Growth of the Vasa Deferentia of Mature Homarus americanus: Conflicting Results from Field and Laboratory Studies

Abstract

Successive samples from mature and maturing male Homarus americanus from the Gulf of St. Lawrence indicated that the vasa deferentia grow rapidly in spring and then regress. Growth of the vasa deferentia was followed in the laboratory in this same stock of lobsters by surgically removing first one and then the other of the paired vasa deferentia during the year. The laboratory study indicated that vas deferens weight, which increases nearly 50% during May and June, continues to increase through autumn and winter at a reduced rate consistent with normal somatic growth. There was no evidence of regression, and no support for an hypothesis of cyclic seasonal change associated with mating activity. The regression suggested by the field study appears to be the effect of ecdysis, which abruptly alters the relationship between animal size and organ size.