Stiphodon semoni Weber, 1895

Maeda, Ken & Tan, Heok Hui, 2013, Review Of Stiphodon (Gobiidae: Sicydiinae) From Western Sumatra, With Description Of A New Species, Raffles Bulletin of Zoology 61 (2), pp. 749-761 : 752-756

Stiphodon semoni Weber, 1895

( Figs. 1 , 5–7 ; Tables 1, 2)

Stiphodon semoni Weber, 1895: 270 (type locality: Ambon, Maluku Islands, Indonesia; lectotype: ZMA 110.972 )

Material examined. — Bengkulu Province (8 males and 7 females): ZRC 54112 (7 males, 28.7–35.0 mm SL; 5 females, 26.2–34.2 mm SL), aquarium trade in Singapore (from South Bengkulu), coll. H. H. Tan, 18 Mar.2008 ; ZRC 46979 (1 male, 23.5 mm SL; 2 females, 23.6, 23.8 mm SL), aquarium trade in Singapore (from Bengkulu), donated by P. Yap, 4 Feb.2002 .

Diagnosis. — First dorsal fin not pointed in male; number of soft-rays in second dorsal fin 9, pectoral fin 15; premaxillary teeth 42–54 in 23.5–35.0 mm SL; dentary with canine-like symphyseal teeth in both sexes; male having a white patch behind pectoral-fin base; scales in longitudinal row 27–30; male usually without scale on occipital region and anterior part of nape; female usually without scale on anterior two thirds of occipital region. Pectoral-fin rays without clear marking in both sexes; dorsal and anal fins generally pale grey on male. Female having somewhat serrated black longitudinal band laterally on trunk and tail with irregular spaced 4–6 brown obscure blotches.

Description. — Morphometric measurements are given in Table 1. Body elongate, cylindrical anteriorly and somewhat compressed posteriorly. Head somewhat depressed with a round snout protruding beyond upper lip. Anterior nostril short tubular, posterior nostril not tubular. Mouth inferior with upper jaw projecting beyond lower jaw. Upper lip thick and smooth with small, medial cleft. Premaxillary teeth 42–54, fine and tricuspid. Dentary with 1–3 canine-like symphyseal teeth in males except for one male without canine-like teeth on right of symphysis (this individual having 2 canine-like teeth on left side); with 1 or 2 small canine-like symphyseal teeth in females; dentary also with a row of unicuspid horizontal teeth (39–56) enclosed in a fleshy sheath. Larger fish having more premaxillary and horizontal teeth ( Fig. 1 ). Male with a white patch behind pectoral-fin base. Urogenital papilla in male rectangular or rounded; female rectangular with two projections at both sides of tip.

