9550

• UCREFRP Catalog Number: 9550
• Author: Snyder, D. E. and R. T. Muth.
• Title: Catostomid Fish Larvae and Early Juveniles of the Upper Colorado River Basin - Morphological Descriptions, Comparisons, and Computer-interactive Key.
• USFW Year: 2004.
• USFW - Doc Type: Fort Collins, CO.
• Copyright Material: NO

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PHASE 1

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PHASE 2

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PHASE 3

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PHASE 4

PHASE 5

ADULT FORM

Fig. 5. Phases of gut coil development in catostomid fish larvae and early juveniles with comparison to adult form
in Catostomus commersoni (latter modified from Stewart 1926). Phase 1 - essentially straight gut. Phase 2 -
initial loop formation (usually on left side), begins with 900 bend. Phase 3 - full loop, begins with straight loop
extending to near anterior end of visceral cavity. Phase 4 - partial fold and crossover, begins with crossing of first
limb over ventral midline. Phase 5 - full fold and crossover, begins with both limbs of loop extending fully to
opposite (usually right) side, four segments of gut cross nearly perpendicular to the body axis. Later in Phase 5
and in adult form, outer portions of gut folds or coils extend well up both sides of visceral cavity.

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