Byssus production ability and degree of byssal‐gland development in the infaunal clam Ruditapes philippinarum

Abstract

Byssus production of Ruditapes philippinarum clams becomes reduced with growth. This tendency is well recognized but has not been analysed in detail. Additionally, it remains uninvestigated whether the lack of competence to produce byssus threads in the adult stage is caused by atrophy of the byssal glands or not. The objective of this study was to evaluate the byssus production ability of clams through the juvenile to adult stages and to examine the importance of two endogenous factors (i.e. shell size, somatic condition) in determining the byssus production probability (proportion of clams with byssus production in a population). This study also histologically confirmed the presence of byssal glands in juvenile to adult clams. For these purposes, field surveys to investigate the relationship among byssus production, shell size and somatic condition of clams collected from four intertidal sites and a histological study for byssal glands of the clams was conducted. This study revealed that byssus production probability decreases with increasing shell size and declining somatic condition and that the lack of byssus production is not caused by the loss of the byssal glands.