S. ornatus S. semoni

Sex Male Female Male Female Number of specimens measured 12 10 8 7 Standard length (mm) 34.9–52.5 38.0–51.8 23.5–35.0 23.6–34.2 Head length 22.4–24.2 22.4–24.3 23.7–25.6 23.3–24.6 Snout length 6.9–8.8 6.6–8.9 7.7–9.1 7.6–8.7 Eye diameter 4.6–6.2 4.5–5.2 5.4–5.7 5.1–5.9 Postorbital length of head 10.3–12.7 11.3–12.9 11.0–12.9 11.6–12.6 Upper jaw length 8.2–9.1 7.6–9.4 8.9–9.8 8.6–9.7 Body depth at P2 origin 12.4–14.6 12.6–14.9 12.3–14.3 12.3–14.2 Body depth at A origin 12.9–16.3 13.2–16.4 14.0–15.8 13.7–14.8 Depth at caudal peduncle 10.5–12.7 10.0–12.4 10.6–11.7 9.9–11.0 Length of caudal peduncle from A base 17.7–20.5 17.4–18.9 18.3–20.6 18.2–20.8 Length of caudal peduncle from D2 base 20.1–22.5 19.9–21.0 20.5–22.6 20.3–22.3 Predorsal length 32.3–35.1 33.5–35.6 33.6–35.9 34.9–36.6 Length of D1 base 16.0–20.0 17.2–20.8 16.2–17.9 15.3–18.7 D1 length 28.9–35.4 18.7–22.2 17.4–22.1 17.4–20.3 Length of longest spine of D1 22.9–29.2 14.3–16.0 15.7–17.8 14.6–16.1 Interval between D1 and D2 bases 1.6–5.9 4.1–6.6 2.9–5.1 3.9–5.7 Length of D2 base 25.1–27.4 23.9–25.9 24.0–26.0 21.9–25.4 D2 length 41.6–50.6 32.4–36.5 34.0–43.4 30.7–31.9 Length of longest ray of D2 17.8–24.9 12.4–15.4 17.0–20.3 14.6–16.8 Preanal length 47.5–50.5 50.8–55.1 48.9–51.9 51.3–55.2 Length of A base 26.5–30.1 24.7–26.6 24.7–27.9 23.7–27.1 A length 42.1–49.0 33.7–36.5 30.6–42.8 31.9–34.5 Length of longest ray of A 16.5–21.5 11.9–12.9 14.0–17.8 12.3–14.7 Anus to A length 3.8–5.4 2.8–5.9 3.1–3.6 3.4–5.0 Length of longest ray of P1 20.2–24.0 13.6–21.8 21.1–23.1 19.6–21.4 C length 29.1–34.6 24.0–26.6 24.3–29.7 22.9–26.1

Dorsal fins VI-I, 9; first dorsal fin in both sexes almost semicircular and spines 2 and/or 3 longest; tip of spines usually not extending to origin of second dorsal fin, but it sometimes touching origin of second dorsal fin in male. Anal fin I, 10, below second dorsal fin. In female, anterior rays (soft-ray 1 or 2 in second dorsal fin, soft-ray 2 in anal fin) longest in second dorsal and anal fins; in male, posterior rays longer than anterior rays (last and/or next to last rays longest) except for smallest male (23.5 mm SL). Caudal fin with 13 branched rays within 17 segmented rays, posterior margin rounded or somewhat truncated, male with larger fin than female (caudal-fin length 24% of SL in smallest male, 27–30% of SL in other males, 23–26% of SL in female). Pectoral fin with 15 rays. Pelvic fin I, 5, paired fins joined together to form a strong cup-like disk with fleshy frenum. Scales in longitudinal row 27–30 ( Table 2); scales in transverse row 10 (n = 2), 11 (n = 13); scales in transverse row in caudal peduncle 9. Occipital region and anterior part of nape usually naked in male ( Fig. 5a ), but occasionally with a few cycloid scales around posterior end of occipital region and anterior part of nape; scales on nape always cycloid. Nape and posterior one third of occipital region usually covered by cycloid scales in female ( Fig. 5b ). Ctenoid scales covering almost entire tail and trunk, but belly covered by cycloid scales. Pectoral-fin base naked. Small gap between posterior side of pectoral-fin base and anterior terminal of scaled area on lateral sides of trunk; some of most-anterior scales on lateral sides of trunk cycloid. Cycloid scales also occurring along first and second dorsal- and anal-fin bases, and on proximal part of caudal fin; a few scales dorsally and ventrally on posterior part of caudal peduncle often cycloid.

Cephalic sensory pore system always A, B, C, D, F, H, K, L, N, and O; pore D singular, all others paired ( Fig. 6 ). Oculoscapular canal separated into anterior and posterior canals between pores H and K. Cutaneous sensory papillae developed over lateral and dorsal surfaces of head ( Fig. 6 ). Females ( Fig. 7b ). Background of body and head cream; black longitudinal band extending from snout to below eye and to middle of pectoral-fin base, band continuing from behind pectoral-fin base to posterior end of caudal peduncle through lateral midline or slightly lower position of midline; this band usually serrated, and often with 4–6 brown irregular spaced obscure blotches. Dorsal part of upper lip black. Small black pigments along anal-fin base and ventral midline of caudal peduncle. Another black longitudinal band from just behind eye extending dorsolaterally to base of upper procurrent caudal-fin rays. Dorsum between upper lateral bands brown, but 0–1, 0–2, and 5 obscure cream transverse bars interrupt brown dorsum on head, trunk, and tail, respectively. Snout with U-shaped black band connecting both eyes. First and second dorsal-fin membranes transparent; first dorsal-fin spines dusky without clear marking; second dorsal-fin rays with 1–2 black spots. Anal fin with faint black pigments on rays, and often with obscure black band running near its Colour in preservation. — Sexual dichromatism well developed.

