AGGREGATION AND FUSION BETWEEN CONSPECIFICS OF A SOLITARY ASCIDIAN

¹ Department of Zoology, University of Reading, Whiteknights, Reading RG6 2AJ, England

Fusion between conspecifics in a solitary ascidian is reported for the first time. Molgula complanata Alder and Hancock showed aggregated settlement on Perspex panels in the field, allowing contact between conspecifics after some increase in size. Histological sections of adult animals which were in contact with one or more conspecifics showed that some individuals were fused to others. The frequency of fusion between contacting specimens was 20%. The outer membranes of the tunics were absent between fused animals but present in unfused ones. Fusion was thus characterized by contiguous matrices, which contained cellular elements. No barrier to interchange of tunic cells between fused animals was observed. It is suggested that fusion may oppose inbreeding in hermaphroditic, viviparous ascidians with minimal dispersal.