DIAMETER OF THE BASE OF THE CAPITULUM AS A BIOMETRIC VARIABLE OF THE GOOSE BARNACLE POLLICIPES POLLICIPES (GMELIN, 1789) (CIRRIPEDIA, LEPADOMORPHA)

摘要

Owing to the peculiar morphology of the goose barnacle Pollicipes pollicipes (Gmelin, 1789), many different biometric variables have been used in its study. The lack of a standard morphological variable makes it difficult to compare results from different authors. This aspect takes on even greater importance, since the goose barnacle is a commercially exploited species and must be regulated with clear-cut technical measures related to its biology. The need to measure a large quantity of specimens in the management and control of the fishery calls for a biometric variable that can be processed easily and requires little training. The base of the rostrum and the apex of the subcarina form two conspicuous clefts in the capitulum of the goose barnacle, allowing a calliper to be fitted quickly and easily. The results of this study showed that the diameter of the base of the capitulum (DBC), defined as the distance between these two clefts, may be considered a consistent variable both when the same specimen is measured by two different technicians and when the measurements taken from a fresh specimen are compared with the measurements taken after the specimen has been frozen and then thawed. In order to make comparisons easier, two linear equations have been found to relate DBC and two of the more usual biometric variables: rostral-carinal distance (RC) and capitulum height (CH). The mean length at sexual maturity was also calculated in terms of DBC (13.35 mm) for specimens collected on the Galician coast (NW Spain).