p. brasiliensis P. aztecus subtilis 



P. setiferus 



P. aztecus aztecus 



t 



c 

 d 



«• 

 %'■•*. 



Figure 4. — Zymogram comparing PGM bands b through d (bands a and e not shown) in Penaeus brasiliensis, P. aztecus subtilis, P. 

 aztecus aztecus, and P. setiferus. Direction (f) of protein migration toward the anode (+) is shown. 



phenotype categories, but with data for sexes 

 combined, the phenotype distribution of P. aztecus 

 subtilis deviated significantly (x^ = 7.086, 

 0.025<P<0.05) from that expected from 

 Hardy-Weinberg equihbrium (Stern 1943). The 

 reason for this deviation is not known. Johnson et 

 al. (1974) noted a deviation from Hardy-Weinberg 

 expectation for PGM phenotype distribution of a 

 pandahd shrimp Pandalus hypsinotus Brandt, in 

 Alaska, and they suggested that it might be re- 

 lated to depth of capture as found in, Pacific 

 ocean perch, Sebastodes alutus (Johnson et al. 

 1971). 



Our study provided an opportunity to compare 

 the subspecies P. aztecus subtilis and P. aztecus 

 aztecus, therefore distribution of PGM pheno- 

 types and frequency of PGM alleles for the lat- 

 ter subspecies (data adapted from Proctor et al. 

 1974) also are shown in Table 1. This comparison 

 is based on the assumption that bands a and e as 

 well as bands b, c, and d are similar in the two 

 species. However, even if this is not the case, the 

 small frequencies of the rare a and e alleles would 

 not appreciably affect the comparison. Both sub- 

 species exhibited eight phenotypes, but not all 

 were the same. Phenotype ad was detected in P. 

 aztecus subtilis but not in P. aztecus aztecus. 

 Phenotype ac was detected in the latter but not in 

 the former. With phenotypes grouped into 

 categories cc, ex, and xx, and with sexes com- 

 bined, a chi-square contingency test detected a 

 significant (P<0.05) difference in phenotype dis- 

 tribution between the subspecies, and this result 



provides an additional characteristic to existing 

 evidence of differences between these subspecies 

 (see Perez Farfante 1969). 



This and previous studies by Proctor et al. 

 (1974) and Marvin and Caillouet (1976) suggest 

 that zymogram analysis may provide a useful 

 tool in the study of population genetics of the 

 Penaeidae. The wide distribution (Mistakidis 

 1968), commercial importance, and relatively 

 short generation time of the Penaeidae should 

 make them particularly attractive subjects of 

 study by population geneticists. 



Acknowledgments 



Through initial efforts by Raphael R. Proctor, 

 Jr., Gulf Coastal Fisheries Center, National 

 Marine Fisheries Service (NMFS), Galveston, 

 Tex., this study was made possible. His helpful 

 suggestions were greatly appreciated. We are 

 grateful to Albert C. Jones, Alexander Dragovich, 

 and Donald M. Allen, Southeast Fisheries Center, 

 NMFS, Miami, Fl., for providing specimens for 

 this study. Fred M. Utter, Northwest Fisheries 

 Center, NMFS, Seattle, Wash., reviewed the 

 manuscript. Frank Patella conducted the statisti- 

 cal analyses for the study. 



Literature Cited 



Johnson, a. G., F. M. Utter, and H. O. Hodgins. 



1971. Phosphoglucomutase polymorphism in Pacific ocean 

 perch, Sebastodes alutus. Comp. Biochem. Physiol. 

 39B:285-290. 



456 



