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Title: Five Natural Hybrid Combinations in Minnows (Cyprinidae)
Author: Cross, Frank B., Minckley, W. L.
Language: English
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Copyright Status: Not copyrighted in the United States. If you live elsewhere check the laws of your country before downloading this ebook. See comments about copyright issues at end of book.

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[Transciber's Note:

The follow suspected error has been corrected in this text:
    Page 3: _C. erythogaster_ changed to _C. erythrogaster_]


UNIVERSITY OF KANSAS PUBLICATIONS
MUSEUM OF NATURAL HISTORY

Volume 13, No. 1, pp. 1-18

June 1, 1960



Five Natural Hybrid Combinations
in Minnows (Cyprinidae)


BY
FRANK B. CROSS AND W. L. MINCKLEY


UNIVERSITY OF KANSAS
LAWRENCE
1960


UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
Robert W. Wilson


Volume 13, No. 1, pp. 1-18
Published June 1, 1960


UNIVERSITY OF KANSAS
Lawrence, Kansas


PRINTED IN
THE STATE PRINTING PLANT
TOPEKA, KANSAS
1960

[Illustration]

28-3424



Five Natural Hybrid Combinations in Minnows (Cyprinidae)

BY FRANK B. CROSS AND W. L. MINCKLEY


The hybrid fishes described herein are _Chrosomus erythrogaster_
(Rafinesque) × _Notropis cornutus frontalis_ (Agassiz), _C.
erythrogaster_ × _Semotilus atromaculatus_ (Mitchill), _Campostoma
anomalum plumbeum_ (Girard) × _S. atromaculatus_, _Gila nigrescens_
(Girard) × _Rhinichthys cataractae_ (Valenciennes), and _Notropis
venustus venustus_ (Girard) × _Notropis whipplei_ (Girard). Two of the
combinations have been reported, without descriptions, in literature
(citations below), and Hubbs (1955: Fig. 3) graphically indicated
hybridization between the same genera with which this paper is
concerned, but did not designate the species involved.

All specimens of _C. erythrogaster_ × _N. c. frontalis_, _C.
erythrogaster_ × _S. atromaculatus_, _C. a. plumbeum_ × _S.
atromaculatus_, and _N. v. venustus_ × _N. whipplei_ were taken in a
period of severe drought in Kansas and Arkansas. All were from small,
spring-fed streams that support large populations of fishes. That the
drought of 1953-1956 had pronounced effects on stream habitats in Kansas
has been documented by Minckley and Cross (1959). Satisfactory sites for
spawning may have been few, but an abundance of adult fishes persisted
from earlier, wet years. Unusual crowding of spawning fishes would
increase the opportunity for fertilization of the eggs of one species by
sperm from another species. We think that the hybrids reported here
(excepting _G. nigrescens_ × _R. cataractae_) are explainable on the
basis of crowding; we have no information about stream-conditions where
the last-named hybrid was found. Generally, hybridization of fishes
seems most common in areas that have been subject to radical climatic
change in the past 20,000 or fewer years (Hubbs, 1955:18-19), and in
streams that have been altered recently by the activities of man (Hubbs
and Strawn, 1956:342, and others). Streams from which we report hybrids
probably were affected by overgrazing of their watersheds; overgrazing
was unusually severe in the drought.

Most of the hybrids were recognized as unusual at the time of capture,
and were saved as part of numerically selective samples from the
streams (rather than being discovered in the laboratory, in random
samples).

Our measurements were made by methods defined by Hubbs and Lagler
(1958); values are expressed as thousandths of the larger dimension.

=_Chrosomus erythrogaster_ × _Notropis cornutus frontalis_=: KU 3872
(26.7 mm. in standard length) and KU 4170 (46.6 mm.) from Deep Creek,
Riley Co., Kansas, Sec. 23, T. 11S, R. 7E, Dec. 14, 1957, and Apr. 26,
1958, respectively; and KU 4185 (39.3 mm.) from Bluff Creek,
Pottawatomie Co., Kansas, Sec. 15, T. 6S, R. 8E, June 29, 1958. Compared
in Table 1 with five specimens of _C. erythrogaster_, KU 3914 (39.3 to
47.3 mm., mean 43.0 mm.) from the same locality and of the same date as
KU 3872 (above); and with five specimens of _N. c. frontalis_, KU 4184
(41.0 to 46.5 mm., mean 42.5 mm.) from the same locality and of the same
date as KU 4185 (above). This cross has previously been recorded by
Trautman (1957:326, 355) and by Minckley (1959:431).

The head-lengths of the hybrids are greater than in specimens of like
size of _C. erythrogaster_ or _N. c. frontalis_ (Table 1). Hubbs and
Miller (1943:373-374) reported that hybrids of _Gila orcutti_ ×
_Siphateles mohavensis_ have larger, more robust heads than either of
the parental species, perhaps because of heterosis. The enlarged heads
in hybrids of _C. erythrogaster_ and _N. c. frontalis_ result primarily
from elongation of the postorbital region, with lesser elongation of the
snout and orbit. The enlarged head affects measurements obtained for
other structures that are parts of the head (and expressed as
proportions of standard length or head-length), causing a tendency
toward _N. c. frontalis_ when the head-part is divided by standard
length, and greater intermediacy or a tendency toward _C. erythrogaster_
when the head-part is divided by head-length. In characters in which the
parental species differ most (size of eye, length of upper jaw, and
width of gape), the hybrids are intermediate between the parental
species, regardless of whether the measurements are expressed as
proportions of head-length or standard length; however, tendencies
toward one or the other of the parental species (dependent on the
divisor) can also been seen in these characters. Some experimentally
propagated hybrids show highly variable, and sometimes extreme
characters, rather than intermediacy of meristic and proportional
characters (Hubbs, 1956).

