| Diagnosis: |
Dorsal spines (total): 0-0; Dorsal soft rays (total): 8-8; Anal spines: 0-0; Anal soft rays: 9-12. Diagnosis: Doumea chappuisi is distinguished from its congeners, except D. reidi and D. stilicauda, by having the dorsolateral and ventrolateral vertebral processes extending through the skin to form longitudinal bony ridges from the region of the base of adipose fin posteriorly to the caudal-fin base and from slightly posterior of the pelvic-fin origin to the caudal-fin base; exposed processes are in the shape of longitudinal bars with slightly corrugated surfaces that form irregular longitudinal ridges (Ref. 85844). It differs from D. reidi by a shorter caudal-peduncle length, 22-29% of standard length vs. 31%; the posterior extent of the adpressed pelvic fin in specimens over 90 mm standard length falling short of the anterior limit of the anal fin, vs. extending distinctly beyond that point; the anterior extent of the exposed vertebral processes along the ventral surface of the body extending to slightly posterior of pelvic-fin origin, vs. extending to the area lateral to the anal-fin base; and the uniform pigmentation pattern of the dorsal surface of the unbranched rays of the pectoral and pelvic fins, vs. with series of irregular dark spots against a lighter background (Ref. 85844). It differs from D. stilicauda in the longer predorsal length, 32-37% of standard length vs. 27-30%; longer head length, 18% of standard length vs. 15-17%; smaller caudal-peduncle length, 22-29% of standard length vs. 35-41%; and caudal-peduncle depth 7.3-14.5 times in caudal-peduncle length, vs. 19.6-25.8 times (Ref. 85844).
Description: Body elongate and progressively tapering posteriorly; greatest body depth located slightly anterior of dorsal-fin origin and greatest width at anterior limit of pectoral-fin insertion; body smooth skinned and firm (Ref. 85844). Middorsal ridge present between terminus of dorsal-fin base and adipose-fin origin; dorsal margins of neural arches apparent through skin in light coloured individuals, but not extending to body surface; abdominal region transversely flattened; dorsal and ventral profiles of body progressively converge from anal-fin origin to posterior end of caudal peduncle; lateral line complete, running along midlateral surface of body; short, variably spaced and grouped, dorsal and ventral branches extending off main portion of lateral line; exposed tips of dorsolateral vertebral processes apparent on skin surface from region of adipose-fin base posteriorly to caudal-fin base; processes on ventral surface of body extend from slightly posterior of pelvic-fin origin to caudal-fin base; exposed processes in shape of longitudinal bars with slightly corrugated surfaces, forming irregular longitudinal ridge; caudal peduncle relatively elongate, slender, and dorsoventrally depressed over much of its length, but approximately as wide as high at caudal-fin base; least depth of caudal peduncle approximately equal to length of eye (Ref. 57128, 85844). Head profile broadly triangular from dorsal view with lateral margin slightly convex and snout tip rounded; head pointed and depressed from lateral view; snout long, relatively slender, and tapering anteriorly; eye situated entirely within posterior half of head; diameter of eye approximately one-half of interorbital distance; distance from posterior naris to anterior margin of eye in smaller individuals less than distance between anterior naris and tip of snout; distances approximately equal in larger specimens; posterior naris closer to anterior naris than to eye; distance between nares of each side slightly less than distance of each to contralateral naris; mouth subterminal, small, ovoid when open, with fleshy tuberculate upper lip and smooth firm lower lip, flanked to each side by tuberculate sections; barbels short, tuberculate, and distally tapered; maxillary barbel longest, reaching approximately to vertical through middle of snout length; inner mandibular barbel shortest, with base situated slightly lateral of midline and of lateral margin of smooth portion of lower lip; outer mandibular barbel arises from angle of mouth and extends posteriorly approximately one-half length of branchiostegal membrane; branchiostegal membrane continuous medially, with ventral portion of posterior margin straight or slightly concave; gill slit extends posterodorsally to above pectoral-fin origin; humeral process located above origin of gill opening, short; supraoccipital process narrow, peg-like, separated by gap from small trilobed nuchal shield (Ref. 85844). Dorsal fin falcate, unbranched ray longest; tip