Female energy dynamics in the southernmost fiddler crab: Mixed breeding strategy in Leptuca uruguayensis

Abstract

At the south of its geographical distribution, the fiddler crab Leptuca uruguayensis shows two population spawning events, with more than 65 % of the females being ovigerous. The aim of this study was to assess the energy dynamics in L. uruguayensis females to estimate how they mix the capital and the income breeding strategies in the first and second spawns of the short reproductive season. The relationship between the hepatosomatic (HIS) and gonadosomatic (GSI) indices was used to assess the contribution of the hepatopancreas to ovary maturation, as indicative of the capital breeding strategy, whereas the feeding rate and the energy available in the food resource (sediment) were estimated to assess the importance of energy intake in ovary maturation, as indicative of the income breeding strategy. Before the first spawn, a significant negative relationship between the HSI and GSI (p < 0.001) and an increase of 28.2 % in the feeding rate were recorded. This suggests that the first spawn was mainly supported by energy reserves in the hepatopancreas, indicating that females used mostly the capital breeding strategy. After the first spawn, total lipid content in the hepatopancreas decreased by 33 %. On the days before the second spawn, the relationship between the HSI and GSI showed a negative but not significant (p = 0.125) trend, whereas the feeding rate increased even more. This suggests that the intense feeding activity provided the most important energetic source for ovary re-maturation, indicating that females used mostly the income breeding strategy. Also, in the second spawn, the GSI was 24.1% smaller, a fact that affected female fecundity and weight of the egg clutches, which were respectively 12 % and 11 % lower than in the first spawn. However, the energy supply allocated to each embryo was equivalent in both spawns. This study shows how L. uruguayensis females mixed the capital and income breeding strategies to take advantage of all available resources to produce two spawns in a short reproductive season.