title: Induction of metamorphosis with potassium ions requires development of competence and an anterior signalling centre in the ascidian Herdmania momus.
abstract: Increased K+concentration in seawater induces metamorphosis in the ascidian Herdmania momus. Larvae cultivated at 24°C exhibit highest rates of metamorphosis when treated with 40 mM KCl-elevated seawater at 21°C. At 24°C, H. momus larvae develop competence to respond to KCl-seawater and initiate metamorphosis approximately 3 h after hatching. Larval trunks and tails separated from the anterior papillae region, but maintained in a common tunic at a distance of greater than 60 μm, do not undergo metamorphosis when treated with KCl-seawater; normal muscle degradation does not occur in separated tails while ampullae develop from papillae-containing anterior fragments. Normal programmed degradation of myofibrils occurs when posterior fragments are fused to papillae-containing anterior fragments. These data indicate that H. momus settlement and metamorphosis only occurs when larvae have attained competence, and suggest that an anterior signalling centre is stimulated to release a factor that induces metamorphosis.
authors.affiliation: Department of Zoology and Centre for Molecular and Cellular Biology, University of Queensland, Brisbane, Queensland 4072, Australia, , , , , , AU.
authors.forename: B M
authors.initials: BM
authors.lastname: Degnan
authors.affiliation: Department of Zoology and Centre for Molecular and Cellular Biology, University of Queensland, Brisbane, Queensland 4072, Australia, , , , , , AU.
authors.forename: Duncan
authors.initials: D
authors.lastname: Souter
authors.affiliation: Department of Zoology and Centre for Molecular and Cellular Biology, University of Queensland, Brisbane, Queensland 4072, Australia, , , , , , AU.
authors.forename: Sandie M
authors.initials: SM
authors.lastname: Degnan
authors.affiliation: Department of Zoology and Centre for Molecular and Cellular Biology, University of Queensland, Brisbane, Queensland 4072, Australia, , , , , , AU.
authors.forename: Suzanne C
authors.initials: SC
authors.lastname: Long
mesh_terms: D000818:Animals; D001315:Australia; D057894:Coral Reefs; D007814:Larva / Q000378:metabolism; D008675:Metamorphosis, Biological; D009210:Myofibrils / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D014561:Urochordata / Q000254:growth & development* / Q000378:metabolism*
chemical_list: D011188:Potassium
keywords: Competence; Key words Ascidian; Metamorphosis; Settlement; Urochordate