Glyptosternon oschanini ( Herzenstein, 1889 )

Thoni, Ryan J., Simonov, Evgeniy, Artaev, Oleg, Asylbaeva, Shaigul, Aibek, Sergek Uulu & Levin, Boris A., 2017, A century in synonymy: molecular and morphological evidence for the revalidation of Glyptosternon osсhanini (Herzenstein, 1889) (Actinopterygii: Sisoridae), Zootaxa 4277 (3), pp. 435-442 : 436-439

Glyptosternon oschanini ( Herzenstein, 1889)

( Fig. 1 )

Exostoma oschanini Herzenstein, 1889: 70 . Type locality: Uzbekistan: Tashkent: Upper Amu Darya (locality unknown), and Upper Syr Darya, Ugam River.

Exostoma gracile Gratzianov, 1907: 58 . Type locality: Uzbekistan: Namanganskaya oblast’: Naryn River Drainage , Upper Syr Darya River.

Diagnosis. Glyptosternon oschanini is distinguished from G. reticulatum in having a high (versus low) adipose fin (vis. Kullander et al. 1999), narrow caudal peduncle (6.1–7.9% SL), adipose fin not extending to (versus extending to) caudal fin ( Kullander et al. 1999), 10 (versus 11) branched pectoral-fin rays, and the absence (versus presence) of a reticulated pigmentation pattern on the body.

Description. Morphometric data are provided in Table 1. Live coloration and form are presented in Figure 1 . Head dorsoventrally flattened; head and nape rising gradually and smoothly from tip of snout to dorsal-fin origin. Dorsal profile having slight rise posteriorly from posterior edge of dorsal-fin base to origin of adipose fin; sloping gently downward to caudal peduncle. Ventral profile flat from snout to anal-fin origin, rises slightly along anal-fin base, rising with concave curvature narrowing at caudal peduncle before slightly deepening at caudal base.

Head blunt, roughly 1/4 SL. Head width roughly 5/6 HL. Mouth inferior; having wide gape, roughly 1/3 HL; post-labial fold on lower jaw incomplete. Teeth forming a thin, arc-shaped patch on upper jaw with homodont dentition; patch broadly arched and posteriorly produced, much wider then deep. Lower jaw with homodont dentition; formed by two laterally symmetrical, sandpaper-like pads of densely packed teeth; each patch anteroposteriorly narrow and laterally elongate. Four pairs of barbels; maxillary barbels extending outward from snout at length roughly equal to HL; nasal barbels roughly 1/3 HL; inner mandibular barbels small, roughly 1/7 HL; outer mandibular barbels roughly twice the length of inner mandibular barbels. Eyes reduced; roughly 1/12 HL, located anterodorsally on head.

Dorsal-fin origin located in anterior half of body; fin height roughly equal to or slightly longer than body depth; base narrower than height of fin; 1 simple and 6 branched rays. Anal fin located in posterior third of body; base roughly 1/13 SL; 1 simple and 5 branched rays. Pectoral fins large, with striations lining thick first ray creating adhesive apparatus; length roughly 1/5 SL; 1 simple and 10 branched rays. Pelvic fin also with striations lining thick first ray creating adhesive apparatus; length slightly less than 1/5 SL; 1 simple and 5 branched rays. Adipose fin long and high; base length slightly more than 1/3 SL; fin height at tallest point roughly 2/3 caudal peduncle height, and 1/14 SL. Doral adipose length roughly 1/7 SL. Caudal fin truncate; 14(1), 15(4), 16(1) branched rays.

Coloration. Body grey to olive with darker blotches and mottling on dorsum and sides of body anterior to anal fin. Head mottled; grey to olive base color; opercle with light cream base. Two vertical dark bars on posterior portion of body starting at anal fin; another less prominent vertical bar anterior to adipose-fin origin. Venter of body anterior to pelvic fins mostly lacking dark pigmentation.

Dorsal fin with large dark spot at base; remainder of fin olive green and translucent; a band of dark pigmentation present roughly 3/4 of the way up the fin, at branching point of fin rays. Adipose fin olive, fading from dark along base to translucent dorsally. Paired fins olive green on dorsal surface, becoming clearer distally; pale and translucent on ventral side. Caudal fin with thick dark band along posterior margin, covering roughly 1/4 of fin length; dark patch at base of fin.

Alcohol-preserved specimens exhibit all pigmentation patterns observed above, except that color has faded to brown or dark grey on body, and pale white on venter. Dark vertical bands on posterior portion of body are more accentuated.

Distribution. Tributaries of the Syr Darya, and possibly Amu Darya Rivers ( Fig. 2 ).

Material examined. 5 specimens, FMNH 130568 , 80.0– 103.5 mm SL, Kyrgyzstan: Osh Province: Syr Darya drainage: Ak-Buura River, 40.4224 N 72.8690 E; 1 specimen, FMNH 130587, 60.6 mm SL, Kyrgyzstan: Jalal- Abad Province : Syr Darya drainage: Kyok-Art River : 40.9319 N 72.9385 E.

Figures

FIGURE 1. Glyptosternon oschanini from the Ak-Buura River, Osh province Kyrgyzstan. FMNH 130568, 103.5 mm SL.

FIGURE 2. Map of collection localities of G. oschanini in Kyrgyzstan.