Life-history traits and shell morphology in the genus Leptoxis Rafinesque, 1819 (Gastropoda: Cerithioidea: Pleuroceridae)

Abstract

Life histories of the imperilled freshwater gastropod genus Leptoxis are poorly known, and this information is required to achieve a basic understanding of the evolution of this diverse group and to develop management strategies for species conservation and recovery. We describe egg-laying behaviours and associated traits for all 13 extant Leptoxis species. We also explore patterns of shell growth and assess the extent to which intraspecific shell variation is a result of phenotypic plasticity or genetic differences. Each Leptoxis species exhibits one of three distinct oviposition strategies: deposition of single eggs, deposition of eggs in a single line or deposition in circular clutches. Temperature cues for initiating egg laying varied from 12 to 26 °C depending on the species. There were significant differences in clutch size among species and between populations of L. ampla and L. taeniata. Furthermore, 1- and 2-year-old female L. foremani laid significantly fewer eggs per clutch than females 4 years or older. Finally, discrete shell morphologies that are characteristic of any given species are genetically controlled and not an ecophenotypic response. Clutch egg laying likely represents increased parental investment compared with other behaviours and clutches may provide individual eggs protection from predation or passive dislodgement. Data from this study, including necessary conditions for successful culturing and period of oviposition for each species, can inform captive propagation efforts for imperilled Leptoxis species and aid in predicting how they will respond to future habitat alteration and climate change.