TABLE 1. COMPARISONS OF THREE SPECIMENS OF CHROSOMUS ERYTHROGASTER ×
NOTROPIS CORNUTUS FRONTALIS WITH SPECIMENS OF THE PARENTAL SPECIES
(MEANS ARE ABOVE, RANGES IN PARENTHESES BELOW)

=====================+=============+=============+=========+==============
                     |_Chrosomus erythrogaster_
                     |             | KU 4170 and 4185
                     |             |             | KU 3872
                     |             |             |         |  _Notropis_
                     |             |             |         |_c. frontalis_
---------------------+-------------+-------------+---------+--------------
Standard lengths     |       43.0  |       43.0  |   26.7  |       42.5
                     | (39.3-47.3) | (39.3-46.6) |   ...   | (41.0-46.5)
                     |             |             |         |
Head-length /        |       253   |       282   |   307   |       276
Standard length      |  (246-262)  |  (280-283)  |   ...   |  (273-283)
                     |             |             |         |
Orbital length /     |       067   |       075   |   101   |       083
Standard length      |  (063-071)  |  (071-079)  |   ...   |  (080-086)
                     |             |             |         |
Orbital length /     |       263   |       266   |   329   |       300
Head-length          |  (252-272)  |  (250-282)  |   ...   |  (291-310)
                     |             |             |         |
Snout-length /       |       069   |       073   |   071   |       068
Standard length      |  (068-071)  |  (071-075)  |   ...   |  (066-071)
                     |             |             |         |
Snout-length /       |       272   |       260   |   232   |       245
Head-length          |  (262-280)  |  (255-265)  |   ...   |  (233-260)
                     |             |             |         |
Interorbital width / |       069   |       074   |   079   |       068
Standard length      |  (065-071)  |  (069-079)  |   ...   |  (067-069)
                     |             |             |         |
Interorbital width / |       272   |       263   |   256   |       245
Head-length          |  (262-286)  |  (245-280)  |   ...   |  (241-250)
                     |             |             |         |
Gape-width /         |       056   |       065   |   064   |       065
Standard length      |  (051-059)  |  (059-071)  |   ...   |  (062-066)
                     |             |             |         |
Gape-width /         |       222   |       230   |   207   |       233
Head-length          |  (204-241)  |  (209-250)  |   ...   |  (224-239)
                     |             |             |         |
Upper jaw-length /   |       057   |       082   |   112   |       083
Standard length      |  (051-061)  |  (076-088)  |   ...   |  (080-086)
                     |             |             |         |
Upper jaw-length /   |       223   |       292   |   268   |       301
Head-length          |  (206-237)  |  (273-311)  |   ...   |  (284-315)
                     |             |             |         |
Postorbital length / |       113   |       130   |   124   |       123
Standard length      |  (108-120)  |  (129-130)  |   ...   |  (121-125)
                     |             |             |         |
Postorbital length / |       444   |       460   |   402   |       446
Head-length          |  (432-456)  |  (455-464)  |   ...   |  (431-457)
                     |             |             |         |
Length of depressed  |             |             |         |
dorsal fin /         |       224   |       250   |   255   |       237
Standard length      |  (217-232)  |  (247-252)  |   ...   |  (233-243)
                     |             |             |         |
Length of depressed  |             |             |         |
dorsal fin /         |       885   |       886   |   829   |       858
Head-length          |  (869-892)  |  (871-900)  |   ...   |  (836-890)
                     |             |             |         |
Number scales in     |             |             |         |
lateral line         |       71.7  |       53.0  |  52(?)  |       38.8
                     |   (68-76)   |      (53.0) |   ...   |   (38-39)
                     |             |             |         |
Pharyngeal teeth     |   0,5-5,0   |   1,5-4,1   | 1,5-4,2 |   2,4-4,2
                     |             |  ((?)-4,1)  |         |
                     |             |             |         |
Anal rays            |         8   |         8   |     8   |  usually 9
                     |             |             |         |
Vertebrae            |    37-40    |        39   |   ...   |    38-39
---------------------+-------------+-------------+---------+--------------

In pigmentation, all three of the hybrids are intermediate between the
parental species. The mid-lateral band (which is dark and discrete in
_C. erythrogaster_, but faint, broad, and diffuse in _N. c. frontalis_)
is broader and fainter in the hybrids than in _Chrosomus_, but is better
developed than in _N. c. frontalis_. The dorsolateral dark band of _C.
erythrogaster_ is present in the hybrids, but is less distinct than in
that species, and less distinct than the mid-lateral band of the hybrids
themselves. The dorsolateral band is not present in _N. c. frontalis_.
The color of the peritoneum in the hybrids is the glossy, jet-black of
_C. erythrogaster_ in two specimens, and the dusky-black of _N. c.
frontalis_ in one.

