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Vol. 42, No. 4
<br />r
<br />" ' (I
<br />t
<br />tiation of nuchal keel.
<br />and some ruptured their chor,'c:_
<br />All hatched between 125 a:1;1
<br />ter fertilization.
<br />;were 6.8 to 7.3 mm TL at ha.;:
<br />1k sac is tubular, and the h
<br />at a 45 degree angle to the be
<br />ectoral fin buds, noted at
<br />nm), became paddlelike at
<br />nm), and first were movablt _
<br />,.0 mm). The continuous, mee
<br />st noted on caudal and pc
<br />-as at 103 hours (5.3 mm), be-
<br />)n the venter (behind the pros-
<br />hours (7.5 mm), and was con::
<br />hours (8.0 mm). The opercles
<br />at 162 hours (8.0 mm). The
<br />appeared at 238 hours (9.0 m
<br />jaw became movable and p
<br />i directed swimming to the
<br />at that time; eye pigment cc
<br />)lack. Melanophores develod:
<br />Id hindbrain and on paired (.orso-visceral, and unpaired In
<br />lent lines between 162 and G:
<br />td 9.0 mm). There was no late;-:
<br />December 1982 MINCKLEY, GUSTAFSON: RAZORBACK SUCKER DEVELOPMENT 561
<br />pigmentation at 9.0 mm. Melanophores on
<br />the dorsum are large and stellate, as also re-
<br />corded by Winn and Miller (1952). At 263
<br />hours (9.0+ mm) fin rays were not yet visible
<br />in any fin.
<br />Yolk was completely assimilated at 311
<br />hours (10.0 mm) and the proctodeum opened
<br />to form the anus. The urostyle became up-
<br />turned between 263 and 311 hours, and 3 to
<br />4, ventral, caudal fin-rays formed by the last
<br />time period. Pectoral fins had developed
<br />three rays, but there were no rays in the dor-
<br />sal and anal fins. Median fin folds were thick-
<br />ened and expanded at the sites of the future
<br />dorsal and anal fins at 430 hours (12.0+
<br />mm), and the opercles fully covered the gills.
<br />Dorsal and anal fin-ray rudiments, and a lat-
<br />eral pigment line appeared at 960 hours (15.5
<br />mm). The gas bladder had by this time con-
<br />stricted toward the two-chambered condi-
<br />tion. Pelvic fins appear as swellings of mesen-
<br />i chyme and the caudal fin becomes
<br />emarginate at 1152 hours (20.0 mm). The
<br />pelvic fin buds were nonmovable, mem-
<br />braneous paddles at 1296 hours (23.5 mm);
<br />movement and pelvic fin-rays had appeared
<br />at 1536 hours (27.0 mm).
<br />Scale rudiments were first noted at 2520
<br />hours (43.0 mm) on ventrolateral body sur-
<br />faces. By 3000 hours, lepidogenesis was com-
<br />plete on all but the median areas of the dor-
<br />sum and ventrum. The nuchal keel appeared
<br />about 5000 hours after fertilization.
<br />ACKNOWLEDGMENTS
<br />This research was supported, in part, by
<br />U.S. Fish and Wildlife Service Contract 14-
<br />16-0002-3585 to Arizona State University.
<br />We thank personnel at Willow Beach Na-
<br />tional Fish Hatchery for assistance in obtain-
<br />ing and rearing young of razorback suckers.
<br />Permits for collection of wild fish were
<br />granted by Arizona Game and Fish Depart-
<br />ment. J. P. Collins and R. W. McGaughey
<br />read and commented on the manuscript.
<br />LITERATURE CITED
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<br />r adult morphology.
<br />1 0 mm
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