LAUSR

Abstract Determining how, when, and why energy allocation occurs based on different life history traits, provides core knowledge for understanding evolution, ecology, and conservation of populations. We assumed that, in seasonal environments, Anodontites trapesialis, a common freshwater mussel in the Pantanal wetland, has to time its maturation, its larvae incubation time, and adjusts its breeding strategy seasonally. From histological analyses of gametes, larval count, and marginal increment of the shell rings, we present information about phenology and growth strategies to investigate the influence of environment and reproductive period on growth. We determined for the first time, asymptotic maximum size and longevity for this mussel. This species is a functional hermaphrodite, with maturation and spawning starting at the end of the flood period, when the water begins to recede and fishes return to the main river channel. The larvae, lasidium in this case, disperse on host fishes at this time. As we predicted, the flood pulse is the main regulatory factor to the growth patterns and reproductive period establishment. The species’ life history traits are discussed in the context of life history theory as adaptive responses to the dynamic balance imposed by the seasonality of the Pantanal.