_Chrosomus_ and _Notropis_ differ greatly in the length and convolution
of the intestine. _Chrosomus_ has a long, coiled gut, which is crossed
by the mid-ventral line eight or nine times; in _N. c. frontalis_, the
intestine forms a flat, S-shaped loop that does not cross the
mid-ventral line. In the two largest hybrids (KU 4170 and 4185), the gut
is intermediate, crossing the mid-ventral line four times. In the
smaller hybrid (KU 3872) the gut crosses the mid-ventral line twice but
the configuration of the anterior loops indicates that the same
intestinal convolutions that were found in the larger specimens would
have developed in KU 3872 as the gut elongated with increase in size of
the fish.

Both Deep and Bluff creeks are clear, gravel-bottomed streams draining
parts of the Flint Hills Area of Kansas. A description of Flint Hills
streams and lists of fishes occurring in them have been published by
Minckley (1956 and 1959), and by Minckley and Cross (1959).

=_Chrosomus erythrogaster_ × _Semotilus atromaculatus_=: KU 2947 (28.0
mm. in standard length) from Mill Creek, Wabaunsee Co., Kansas, Sec. 30,
T. 12S, R. 9E, Mar. 22, 1953. Compared in Table 2 with five specimens of
_C. erythrogaster_, KU 2836 (27.2 to 31.0 mm., mean 28.5) from the same
locality and of the same date as KU 2947 (above); and with five
specimens of _S. atromaculatus_, KU 1954, 2499, 2703, and 2838 (25.5 to
31.1 mm., mean 28.9 mm.) from streams in the same area.

This hybrid is intermediate between the two species in number of scales
and pharyngeal teeth, and has a composite of the pigmentation found in
the parental fishes (Table 2). For diagnostic purposes, greater
importance is attached to the characters mentioned above than to
proportional measurements, which are subject to considerable error
because of the small size of the specimens. The few measurements that
were taken indicate that this hybrid, like _C. erythrogaster_ × _N. c.
frontalis_, has a larger head than do specimens of like size of either
parental species. The enlarged head affects measurements obtained for
other structures that are parts of the head; only the length of the
upper jaw, which is greatly different in the parental species, is
actually intermediate in KU 2947.

Mill Creek is a clear stream, similar to Deep and Bluff creeks but
somewhat larger. Mill Creek had an exceptionally large population of
fishes at the time the hybrid was found, but _Chrosomus_ and _Semotilus_
were neither unusually common nor rare.

Two other crosses, both of which have been described in the literature,
also have been found in Mill Creek. These are _N. c. frontalis_ × _S.
atromaculatus_, and _N. c. frontalis_ × _Notropis rubellus_ (Agassiz).

TABLE 2. COMPARISON OF ONE SPECIMEN OF CHROSOMUS ERYTHROGASTER ×
SEMOTILUS ATROMACULATUS WITH SPECIMENS OF THE PARENTAL SPECIES (MEANS
ARE ABOVE, RANGES IN PARENTHESES BELOW)

========================+==============+================+=================
                        | _Chrosomus erythrogaster_
                        |              |    KU 2947
                        |              |                |   _Semotilus_
                        |              |                | _atromaculatus_
------------------------+--------------+----------------+-----------------
Dark lateral band       | intense      | intense        | intense
                        |              |                |
Light dorsolateral band | well-defined | poorly         | absent
                        |              | developed      |
                        |              |                |
Dark dorsolateral band  | intense      | poorly         | absent
                        |              | developed      |
                        |              |                |
Color of peritoneum     | black        | black          | silvery
                        |              |                |
Length of gut           | long with    | short, with a  | short, with a
                        | transverse   | single forward | single forward
                        | coils        | loop           | loop
                        |              |                |
Pharyngeal teeth        |   0,5-5,0    |    1,5-5,2     | usually 2,5-4,2
                        |              |                |
Number scales in        |              |                |
lateral line            | usually 70   | about 67       | usually fewer
                        | or more,     | slightly       | than 65, not
                        | embedded     | embedded       | embedded
                        |              |                |
Barbels                 | absent       | absent         | usually present
                        |              |                |
Vertebrae               |    37-40     |       39       |      42-43
                        |              |                |
Head-length /           |       272    |      310       |         300
Standard length         |  (266-277)   |                |    (292-308)
                        |              |                |
Upper jaw-length /      |       071    |      097       |         110
Standard length         |  (069-074)   |                |    (104-114)
                        |              |                |
Upper jaw-length /      |       263    |      310       |         366
Head-length             |  (254-273)   |                |    (356-382)
                        |              |                |
Interorbital width /    |       103    |      114       |         116
Standard length         |  (101-106)   |                |    (114-118)
                        |              |                |
Interorbital width /    |       381    |      372       |         388
Head-length             |  (372-400)   |                |    (380-400)
                        |              |                |
Orbital length /        |       081    |      083       |         078
Standard length         |  (075-085)   |                |    (076-084)
                        |              |                |
Orbital length /        |       296    |      267       |         261
Head-length             |  (271-313)   |                |    (255-273)
------------------------+--------------+----------------+-----------------

=_Campostoma anomalum plumbeum_ × _Semotilus atromaculatus_=: KU 4013
(three males, 86.0 to 96.0 mm. in standard length, mean 89.5 mm.) from
Timber Creek, Scott Co., Kansas, Sec. 2, T. 16S, R. 33W, June 19,
1958. Compared in Table 3 with five specimens of _C. a. plumbeum_, KU
4034 (85.7 to 93.1 mm., mean 90.2 mm.) from the Smoky Hill River,
Wallace Co., Kansas, Sec. 26, T. 13S, R. 39W, June 20, 1958; and with
five specimens of _S. atromaculatus_, KU 4012 and 4047 (85.0 to 97.5
mm., mean 91.7 mm.) from the same locality and of the same date as KU
4013 (above), and Sappa Creek, Decatur Co., Kansas, Sec. 29, T. 2S, R.
28W, June 23, 1958, respectively. This hybrid combination has previously
been recorded by Johnson (1945).

