Stiphodon palawanensis, Maeda, Ken & Palla, Herminie P., 2015

Maeda, Ken & Palla, Herminie P., 2015, A new species of the genus Stiphodon from Palawan, Philippines (Gobiidae: Sicydiinae), Zootaxa 4018 (3), pp. 381-395 : 382-391

Stiphodon palawanensis , new species

( Figs. 1–5 ; Table 1)

Material examined. 57 specimens (24 males and 33 females, 27.0– 63.9 mm SL) collected from Palawan, Philippines.

Holotype. WPU-PPC-P 5, male (62.2 mm SL), Balsahan Stream in the Iwahig Prison and Penal Farm, Puerto Princesa City, Palawan, 18 May 2015, coll. K. Maeda and H. P. Palla.

Paratypes. CMK 11966, 2 males (37.3 and 43.1 mm SL) and 8 females (28.5–47.2 mm SL), Malatgao River, Narra, Palawan, 29 September 1994, coll. J. Margraf; CMK 11974, 3 females (41.9–48.5 mm SL), Estrella Falls (tributary of Malatgao River), Narra, Palawan, 29 September 1994, coll. J. Margraf; NSMT-P 45091, 45092, and 45094, 2 males (27.7 and 38.8 mm SL) and female (36.6 mm SL), Iwahig River, Puerto Princesa City, Palawan, 13 November 1988, coll. K. Matsuura; URM-P 31438, female (27.0 mm SL), Nagsagoiri River, Palawan, 9 August 1985, coll. S. Shokita; URM-P 31439, 6 males (34.1–36.8 mm SL) and 7 females (32.4–36.2 mm SL), Papait River, Palawan, 9 August 1985, coll. S. Shokita; URM-P 31440, 2 females (38.6 and 40.7 mm SL), Iraan River, Palawan, 5 August 1985, coll. S. Shokita; URM-P 31441, 6 males (31.3–41.4 mm SL) and 3 females (30.7–39.1 mm SL), Tagbariri, Palawan, 9 August 1985, coll. S. Shokita; URM-P 48659–48662, 2 males (46.2 and 51.1 mm SL) and 2 females (41.1 and 47.2 mm SL), Barake Stream (tributary of Aborlan River), Barangay Magbabadil, Aborlan, Palawan, 15 May 2015, coll. K. Maeda and H. P. Palla; URM-P 48663–48666, 2 males (59.7 and 63.9 mm SL) and 2 females (58.5 and 63.6 mm SL), same data as holotype; WPU-PPC-P 2–4, 2 males (52.6 and 59.2 mm SL) and female (46.3 mm SL), Barake Stream (tributary of Aborlan River), Barangay Magbabadil, Aborlan, Palawan, 15 May 2015, coll. K. Maeda and H. P. Palla; WPU-PPC-P 6–9, male (59.4 mm SL) and 3 females (57.5– 62.1 mm SL), same data as holotype.

Diagnosis. Second dorsal fin usually with one spine and nine segmented rays, pectoral fin usually with 15 segmented rays; first dorsal fin pointed in male; relatively large caudal fin (26–34% of SL) in male; premaxilla with 45–71 tricuspid teeth, dentary with 2–6 (male) or 1–4 (female) symphyseal teeth and 45–79 unicuspid horizontal teeth; nape and posterior part of occipital region covered by cycloid scales; 9–11 dusky transverse bars laterally on trunk and tail; first dorsal fin gray or dusky after preservation (orange or reddish brown in life) without any distinct markings, having a line of black blotches (male) or a black band (female) on distal part of second dorsal fin; pectoral fin without clear markings.

Description. Morphometric measurements 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 tubular and short, posterior nostril round or oblong, not tubular. Mouth inferior with upper jaw projecting beyond lower jaw. Upper lip thick with small medial cleft. Premaxillary teeth 45–71, fine and tricuspid. Dentary with canine-like symphyseal teeth (number of teeth 2–6 in male, 1–4 in female) and a row of unicuspid horizontal teeth enclosed in fleshy sheath (number of teeth 45–79). Larger fish having more premaxillary and horizontal teeth ( Fig. 2 ). Urogenital papilla in male rounded with one cleft at posterior tip; that in female rectangular, bearing one small projection at each corner of the posterior margin.

TABLE 1. Morphometrics of Stiphodon palawanensis , expressed as a percentage of standard length. D1, first dorsal fin; D2, second dorsal fin; A, anal fin; C, caudal fin; P1, pectoral fin; P2, pelvic fin.

