OBSERVATIONS ON THE REPRODUCTION AND DEVELOPMENT OF LIOTHYRELLA-NEOZELANICA THOMSON 1918 (TEREBRATULACEA, ARTICULATA, BRACHIOPODA)

Mature individuals of the terebratulid brachiopod Liothyrella neozelan ica Thomson, collected from Doubtful Sound on 25-26 February 1990 at C ampbell Kingdom, spawned in the laboratory. The females brooded their opaque, white zygotes, embryos and larvae in the space bounded by the brachial membrane and its associated cirri in the apical region of the median spiral arm of the plectolophe. The coeloblastula gastrulated b y invagination. The circular blastopore gradually elongated during gas trulation. Cilia, which first appeared during the gastrula stage, comp letely covered the embryo and persisted throughout larval life. The cy lindroid gastrula developed into a wedge-shaped larva, which returned to a cylindroid shape before the mantle fold appeared. Two grooves for med on each side of the mantle fold to constrict the larva into a thre e-lobed body without eye spots. An occasional two-lobed stage interven ed whenever the two grooves developed asynchronously. Three-lobed larv ae could be classified by morphological features into early, late and pre-settlement stages. Large ova developed into large larvae or occasi onally into large incomplete larvae. Small ova produced miniature but otherwise normal larvae and some miniature incomplete larvae. Incomple te larvae did not differentiate further, had no pedicle lobe, and soon died. The reproduction and development of this species were discussed .