Advisor: Andreas Wanninger

Master's Defensio
Friday, July 7th 2023, 9:45 CET
SR 1.7, UBB, Djerassiplatz 1, 1030 Vienna

Abstract

The scyphozoan Cassiopea xamachana is an emerging cnidarian model system. In addition to common scyphozoan life cycle stages that include a sessile polyp, free swimming ephyra larva,medusa, and sexually produced planula larvae, its polyps may reproduce asexually by budding off free swimming planuloid buds. While development and metamorphosis of planuloid buds and polyps are known in some detail, neuromuscular development in the sexually produced planula larva remains unknown. Using immunofluorescence labeling and confocal microscopy we examined neuromuscular development during metamorphosis of the planula larva into the juvenile polyp of Cassiopea xamachana using α-tyrosinated- tubulin, FMR Famide andserotonin-like immunoreactivity together with phalloidin labeling. Our results show a planular nervous system, consisting of a basiectodermal neural plexus with mostly longitudinal oriented neurites. This is connected to sensory neurons in the superficial stratum of the ectoderm on the aboral half of the larva. During settlement this planular, aborally concentrated nervous system degenerates and an orally concentrated nervous system is formed. The polyp‘s nervous system shows a nerve net with a loose concentration in the oral disc. These results are consistent with those on other scyphozoan planula larvae and are most likely a conserved feature of scyphozoan Discomedusae. As a ground pattern for cnidarian planulae our results support an aborally concentrated planular nervous system including sensory cells. The reorganization of the nervous system from anterior to posterior in planula-to-polyp metamorphosis is also most likely part of the ground pattern of cnidarians.

Keywords: Cnidaria, Cassiopea xamachana, neurogenesis, myogenesis, planula, polyp