GROWTH AND REPRODUCTION OF THE SLUG LIMAX VALENTIANUS FIRUSSAC IN EXPERIMENTAL CONDITIONS

Growth and reproduction of batches and isolated Limax valentianusFérussacslugs reared under long-day photoperiods were compared withthosereared under short-day photoperiods combined with highertemperaturesduring the dark period. Weight increase in L. valentianusoccurredin three distinct phases: an initial phase of rapid growth(infantilephase), followed by a phase with a smaller increase inweight(juvenile phase) and finally a phase with minimal growth,duringwhich reproduction occurred (adult phase). This phase endedwitha weight decrease, due to senescence. Short days associatedwithan increase in temperature during the night reduced thereproductiverate, but did not affect growth. Long days werefavourable forreproduction. Growth rate was fastest in isolatedindividuals rearedunder long days and warm nights, while reproductionwas greatest inisolated individuals reared under long daysand cool nights. Fertilitygenerally decreased with age, butegg production of slug batchesevolved through a maximum, occurringbefore mean life span. High slugdensity reduced reproductiverate and longevity. (Received 22 December 2000; accepted 10 October 2000)