FISHERY BULLETIN: VOL. 74, NO. 3 



provide biochemical evidence for the taxonomic 

 relationship among four members of the genus 

 Cynoscion (including the degree of divergence), 

 and to compare this information with existing 

 phylogenetic schemes. Although no attempt has 

 been made to construct a phylogeny based on 

 biochemical data, qualitative differences (and 

 similarities) allow some taxonomic conclusions to 

 be drawn. 



Serum Proteins 



Environmentally induced changes in blood ser- 

 um components have been well substantiated 

 (Thurston 1967). This evidence, nonetheless, would 

 not preclude blood serum patterns from being a 

 useful taxonomic tool if one additional step is 

 taken. It is obvious that the classical mor- 

 phologists in comparing populations of animals (or 

 plants) are including the influence of the environ- 

 ment in the range of variation they are describing. 

 For example, it is commonly observed that counts 

 of meristic characters (fin rays, scales, etc.) in- 

 crease in the northerly direction of the animal's 

 range (in the Northern Hemisphere). This, how- 

 ever, will not affect the conclusions drawn as long 

 as sufficient samples are taken to cover the full (or 

 nearly so) range of variation in the population. 

 Once adequate samples are obtained, accurate 

 modes may be calculated for each character and 

 the relationship between two forms established. 

 Within this framework utilization of highly var- 

 iable patterns such as that found for serum pro- 

 teins are justified. 



In this study we have been able to sample only a 

 relatively small number of each species, with the 

 exception of C. nebulosus (Table 2). Hence, any 

 conclusions regarding the biochemical relation- 

 ship among the four taxa must be provisional. 



Although the blood patterns of the species of 

 Cynoscion are somewhat more variable than has 

 been reported for many fishes and other verte- 

 brates, we can present evidence for relationships 

 among the Gulf of Mexico and Atlantic Ocean 

 seatrouts. The Taxonomic distances calculated for 

 members of this genus are listed in Table 2. The 

 value (54.7) for the alleged cognates, C. arenarius 

 and C. regalis, is surpassed only by the value (43.9) 

 for C. nothus and C. regalis. Only 10 bands of the 

 41 present were unique to one of the four species; 7 

 were found in C. nebulosus, 2 in C. nothus, and 1 in 

 C. regalis. Cynoscion arenarius did not display 



any species-specific bands. Therefore, a consider- 

 able portion of the differences among the four 

 seatrouts, as expressed by 4^, are generated by 

 different percentage compositions of the serum 

 proteins. 



The similar values obtained for C. regalis and C. 

 nothus may be interpreted in three ways: 1) these 

 species may actually be more closely related than 

 are C. regalis and C. arenarius; 2) similar envi- 

 ronmental selection pressures have produced an 

 example of ecological convergence; 3) sample size 

 may be insuflRcient to yield accurate results. Three 

 of the 19 samples of C. regalis were taken from the 

 same estuary (Wassaw Sound) as were all samples 

 of C nothus; the remaining sera from C. regalis 

 were collected in an estuary (Peconic Bay) sharing 

 several physical and chemical parameters with 

 Wassaw Sound (Odum et al. 1974). Thus, a measure 

 of ecological convergence may be involved. Similar 

 reasoning might explain the d,f, calculated for C. 

 arenarius versus C. nothus; the value (63.8) might 

 be reduced if several other gulf populations of C. 

 nothus were added to the total sample. 



It could be argued that the much larger sample 

 of C. nebulosus (n = 500) was responsible for most 

 of the difference in the taxonomic distance value 

 since rare bands are being included. This could 

 only be the case for band 38 which occurred in only 

 2.1% of the specimens sampled. The values (per- 

 cent occurrence) of the remaining six unique 

 bands (8%, 23%, 66%, 67%, 89%, 89%) argue against 

 this possibility. The average value of 72.8 is 

 therefore taken to mean that C. nebulosus is the 

 most divergent of the four species investigated. 

 Possible reasons for this observation have been 

 elaborated previously. 



A significant observation in our study is that 

 relatively few species-specific (i.e., unique) pro- 

 teins have been detected, a phenomenon not 

 without precedence, however (Lewontin 1974). In 

 a study of 10 species of Drosophila, the number of 

 unique proteins ranged from 2.6 to 28.2%, with an 

 average of 14.3% (Hubby and Throckmorton 1968). 

 Our own figures compare favorably with these: C 

 nebulosus, 23%; C nothus, 7%; C. regalis, 5%; and C. 

 arenarius, 0%. 



Eye Lens Proteins 



In a review of intraspecific variation in lens 

 proteins. Day and Clayton (1973) detected no 

 polymorphisms and concluded that observed dif f er- 



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