First dorsal fin with six spines, except two specimens with five spines; second dorsal fin usually with one spine and nine segmented rays (one specimen with one spine and eight segmented rays). In female, first dorsal fin rounded, almost semicircular, usually second and/or third spines longest, but its posteriormost tip never extending to origin of second dorsal fin. In male, first dorsal fin spines elongate (usually fourth spine longest) and posteriormost point of first dorsal fin (tip of fourth spine) extending to base of first to sixth segmented ray of second dorsal fin when depressed. Anal fin with one spine and ten segmented rays. In female, usually first or second and second or third segmented rays longest in second dorsal and anal fins, respectively; in male, posterior rays longer than anterior rays (last ray and/or penultimate ray usually longest). Caudal fin usually with 17 segmented rays, including 13 branched rays, posterior margin rounded; caudal fin relatively larger in male than in female (caudal-fin length 26–34% of SL in male, 21–26% of SL in female). Pectoral fin with 14 (n=7), 15 (n=47), or 16 (n=3) rays. Pelvic fin with one spine and five segmented rays; pelvic fins joined together to form strong, cuplike disk with fleshy frenum.

Scales in a longitudinal series 29 (n=4), 30 (n=13), 31 (n=19), 32 (n=15, including holotype), or 33 (n=6); scales in a transverse series 9 (n=1), 10 (n=3), 11 (n=52, including holotype), 12 (n=1); circumpeduncular scales 15 (n=1) or 16 (n=55) (not including one broken specimen). Ctenoid scales covering tail, sides and dorsum of posterior trunk. Pectoral-fin base naked. Small naked area behind pectoral-fin base; some anteriormost scales on lateral sides of trunk cycloid. Belly covered with cycloid scales. Nape and posterior part of occipital region covered by cycloid scales ( Fig. 3 ); in female, scaled area slightly exceeding middle of occipital region; male similar, but sometimes not exceeding the middle. Cycloid scales also occurring on first and second dorsal-fin bases, anal-fin base, caudal-fin base, and proximal part of caudal fin.

Cephalic sensory pore system always with A´, B, C, D(S), F, H´, K´, L´, N´, and O ´( Fig. 4 ). Oculoscapular canal interrupted between pores H´and K´. Cutaneous sensory papillae developed over dorsal, lateral, and ventral surface of head ( Fig. 4 ).

The largest male and female specimens were 63.9 and 63.6 mm SL (82.9 and 77.9 mm in total length), respectively.

Color in preservative. In male, background brown; 9–11 (usually 10) dusky transverse bars laterally and dorsally on trunk and tail. First dorsal fin gray or dusky without distinct markings. Second dorsal fin gray or dusky; each ray having a black blotch surrounded by a translucent margin, these black blotches forming a line along second dorsal fin margin, but posterior part of the fin sometimes lacking this black blotch. Anal fin gray or dusky. Caudal fin with dusky longitudinal band on upper part; dorsal to this band, gray; ventrally along this band translucent; middle and lower parts of caudal fin gray. Pectoral fin pale gray without clear markings, but sometimes with one to four obscure, dusky spots on each of middle rays. Pelvic disk dusky, but margin of anterior and middle parts translucent.

In female, background brown or yellowish brown; blackish longitudinal band extending from snout and upper lip 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; nine or ten (usually ten) dusky transverse bars laterally on trunk and tail intersecting with the mid-lateral longitudinal band. The longitudinal band often unclear if the transverse bars accentuated, and transverse bars often unclear if the longitudinal band accentuated. Additional blackish longitudinal band above the mid-lateral band from dorsoposterior edge of eye to base of upper procurrent caudalfin rays, but often obscure. First dorsal-fin gray without distinct markings. Second dorsal and anal fins gray with a black submarginal band and translucent margin; the black band on second dorsal fin thicker than that on anal fin.

Black blotch on middle of proximal part of caudal fin; other part of caudal fin translucent with a black band (upside-down “L” shape) along dorsal and posterior margins and one to four black vertical stripes on middle part. Pectoral fin pale gray without clear markings, but sometimes with one or two obscure, dusky spots along middle rays. Pelvic fin translucent, but middle parts of rays, membranes, and frenum often dusky, forming a ring in ventral view.

Color in life. Body and fin markings of male and female similar to those of preserved specimens, but in male ( Fig. 5 a–d), background of body grayish, purplish, or yellowish brown; first and second dorsal fins orange or reddish brown; black blotches on second dorsal fin surrounded by white or yellow margins; anal fin brown, gray, or orange; and dorsal part of caudal fin reddish or yellowish with bluish-white margin. In female ( Fig. 5 e, f), first dorsal fin reddish brown; second dorsal fin reddish brown with a black submarginal band and bluish white margin; white spots often lining proximal side of this band; anal fin brown with a black submarginal band and bluish white margin; upper and middle parts of caudal fin fringed by bluish white margin; area between the white margin and the black band orange.

