Estimation of the reproductive output of the burrowing shrimp Callianassa tyrrhena : a comparison of three different biometrical approaches

Abstract

Reproductive output, as the percentage of the mother weight devoted to egg production, was estimated for the burrowing shrimp Callianassa tyrrhena in wet, dry and ash-free dry weight. Three biometrical approaches were used. First, the relationship between the egg mass and the mother weight was determined. A second approach was to estimate the weight loss of the female caused by oviposition. Similar results were obtained from these methods for dry and ash-free dry weight (about 20 and 35%, respectively), but not for the wet weight estimation. The third approach, based on the weight loss of the ovary, did not reveal a constant value for reproductive output throughout the female size range, although it was found that the ovary loses a constant percentage of its weight during oviposition. This discrepancy is due to the fact that the ovary weight shows positive allometry to the weight of the female body. The comparison of the three methods offers insight into the biological events that are related to ovary maturation and oviposition. It is suggested that molting just before oviposition and its inhibition during the yolk accumulation in the ovary play dominant roles in the expression of the reproductive output in the different approaches used.