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

Size at apparent onset of selected develop-
mental events was documented for fully ana-
lyzed and cursorily examined specimens. Selec-
ted events were hatching, attainment of eye
pigment, formation of pectoral- and pelvic-fin
buds, loss of yolk and preanal finfold, formation
of first and last principal fin rays in each of the
median fins, formation of first and last fin rays
in the paired fins, formation of first and last
rudimentary rays of the caudal fin, and initial
and complete formation of lateral scales on the
body.
Among other characters considered, devel-
opmental phase and extent of gut folding were
determined for all analyzed and many other
specimens. Gut folding was classified as one of
five gut phases (Fig. 5). Changes in mouth posi-
tion, lower-lip-lobe separation, and other struc-
tures were noted when appropriate. Variation in
pigmentation patterns was studied by sketching
or categorizing observed patterns and noting
their frequency.
Continuous-tone graphite and black-ink
drawings of all species (except four drawings of
white sucker by other authors) were prepared to
document typical body form and pigmentation at
the beginning and middle of the proto larval,
meso larval, metalarval, and early (young-of-the-
year) juvenile phases of development. Black ink
was used only for surface or near-surface
pigmentation to distinguish it from deeper pig-
mentation, other structure, and shading. Each
drawing consists of dorsal, lateral, and ventral
views. Enlarged photographs or digital prints of
primary drawing specimens were traced to
assure accurate body proportions. Various
structures were checked and detail added while
drawing specimens were examined under a
microscope. Ifnecessary, drawings were ideal-
ized (e.g., closed or frayed fins opened and
smoothed and curved bodies straightened), and
melanophore distribution and other structures
were modified to represent a more typical
pattern or condition based on secondary drawing
speCImens.
Selected specimens were cleared and
stained for examination of potential osteological
characters and vertebra counts, as well as to
verify fin meristics. Postflexion mesolarvae

were stained with alcian blue for cartilage, and
they, metalarvae, and juveniles with alizarin red
for bone using procedures given below. Shape
and size of the frontoparietal fontanelle, inter-
neurals, and anterior-dorsal maxillary projec-
tions; position of mandibles relative to maxillae;
and (to a less consistent extent) the angle at
which the base of the postcleithra extends from
the cleithra were found to be diagnostically use-
ful (Fig. 6). Changes in the state of these char-
acters were documented photographically for
each species.
All descriptive data are summarized in spe-
cies accounts with associated illustrations or the
comparative summary of diagnostically useful
characters. Most of those data are also used by,
and accessible in, the computer-interactive key.

Interne urals
I

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- Postcleithrum

Anterior-Dorsal Projection

Fig. 6. Location of selected skeletal features of
metalarval and early juvenile catostomids. Top -lateral
view. Middle - dorsal view. Bottom - ventral view.

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