Distribution. The new species is currently known only from Palawan, in the western Philippines. All known habitats are streams flowing into the Sulu Sea in the central part of the island ( Fig. 6 ). When we explored the Iwahig River where it flows into the South China Sea at Quezon ( Fig. 6 ) for two days in May 2015, S. palawanensis was not found, but other areas, such as the northern and southern parts of the island, have not yet been explored. Given its amphidromous life cycle with the high dispersal ability of the larvae suggested in this genus ( Yamasaki et al., 2007; Maeda et al., 2012b), and the geographically limited survey made to date, S. palawanensis is expected to be found elsewhere in the region in the future.

Ecology. The new species was one of the dominant fish species observed in the middle reaches of Balsahan Stream (Puerto Princesa City) and Barake Stream (Aborlan) in May 2015. Stiphodon palawanensis inhabits pools with a substrate that is a mixture of boulders, gravel, and pebbles with exposed bedrock in some places. It also inhabits rapids. The water was clear. The fish were clinging to the rocks while feeding on algae. When disturbed, they swam to nearby rocks or hid in crevices under or between rocks. The maximum water depth of the sites was 1.5 m in May, but it could reach 3.0 m during the wet season. Normally, that occurs from June to December, while the dry season runs from January to May. In these two sites sampled, two cyprinid species Barbodes palavanensis (Boulenger) and Rasbora everetti Boulenger were very abundant with S. palawanensis . Other common species at these sites were two gobioids, Glossogobius illimis Hoese & Allen and Redigobius sp., and a halfbeak Dermogenys palawanensis Meisner.

Etymology. The name of the new species is derived from Palawan, the type locality, and the Latin suffix -ensis.

Comparison. The new species was compared with congeners sharing the second dorsal- and pectoral-fin ray counts (one spine and nine segmented rays in the second dorsal fin, and usually 15 or 16 rays in the pectoral fin). Stiphodon palawanensis shares 9–11 dusky transverse bars laterally on the trunk and tail with S. maculidorsalis Maeda & Tan and S. multisquamus Wu & Ni , but it differs from S. maculidorsalis in the lack of clear markings on the pectoral fin (vs. having fine black spots along rays), dorsal markings (black spots scattered dorsally on the head and tail of S. maculidorsalis , but not on S. palawanensis ), and predorsal scalation (the posterior part of the occipital region is scaled in S. palawanensis , Fig. 3 , vs. an occipital region that is almost naked in S. maculidorsalis ); and from S. multisquamus by the lack of distinct markings on the first dorsal and pectoral fins (vs. having a black blotch on the posterior part of the first dorsal fin in males, thick dusky lines along spines of the first dorsal fin in females, and fine black spots along the pectoral-fin rays in both sexes), having a line of black blotches (in males) or a black band (in females) on the distal part of the second dorsal fin (vs. no such black markings), and predorsal scalation of males (posterior part of the occipital region scaled in S. palawanensis , Fig. 3 , vs. an occipital region that is almost naked in S. multisquamus ).

Stiphodon niraikanaiensis Maeda males have black longitudinal bands on the second dorsal and caudal fins, but females lack them. Although a line of black blotches on the second dorsal fin in S. palawanensis males resembles a black band when the fin is not fully open, S. palawanensis differs from S. niraikanaiensis also by the lack of conspicuous markings on the first dorsal and pectoral fins (vs. having black spots), and in the mode of the pectoral-fin ray count (15 vs. 16).

Stiphodon palawanensis differs from S. alcedo Maeda, Mukai & Tachihara by having a line of black blotches (in males) or a black band (in females) on the distal part of the second dorsal fin (vs. no such markings), having more premaxillary and horizontal teeth ( Fig. 2 ), and the mode of the pectoral-fin ray count (15 vs. 16); from S. martenstyni Watson (of which only the male holotype is known) by lack of clear markings on the first dorsal fin (vs. having two to five dusky spots along each spine) and having a line of black blotches on the second dorsal fin (vs. lack of it); from S. atratus Watson , S. imperiorientis Watson & Chen , S. ornatus Meinken , S. pelewensis Herre , S. pulchellus , and S. weberi Watson, Allen & Kottelat by lack of distinct markings on the pectoral fin (vs. having many black spots along rays), having a line of black blotches (in males) or a black band (in females) on the second dorsal fin (vs. lack of it), and having more premaxillary and horizontal teeth ( Fig. 2 ); and from S. atropurpureus , S. carisa Watson , S. kalfatak Keith, Marquet & Watson , S. larson Watson , and S. semoni Weber by having a line of black blotches (in males) or a black band (in females) on the second dorsal fin (vs. lack of it), a pointed first dorsal fin in males (vs. rounded, except S. carisa males having a pointed fin), and the predorsal scalation of males (the posterior part of the occipital region is scaled, Fig. 3 , vs. an occipital region that is almost naked).