TABLE 3. COMPARISONS OF THREE SPECIMENS OF CAMPOSTOMA ANOMALUM PLUMBEUM
× SEMOTILUS ATROMACULATUS WITH SPECIMENS OF THE PARENTAL SPECIES (MEANS
ARE ABOVE, RANGES IN PARENTHESES BELOW)

=====================+=================+===============+=================
                     | _Campostoma a._ |    KU 4013    |   _Semotilus_
                     |   _plumbeum_    | (three spec.) | _atromaculatus_
---------------------+-----------------+---------------+-----------------
Standard lengths     |          90.2   |        89.5   |          91.7
                     |    (85.7-93.1)  |  (85.7-96.2)  |    (85.0-97.5)
                     |                 |               |
Predorsal length /   |           511   |        533    |          557
Standard length      |      (505-517)  |   (523-542)   |     (547-564)
                     |                 |               |
Head-length /        |           251   |        276    |          289
Standard length      |      (244-258)  |   (273-278)   |     (280-299)
                     |                 |               |
Snout-length /       |           090   |        088    |          085
Standard length      |      (086-096)  |   (087-091)   |     (082-087)
                     |                 |               |
Orbital length /     |           044   |        048    |          049
Standard length      |      (043-045)  |   (047-049)   |     (048-050)
                     |                 |               |
Interorbital width / |           075   |        094    |          110
Standard length      |      (073-078)  |   (091-099)   |     (104-113)
                     |                 |               |
Distance from tip of |                 |               |
mandible to tip of   |                 |               |
maxillary /          |           057   |        076    |          098
Standard length      |      (053-063)  |   (072-078)   |     (095-104)
                     |                 |               |
Gill rakers          |           30    |        17     |          9
(1st arch)           |       (29-31)   |    (16-18)    |       (8-10)
                     |                 |               |
Number scales in     |           54    |        54     |          56
lateral line         |       (53-55)   |    (54-55)    |      (52-64)
                     |                 |               |
Predorsal scale-rows |           25    |        27     |          35
                     |       (23-27)   |    (27-28)    |      (34-36)
                     |                 |               |
Anal rays            |           7     |        7.3    |          8
                     |        (6-7)    |     (7-8)     |          8
                     |                 |               |
Vertebrae            |           40    |     42-44[A]  |       42-43
---------------------+-----------------+---------------+-----------------

[A] Three deformed vertebrae in one specimen with 44; other two
specimens have 42 vertebrae.

The hybrids seem uniformly intermediate between the parental species.
Application of the hybrid index to the characters listed in Table 3
results in a value of 55.7 when _C. a. plumbeum_ is assigned the value
0.

The pharyngeal arches of the hybrids are peculiarly deformed. Expressed
in terms of the one-or two-rowed arrangement common to all North
American cyprinids, tooth-counts of 0,5-4,1; 1,3(?)-4,0; and 2,5-4,1
best fit the three fish. However, one arch bears only three teeth, all
deformed and badly aligned, plus a pit that presumably represents a lost
fourth tooth. At the other extreme, one arch bears eight teeth, some of
which are attached to the arch between and behind others that are
countable as part of the basic main row. Supernumerary teeth and other
deformities may have resulted from abnormalities in the replacement
process. In some cases, replacement teeth probably failed to develop; in
others, replacement teeth seemingly developed, but attached to the arch
in abnormal positions, with or without loss of previous teeth, causing
irregularity in alignment. Hubbs (1951) described an irregular
(seemingly three-rowed) alignment in a fish that Hay (1888:249) reported
from western Kansas as _Squalius elongatus_. However, Hubbs considered
the specimen to be an aberrant example of _S. atromaculatus_, and the
characteristics that he lists for it do not correspond closely with
those of the hybrid specimens that we have. Evans and Deubler (1955:32)
found three rows of teeth in two of 150 specimens of _Semotilus_, and
attributed the abnormality to failure of old teeth to fall out after
formation of new teeth. The teeth of _Campostoma_ usually number
0,4-4,0, and those of _Semotilus_ 2,5-4,2. The pharyngeal arches are
much smaller in _Campostoma_ than in _Semotilus_.

The peritoneum is mottled dark and silvery in the hybrids; it has a
composite of the coloration in the parental species rather than a
blended shade. The intestine has two diagonal loops crossing the ventral
part of the body cavity, and the hindgut lies high in the cavity, along
the left side of the air bladder. In _Campostoma_, the long gut is
transversely coiled around the air bladder, whereas in _Semotilus_ the
gut forms a longitudinal, flattened, S-shaped loop, ventral to the air
bladder.

