Colony specificity in Botrylloides leachi (Savigny): preliminary reports

A morphological and histochemical study of colony specificity in the compound ascidian Botrylloides leachi was undertaken. Preliminary results indicate that fusion occurs when genetically related colonies encounter, whereas subcuticular rejection is observed between unrelated colonies. The latter is characterised by limited tunic fusion and leakage of morula cells from the circulation into the tunic, where they contribute to form dark-brown necrotic spots. In the case of contact between incompatible colonies at cut surfaces, a wide necrotic area forms along the contact border within 24-48 h. In both cases, the nonfusion reactions of B. leachi resemble those of the Japanese species Botrylloides simodensis.