Brooding is the other reproductive pattern exhibited by the small adult 

 brittle stars of this study. This reproductive mode appears to be a clear 

 adaptation to low fecundity resulting from small size. Hendler (1979) noted 

 an association between size and brooding in ophiolepid brittle stars and 

 suggested that there was selective pressure for brooding because of low 

 fecundity. Also, Menge (1975) and Emson and Crump (1979) found similar 

 associations between size and brooding in the sea stars and suggested the 

 same cause. 



A general relationship between small adult size and brooding has been 

 documented for many groups of invertebrates including echinoderms, and 

 hypotheses explaining the association have been advanced by Strathmann and 

 Strathmann (1982). However, brooding is rare among brittle stars, although 

 it is obvious in the present study. Hendler (1979) noted that only 57 of all 

 known brittle stars brood, and of these only 7 are tropical. It seems that, 

 although the particular conditions of the habitats sampled here favor this 

 life history pattern, elsewhere other methods are selected. 



The alternative to brooding, abbreviated development (Hendler, 1975), is 

 also characteristic of species with relatively small disks that are capable 

 of producing eggs in numbers of the same order of magnitude as fissiparous 

 species (e.g., Amphiura chiajei ; Hendler, 1975). Species with this reproductive 

 pattern are present on coral reefs but were not found in our study. 



Fission is also uncommon in brittle stars. Emson and Wilkie (1980) 

 reported that only 34 species possess this habitat, although they failed to 

 record 0. isacanthum as fissiparous (Hotchkiss, 1982). By contrast with 

 brooding, however, fissiparity is largely a warm water phenomenon. Emson and 

 Wilkie (1980) recorded that 24 of the 34 fissiparous species were tropical in 

 distribution. The reasons for these patterns are unknown and would bear 

 further investigation. 



The similarity of these results to the situation described by Boffi 

 (1972) for Brazil is considerable. Not only are the fissiparous ophiactids 

 Ophiactis lymani and Amphiphol is squamata the predominant species in the 

 algal turfs examined by Boffi , but the other species in which adults were 

 present were Amphi phol i s januari i and Ophiacti s savignyi . The remaining four 

 species were represented by juveniles and uncommon. 



It thus seems possible that these reproductive patterns may prevail 

 among small brittle stars inhabiting algae throughout the tropical and 

 subtropical Atlantic, since the present authors have established that similar 

 reproductive patterns are characteristic of small brittle stars from Bermuda 

 and Carrie Bow Cay, Belize. Hotchkiss (1982) observed many of the same 

 species in discarded conch shells, demonstrating that these reproductive 

 patterns probably are adaptive for many cryptic habitats in sheltered areas 

 of coral reefs. 



Evolution to a small size is infrequent in brittle stars, but those 

 species which achieve it may become very successful. The brooding Amphi phol is 

 squamata and the fissiparous Ophiactis savignyi are among the most abundant 

 brittle stars. Their size apparently allows them access to an underexploited 



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