Project description:Xenoturbella bocki, a marine animal with a simple body plan, has recently been suggested to be sister group to the Acoelomorpha, together forming the new phylum Xenacoelomorpha. The phylogenetic position of the phylum is still under debate, either as an early branching bilaterian or as a sister group to the Ambulacraria (hemichordates and echinoderms) within the deuterostomes. Although development has been described for several species of Acoelomorpha, little is known about the life cycle of Xenoturbella. Here we report the embryonic stages of Xenoturbella, and show that it is a direct developer without a feeding larval stage. This mode of development is similar to that of the acoelomorphs, supporting the newly proposed phylum Xenacoelomorpha and suggesting that the last common ancestor of the phylum might have been a direct developer.
Project description:Two types of endosymbiotic bacteria were identified in the gastrodermis of the marine invertebrate Xenoturbella bocki (Xenoturbellida, Bilateria). While previously described Chlamydia-like endosymbionts were rare, Gammaproteobacteria distantly related to other endosymbionts and pathogens were abundant. The endosymbionts should be considered when interpreting the poorly understood ecology and evolution of Xenoturbella.
Project description:Xenoturbella is a marine invertebrate with a simple body plan, with recent phylogenomic studies suggesting that it forms the phylum Xenacoelomorpha together with the acoelomorphs. The phylogenetic position of the phylum is still under debate, whether it is an early branching bilaterian or a sister group to the Ambulacraria. Phylogenetic traits often appear during development, and larva resembling the cnidarian planula has been reported for Xenoturbella. However, subsequent developmental studies on Xenoturbella have been scarce. This is mainly due to the difficulties in collecting and keeping adult animals, resulting in the lack of data on the reproduction of the animal, such as the breeding season and the spawning pattern. Here we report on the reproduction of X. bocki and confirm that its breeding season is winter. Spawning induction resulted in gametes being released from body ruptures and not the mouth. No evidence supported the animal as a simultaneous hermaphrodite.
