Physoschistura chulabhornae, Suvarnaraksha, Apinun, 2013

Suvarnaraksha, Apinun, 2013, A new species of Physoschistura (Pisces: Nemacheilidae) from northern Thailand, Zootaxa 3736 (3), pp. 236-248 : 237-244

Physoschistura chulabhornae , new species

( Figs. 1 , 2 )

Holotype. MARNM 3998, 6 May 2008, Huay Maetalanoi, Ban Maetala, T. Maedaed, Maechaem District, Chiangmai, near a village, 18°55' 35.43''N, 098°22'45.63''E; tributary of Ping River, northern Chaophraya River basin, Maechaem District, Chiangmai Province, coll. A. Suvarnaraksha, R. Wattanasiriserekul and colleagues.

Paratypes. MARNM 3999, 36 ex., 26.6–36.5 mm SL, 34.8–47.6 mm TL, NIFI: 0 4836, 3 ex., 31.0– 33.8 mm SL, 38.5–42.4 mm TL, and UF 185354, 3 ex., 28.4–33.2 mm SL, 38.0– 43.4 mm TL; same data as holotype.

Diagnosis. This new species can be distinguished from other members of Physoschistura by the following combination of characters: incomplete lateral line with 62–83 pores, reaching between anal-fin origin and anal-fin tip; no axillary lobe on pelvic-fin base; male with hammer head-shaped suborbital flap ( Fig.1 ).

Description. Morphometric measurements, proportions and meristic counts of the holotype and 42 paratypes are presented in Tables 1 –3. A relatively small to medium-sized species compared to other species of Physoschistura with a moderately elongated body; body sub-cylindrical anteriorly in cross section, compressed posteriorly; dorsal profile slightly arched, ventral profile straight throughout; snout obtuse to pointed; strongly arched mouth, 1.5–1.7±0.08 times wider than long with medially interrupted lower lip forming two lateral broadly triangular pads with deep furrows, pads 1.5±0.07 times wider than long ( Fig. 3 ); lips thin, upper lip with small incision in middle, lower lip with deep median interruption; anterior nostril in front of flap-like tube with pointed tip; eye small, 4.0–4.8 times in HL (mean 4.3±0.2), eye diameter 3.0–3.8 times in interorbital space. Inner rostral barbel longer than outer rostral barbel and maxillary barbel, extending to middle of eye, longer than snout (0.7– 0.96±0.06); outer rostral barbel not reaching to anterior margin of eye; maxillary barbel reaching to posterior margin of eye. Processus dentiformis present, not prominent. Free posterior chamber of air bladder well formed, not encapsulated, and slightly oval ( Fig. 4 ).

Morphometric characters Holotype Paratypes (n = 42)

Range mean SD

Standard length (mm) 30.49 25.82–39.98 31.16 2.2 % SL

Total length 126.2 123.3–133.7 128.6 2.3

Fork length 121.9 117.5–126.9 122.4 2.2

Prepectoral-fin length 25.0 21.8–28.7 24.2 1.5

Pectoral-fin length 21.7 20.8–25.3 23.2 1.1

Predorsal-fin length 50.2 46.8–52.7 49.4 1.4

Preanal-fin length 76.2 71.5–79.8 75.9 1.7

Prepelvic-fin length 48.5 47.0–53.9 49.9 1.6

Pelvic-fin length 21.3 18.4–23.5 20.3 1.1

Pelvic to vent distance 21.3 20.5–27.1 23.0 1.5

Dorsal-fin base length 17.7 15.3–22.9 17.9 1.5

Dorsal-fin length 23.1 19.5–26.7 23.6 1.8

Anal-fin base length 9.4 7.1–13.9 11.1 1.6

Anal-fin length 19.9 16.8–24.7 20.5 1.6

Body depth at dorsal-fin origin 17.8 15.6–23.2 19.6 1.8

Body width at dorsal-fin origin 10.1 8.6–18.8 12.8 2.2

Body depth at anal-fin origin 13.6 13.0–16.3 14.1 0.8

Body width at anal-fin origin 6.2 5.3–8.5 7.0 0.8

Caudal-peduncle length 12.4 10.7–15.0 12.4 1.0

Caudal-peduncle depth 10.7 8.2–11.9 10.7 0.6

Caudal-fin length 26.2 23.3–33.7 29.2 2.3

Head length 22.3 22.3–26.6 24.1 1.2

Dorsal head length 18.3 18.2–23.4 20.6 1.2

Head width 10.7 10.0–12.7 11.3 0.6

Head depth at occiput 13.2 12.7–15.2 13.8 0.6 % HL

Dorsal head length 82.0 81.2–86.1 84.8 1.4

Head width 48.0 42.6–48.9 44.9 1.7

Head depth at occiput 56.4 52.3–56.4 55.1 1.0

......continued on the next page Morphometric characters Holotype Paratypes (n = 42)

