VALENTINE, SOULE, and SAMOLLOW: ASYMMETRY ANALYSIS IN FISHES 



Arguments Against 

 Category B Hypotheses 



If asymmetry were to correlate well with 

 mean annual water temperature, we would 

 expect that it should continue to increase with 

 latitude. Our data for barred surf perch are 

 inconsistent with this hypothesis, as are those of 

 Hubbs and Hubbs (1945), who have conducted 

 the only large-scale study of asymmetry en- 

 compassing a large latitudinal transect. Hubbs 

 and Hubbs (using a statistic differing from that 

 used here) studied the asymmetry of pectoral 

 fin rays in the Pacific staghorn sculpin, Lep- 

 tocottus armatus, from Sitkalidak Island, 

 Alaska, to Mission Bay, in southern California. 

 Of the 12 populations examined, the highest 

 asymmetry values were from their southern 

 most samples, Anaheim and Mission Bays in 

 southern California (Table 10). The Tau coef- 

 ficient (Snedecor, 1956), applied to these data, 

 indicate a significant negative asymmetry cor- 

 relation, P < 0.05, with increasing latitude. 



Finally, not only are asymmetry values in- 

 creasing clinally, they also appear to be in- 

 creasing temporally. We know of no environ- 

 mental variable showing these continuous 

 trends. Most variables show cyclic fluctuations, 

 whereas our asymmetry values apparently 

 do not. 



Arguments for 

 Category C Hypotheses 



This hypothesis assumes only that as environ- 

 mental stress increases so should asymmetry. 

 At this point in time we must leave unspecified 

 what type of stress may produce increases in 

 asymmetry, although preliminary experiments 

 with grunion would seem to indicate that 

 p,p-DDT may have this effect (Valentine and 

 Soule, 1972). 4 As a first approximation, we 

 might assume that specific ubiquitous pollu- 

 tants known to interfere with various metabolic 

 processes might logically be suspect. Two such 

 groups of agents are known to occur in the 

 southern California environment (marine, ter- 

 resterial, and atmospheric), chlorinated hydro- 

 carbons (Risebrough et al., 1967; Schmidt, 



Table 10. — Pectoral fin ray asymmetry in the Pacific 

 staghorn sculpin, LeptucottH.s arniutns.^ 



•* Valentine, D. W., and M. Soule. 1972. Asymmetry: 

 The effect of p, p'-DDT on the development of fins in the 

 grunion (Leuresthes tenuis). Unpublished manuscript. 



' Data recalculoted from Hubbs and Hubbs (1945, Tables VII 

 and VIII). 



- Hubbs and Hubbs used this statistic to express "the amount 

 of overall asymmetry ... as a percentage figure in which / and 

 '■ represent counts that are higher ... on the left and right 

 sides, respectively, and N is the total number of specimens, 

 symmetrical plus asymmetrical, in the sample." 



Risebrough, and Gress, 1971; Duke and Wilson, 

 1971; Burnett, 1971; Munson. 1972) and heavy 

 metals (Tatsumoto and Patterson, 1963; Brooks, 

 Presley, and Kaplan, 1967; Schroeder, 1971; 

 Galloway, 1972). The distribution of pollutants 

 in southern California waters is similar to the 

 distribution of asymmetry values (Burnett, 

 1971; Galloway, 1972). This hypothesis would 

 attribute the increases in asymmetry in the 

 species studied to the presence of pollutants and 

 possibly to duration of exposure. 



Arguments Against 

 Category C Hypotheses 



The only contraindicative evidence thus far 

 is that if these asymmetries were the result of 

 toxicants, we might expect to find behavioral 

 and reproductive effects. None has as yet been 

 observed, although our preliminary observa- 

 tions on the low viability of first spawned 

 grunion eggs is suspicious (Valentine and 

 Soule, see footnote 4). 



CONCLUSIONS 



Several of the explanations presented assume 

 a genetic origin of the asymmetries and involve 

 altered demographic parameters: improved 

 conditions leading to population growth; de- 



367 



