coralline algal habitat occupied by 0. ophiactoides and adjacent turtle grass, 

 a number of other small brittle stars were present, some in abundance. Of 

 these species, some showed evidence of f issi parity ; others, however, were 

 nonfissiparous brooding species which nevertheless shared certain characteristics 

 with the fissiparous forms. In this paper, we present data on the relative 

 abundance of brittle stars in these microhabitats, briefly review some of the 

 life history characteristics of these brittle stars, discuss the similarities 

 and differences between them, speculate on the reasons for the abundance of 

 small brittle stars in these habitats, and comment on the association of small 

 size with fissiparity and brooding in brittle stars. 



STUDY SITES AND METHODS 



The study sites consisted of (1) a shallow, sheltered cove (known locally 

 as Maze Cove or the Blue Maze) located in a part of the back reef just west of 

 the dive locker of the Discovery Bay Marine Laboratory, Jamaica, and (2) a 

 closely adjacent bed of turtle grass. 



The rocky walls of the cove are covered with a deep carpet of coralline 

 and other red algae in which Amphiroa rigida and A^_ fragillisima are most 

 prominent. These algae are all dark in color and, except at the bases of the 

 fronds, relatively free of detritus. During August 1981 and July 1984, clumps 

 of algae were carefully transferred to polythene bags underwater, removed to 

 the laboratory, and searched for brittle stars and other fauna. The brittle 

 stars were identified, examined for evidence of cross-disc division (three long 

 arms and three shorter regenerating arms on the disc), counted, and measured 

 (the parameters noted were the greatest dimension of the disc and, in the case 

 of the fissiparous species, the length of the arms). The sexual condition of 

 the animals was later examined by dissection. In the case of Ophiocomel la 

 ophiactoides , egg size was obtained by measuring the diameter of spawned, 

 fertil ized eggs. For the other species studied, the diameter of the largest 

 oocytes present in histological sections of ripe females was measured. For 

 estimation of total egg number, the ovaries were removed, blotted free of excess 

 moisture, and weighed. A small fraction was then separated, weighed, and the 

 number of eggs counted. Total egg number was obtained by multiplication. 



The site adjacent to the cove has a sand and silt substratum that supports 

 an abundance of turtle grass, Thalassia testudinum , as well as a variety of 

 algae. The bases of the Thalassia are uniformly pale, due to attached detritus 

 and the presence of dead decaying leaf bases on the outsides of the plants. 

 Detritus is abundant around and between the plants. Thalassia shoots were 

 pulled from the substratum and placed in polythene bags underwater along with 

 samples of the surface of the substratum from immediately around the base of 

 the plants. This material subsequently was treated similarly to that obtained 

 from the algal clumps. 



RESULTS 



The Species and Their General Characteristics 



The brittle stars found in the algal turf are listed in table 1A. This 

 table also shows their relative abundances in these microhabitats and gives 



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