QUANTIFICATION OF THE EFFECTS OF SPORELING COALESCENCE ON THE EARLY DEVELOPMENT OF GRACILARIA-CHILENSIS (RHODOPHYTA)

Sporeling coalescence in species of Gracilariales and Gigartinales is predicted to result in larger basal areas of growing disks as well as earlier initiation, increased abundance, and faster growth rates of er ect shoots as compared to noncoalescent sporelings. These responses ha ve been interpreted as providing mutual benefits for organisms living in aggregation, counterbalancing disadvantages associated with crowdin g. Quantitative evaluations of sporelings of Gracilaria chilensis fail ed to support several of these predictions. Sporelings were grown in t he laboratory from a range of single sporelings to coalescent masses o f 20 sporelingus. Coalescent sporeling masses of G. chilensis exhibite d larger basal areas than noncoalescent ones, but because the specific growth rates were inversely related to the original number of carposp ores, no significant differences in actual area increments, during mos t of the experiment, were found among sporelings derived from one, two , or three to five coalescing sporelings. Initiation of erect shoots o ccurred at a similar time, regardless of their origin, i.e. coalescent or noncoalescent. Abundance of erect shoots was only loosely related to the number of coalescing sporelings. Even though by the end of the experiment (week 18), the total length of she longer erect shoots aris ing from coalescent sporeling masses was significantly greater than th at of shoots arising from noncoalescent sporelings, total length teas independent of the original number of coalescing sporelings. Furthermo re, specific elongation rates between week 12 and week 18 were signifi cantly greater for noncoalescent sporelings than SOT coalescent sporel ing masses. Quantitative screening of other species seems necessary be fore generalizations on the ecological advantages of sporeling coalesc ence in seaweeds can be made.