The axils and detrital layer around the bases of Thalassia are also 

 inaccessible to large brittle stars. There appears, however, to be no reason 

 why the equally cryptically colored adults of, for example, the species 

 of Ophiodenna should not be successful in the sandy areas between Thalassia 

 plants. 



It seems reasonable to suppose that similar sized crevices elsewhere on 

 the reef would also be populated by small species, providing that food is 

 available, and evidence for this has recently been obtained by Hotchkiss 

 (1982, who found many of the species considered here living in empty conch 

 shells), Hendler (in press), and the present authors. 



The two microhabitats considered in this study, coralline algal turf and 

 Thalassia beds, are sufficiently different that no single species is predominant 

 in both. This has several potential causes. Feeding opportunities will 

 likely be different in the algal turf and around Thalassia beds. Apparent 

 detritus feeders such as 0. isacanthum are favored in Thalassia , whereas the 

 scavenging and apparently predatory 0. ophiactoides (Emson and Mladenov, in 

 prep.) is favored in algal turf. It is interesting that the highly adaptable 

 onmivorous detritivore A. squamata achieves moderate abundance in both 

 habitats. Perhaps reflecting predation pressures, body coloration is also 

 probably important, since the algal turf generally hosts dark colored species 

 and the Thalassia paler species. 



Small size in brittle stars clearly has resulted in reproductive 

 constraints. Small size inevitably means that small numbers of eggs can be 

 produced. Thus the production of long lived, planktotrophic larvae is unlikely 

 to be a successful mode of reproduction for small species, unless perhaps 

 gametes are shed several times a year. Several alternatives appear to be 

 open to small species. Two are alternative means of sexual reproduction. 

 One is abbreviated development (Hendler, 1975) in which rapid development 

 results in a post larva. The other involves direct development, often with 

 associated viviparity or brooding. A third alternative is to supplement 

 sexual reproduction with asexual multiplication. 



All the brittle stars in this sample of small adult size either reproduce 

 asexually or brood the young. The similarity in life history traits among 

 the three abundant fissiparous species is remarkable. Despite the fact that 

 they are from three different families, they are small in size, they reproduce 

 asexually by fission, and they can produce only a very small number of small 

 eggs which apparently develop into planktotrophic larvae. Rearing experiments 

 already have demonstrated that fertilized eggs of 0. ophiactoides develop 

 into typical planktotrophic ophioplutei (Mladenov and Emson, 1984), and the 

 egg sizes suggest that this is probably the case for the other species as 

 wel 1 . 



Asexual reproduction appears to be the dominant mode of propagation in 

 all three fissiparous species. It is probably responsible for reliable local 

 recruitment, whereas sexual reproduction may result in dispersal of small 

 numbers of larvae which, on occasion, found new populations or recruit into 

 existing populations maintained mainly by asexual reproduction. 



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