7724

• UCREFRP Catalog Number: 7724
• Author: Snyder, D. E.
• Title: Contributions to a Guide to the Cypriniform Fish Larvae of the Upper Colorado River System in Colorado.
• USFW Year: 1981.
• USFW - Doc Type: \
• Copyright Material: NO

16 KEY TO THE METALARVAE

Preliminary Key to the Cypriniform Metalarvae
of the Upper Colorado River System in Colorado

1.
a. Snout-to-vent length 72% or greater. Dorsal
fin (principal) ray count 10 or more (rarely 9),
anal fin ray count less than 9, typically 6 or
7; and caudal fin ray count typically 18 or

19. . . . . . . . . . . . . . . . . 2.

2.
a. Dorsal fin very long with a ray count greater
than 17 and an insertion well posterior to the
vent. Caudal ray count typically 19. Robust
body with greater proportional widths, depths,
and head lengths than for other metalarvae.
. . . Cyprinus carpio (Cyprininae, Cyprinidae).

3.
a. Anal rays typically 7, dorsal rays typically

8. . . . . . . . . . .. 4.

4.
a. Dorsal fin origin posterior to pelvic fin
origin. Dark area of melanophore pigmentation
on lateral surface of the snout and late in the
phase in the form of a lateral band on the body.
Myomeres 23-27 to vent, typically 24-27, and
36-41 total, typically 38-41. .......
. . . . . . . . . . . " 5. (Rhinichthys)

5.
a. Groove between upper lip and the re~t of the
snout broken by frenum along its most anterior
junction. Myomeres 24-27 to the vent, typically
25-27, and 37-41 total, typically 40-41.
. . . . . . . . .. Rhinichthys cataractae.

6.
a. Peritoneum usually dark laterally, sometimes
ventro-laterally. Pigment under dorsal and
anal fins but not as an "intense" dash. Dorsal
fin origin located somewhat beyond 1/2 the
standard length (53-56% Sl), usually over or
slightly behind pelvic fin origin. Mouth
oblique. Myomeres to the vent typically
23-24. ..... Pimephales ppomelas.

7.
a. Anal rays typically B. Insertion of dorsal fin
well forward of vent. ..... B.

8.
a. Dorsal and pelvic rays typically 9. No series
of melanophores along the lower margin of the
opercula. . . . . . . . Gila atparia.

9.
a. Dorsal fin orlgln over or anterior to pelvic
fin origin. Myomeres about 24-26 to the vent
and 35-39 total. Mid-ventral surface anterior
to the vent pigmented with a single line of
melanophores. No lateral band of melanophores.
Metalarvae about 8 mm Sl (9 mm TL) or larger.
. . . . . . . . . . . Hybognathus hankinsoni.

10.
a. Dorsal rays typically 8. Myomeres 19-24 to
vent, typically 21-23, and 34-37 total, typ-
ically 35-36. Metalarvae about 8-10 mm Sl
(9- 1 3 mm Tl). ...... Notpopis lutpensis.

b. Snout-to-vent length less than 72% SL. Dorsal
fin rays less than 10, typically 8 or 9, rarely
11; anal ray count rarely less than 7 or more
than 12; caudal fin ray count typically 19. "
. . . . . . . . 3. (leuciscinae, Cyprinidae).

b. Dorsal fin shorter with ray count less than 17
and insertion well anterior to the vent. Caudal
ray .count typically 18. .. 15. (Catostominae,
Ca tos tomi dae).

b. Anal and dorsal rays typically 8 or more

each. ................

7.

b. Dorsal fin origin over, slightly anterior, or
slightly posterior to pelvic fin origin. No
concentration of pigment on lateral surface of
snout or in the form of a lateral band on the
body. Myomeres 20-25 to vent, typically 21-24,
and 33-38 total, typically 34-36. ..... 6.

b. Groove between upper lip and the rest of the
snout continuous, no frenum. Myomeres 23-27
to the vent, typically 24-25, and 36-40 total,
typically 38. ..... Rhinichthys oscalus.

b. Peritoneum light. "Intense" dash of melanophores
usually under middle of both dorsal and anal
fins. Dorsal fin origin located at or before
1/2 the standard length (46-50% SL), usually over
or slightly anterior to pelvic fin origin.
Mouth nearly horizontal. Myomeres to the vent
typically 21-23. .... Notropis stramineus.

b. Anal rays typically 9 or greater. Insertion of
dorsal fin variable. ...... 10.

b. Dorsal and pelvic rays typically 8. Series of
melanophores along the lower edge of the
opercule. . . . . . . . . . . . 9.

b. Dorsal fin origin posterior to or1g1n of pelvic
fins. Myomeres about 26-29 to the vent, typ-
ically 27-29, and 40-44 total, typically 40-42.
No mid ventral line of melanophores anterior to
the vent. Prominent lateral band of melanophores
on the body and continued on the snout. Meta-
larvae about 11 mm SL (13 mm Tl) or larger. ..
. . . . . Semotilus atromaculatus.

b. Dorsal rays typically 9 or greater. Myomeres
typically 24 or greater to vent and 37 or
greater total. Metalarvae about 10 mm SL
(12-13 mm TL) or larger. ........ 11.