counterparts, therefore, these fissiparous brittle stars broadcast exceedingly 

 small numbers of larvae at each spawning, with important potential consequences 

 for recruitment. Even if these species spawned 10 times a year, their output 

 would be low. As only a small proportion of the population is sexually 

 mature, the output of larvae must be very small. 



The three nonf issiparous species present as adults ( A. squamata , A. 

 stimpsoni , and 0. paucispina ) share similar reproductive methods. They are 

 hermaphroditic species which produce a small number of relatively large yolky 

 eggs. These are brooded within the genital bursae and released, quite possibly 

 throughout the year, as competent juveniles (although Hendler, 1975, and 

 Emson, unpub. obs. , have noted that release is reduced at some seasons). 



Observations of Potential Predators 



Many species of fishes live in the water adjacent to the algal carpets. 

 During our collections, fish were observed picking at the surface of the 

 algae on several occasions. Blue Tangs ( Acanthurus coeruleus ), Surgeon Fish 

 ( Acanthurus chirurgus ), and, in particular, Slippery Dicks ( Halichoeres 

 bivittatus ) were observed darting at and pushing into the algal clumps. The 

 latter species is known to eat invertebrates (Randall, 1967). 



DISCUSSION 



Throughout the Discovery Bay area, brittle stars are an abundant and 

 obvious component of the benthic macrofauna. In most areas, large species 

 predominate, although crevices and algae such as Hal imeda sp. harbor both 

 juveniles of large species and individuals of small species. The algal turf 

 and turtle grass habitats studied here, however, were unusual in having a 

 large number of very small, inconspicuous species of brittle stars occurring 

 in abundance. Large species were extremely rare at these sites and, when 

 present, were represented only by small juvenile forms. It appears that 

 these microhabitats are particularly favorable for small species and not 

 suitable for large species. Brittle stars are considered to be subject to 

 considerable predation pressure in Discovery Bay (Sides, 1982) and our obser- 

 vations suggest that fish may pose a threat to brittle stars easily visible 

 in the algal clumps. It seems possible that a similar situation exists 

 around the bases of Thalassia . 



Larger brittle stars survive by concealment beneath rocks, within rubble, 

 or in crevices, and by burying within the sediment; many also are nocturnal 

 in activity. They are probably absent from algal turf because it would be 

 difficult for them to move through, would offer inadequate concealment, and 

 perhaps would not provide suitable feeding opportunities. Conversely, the 

 stiff, narrowly spaced strands of the algal turf provide an ideal microhabitat 

 for the small species which dominate it, a microhabitat that allows movement, 

 provides concealment, and, if abundance is a guide, offers good feeding 

 conditions. The juveniles of large species that settle in this microhabitat 

 presumably emigrate when they "outgrow" it or become victims of predation. 



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