Briefly, the new species is most easily distinguished by its unique fin markings: any Stiphodon with a line of black blotches (in males) or a black band (in females) on the distal part of the second dorsal fin, and without distinct markings on the first dorsal and pectoral fins can be identified as S. palawanensis .

Other Stiphodon species found in Palawan. During our two-day exploration in the type locality of the new species (Balsahan Stream in the Iwahig Prison and Penal Farm, Sulu Sea side of Puerto Princesa City) in May 2015, two other Stiphodon species were found; three female individuals of S. atropurpureus and one male individual of S. percnopterygionus Watson & Chen ( Fig. 6 ). Two of the three S. atropurpureus individuals were collected ( Fig. 7 c) and listed as comparative material in this paper. Stiphodon percnopterygionus was not collected, however a wild individual was identified on site by snorkel based observation of characteristic markings of the body and fins ( Fig. 8 ) and its unique, high triangular first dorsal fin. While S. palawanensis was very abundant, both S. atropurpureus and S. percnopterygionus were rare at this site.

Four Stiphodon specimens collected in the Iwahig River at Puerto Princesa City in 1988 have been deposited in the National Museum of Nature and Science (Ibaraki, Japan). The Iwahig is a relatively large river next to the Balsahan Stream. The specimens are composed of three S. palawanensis (NSMT-P 45091, 45092, and 45094) and one S. pulchellus (NSMT-P 45093), but the latter species was not found in our exploration in Balsahan Stream in May 2015.

In Barake Stream (Sulu Sea side of Aborlan), the only Stiphodon species found during our one-day exploration was S. palawanensis . All collections from Aborlan and Narra, examined in the present study (CMK and URM), also comprised entirely of individuals of S. palawanensis ( Fig. 6 ).

We also explored another river bearing the name Iwahig at Quezon, on the South China Sea side of the island ( Fig. 6 ) in May 2015. Stiphodon pulchellus ( Fig. 7 a, b) was abundant, but S. palawanensis could not be found there.

Thus, the species composition of any Stiphodon assemblage seems to depend on the location on the island. Stiphodon palawanensis may be the dominant species in some areas, whereas S. pulchellus may be dominant in others. However, because only a small survey effort has been applied at each site and only a small part of the island has been explored so far, comprehensive surveys will be required to understand the distribution of Stiphodon species on Palawan.

Figures

FIGURE 1. Stiphodon palawanensis immediately after fixation. a, WPU-PPC-P 5, holotype (male, 62.2 mm SL); b, URM-P 48659, paratype (male, 51.1 mm SL); c, URM-P 48666, paratype (female, 58.5 mm SL); d, URM-P 48661, paratype (female, 41.1 mm SL).

FIGURE 2. Number of premaxillary and horizontal dentary teeth of Stiphodon palawanensis (red circles), S. alcedo (pink circles), S. atratus (black diamonds), S. imperiorientis (light blue triangles), S. maculidorsalis (light green triangles), S. multisquamus (deep blue circles), S. ornatus (orange triangles), S. pelewensis (gray diamonds), S. pulchellus (deep green triangles), and S. weberi (purple diamonds).

FIGURE 3. Dorsal scalation on head and nape in Stiphodon palawanensis. a, male (43.1 mm SL, CMK 11966); b, female (41.9 mm SL, CMK 11966).

FIGURE 4. Diagrammatic illustration of head showing arrangement of cephalic sensory pores and cutaneous sensory papillae in Stiphodon palawanensis (41.9 mm SL, CMK 11966). a, dorsal view; b, lateral view; c, ventral view. AN, anterior nostril; PN, posterior nostril.

FIGURE 5. Males (a – d) and females (e, f) of live Stiphodon palawanensis observed in Balsahan Stream, Puerto Princesa City (b, e, f, 18 May 2015; a, c, 19 May 2015) and Barake Stream, Aborlan (d, 15 May 2015).

FIGURE 6. Location of Palawan in the Philippines (inset map) and sites where Stiphodon species have been found on Palawan. Red circles, S. palawanensis; green circles, S. pulchellus; blue circle, S. atropurpureus; and orange circle, S. percnopterygionus.

FIGURE 7. Stiphodon pulchellus (a, WPU-PPC-P 29, male, 45.9 mm SL; b, URM-P 48681, female, 39.6 mm SL) and Stiphodon atropurpureus (c, WPU-PPC-P 10, female, 43.7 mm SL) specimens collected from Palawan immediately after fixation.

FIGURE 8. Stiphodon percnopterygionus (a) with Stiphodon palawanensis observed in Balsahan Stream, Puerto Princesa City, Palawan, on 18 May 2015.