Some observations on the life history of the freshwater amphipod Echinogammarus longisetosus Pinkster, 1973 (Gammaridae) from Catalonia (Spain, N Iberian peninsula)

Abstract

Aspects of the population structure and reproductive biology of the freshwater amphipod Echinogammarus longisetosus were studied in the northeastern Iberian Peninsula (Catalonia, Spain). Amphipods were sampled at approximately monthly intervals from September 1999 to October 2000. Pairs in precopula and ovigerous females were present all year round. The sex ratio was not significantly different from 1:1. Juveniles were abundant in all samples (> 40%). The number of eggs carried by females (N) was related to the size of the females (LP3) (range: 9-68, mean value: 28.2): N = 0.594 LP33.141 (n = 80, r = 0.7136, LP3 were measured from the anterior part of the head to the posterior edge of the third pereional segment; total length was approximately 3.5 times greater than LP3 ). The mean embryo diameter was 0.45 mm (mean of measurements of the long and short axes of recently laid eggs). The egg volume increased during development (2 fold by eggs close to hatching)