Survivorship of post-split fission products of Holothuria atra Holothuroidea Aspidochirotida on the southern Great Barrier Reef
Thorne, B.V.; Byrne, M.
Invertebrate Reproduction and Development 57(4): 293-300
Asexual propagation through fission to make new whole individuals is a common mode of clonal reproduction in invertebrates. For the fissiparous tropical sea cucumber Holothuria atra population densities remain stable indicating that asexual propagation through fission may balance mortality and that a portion of fission products suffer post-split mortality. The reason why this clonal species severs its body with the potential death of one half is not known. Fission in H. atra results in production of anterior and posterior fission products that differ in anatomy with the anterior portion containing the buccal complex and gonads, while the posterior product has the cloaca and respiratory trees. We investigated post-split survivorship of the two fission products at three sites to address the possibility that there is a sacrificial half . Due to possession of the feeding complex and gonads, the anterior portion might be the more physiologically valuable body portion to maintain, and we hypothesised that the anterior section would exhibit differential survival. Over this 6?year study however, there was no difference in survival success of anterior and posterior segments across all sites and months sampled, with ca. 1000 individuals examined. A similar outcome was evident for data when pooled by season.