Males ( Fig. 7a ). Background of body and head pale brown; lateral sides of trunk and tail dusky; lateral sides of head, dorsum on snout, upper lip, and pectoral-fin base blackish; other part of dorsum brown. First and second dorsal fin pale grey without clear marking. Anal fin pale grey often with transparent narrow margin. Caudal fin pale grey with dusky spots on central 5–8 rays forming 7–11 black transverse stripes. Pectoral-fin rays grey without clear markings, membranes transparent but pale grey proximally. Pelvic fin grey with translucent margin. Colouration of smallest male very similar to smallest females.

margin. Black blotch at centre of proximal part of caudal fin; 1–2 black spots along 3–9 central caudal-fin rays, membrane mostly transparent. Black lateral band on pectoral-fin base often spreading to proximal part around rays 5–8 of pectoral fin; pectoral-fin rays without clear marking or with 1 black spot on some of central rays; membranes transparent. Pelvic fin translucent without pigment. Two smallest females (23.6 and 23.8 mm SL) lacking black spots on second dorsal-, caudal-, and pectoral-fins.

Distribution. — Watson (2008) reported S. semoni from Lampung Province, south-eastern Sumatra. The record from Bengkulu Province in the present study is the first report of this species from western Sumatra, and it expands the westernmost limit of the range of this widespread species, which has been known to be distributed on north-eastern Australia, Solomon Islands, Papua New Guinea, and Indonesia (islands of Yapen, New Guinea, Ambon, Ceram, Halmahera, Sulawesi, Flores, Bali, and Sumatra) ( Watson, 1996, 2008; Watson et al., 1998; Ebner & Thuesen, 2010; Ebner et al., 2012).

Remarks. — The smallest specimen (23.5 mm SL) is considered to be an immature juvenile and identified as male because its occipital region is totally naked. It is generally observed that male juvenile exhibits resemblance to the female in Stiphodon species (Maeda, unpublished data).

Stiphodon semoni is strikingly similar to S. atropurpureus (Herre, 1927) , but can be distinguished by the dorsal scalation on head and trunk: anterior half of nape is usually naked in S. semoni male vs scaled in S. atropurpureus ; posterior one-third of occipital region is scaled in S. semoni female vs two-thirds scaled in S. atropurpureus . Scales in longitudinal row of S. semoni is fewer than that of S. atropurpureus (27–30 vs 29–31). Comparative material of S. atropurpureus is listed in Maeda et al. (2012b).

Figures

Fig. 1. Number of premaxillary and horizontal dentary teeth of Stiphodon ornatus (triangles), S. semoni (squares), and S. maculidorsalis (circles) fromWest Sumatra and Bengkulu Provinces, Sumatra. Solid and open symbols represent males and females, respectively.

Fig. 5. Dorsal scalation on head and nape in Stiphodon semoni: a, male (33.6 mm SL, ZRC 54112); b, female (29.2 mm SL, ZRC 54112).

Fig. 6. Diagrammatic illustration of head showing arrangement of the cephalic sensory pores and cutaneous sensory papillae in Stiphodon semoni (33.6 mm SL, ZRC 54112): a, dorsal view; b, lateral view; c, ventral view.

Fig. 7. Stiphodon semoni: a, male, 31.6 mm SL (ZRC 54112); b, female, 33.5 mm SL (ZRC 54112).