FACTORS AFFECTING GASTROPOD LARVAL DEVELOPMENT AND PERFORMANCE: A SYSTEMATIC REVIEW

The goal of this article was to use a systematic review of studies on the larval stages of gastropods reared to metamorphosis to determine whether there are general patterns for the effects of temperature, rearing density, and food availability on larval development and performance among species, major taxa, and modes of development. Most studies did not include sufficient metadata to be included in many of the analyses. For all analyses, there were differences among major groups of taxa in terms of response to the considered variables. Increased temperature was frequently correlated with decreased development time and increased growth but often not for the same taxa. Increased larval density was generally correlated with increased development time, but again, the patterns were not consistent across taxa. The most consistent pattern was the positive correlation between per capita food availability and larval growth. In all but two cases, patterns for the most studied species, Crepidula fornicata, were opposite those of other caenogastropods. This indicates that caution should be used when drawing general patterns among species based on studies of C. fornicata. Among lecithotrophs, the vetigastropod Haliotis rufescens was the most studied. In this case, patterns found for this species were similar to those for all other vetigastropods; however, few species outside the genus Haliotis have been studied. Increased temperature was associated with reduced survivorship and, in the most studied clade, the Vetigastropoda, reduced time to metamorphosis, which suggests that there may be an energetic cost to more rapid development or physiological mechanisms for coping with heat stress. Curiously, increased larval density was associated with increased survivorship for lecithotrophs. In several cases, however, there were too few studies, or the studies that were found did not provide enough metadata to be included in analyses. Although some patterns emerged from existing research on gastropod larvae, studies on a more diverse set of species that report all metadata are required for cross-study comparisons, which are crucial for drawing robust general conclusions.