A Shift In Feeding Behavior From The Juvenile To Adult In The Giant Acorn Barnacle Balanus nubilus Darwin With Observations On The Developmental Time Course Of Larvae.

Abstract

Barnacles exhibit diverse cirral behaviors during feeding with the repertoire of cirral fan behaviors of species associated with their physiology, ecology, and phylogeny. However, feeding behaviors of juveniles has not been significantly investigated. This study was conducted to investigate the disparity of feeding behaviors of juveniles to adults in Balanus nubilus. Specimens of diverse cirral fan lengths, including recently metamorphosed juveniles, were collected and tried at three seawater flows and in food presence or absence. Observations were made of cirral behavior types, total active time, and rates of cirral activity. Cirral activity and total time active were found to be inversely correlated to cirral fan length. The feeding strategies of juveniles differed from adults with active feeding predominating. Juveniles were also found to exhibit cirral behaviors undescribed for this species including a backward beating previously undistinguished in barnacles. For many species, including Balanus nubilus, little information is available on the developmental time course of the larval stages. Larvae of Balanus nubilus were cultured from the eggs of gravid adults and subsamples collected every other day elucidated a developmental time course that was longer in contrast to others of the genus.