The Growth Rate of Balanus balanoides (L.)

A detailed study has recently been made on the growth rate of the two common barnacles, Balanus balanoides and B. crenatus, (BARNES and POWELL, 1953, q.v. for a review of data on the growth rates of these two species). When individuals are grown on panels which are kept free from other organisms, and which are maintained continuously submerged, the observed growth rates are far greater than those found for animals in their normal habitat. For example, under the above experimental conditions, B. crenatus virtually reaches its maximum adult size (20-25 mm rostro-carinal diameter) in its first season; B. balanoides, although still increasing in size a little during the second season does reach some 17 mm in the first season's growth. In their natural habits both species are only some 3-5 mm diameter (varying according to local conditions) at the end of the first summer. Total submersion is in part responsible for the enhanced growth rate in the intertidal species, B. balanoides, but even on experimental panels at 7.2 ft. above Chart Datum a size of 12 mm was reached in the first season; it was also found that there was little difference in growth rate at any point below this level when compared with that for continuous immersion. In the case of both species, therefore, there is some important factor, as yet undefined, which gives rise to an enhanced growth rate under the experimental conditions. The above observations relate to individuals growing on panels that were carefully cleaned at short intervals (3-4 weeks) and kept relatively free from other sedentary organisms throughout the whole period of the observations; algae were carefully removed not only from the panels but also as far as possible from the barnacles themselves. The greatly enhanced growth rates under these conditions suggest that the presence of other organisms and in particular heavy algal growth is an important factor in restricting the growth rate under natural conditions. 8 OIKOS 6:11, Copenhagen 1955