FISHERY BULLETIN: VOL. 71, NO. 1 



Table 1. — Summary of changes in ash and caloric content of decalcified and nontreated 

 tissues of some estuarine molluscs. In each case, six organisms were combined and six 

 caloric measurements made for each combined sample. HCl treatments were for 15 min. 



Organism 



Collection 

 area 



Treatment 



Ash 



% 



kcal/g 



ash-free 



dry weight 



±: Standard 

 deviation 



'Significantly different at the 0X)5 level. 



Significant differences in energy content be- 

 tween phyla were observed on the basis of ash- 

 free dry weights and live weights. The phyla 

 show an orderly phylogenetic progression of 

 energy content only on the basis of live weight 

 (Table 2). This is partially the result of de- 

 creasing water content of more structurally ad- 

 vanced phyla; we observed significant differen- 

 ces among phylum means for water content 

 which followed a similar trend. Not all phylum 

 means were significantly different, however. The 

 significant overall phylum effect can be attri- 



Table 2. — Analysis of variance of energy content, in 

 kilocalorie per gram live weight, for all species examined, 

 and listed in Appendix Table 1, and the mean kilocalorie 

 per gram live weight for each taxon. 



Source of 

 variation 



Degrees of 

 freedom 



Mean 

 square 



F ratio 



Among phyla 

 V^ithin phyla 

 Total 



5 



87 

 92 



2.494 

 0.073 

 2.567 



34.01** 



Phylum 



Mean kcal/g 

 live weight 



Ctenophora 



Mollusca 



Echinodermata 



Annelida 



Arthropoda 



Chordota 



0.049 

 0.373 

 0.393 

 0.850 

 1.027 

 1.156 



"Significant at the 0.01 levd. 



buted to ctenophores' having a significantly low- 

 er energy content than the annelids, arthropods, 

 and chordates, but there are no significant dif- 

 ferences among the foregoing three phyla nor 

 among the ctenophores, echinoderms, and mol- 

 luscs (Table 2). Also, within the phylum Mol- 

 lusca and the class Crustacea the more advanced 

 or more specialized groups (Cephalopoda and 

 Decapoda) had significantly higher caloric con- 

 tents per gram live weight than the less advanced 

 groups. Although the values we obtained in this 

 study may have resulted from a fortuitous selec- 

 tion of organisms, we feel that the species an- 

 alyzed are representative of their phyla and thaP 

 the relation between caloric content, percent dry 

 weight, and percent organic matter, and the 

 phylogenetic position reflects an evolutionary 

 trend for increased caloric content per gram live 

 weight as a result of increased proportion of 

 living tissue with increasing phylogenetic posi- 

 tion. 



The differences in caloric content may have 

 arisen from variation in the growth or reproduc- 

 tive stage, or the energy content of the food 

 source. The ctenophores and gastropods showed 

 differences of as much as 1 kcal/g between sam- 

 pling periods (Appendix Table 1, columns C and 

 D). The variation in the gastropods may have 



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