FISHERY BULLETIN: VOL. 72, NO. 3 



histories of the species. Among spiny lobsters, 

 whose larvae are seemingly better fitted for tem- 

 porary pelagic existence than crab larvae because 

 of leaflike shape, up to 6 mo or greater duration of 

 larval life occurs (Lewis, 1951; Austin, 1972). 

 Phyllosomas of some spiny lobsters are rarely 

 found beyond the latitudinal geographic limits of 

 the coastal adult population. George and Main 

 ( 1967) attributed this result to behavioral re- 

 sponses of the larvae, vertical migration, etc., 

 within prevailing current systems which act to 

 preserve integrity of distribution, but Austin 

 (1972) held open the idea of long distance trans- 

 port over considerable lengths of time. Some dis- 

 persal of larvae at the fringes of less pelagic Cal- 

 linectes populations obviously occurs, but the 

 wanderers are at a competitive disadvantage in 

 establishing temporary range extensions. 

 Nevertheless, larval dispersal of Callinectes 

 coupled with movement of adults, judged to be 

 minor except within an estuarine system (Fischler 

 and Walburg, 1962; Tagatz, 1968), seems to assure 

 genetic continuity over broad areas. 



If one accepts the tenet that the center of evolu- 

 tion for a group contains the largest number of 

 species, Neotropical Atlantic American shores 

 seem to be the primary center in which the genus 

 Callinectes developed and from which it radiated. 

 Fossil evidence indicates that this radiation took 

 place in the Tertiary, a period of time in which 

 land-water relationships of that region diverged 

 widely from their positional and areal extent 

 today (Woodring, 1966, 1971). Olsson (1972) re- 

 garded the Miocene as the time when Panama- 

 nian molluscan biotas related to those of today 

 evolved under conditions of general subsidence 

 and when parts of present day Central America 

 were reduced to an archipelago of large islands 

 separated by straits between the Caribbean and 

 east Pacific. Ekman ( 1953), Fell ( 1967), and others 

 regarded the marine fauna that evolved in this 

 region as an impoverished western outpost of the 

 Tethyan fauna, related most closely to that of the 

 eastern Atlantic and southern Europe. Though 

 the tropical Atlantic and neighboring east Pacific 

 regions both shared in the radiation of Cal- 

 linectes, the conservatism of this offshoot contrasts 

 remarkably with the far richer divergence of its 

 parent stock. Stephenson (1962) considered the 

 Indo-Pacific, with 175 living species, as the ger- 

 minal center for the Portunidae. It seems reason- 

 able to view Callinectes as a portunid group evolv- 

 ing at the geographic limits of the family, 



specializing in occupation of estuaries, and paral- 

 leling in many ways the heavy- bodied Indo- 

 Pacific Scy//a serrata (Stephenson, 1962). 



If Callinectes evolved mainly in the Caribbean 

 faunal province, the present distribution of 

 species in essentially three isolated centers raises 

 questions concerning dispersal. Separation of the 

 east Pacific from the Caribbean by elevation of the 

 Panamanian isthmus near the close of the Ter- 

 tiary understandably isolated certain elements of 

 the genus and may have promoted further radia- 

 tion, but close relationship of species in the two 

 areas is emphasized by an obvious geminate pair 

 — danae-arcuatus — similar in a number of mor- 

 phological features, which occurs today on east 

 and west coasts of Middle and South America. 

 Separation of the east and west Atlantic frag- 

 ments of the genus is harder to resolve because 

 not only does one species bridge this gap, but two 

 species groups (short and long first gonopods) are 

 represented on both sides of the ocean, seemingly 

 specialized along the same general lines. Which is 

 the ancestral stock? Were pelagic larvae the 

 mechanism of transport, as Fell (1967) proposed 

 for analogous but cold-tolerant echinoderms, 

 perhaps aided by island stepping stones in the mid 

 Atlantic? (Fell rejected continental drift as a 

 plausible explanation for transport, an idea more 

 acceptable today than it was in 1967, but involv- 

 ing a time span greater than concerned here 

 [McKenzie, 1972].) Length of life of the larvae of 

 most species of Callinectes under pelagic condi- 

 tions remains unknown. West Africa is upstream 

 from the Western Hemisphere in prevailing 

 equatorial surface currents. It seems unlikely that 

 the larvae could move counter to this current from 

 a center in the west or survive the much longer 

 (and today, colder) northern transit from the West 

 Indies via the Gulf Stream beyond Bermuda to the 

 Azores, Canaries, and finally to west Africa. So far 

 as known, all Callinectes utilize estuaries during 

 part of their lives. Populations on small islands 

 may be nonbreeding, transitory implants, or un- 

 successful breeders. Means and paths of long- 

 distance transport, and effectiveness of transients 

 in colonization, among these forms will remain 

 unknown until more data are collected. 



Finally, the clustering of species by numerical 

 methods employed by Stephenson et al. (1968) 

 does not reflect the three groups suggested by first 

 gonopod types, but it does support classical in- 

 terpretation setting C marginatus and perhaps C. 

 gladiator aside as the most peripheral morpholog- 



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