Table 2. --Group size as a measure of colonial integrity 



Colony 



size Group size 



class Z. sociatus Z. solanderi t-test 



< 20 X = 3.6 polyps per group 2.3 polyps per group 



polyps Range =1-13 1-8 3.68 



n = 63 groups in 31 colonies 84 groups in 40 colonies p < 0.001 



20 < 40 J = 6.9 2.3 



polyps Range =1-27 1-5 4.40 



n = 15 in 4 colonies 49 in 4 colonies p < 0.001 



40 < 60 I = 5.3 2.7 



polyps Range =1-30 1-5 1.25 



n = 11 in 1 colony 18 in 1 colony N.S. 



of colonial integrity, I have counted the number of unconnected polyp groups 

 and the number of polyps within each group. There were a total of 89 polyp 

 groups within 36 colonies of Z^_ sociatus and 151 polyp groups within 45 colonies 

 of Z. solanderi (table 2). Zoanthus solanderi had significantly fewer polyps 

 per group than did Z. sociatus in the two smallest colony size classes. The 

 maximum number of polyps per group was also much higher in Z. sociatus than Z. 

 solanderi . 



These significant differences in polyps per group may have important life 

 history implications. Variation at this low level of colonial integrity is 

 likely to influence the size of colony fragments and the size frequency 

 distribution of zoanthid colonies. Among colonial species, survivorship, 

 fecundity, fragmentation, and fusion are highly dependent on colony size (e.g., 

 Hughes and Jackson, 1980, and ms. in review; Buss, 1980, 1981; Sebens, 1982J3; 

 Hughes, 1984). Small fragments of Z. sociatus colonies have higher mortal ity 

 rates than do fragments of the same size for Z. solanderi (Sebens, 1982a_; 

 Karlson, in preparation). In addition, small colonies of Z. sociatus are 

 nonreproducti ve (table 1). The high level of colonial integrity in Z. sociatus 

 suggests a benefit to large group (and colony) size in this species and, 

 conversely, a cost (e.g., lower survivorship) associated with small size. 

 There appears to be little cost to small size in Z. solanderi . This zoanthid 

 is more resistant to predation than Z. sociatus (Sebens, 1982a_) and does not 

 delay sexual reproduction. Low colonial integrity in Z. solanderi is likely to 

 enhance fragmentation of small clusters of polyps. Higher colonial integrity 

 in Z. sociatus may enhance production of larger clusters by fragmentation or, 

 alternatively, it may enhance resistance to fragmentation. 



In our last presentation, Mladenov briefly reviewed some of the life 

 history characteristics of seven shallow-water Jamaican ophiuroids. All of the 



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