Range mean SD

Eye diameter 25.8 22.5–26.0 24.4 1.0

Interorbital length 29.9 28.0–31.9 29.9 0.7

Inter-nostril distance 20.9 19.0–21.7 20.4 0.6

Snout length 35.1 33.2–35.9 35.0 0.7

Mouth width 28.7 25.9–29.9 28.4 0.9

Mouth length 18.6 16.3–19.1 17.6 0.7

Rostral barbel I length 29.5 27.3–29.9 29.2 0.7

Rostral barbel II length 42.0 39.1–43.0 41.4 1.0

Maxillary-barbel length 35.2 34.2–36.9 35.1 0.7 Ratios

Mouth width/mouth length 1.5 1.5–1.7 1.6 0.08

Snout/maxillary-barbel length 1.0 0.9–1.0 1.0 0.03

Head length/eye diameter 3.9 3.9–4.4 4.1 0.2

Eye diameter/Interorbital space 0.9 0.7–0.9 0.8 0.04

Lateral head length/pectoral-fin length 1.0 0.9–1.2 1.0 0.06

Caudal-peduncle depth/caudal-peduncle length 1.2 1.0–1.4 1.2 0.12

Standard length/pelvic-fin length 4.7 3.9–4.8 4.3 0.06 males 4.7 4.3–5.0 4.7 0.2 females - 4.6–5.4 5.0 0.2

Body depth/body width at dorsal-fin origin 1.8 0.9–2.1 1.5 0.2 males 1.8 1.4–2.1 1.8 0.2 females - 0.9–1.6 1.5 0.1

Pelvic-fin length/vent to anus distance 1.0 0.8–1.1 0.9 0.1 males 1.0 0.78–1.0 0.95 0.07 females - 0.78–0.96 0.87 0.05

Body depth at dorsal fin/body depth at anal fin 1.3 1.2–1.6 1.4 0.1 males 1.3 1.2–1.4 1.3 0.1 females - 1.3–1.6 1.4 0.1 Body covered with embedded minute scales, except belly naked between pectoral fin bases. Incomplete lateral line reaching between anal-fin origin and tip of anal fin with 62–83 pores. Cephalic lateral-line system with 7 supraorbital, 4+8–10 infraorbital, 7 preoperculo-mandibular, and 3 supratemporal pores. Unculi present on lips, barbels, and pectoral-fin rays. Dorsal fin half-way between tip of snout and caudal-fin base; dorsal fin with 4 simple and 8½ branched rays, distal margin slightly convex. Pectoral fin rounded, the length 1.04±0.06 times lateral head length, origin near surface of breast, with 1 simple and 11 branched rays, reaching two-thirds distance to pelvic-fin origin in female, but close to pelvic-fin origin in male. Pelvic-fin origin slightly behind dorsal-fin origin, at vertical from 1st or 2nd branched dorsal-fin rays, with 1 simple and 7 branched rays. Distal margin of pelvic fin not reaching vent in female, nearly reaching vent in male when adpressed. Pelvic-fin length 20.3±1.1% SL; fin not extending beyond anus, except reaching anus in some males (0.96±0.04% HL). Anal fin not reaching base of caudal fin, with 3 simple rays and 5½ branched rays; no adipose crest on caudal peduncle. Anus is much nearer to anal fin than to caudal-fin base. Intestine curved toward lower part of stomach ( Fig. 5 ). Caudal fin with 8– 9 upper and 8 lower branched rays, forked, upper lobe slightly shorter than lower lobe, both lobes with rounded tips. Caudal peduncle 1.2±0.1 times longer than deep. Largest recorded size: 36.5 mm SL (47.6 mm TL) female (paratype, MARNM 3999/14).

