the two habitats, since 0^ isacanthum , Ophiolepis pauci spina , and A^_ squamata 



are the prominent species in this habitat. Only A. squamata achieves a similar 



abundance in both habitats, and fissiparous species are numerically predominant 

 in both habitats. 



Two features were common to all the species in these habitats. One is 

 small body size. No species exceeds 4.5 mm maximum disc diameter, and most 

 species are smaller than this. All species except 0. cinereum and Ophiothrix 

 oerstedi included reproducti vely active adult individuals. The second feature 

 common to these species is the color pattern of the brittle stars. All are 

 very difficult to see in the natural habitat because of their size and because 

 the coloration of the animals renders them cryptic; the banded arms of several 

 species are particularly concealing. Even when the algae were dissected in the 

 laboratory, many brittle stars were detected only when they moved. Furthermore, 

 for those residing in coralline algae, the arms were similar in diameter to the 

 algal strands. It was noticeable that other fauna found within the algal 

 clumps, notably the small (2-5 cm) holothuroid Synaptula hydriformis and some 

 unidentified amphipods, also were cryptically patterned. A dark green with 

 paler blotches, S. hydriformis is very similar to 0. ophiactoides in color. 



Asexual Reproduction in the Fissiparous Species 



The overall percentage of individuals showing evidence of fission in each 

 of the three common fissiparous species is very high (table 3) and is clearly 

 an important means of population increase in all three. This similarity is 

 only one of several that can be discerned. For instance, the range of disc 

 size was very similar (table 3), and the size frequency histograms (fig. 1) 

 were virtually identical in pattern, each population being dominated by 

 individuals with disc diameters of 1.0-2.5 mm. Few animals of larger disc size 

 were evident, and very small animals also were missing. Data were available 

 only for August 1981 and July 1984 for 0^ savignyi and 0j_ isacanthum , but for 

 0. ophiactoides data were also available for June, July, and December of 1981 

 "[Mladenov, et al., 1983) and July of 1984; the size frequency patterns were 

 identical at all times. No evidence of larval recruitment was apparent in that 

 species at any time. While it remains possible that larval recruitment occurred 

 in intervening months, we suspect that the populations of all three species 

 are, at these sites, maintained almost solely by asexual reproduction. 



Another similarity between the species is in the relationship between disc 

 size and evidence of recent fission. Table 4 shows the proportion of animals 

 with different disc sizes found in each of four regeneration categories. In 

 all three species, there is a clear trend: most small animals show evidence of 

 recent splitting (i.e., a low ratio for length of short/long arms), while a 

 high proportion of large animals do not. 



Sexual Reproduction in the Fissiparous Species 



Larger individuals in all three fissiparous species may contain mature 

 functional gonads (table 3 and below). Mladenov and Emson (1984) already have 

 reported that 0. ophiactoides with disc diameters greater than 2.2 mm can 



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