Budding, bud morphogenesis, and regeneration in Carybdea marsupialis Linnaeus, 1758 (Cnidaria: Cubozoa)

Abstract

The cubopolyp of the box jelly Carybdea marsupialis (L.) reproduces asexually by lateral budding, and by almost total transformation of the polyp into a cubomedusa. Buds, one or more at a time, emerge laterally from the body column and separate from the parent as secondary polyps bearing hypostome and some tentacle anlagen. We describe at the light microscopic level the consecutive steps of bud formation and propose to discriminate a series of eight developmental stages. Once detached, these buds elongate and pass through a vagile phase, creeping over the substratum with the tentacular region ahead. The vagile time period appears to depend on the culture condition; it ends with the firm attachment of the young polyp which then develops the full complement of tentacles along with further growth. The budding rate is positively correlated with the frequency of feeding, in contrast to conditions leading to medusa formation, and is enhanced in the dark. The ‘creeping polyp stage’ reveals a high regeneration potential both oral and aboral fragments, obtained by midbody transection, regenerate the ablated portion within 72 h. Regeneration in fragments excised from the body column restores also polyp morphology according to the original polar organization. Results of pilot experiments involving excision of the tentacle and hypostomial portion of adult budding and non-budding cubopolyps lead us to discuss a possible interplay between regeneration of oral structures and bud formation.