WILLIAMS: CRABS OF THE GENUS CALLINECTES 



Figure 26. — Respective geographic distributions of Callinectes exasperatus (Gerstaecker) and C. sapidus Rathbun in the western 

 Atlantic Ocean with introductions to the eastern Atlantic and Mediterranean Sea, based on specimens studied and verified published 

 records. 



(Williams, 1971), showing one of the generic dis- 

 tinctions at an early phase of development. 



Costlow ( 1965, 1967) followed the early work on 

 larvae with a series of experimental studies show- 

 ing that development of C. sapidus is subject to 

 variation both in staging and duration. Total de- 

 velopment time of C. sapidus from hatching of egg 

 to transformation of the megalopa to first crab 

 stage has varied from 31 to 69 days in the labora- 

 tory in various combinations of salinity and tem- 

 perature, but duration of individual stages is vari- 

 able even in a single salinity-temperature combi- 

 nation. The stages are constant enough, however, 

 that Van Engel ( 1958), Cargo (1960), Nichols and 

 Keney (1963), Pinschmidt (1964), Tagatz (1968), 

 More (1969), and Williams (1971) were able to 

 identify zoeae or megalopae from nearshore 

 oceanic and estuarine plankton. In nature as in 

 experiments, development time may be extended 



by environmental conditions. Megalopae have 

 been found throughout the year in North Carolina 

 estuaries. 



FOSSIL RECORD 



Hard parts of portunids most abundant as fossils 

 in Tertiary formations in eastern North and Mid- 

 dle America are portions of the chelipeds, usually 

 the dactyls and portions of the propodi. Some de- 

 posits contain remains of carapaces and/or sterna, 

 occasionally almost whole exoskeletons of crabs, 

 but any of the remains are scarce. It was largely on 

 the basis of cheliped fragments that Rathbun 

 (1919a, b, 1926, 1935) listed and described Cal- 

 linectes species from formations attributed to ages 

 as old as the Oligocene. Withers ( 1924) described a 

 fragment of chela from the Eocene of Jamaica as 

 Callinectes, and Blake (1953) added information 



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