In the hybrids, the mouth is slightly oblique and nearly terminal. The
lower lip is thick and fleshy, but has only a suggestion of the
projecting mandibular shelf that is unique in _Campostoma_. The upper
lip is uniform in width, not medially expanded as in _S. atromaculatus_.
One of the hybrids lacks barbels, one has a _Semotilus_-like barbel on
the right side only, and one has a vestigial barbel on the right side
and an anomalous barbel that is nearly terminal on the left upper lip.

In coloration, the hybrids lack the spot in the anterior base of the
dorsal fin that is characteristic of _Semotilus_, but each has a
poorly-developed dark lateral band, and a weak basicaudal spot. This
band and spot are usually prominently developed in _S. atromaculatus_
and usually are absent in adults of _C. a. plumbeum_.

In the position and obliquity of the mouth, basic color pattern (diffuse
lateral band and basicaudal spot), and the presence in one specimen of a
nearly terminal, barbel-like structure, the hybrids somewhat resemble
_Hybopsis biguttata_ (Kirtland), which occurs rarely in the Kansas River
Basin. These partial similarities are coincidental, because other
characters of the hybrids make relationship with _H. biguttata_
implausible. The high number of gill rakers (Table 3) and the length and
position of the gut indicate strongly that the three specimens are
hybrids with _C. anomalum_ as one parent; the pharyngeal arches, though
deformed, indicate that the other parental species has two rows of
teeth, with five teeth in the main row. Only _S. atromaculatus_, among
species in the Kansas River Basin, usually has such a dental formula,
and other characters of our three specimens fit expectations in a hybrid
between that species and _C. a. plumbeum_.

Timber Creek, where the three hybrids were collected, is a small,
spring-fed, sandy-bottomed tributary to Scott County State Lake in the
extreme southwestern part of the Kansas River Basin. The stream was less
than 10 feet wide and six inches deep, except in three pools near road
crossings. The hybrids were found in two of these pools, along with
numerous _S. atromaculatus_ and one adult _C. a. plumbeum_.

Another specimen of _C. a. plumbeum_ × _S. atromaculatus_ (KU 4841, 39.3
mm. in standard length) was taken in the North Platte River at Lisco,
Garden County, Nebraska, on September 11, 1959. That specimen has 7 anal
rays and 52 scales in the lateral line; otherwise, it is similar to the
three hybrids described above.

=_Gila nigrescens_ × _Rhinichthys cataractae_=: KU 4253 (a male, 60.6
mm. in standard length), from New Mexico, Bernalillo County, Rio Grande
12 mi. S Bernalillo on U. S. Highway 85 (Corraleo Bridge). Compared in
Table 4 with six specimens of _G. nigrescens_: KU 4251, 4254, and 4262
(63.1-72.4 mm. in standard length, mean 66.4 mm.); and with five
specimens of _R. cataractae_: KU 4248, 4258, and 4264 (55.6-65.0 mm.
standard length, mean 59.5 mm.). Comparative material was taken at the
same locality as KU 4253 and at nearby localities in the Rio Grande.

The hybrid is intermediate in almost all of the features in which the
parental species differ from each other. For six of the characters
included in Table 4, the hybrid index is 49.7 per cent, when _Gila_ is
assigned the value 0 (height of dorsal fin and numbers of fin rays and
teeth excluded). There is no enlargement of the head in KU 4253, such as
was found in _Gila orcutti_ × _Siphateles mohavensis_ (Hubbs and Miller,
1943:373), _Chrosomus erythrogaster_ × _Notropis cornutus frontalis_,
and _C. erythrogaster_ × _Semotilus atromaculatus_. The height of the
dorsal fin, which Hubbs and Miller (_loc. cit._) found to be extreme in
_G. orcutti_ × _S. mohavensis_, exceeds the average for the parental
species in _G. nigrescens_ × _R. cataractae_ also; but, dorsal fins as
high as that of the hybrid were found in some individuals of both
parental species. In _R. cataractae_, all fins are more rounded and more
expansive than in _G. nigrescens_, and fins other than the dorsal have
an intermediate size in the hybrid. This intermediacy has doubtful
significance, because fin-size in _Rhinichthys_ varies greatly with
body-size, sex, and probably with the state of sexual development.
_Rhinichthys_ matures at smaller size than _Gila_, and never becomes so
large as that species.

_Gila nigrescens_ and _R. cataractae_ differ strikingly in features
involving the snout and mouth, and these differences provide the most
conclusive evidence that KU 4253 is a hybrid of these species. The
projecting, fleshy snout of _R. cataractae_ is bridged to the ventral
mouth by a frenum that is approximately 3 mm. wide in specimens 60 mm.
in standard length. In _Gila_, the snout does not project beyond the
mouth, which is oblique, lacks a frenum, and is larger than in
_Rhinichthys_. The snout of the hybrid projects less than in _R.
cataractae_ and is bridged to the upper lip by a frenum 1.7 mm. wide.
The mouth of the hybrid is intermediate in size, obliquity, and
thickness of the lips. _Rhinichthys_ has barbels, _Gila_ lacks them, and
the hybrid has one vestigial barbel, on the right side. The lower
surface of the head of _Rhinichthys_ is broad and flattened, with
pronounced rugosity on the gular area and isthmus. In _Gila_ the
underside of the head is convex, with comparatively smooth membranes;
the hybrid is intermediate, but tends toward _Gila_.

