REPRODUCTIVE-BIOLOGY OF MEGASCOLIDES AUSTRALIS MCCOY (OLIGOCHAETA, MEGASCOLECIDAE)

Observations of gametogenesis facilitated understanding life history a nd reproductive processes in Megascolides australis, whose reproductiv e strategies are correlated with longevity, low density and poor dispe rsal ability. Worms are biparental and have a discrete breeding (egg l aying) season in spring and summer. This coincides with the greatest n umber of mature ova and the glandular epidermis of the clitellar regio n being thickest. Gametogenesis occurs throughout the year, with sperm present in the spermathecae and available on male funnels ail year. N on-seasonal copulation may occur when two worms meet and conditions ar e favourable; this trait is advantageous for species in low densities with poor dispersal abilities. The spermathecal structure of M. austra lis differs from that of other megascolecids recorded in that the stru cture of the diverticulum includes many multiloculate chambers that do not connect directly with the spermathecal duct. The sperm form orien tated bundles (spermatozeugmata) not previously described for Megascol ecidae and are stored in the ampulla rather than the diverticula.