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Vol. 42, No..1
<br />OpF
<br />ibr Eph St
<br />4 when applicable,
<br />,ctoral fin musculati-
<br />;; no trace of do.,
<br />.
<br />g posterior to ii"
<br />ord (urostyle)
<br />used on all asp,_
<br />ine; melanoph.
<br />i rva, day 17,
<br />n-rays increases:.
<br />Is. Median fin
<br />t sites of anal
<br />in stomach; f?
<br />All pigmentat.:
<br />ine intensified.
<br />anal fin-ray r--
<br />15.5 mm (Fib;.
<br />sal and anal
<br />dement of ossil
<br />ng into two cl_;
<br />iring on poste:
<br />rva, day 48,
<br />orsal and anal
<br />ns rudimentary
<br />caudal fin beci-
<br />°r two chambe-
<br />t. Mouth termir
<br />Mp
<br />f
<br />when applicable,
<br />December 1982 MINCKLEY, GUSTAFSON: RAZORBACK SUCKER DEVELOPMENT 559
<br />lips formed, small papillae on both upper and
<br />lower lips. Melanophores increasing over
<br />body; ossified fin rays and gills acquiring pig-
<br />ment; larvae dark dorsally and lighter ven-
<br />trally and in eye region.
<br />Stage 38: pelvic fin rudiments, day 50,
<br />1200 hours, 20.8 mm. Pelvic fin rudiments in
<br />form of small crescentic folds.
<br />Stage 39: pelvic fin buds, day 54, 1296
<br />hours, 23.5 mm. Pelvic fin buds in form of
<br />thin membranous paddles, not movable.
<br />Stage 40: pelvic fin rudiments, day 64,
<br />1536 hours, 27.0 mm. Six pelvic fin-ray rudi-
<br />ments within pelvic fin membranes; fin mov-
<br />able. Dorsal and anal fin-rays completely
<br />ossified. Mouth beginning to shift ventrally,
<br />papillae highly developed on lips.
<br />Stage 41: ossification of pelvic fin-rays, day
<br />70, 1680 hours, 32 mm. Rays partially os-
<br />sified in pelvic fins; median fin membrane
<br />persisting ventrally and anterior to pelvic fins
<br />greatly reduced; dorsal and anal fins sepa-
<br />rated from caudal fin.
<br />Stage 42: late postlarva, day 75, 1800
<br />hours, 35 mm (Fig. 8). Pelvic fin-rays ossified.
<br />Median fin membrane persisting only be-
<br />tween anus and pelvic fins. Full complements
<br />of fin-rays in all fins: dorsal, 15-16; caudal,
<br />19; anal, 8; pelvic, 9-9; and pectoral, 13-
<br />15-13-15. Narial flap formed. Alimentary
<br />tract looped once to left just posterior to
<br />stomach, mouth ventral. Acoustico-lateralis
<br />system formed on anterior half of body.
<br />Juvenile Development
<br />Stage 43: scale rudiments, day 105, 2520
<br />hours, 43.0 mm. Scale rudiments present on
<br />ventro-lateral surfaces; median fin membrane
<br />eliminated.
<br />Stage 44: scales, day 125, 3000 hours, 45.0
<br />mm. Scales distinctly visible except medially
<br />on dorsum and ventrum.
<br />Stage 45: nuchal keel, day 227, 5448 hours,
<br />90.0 mm (Fig. 9). Scalation completed.
<br />Acoustico-lateralis system completed. Nuchal
<br />Fig. 7. Postlarva of razorback sucker, Xyrauchen texanus, at beginning of fin-ray development; legend as in Fig-
<br />ures 1 to 6 when applicable, and AFr = anal fin-rays, An = anus, CFr = caudal fin-rays, DFr = dorsal fin-rays,
<br />DPL = dorsal pigment line, G = gills, LPL = lateral pigment line, N = naris, PFr = pectoral fin-rays, and VPL
<br />= ventral pigment line.
<br />Fig. 8. Late postlarva of razorback sucker, Xyrauchen texanus; legend: LL = lateral line, Lip = papillose lips,
<br />NF = nasal flap, P2F = pelvic fin, and UgP = urogenital papillus.
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