Colour in life. Body translucent and light yellowish-brown. Eight-10 dark olivaceous blotches on side of body, 8–10 dark saddles on back not extending to belly; large males have fewer blotches on side of body and faint dorsal saddles; iridescent stripes on belly and lower half of body from pectoral fin to anus ( Fig. 2 ). Lower lip without black mark on each side of median interruption ( Fig. 3a ). Dorsal and dorso-lateral portion of head with few irregular dark spots. Basicaudal bar fragmented into small blotch on upper caudal-fin base, vertical olivaceous blotch on lower caudal-fin base; thin, horizontally oriented, faint Vs on median part of caudal fin. Black spot at base of simple ray of dorsal fin. Pectoral, pelvic and anal fins hyaline.

Colour in preservative. Body creamy white; head and snout with few, scattered dark brown spots; basicaudal bar dissociated into two blotches, one blotch at upper caudal-fin base, larger vertical blotch on lower caudal fin base.

Sexual dimorphism. Male with hammer head-shaped suborbital flap ( Fig. 3 b), and stiff first branched pectoral-fin ray with numerous rows of unculi on upper surface. Pectoral-fin length slightly longer or same length as head (vs. shorter in female); tip of pectoral fin length reaches pelvic-fin origin (vs. not reaching in female). Some females have a small groove in same position as suborbital flab in male. Fewer lateral blotches in large male, changing to longitudinal stripe along lateral line. Male has more slender body; body depth/body width at dorsal-fin origin 1.4–2.1 in male vs. 0.9–1.6 in female ( Table 1). Pelvic-fin/SL 4.3–5.0 in males vs. 4.6–5.4 in females. One female (MARNM 3999/14 30.0 mm SL) contained 260 large eggs (0.6 mm diameter).

Habitat. Specimens were collected from the Huay Maetalanoi, Ban Maetala, T. Maedaed, Maechaem District, Chiangmai ( Fig. 6 ). The stream has a mixed sand, gravel, pebble, silt, mud and rock bottom, with clear running water ( Fig. 7 ). Elevation at the type locality is 764 m above mean sea level, and annual rainfall is over 1450 mm. The surrounding landscape has semi-evergreen forest, plantations, and agricultural crops (mainly corn, cabbage and tomato). Water temperature was 17°C, air temperature 20.5°C, pH 7.7, DO 6.5 mg /l, and conductivity 20 ΜS. Stream width averaged 4 meters, and water depth 40–60 cm. All specimens were collected during the daylight. The holotype and paratypes were caught by electro-fishing. Other species collected at the type locality were: Nemacheilidae : Schistura breviceps , Schistura maejotigrina ; Sisoridae : Oreoglanis siamensis ; Cyprinidae : Devario sp., Scaphiodonichthys burmanicus , Opsarius pulchellus , Garra cambodgiensis , Puntius brevis , Puntius stoliczkanus ; Synbranchidae : Monopterus albus ; and Channidae : Channa gachua .

Distribution. This species has only been collected at the type locality in the Maechaem River basin ( Fig. 7 ), a tributary of Ping River, northern Chaophraya River Basin, Maechaem District, Chiangmai Province, Thailand.

Etymology. The species epithet honours Her Royal Highness Princess Chulabhorn for her valuable scientific works.

Figures

FIGURE 1. Lateral view of holotype of Physoschistura chulabhornae sp. nov.

FIGURE 2. Live individual of Physoschistura chulabhornae (uncataloged).

FIGURE 6. Map of Maechaem River basin indicating type locality of Physoschistura chulabhornae.

FIGURE 7. Huay Maetalanoi, Ban Maetala, T. Maedaed, Maechaem District, Chiangmai, Province, Thailand. Type locality of Physoschistura chulabhornae.

FIGURE 3. A) Ventral view of head of Physoschistura chulabhornae, MARNM 3999 / 7, 32.37 mm SL; B) lateral view of head of Physoschistura chulabhornae. showing suborbital flap of male, MARNM 3999 / 20, 30.03 mm SL.

FIGURES 4 – 5. 4. Free posterior chamber of air bladder of Physoschistura chulabhornae. Scale bar 1 mm. 5. Stomach and loop of intestine of Physoschistura chulabhornae. Scale bar 1 mm.