The embyonic and laval development of the turbellarian Notoplana australis (Schmarda, 1859) (Polycladida : Leptoplanidae)

Abstract

N. australis spawns throughout the year, with a peak of spawning activity in spring and early summer (September-December). The egg mass is a coiled, gelatinous string of individually encapsulated eggs 120-125 µm in diameter. Embryonic development includes spiral cleavage, epibolic gastrulation and the specialization of macromeres as yolk reserves in the usual leptoplanid manner. The larva which hatches at 12-14 days, however, is a four-lobed ciliated larva resembling Gotte's larva. The larva is planktonic lecithotrophic for 1 week and demersal lecithotrophic for 2 weeks, with gradual metamorphosis to a juvenile flatworm. The unexpected finding of a four-lobed ciliated larva in a schematommatan polyclad is discussed.