TABLE 4. COMPARISONS OF ONE SPECIMEN OF GILA NIGRESCENS × RHINICHTHYS
CATARACTAE WITH SPECIMENS OF THE PARENTAL SPECIES (MEANS ARE ABOVE,
RANGES IN PARENTHESES BELOW)

======================+==============+=================+=================
                      |    _Gila_    |                 |  _Rhinichthys_
                      | _nigrescens_ |     KU 4253     |  _cataractae_
----------------------+--------------+-----------------+-----------------
Standard lengths      |        66.4  |            60.6 |          59.5
                      |  (63.1-72.4) |                 |    (55.6-65.0)
                      |              |                 |
Head-length /         |        282   |           281   |          281
Standard length       |   (277-290)  |                 |     (273-293)
                      |              |                 |
Orbital length /      |        063   |           054   |          044
Standard length       |   (063-065)  |                 |     (041-047)
                      |              |                 |
Snout-length /        |        083   |           092   |          106
Standard length       |   (081-085)  |                 |     (099-113)
                      |              |                 |
Dorsal fin-height /   |        225   |           234   |          221
Standard length       |   (212-238)  |                 |     (206-234)
                      |              |                 |
Postorbital length /  |        140   |           135   |          131
Standard length       |   (134-142)  |                 |     (127-136)
                      |              |                 |
Distance from tip of  |              |                 |
mandible to tip of    |              |                 |
maxillary /           |        081   |           076   |          066
Standard length       |   (079-085)  |                 |     (064-069)
                      |              |                 |
Length of             |              |                 |
infralabial groove /  |        060   |           045   |          036
Standard length       |   (058-064)  |                 |     (034-038)
                      |              |                 |
Upper jaw             | protractile  | non-protractile | non-protractile
                      |              |                 |
Number scales in      |              |                 |
lateral line          |        60    |            63   |          65
                      |    (58-63)   |                 |      (63-67)
                      |              |                 |
Anal fin-rays         |        8     |             7   |          7
                      |     (7-8)    |                 |         (7)
                      |              |                 |
Pelvic fin-rays       |        9     |             8   |          8
                      |       (9)    |                 |       (8-9)
                      |              |                 |
Pectoral fin-rays     |        16    |         16-15   |          13
                      |    (16-18)   |                 |      (13-14)
                      |              |                 |
Pharyngeal teeth      |    2,5-4,2   |       2,5-4,2   |      2,4-4,2
----------------------+--------------+-----------------+-----------------

TABLE 5. COMPARISONS OF ONE SPECIMEN OF NOTROPIS V. VENUSTUS × NOTROPIS
WHIPPLEI WITH SPECIMENS OF THE PARENTAL SPECIES, AND WITH N. LUTRENSIS ×
N. V. VENUSTUS. MEASUREMENTS (LENGTHS AND DEPTHS) ARE EXPRESSED AS
THOUSANDTHS OF STANDARD LENGTH (MEANS ABOVE, RANGES IN PARENTHESES
BELOW)

Column headings:

A: _Notropis whipplei_
B: KU 3516
C: _Notropis venustus_, KU 3510
D: _Notropis venustus_, from Gibbs (1957a)
E: _Notropis lutrensis_ × _N. venustus_

=================+=============+=========+=============+=========+=============
                 |      A      |    B    |      C      |    D    |      E
-----------------+-------------+---------+-------------+---------+-------------
Standard length  |       50.6  |    47.8 |       47.3  |         |       44.7
                 | (45.0-54.0) |         | (44.5-49.6) |         | (43.3-47.3)
                 |             |         |             |         |
Predorsal length |       525   |    523  |       534   |    523  |       532
                 |  (513-535)  |         |  (519-547)  |         |  (528-538)
                 |             |         |             |         |
Dorsal origin to |             |         |             |         |
caudal base      |       497   |    508  |       497   |    496  |       508
                 |  (493-502)  |         |  (478-504)  |         |  (502-514)
                 |             |         |             |         |
Prepelvic length |       505   |    492  |       505   |         |       499
                 |  (498-518)  |         |  (500-510)  |         |  (486-517)
                 |             |         |             |         |
Head-length      |       257   |    255  |       261   |    260  |       263
                 |  (250-262)  |         |  (256-267)  |         |  (261-267)
                 |             |         |             |         |
Caudal           |             |         |             |         |
peduncle-length  |       217   |    221  |       224   |         |       224
                 |  (211-220)  |         |  (213-230)  |         |  (214-231)
                 |             |         |             |         |
Caudal           |             |         |             |         |
peduncle-depth   |       110   |    119  |       127   |    125  |       126
                 |  (106-116)  |         |  (124-133)  |         |  (122-131)
                 |             |         |             |         |
Head-depth       |       170   |    182  |       186   |         |       190
                 |  (167-173)  |         |  (182-190)  |         |  (189-192)
                 |             |         |             |         |
Snout-length     |       079   |    079  |       080   |         |       081
                 |  (076-083)  |         |  (072-083)  |         |  (078-082)
                 |             |         |             |         |
Eye-diameter     |       069   |    069  |       070   |  073[A] |       070
                 |  (063-078)  |         |  (066-072)  |         |  (068-074)
                 |             |         |             |         |
Postorbital      |             |         |             |         |
length, head     |       112   |    115  |       116   |         |       117
                 |  (108-115)  |         |  (112-120)  |         |  (115-120)
                 |             |         |             |         |
Upper jaw,       |             |         |             |         |
length           |       078   |    077  |       081   |    079  |       077
                 |  (076-081)  |         |  (076-082)  |         |  (076-081)
                 |             |         |             |         |
Body depth       |       239   |    253  |       278   |    274  |       282
                 |  (233-248)  |         |  (261-288)  |         |  (275-294)
                 |             |         |             |         |
Lateral-line     |             |         |             |         |
scales           |     36-37   |     36  |     36-38   |    36.5 |
                 |             |         |             | (34-39) |
                 |             |         |             |         |
Scales above     |             |         |             |         |
lateral-line     |        13   |     14  |        15   |     15  |
                 |             |         |             | (13-16) |
                 |             |         |             |         |
Anal fin-rays    |         9   |      9  |         8   |     8   |
                 |             |         |             |  (7-8)  |
                 |             |         |             |         |
Pectoral         |             |         |             |         |
fin-rays         |        14   |  14-14  |        15   |    14.2 |
                 |    (14-15)  |         |    (14-16)  | (12-17) |
                 |             |         |             |         |
Caudal spot      | Absent      | Present | Present     | Present | Present
                 |             |         |             |         |
Vertebrae        |     37-38   |     38  |        37   |         |
-----------------+-------------+---------+-------------+---------+-------------

