EFFECT OF p,p -DDT ON DEVELOPMENTAL STABILITY OF 

 PECTORAL FIN RAYS IN THE GRUNION, LELRESTHES TENUIS 



David W. Valentine' and Michael Soule^ 



ABSTRACT 



Experiments are described that test the validity and utility of using bilateral asymmetry for 

 the early detection of environmental deterioration. The first experiment, using a continuously 

 flowing water system, was designed to test the effects of a ubiquitous pollutant, p,p'-DDT, on 

 the pectoral fin ray asymmetry of grunion, Leuresihes tenuis, fry. Toxicant concentrations 

 ranged from a low of 0.001 to a high of 500 parts per billion. The two highest p,p'-DDT con- 

 centrations, 100 and 500 parts per billion, proved lethal to grunion fry. For the other concen- 

 trations, increases in pectoral fin ray asymmetry with increasing toxicant concentration were 

 observed. Increases in asymmetry were statistically significant. 



The second experiment, which utilized a recirculating static water system, was designed to 

 determine inherent differences in the level of pectoral ray fin asymmetry in fish from different 

 localities. Results for grunion fry paralleled previously published results for adult grunion. 

 Grunion from the relatively polluted southern California region had higher asymmetry levels 

 than did those from Baja California. The significance of these results as they relate to the 

 general question of asymmetry as a statistical indicator of environmental stress is discussed. 



Asymmetry of bilateral characters has been pro- 

 posed as a morphological measure of environ- 

 mental stress in fish populations (Valentine, 

 Soule, and Samollow, 1973). The theory under- 

 lying such an analysis is that various environ- 

 mental stresses may reduce the efficiency of 

 developmental homeostatic mechanisms, thus 

 leading to an average increase in the within- 

 individual variation of morphological structures 

 (Adams and Niswander, 1967). An asymmetry 

 index, then, might provide a relative estimate of 

 the physiological stress to which a population is 

 being subjected. 



Data from three wild-caught fish species 

 supporting this hypothesis have previously been 

 presented (Valentine, Soule, and Samollow, 

 1973). We now present experimental results 

 supporting the theory. 



METHODS AND MATERIALS 



Grunion, Leiiresthes tenuis, were chosen as 



' Department of Biology, University of California, San 

 Diego, La Jolla, CA 92037; present address: Dames & 

 Moore, 1100 Glendon Avenue, Suite 1000, Los Angeles, 

 CA 90024. 



- Department of Biology, University of California, San 

 Diego, La Jolla, CA 92037. 



Manuscript accepted May 1973. 



FISHERY BULLETIN: VOL. 71, NO. 4, 1973. 



our experimental organism. Grunion are small, 

 rapidly maturing, marine atherinids endemic to 

 the Californias. They possess many features 

 which make them attractive as a laboratory 

 organism. Grunion spawn biweekly on sandy 

 beaches during the high tides from late Feb- 

 ruary or early March through August or Sep- 

 tember, and wild-spawned eggs may be easily 

 collected by digging in wet sand after such a 

 spawning run. The eggs mature into fry in about 

 10 days (Walker, 1952). Fry are large and easily 

 maintained in the laboratory. 



The approximate straight-line distances in 

 miles to the localities mentioned in this paper 

 from Point Fermin, the prominent point located 

 adjacent to the entrance of the Los Angeles Har- 

 bor, are Belmont Shore, 9; Del Mar, 87: La 

 Jolla Shores. 91; San Diego. 101; and Bahia 

 San Quintin, 270. All of these localities are 

 south of Point Fermin. 



The toxicant chosen was p,p-DDT(l,l,l-tri- 

 chloro-2,2-bis(p-chlorophenyl) ethane), the meta- 

 bolic products of which are known to be ubiqui- 

 tous in the world ecosystem (Risebrough, Hug- 

 get, Griffin, and Goldberg, 1968). Such com- 

 pounds are found in fairly high concentrations 

 in marine organisms from California waters 



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