66 
PACIFIC SCIENCE, Vol. XVII, January 1963 
TABLE 8 
Axial Deformities in Gillichthys mirabilis 
FROM S ALTON SEA 
MONTH 
TOTAL 
FISH 
DEFORMED 
FISH 
PERCENT 
DEFORMED 
1955 
April 
19 
5 
26 
May 
98 
26 
27 
June 
124 
34 
27 
July 
37 
11 
30 
August 
45 
14 
31 
October 
15 
8 
53 
December 
98 
36 
37 
1956 
January 
136 
33 
24 
February 
32 
8 
25 
The Gulf fish have higher fins and longer jaws, 
the head is more depressed, and they tend to be 
more completely scaled verier ally and have 
slightly larger scales. The head is shorter, how- 
ever. Except for the slightly shorter head length, 
the form of mirabilis from the Gulf is consistent 
with a hypothesis of rapid development. As seen 
in the fish from the Salton Sea, shorter head 
length is correlated with lower fins, shorter jaws, 
and reduced scalation, and presumably this has 
resulted from retarded development. If, as sug- 
gested, the Gulf fish differ morphologically be- 
cause of faster development, then they should 
have longer, not shorter, heads. This contradic- 
tion probably stems from genetic differences. 
No satisfactory explanation can be given for 
the distinctly greater distance between dorsal 
fins of the specimens of mirabilis from the up- 
per Gulf as compared with the other popula- 
tions. The form of the fish from the upper Gulf, 
however, resembles that of fish from the lower 
Gulf, except for the distance between dorsal 
fins. Environmentally induced changes usually 
manifest themselves in several ways, instead of 
being expressed in one character only. The in- 
creased space between dorsal fins, therefore, 
most likely has a genetic basis. 
Countable characters 
One of the commonly accepted generaliza- 
tions in ichthyology is that the number of ele- 
ments in serially repeated characters tends to 
be greater at higher latitudes (Vladykov, 
1934: 102). Hubbs (1922, 1926) argued that 
this relationship depends chiefly on the tem- 
perature of the water during early development; 
lower temperatures were thought to result in 
increasing numbers of elements, and higher 
temperatures in lower numbers. Local temper- 
ature conditions have been observed to be asso- 
ciated with the anticipated changes in counts 
(reviewed in Barlow, 1961$). Moreover, any 
factor of the environment affecting rate of de- • 
velopment, such as salinity or oxygen tension, 
seems to have effects similar to those thought 
to be produced by the thermal regime (Hubbs, 
1926; Taning, 1952; Seymour, 1956). 
There are exceptions, however, where the 
change in counts goes contrary to- expectations. 
In certain instances (Schmidt, 1919: 148; 
Hubbs, 1921: 150; 1924; Schultz, 1927: 420) 
the counts from one fin only showed an increase 
associated with warmer temperatures. The other 
fins manifested the normal negative correlation 
between number of elements and water tem- 
perature. 
In spite of laboratory findings that the rela- 
tionship between meristic structures and devel- 
opmental temperatures is exceedingly complex, 
the pattern in natural populations of the same 
species is usually straightf orward : higher tem- 
peratures during development normally bring - 
about lower counts (Barlow, 1961$). 
At first glance the changes in countable char- 
acters over the geographic range of mirabilis 
seem to indicate a gradient resulting from direct 
modification by the environment. Presumably, 
factors which cause a decrease in the dorsal and 
anal fin counts conversely bring about an in- 
crease in the number of pectoral fin rays. 
Geographically, then, the number of median 
fin rays is negatively correlated with the num- 
ber of pectoral fin rays. Johnsen (1936: 8-9) 
reported the same relationship between fins for 
various populations of Gobius flavescens and 
Gobius minutus .. These changes could be con- 
strued as the result of dissimilar water tempera- 
tures or some related factors. 
It is more probable, nonetheless, that the 
cline in meristic characters results primarily 
from different genotypes, not exclusively from 
environmental modification. This hypothesis can 