[A] Orbital diameter.

The air bladder of KU 4253 is nearly as large as in _Gila_, and much
larger than the degenerate air bladder of _R. cataractae_. Although the
hybrid appears to be male, the gonads (especially the right one) are
poorly developed. The hybrid is intermediate in curvature of the lateral
line, which is nearly straight in _Rhinichthys_ and strongly decurved in
_Gila_.

Specimen No. 4253 is mostly pallid, resembling _Gila_ much more than
_Rhinichthys_ in pigmentation. A mid-dorsal dark streak is conspicuous
in the hybrid, especially anteriorly, but is less intense than in
_Gila_. _Rhinichthys_ lacks a well-developed dorsal stripe. The
preorbital and suborbital areas are more heavily pigmented in the hybrid
than in _Gila_, but not nearly so dark as in _Rhinichthys_. The hybrid
has a faint dark basicaudal spot that is variably developed in
_Rhinichthys_ but absent in _Gila_.

=_Notropis venustus venustus_ × _Notropis whipplei_=: KU 3516 (a male,
47.8 mm. in standard length), from Arkansas, Sevier Co., Winters Creek
where it is crossed by U. S. Highway 71, 5 mi. N of Little River Bridge,
March 8, 1956. Compared in Table 5 with four specimens of _N. whipplei_,
KU 3517 (45.0-52.6 mm. in standard length, mean 50.6 mm.), same locality
and date as KU 3516; four specimens of _N. v. venustus_, KU 3510
(44.5-49.6 mm. in standard length, mean 47.3 mm.), Louisiana, Winn
Parish, Little Naches Bayou on U. S. Highway 71, 8.8 mi. NW Montgomery,
March 4, 1956; three specimens of _Notropis lutrensis_ (Baird and
Girard) × _N. v. venustus_, KU 3510 (43.3-47.3 mm. in standard length,
mean 44.7 mm.), same locality and date as _N. v. venustus_ above; and
with tabulated data on _N. v. venustus_ from Gibbs (1957a:185-186). All
specimens are from the lower Red River Drainage; other series of _N.
whipplei_, _N. venustus_, and _N. lutrensis_ × _N. venustus_, from the
Red River Drainage and elsewhere, were examined but are not tabulated
because of differences in size, and because of geographic variability
that has been discussed by Gibbs (1957a).

The Subgenus _Cyprinella_ of _Notropis_, to which _N. venustus_ and _N.
whipplei_ belong, has been studied intensively by Gibbs (1957a and b).
_Notropis venustus_ differs conspicuously from _N. whipplei_ in having a
large dark basicaudal spot; also, _N. venustus_ usually has 8 (rather
than 9) anal rays, and 15 (rather than 13) scales above the lateral line
immediately anterior to the dorsal fin. Specimens of _N. v. venustus_
from the Red River Drainage, where the most robust representatives of
the species are found, differ from _N. whipplei_ in depth of head, body,
and caudal peduncle (Table 5).

KU 3516 has a composite of the 9-rayed anal fin of _N. whipplei_ and the
caudal spot (albeit diffuse) of _N. venustus_; and, the hybrid is
intermediate in body-proportions that distinguish the two species,
especially depth of head, body, and caudal peduncle. In other features
KU 3516 has values within the overlapping ranges of variation of
_whipplei_ and _venustus_ except that the ratio of postdorsal length to
standard length is extremely long in the hybrid, and the ratio of
prepelvic length to standard length is extremely short (Table 5). Both
extreme values for the hybrid seem to result from the cumulative
influence of characters in which the parental species differ slightly in
mean value (especially head-length, in which the hybrid is like
_whipplei_, and caudal peduncle-length, in which the hybrid approaches
_venustus_, despite the 9-rayed anal fin of the hybrid). The basicaudal
spot of the hybrid is like that of _N. v. venustus_ except for being
less intense.