of adpressed dorsal fin extends to vertical through middle of pelvic fin; adipose-fin origin situated above middle of anal-fin base; fin small with length of base approximately one-third distance between posterior terminus of dorsal-fin base and adipose-fin origin; fin adnate, with posterior limit of fin situated posterior of vertical through anal-fin base, but not past posterior of vertical through tip of adpressed anal fin; pectoral fin large and falcate with outer ray curved, pectinate, broad, and with fleshy pad covering ventral surface; innermost pectoral-fin rays short, posterodorsally orientated, and adpressed to body wall; tip of adpressed pectoral fin falling distinctly short of pelvic-fin origin and reaching to vertical through posterior terminus of dorsal-fin base; pelvic fin large, slightly shorter than pectoral fin; outer pelvic-fin ray pectinate with ventral surface covered by fleshy pad; pelvic-fin origin located distinctly posterior of vertical through posterior end of dorsal-fin base; tip of adpressed pelvic fin extending past anal-fin origin in smaller individuals, but falling short of that point in larger examined specimens; anal fin large, with distal margin straight; caudal fin forked, nearly symmetrical but with ventral lobe slightly longer than dorsal lobe; fin lobes small and acutely pointed; middle rays of caudal fin slightly more than one-half length of longest rays; dorsal fin rays i,6,i or i,7; pectoral-fin rays i,9-10 or i,9,i; pelvic-fin rays i,5; anal-fin rays iii-iv,5-7,i; principal caudal-fin rays i,6-7,6-7,i (Ref. 85844).
Colouration; Body marbled dark brown, with several paler irregular cross-bars and spots on back; belly beige or mottled with brown; fin rays brown, with dark cross-bars at tips, fin membranes clear (Ref. 57128). In alcohol, body colouration ranging from light tan overall with scattered small dark chromatophores through darker with distinct pigment patterns on overall dark brown body; pigmentation in all conditions darker dorsally with brown colouration extending ventral of lateral line on abdomen and caudal peduncle, more so in darker individuals; boundary between brown pigmentation of dorsal and dorsolateral regions and lighter colouration of ventrolateral and/or ventral regions irregular albeit relatively distinct in specimens with well-developed darker colouration; darker individuals with more intense pigmentation extending further ventrally and then gradually becoming somewhat lighter; specimens with distinct pigmentation patterns having irregular midlateral dark pigmentation continuous dorsally with ventral portions of four distinct saddles of dark pigmentation extending ventrally from middorsal line; first saddle extends longitudinally from supraoccipital-spine tip to beyond origin of dorsal fin and angles posteroventrally; second saddle begins posterior of dorsal-fin base and terminates distinctly anterior of adipose-fin origin; third saddle originates slightly anterior of anterior limit of adipose-fin base and extends posteriorly along two-thirds of fin base; fourth saddle begins somewhat posterior of adipose-fin base and continues posteriorly for distance about equal to three orbital diameters and continuous posteriorly with irregular dark middorsal stripe; combination of dark brown midlateral stripe and dark brown saddles enclose more lightly coloured saddles; ventrolateral portion of abdomen and ventral part of caudal peduncle with scattered dark chromatophores, but chromatophores absent on ventral portion of abdomen even in darker examined specimens; lateral-line canal variably paler than background colouration, more obviously so posteriorly in many specimens (Ref. 85844). Dorsal and lateral portions of head brown, with scattered darker regions throughout; ventral part of head tan with fine darker pigmentation ventrolaterally in many individuals; maxillary barbel dusky, especially dorsally; mandibular barbels unpigmented (Ref. 85844). Dorsal surfaces of leading unbranched pectoral- and pelvic-fin rays ranging from tan to brown, without any distinct colouration pattern; dorsal surface of both fins darker brown basally and with medially narrowing band of dark brown pigmentation on distal half of rays, but pigmentation falls short of distal margin; ventral surfaces of paired fins, particularly fleshy basal pad, more lightly pigmented, but with darker pigmentation of dorsal surface of rays apparent to varying degrees; dorsal-fin rays pale to dusky, and with broad, dark patch on distal portions of anterior rays; some individuals with dark brown band on basal portions of posterior fin rays (Ref. 85844). |
