SHAKLEE and SAMOLLOW: GENETIC VARIATION IN SPINY LOBSTER 



pooled). Only one out of these seven contingency x 2 

 tests was significant — Pep-1 (x 2 x = 4.50 P < 0.05). 

 Thus, in spite of the considerably larger sample 

 sizes resulting from pooling, there is still no strong 

 evidence of stock heterogeneity. 



The third analysis involved the three cases of 

 year-to-year differences in Umb allele frequency 

 (Table 3). In each of the three cases, the frequency 



TABLE 3. — Umbelliferyl esterase allele frequencies in Panul- 

 irus marginatus at three localities in successive years. 



of the two rare alleles (allelic classes) was higher 

 in the 1980 collections than in those from 1979. 

 When the rare alleles were pooled to allow x 2 tests 

 of the distributions, all three cases exhibited sig- 

 nificant year-to-year changes: Kure Atoll A vs. B 

 (X 2 i = 3.85 P 0.05), Maro Reef A vs. B 

 (X 2 i = 4.44 P < 0.05), and Necker Island A vs. B 

 (X 2 j = 5.81 P < 0.025). However, when allele dis- 

 tributions were compared among localities in 

 either 1979 or 1980 (or in pooled 1979 + 1980) no 

 significant differences between localities were ob- 

 served. These results suggest annual fluctuations 

 in Umb allele frequency within at least the NWHI. 

 Unfortunately the sample sizes from the main 

 Hawaiian Island localities were not large enough 

 to be subdivided by year to see whether or not this 

 annual fluctuation in Umb allele frequency oc- 

 curred there also. Given that statistically signifi- 

 cant annual fluctuations in Umb allele frequency 

 were occurring at all three localities where this 

 could be tested, it is important that they were 

 parallel and did not lead to any significant differ- 

 ences in allele frequency between localities. This 

 pattern of fluctuating allele frequency, common to 

 the three NWHI localities, argues for the exis- 

 tence of a single panmictic lobster population 

 throughout this region and suggests that a cohort 

 having "unusual" Umb allele frequency was re- 

 cruited into the fishery throughout the NWHI in 

 1980. 



DISCUSSION 



Electrophoretic studies of genetic variation 

 have been reported for several decapod crustacean 

 species. With the exception of Panulirus argus 

 (Menzies 1981), all species that have been 

 examined exhibit relatively little genetic diver- 

 sity either within or between populations (Tracey 

 et al. 1975; Mulley and Latter 1980; Nelson and 

 Hedgecock 1980; Redfield et al. 1980; Smith et al. 

 1980; Hanley 1980). Nevertheless, several of the 

 enzymes found to be polymorphic in P. margina- 

 tus in the present study have been shown to be 

 variable in other decapods. Because of their 

 relevance to the genetic interpretations in the 

 present investigation, published accounts of 

 genetic variation for these enzymes are summa- 

 rized below. 



Esterases (EST). Nearly all species of decapod 

 crustaceans studied to date exhibit multiple es- 

 terases which hydrolyze naphthol esters. In many 

 species, one or more esterase loci are reported to be 

 polymorphic and, in virtually all published 

 studies where banding patterns of heterozygotes 

 have been described, the variable esterases ap- 

 pear to be monomeric proteins (Menzies and Ker- 

 rigan 1979b). Analysis of the mode of inheritance 

 of variable esterases has only been accomplished 

 for one esterase locus in decapods (Hedgecock et al. 

 1975). This locus exhibited simple Mendelian 

 segregation of alleles. The genetic interpretation 

 of EST-3 variation in P. marginatus (single- and 

 double-banded phenotypes) is consistent with 

 these findings. Since there have been no published 

 reports of UMB (= EST-D) variation in decapod 

 crustaceans, the observed variation in UMB in P. 

 marginatus must stand on its own. However, as 

 shown in Figure 2, the staining intensities of the 

 three isozymes in presumed heterozygotes are ap- 

 proximately those expected for a dimeric enzyme 

 (i.e., 1:2:1). Furthermore, as noted above, no devia- 

 tions from Hardy- Weinberg expectations were ob- 

 served for this enzyme. 



Glucosephosphate Isomerase (GPI). The en- 

 zyme glucosephosphate isomerase is frequently 

 variable in decapod crustaceans. Although as 

 many as three loci have been reported in decapods, 

 most investigations have focused on a single locus 

 whose apparently dimeric protein product is pre- 

 dominant in muscle extracts. The inheritance of 

 this enzyme in Homarus americanus follows a 

 simple Mendelian pattern (Hedgecock et al. 1975). 

 It would appear that the polymorphic GPI in P. 



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