_Notropis venustus_ hybridizes extensively with _N. lutrensis_ (Hubbs,
Kuehne, and Ball, 1953:226-230; Hubbs and Strawn, 1956), and that
combination occurs in streams near the locality where KU 3516 was taken.
KU 3516 resembles _N. lutrensis_ × _N. v. venustus_ in many ways, but is
more slender than the latter hybrid. The depth of head, body, and caudal
peduncle are greater in _N. lutrensis_ than in _N. venustus_ (much
greater than in _N. whipplei_); therefore, specimens of _N. lutrensis_
× _N. venustus_ are usually deeper than _N. venustus_, whereas KU 3516
is less deep. KU 3516 has a rather sharp snout and thin, straight lips
that are strongly suggestive of _N. whipplei_, rather than _N.
lutrensis_, in which the snout is rounded and the lips are more
obliquely decurved. There is less pigment underlying the anterior
lateral-line scales in KU 3516 than in _N. lutrensis_ × _N. venustus_,
and melanophores on the scale-pockets of KU 3516 are arranged in
narrower, more distinct submarginal bars than in _N. lutrensis_ × _N.
venustus_. Because of the difference in pigmentation, the lateral scales
of _N. whipplei_ (and of KU 3516) appear more narrowly diamond-shaped
than the lateral scales of _N. lutrensis_ or _N. lutrensis_ × _N.
venustus_. The lengths and heights of the scales are approximately the
same in all three species.

Winters Creek, where KU 3516 was taken, flowed approximately five cubic
feet per second at the time our collection was made; a landowner on the
stream stated that it had been dry, except for pools, in the previous
two summers. The water was somewhat gray, but nearly clear. The habitat
consisted mainly of short riffles, with average depth of four inches,
and pools to depths of two feet. Twelve species of fish, including _N.
whipplei_ but not _N. lutrensis_ or _N. venustus_, were found; other
minnows were _Semotilus atromaculatus_, _N. chalybaeus_, _N. cornutus_,
_N. umbratilis_, and _Campostoma anomalum_.



LITERATURE CITED


EVANS, H. E., and DEUBLER, JR., E. E.

    1955. Pharyngeal tooth replacement in _Semotilus atromaculatus_
          and _Clinostomus elongatus_, two species of cyprinid
          fishes. Copeia, 1955 (1):31-41, February 18.

GIBBS, JR., R. H.

    1957a. Cyprinid fishes of the Subgenus _Cyprinella_ of
          _Notropis_. III. Variation and subspecies of _Notropis
          venustus_ (Girard). Tulane Studies in Zoology,
          5(8):175-203, August 7.

    1957b. Cyprinid fishes of the Subgenus _Cyprinella_ of
          _Notropis_. I. Systematic status of the Subgenus
          _Cyprinella_, with a key to the species exclusive of the
          _lutrensis-ornatus_ complex. Copeia, 1957(3):185-195,
          August 26.

HAY, O. P.

    1888. A contribution to the knowledge of the fishes of Kansas.
          Proc. U. S. Nat. Mus., 10:242-253, March 1.

HUBBS, C. L.

    1951. Identification of cyprinid fish reported from Kansas as
          _Squalius elongatus_. Trans. Kansas Acad. Sci.,
          54(2):190-192, June 15.

    1955. Hybridization between fish species in nature. Systematic
          Zoology, 4(1):1-20, March.

HUBBS, C. L., and LAGLER, K. F.

    1958. Fishes of the Great Lakes Region. Cranbrook Inst. Sci.,
          Bull. 26, revised ed., xiii + 213 pp.

HUBBS, C. L., and MILLER, R. R.

    1943. Mass hybridization between two genera of cyprinid fishes
          in the Mohave Desert, California. Papers Michigan Acad.
          Sci., Arts, and Lett., 28(1942):343-378, pls. 1-4,
          February.

HUBBS, C.

    1956. Relative variability of hybrids between the minnows,
          _Notropis lepidus_ and _N. proserpinus_. Texas Jour.
          Sci., 8 (4):463-469, December.

HUBBS, C., KUEHNE, R. A., and BALL, J. C.

    1953. The fishes of the upper Guadalupe River, Texas. Texas
          Jour. Sci., 5(2):216-244, June.

HUBBS, C., and STRAWN, K.

    1956. Interfertility between two sympatric fishes, _Notropis
          lutrensis_ and _Notropis venustus_. Evolution,
          10(4):341-344, December.

JOHNSON, R.

    1945. Ever hook a hybrid? Minnesota Conservation Volunteer,
          8(49): 18-22.

MINCKLEY, W. L.

    1956. A fish survey of the Pillsbury Crossing Area, Deep Creek,
          Riley County, Kansas. Trans. Kansas Acad. Sci.,
          59(3):351-357, October 31.

    1959. Fishes of the Big Blue River Basin, Kansas. Univ. Kans.
          Publ., Mus. Nat. Hist., 11(7):401-442, May 8.

MINCKLEY, W. L., and CROSS, F. B.

    1959. Distribution, habitat, and abundance of the Topeka
          shiner, Notropis topeka (Gilbert) in Kansas. Amer.
          Midl.-Nat., 61(1):210-217.

TRAUTMAN, M. B.

    1957. The fishes of Ohio. Ohio State Univ. Press, xviii + 683
          pp.


_Transmitted March 2, 1960._

28-3424





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