% (82.5%) in SnL; orbit diameter 23.7% (23.9%) in HL; post-orbital length 44.8% (45.2%) in HL; coronet well–developed with a broad transverse flange anteriorly, a narrower one posteriorly, connected by a narrow longitudinal ridge; pectoral fin base raised; pectoral fin rays 9.

Trunk rings 12; trunk length 31.3% (28.6%) in SL; trunk depth just anterior to dorsal fin base 15.0% (10.7%) in SL; dorsal fin base strongly raised posteriorly; dorsal fin base starting immediately posterior to 9 th trunk ring and ending posterior to 12 th trunk ring (covering 3+0 rings); dorsal fin rays 13; no external pouch visible, male with young carried within the trunk region; anal fin not visible in either specimen; first tail ring quadrangular; tail rings 27 (28); tail length 46.3% (49.7%) in SL.

No pronounced differences in shape were observed between the sexes beyond those of the genital region.

Body ornamentation: double spines above each eye; angular nose–spine; heavy square–tipped lateral spines (Y–shaped in cross–section) on temporals; long cheek (throat) spine curving slightly anteriorly; mid–cleithral spine (upper shoulder–ring spine) located at base of pectoral fin; broad 'wing–like' projections from superior ridge of TrR1,2 and large spines also on superior ridge of TrR5,8 and 12 and TaR4,8,11,14; numerous scattered spines on trunk (giving it a rough appearance); spines square– or sharp–tipped; spines supported by bony extrusions visible in radiographs; small (unbranched) dermal filaments stemming from anterior part of coronet.

Colour in life: white to pale brown or greyish base colour; black spot immediately anterior to eye; blotchy red markings on operculum and on dorsal and lateral surfaces of TrR5 and TaR4; brown transverse bands across TaR8,11,14 etc ( Figure 4C ). Colour in alcohol: pale grey, almost transparent (internal organs clearly visible through skin); black orbital ring; black spot anterior to eye; coronet dark; slightly darker transverse bands on tail ( Figure 3C ).

Etymology. This species is named in honour of Miss Satomi Onishi, the dive guide who collected the type specimens.

Distribution and ecology. Hippocampus satomiae is known from scattered localities in Indonesia, including Derawan (type locality), and Lembeh Strait (northern Sulawesi), as well as northern Borneo, Malaysia. See figure 5C for map. It congregates at night in groups of 3–5 individuals on small seafans, at depths of 15–20 m depth on the bottom below reef overhangs. Photographed individuals (in Boyer, 2007) from the Togean Islands, Indonesia on a species of Nepthea Auduoin, 1826 on the reef front in water as shallow as 5 m are tentatively identified as H. satomiae .

During the day H. satomiae are difficult to find, even in areas where they are known to occur. At dawn individuals become active. Birth has been observed on a number of occasions and also photographed. At birth, the young are jet–black, about 3 mm in height and shaped similarly to the adults. They settle on the bottom near to their place of birth (Onishi, pers. comm.). The holotype, collected in October, was pregnant and carrying approximately eight young.

Figures

FIGURE 2. Radiographs of holotype specimens: A) Hippocampus pontohi (MZB 13593, 16.9 mm), B) Hippocampus severnsi (MZB 13594, 16.6 mm), and C) Hippocampus satomiae (NMV A25420–001, 13.8 mm). Scale bar = 2 mm in each case.

FIGURE 3. Preserved holotype specimens of A) Hippocampus pontohi (MZB 13593, 16.9 mm), B) Hippocampus severnsi (MZB 13594, 16.6 mm), and C) Hippocampus satomiae (NMV A25420–001, 13.8 mm). Scale bar in mm.

FIGURE 4. Live specimens of new species of pygmy seahorses from Indonesia. A) Hippocampus pontohi: Bunaken, Sulawesi, M. Boyer; Bunaken, Sulawesi, M. Aw; Raja Ampat, West Papua, L. Tackett. B) Hippocampus severnsi: Bunaken, Sulawesi, S. Wong & T. Uno; Bunaken, Sulawesi, M. Severns (type specimens); Raja Ampat, West Papua, L. Tackett. C) Hippocampus satomiae: Derawan Kalimantan, S. Wong & T. Uno; Derawan, Kalimantan, J–S. Chen; Derawan, Indonesia, S. Onishi (type specimen).