Ctenophores: Basal Metazoa with Stunning Iridescence

1. Pictures of the Day Ctenophores from Ernst Haeckle’s “Art forms of Nature” Iridescense Bioluminescence

2. Ctenophora and Speculations About the Basal Metazoa (Urmetazoa) (see Ch 7 and Ch 4 pp 87-88) Ctenophora characteristics II. Current views About Phylogeny

3. Sea Walnut Mnemiopsis leidyi Fineartamerica.com Voracious planktivores

4. Ecological Importance of Ctenophores: The Black & Caspian Sea Stories -- deterioration of the Black Sea due to eutrophication and fisheries (bonito, mackarel, dorado); In 1989 Mnemiopsis causes crash of anchovy fishery -- 1997 predatory Ctenophore Beroe invades the Black sea and begins to control Mnemiopsis . -- 1999 Mnemiopsis in the Caspian Sea threatens kilka fishery;Iran’s landings down to 15000 tons, an 82 % decrease by 2004. -- Has since spread to North Sea and Baltic Sea, though no one can explain how.

5. Spread of Mnemiopsis leidyi in European seas http://www.ilvo.vlaanderen.be/memo

6. Phylum Ctenophora Normally aligned with Phylum Cnidaria on the basis of body plan, life style but clearly a valid distinct phylum

7. Characteristics of Ctenophora • Cnidaria Like • Gelatinous, planktonic • Epithelia, mesoglea • Mouth, pharynx, G-V canals • No circulatory, excretory systems • Nerve net present • Unique to Ctenophora • Muscles* from cells in mesoglea; widely believed to be mesoderm • Biradial symmetry • Locomotion by comb rows • 2 digestive canals open to the outside by anal pores…… more on this

8. The Presence of a Functionally Tripartite Through-Gut in Ctenophora Has Implications for Metazoan Character Trait Evolution (2016) Did a complete digestive system evolve independently in the Ctenophores and in Bilateria? “Advanced” characters in Ctenophora (compared to sponges) • Through-gut • 2. • 3. • 4. Jason S. Presnell, Lauren E. Vandepas, Kaitlyn J. Warren, Billie J. Swalla, Chris T. Amemiya, William E. Browne null, Volume 26, Issue 20, 2016, 2814–2820

9. The Presence of a Functionally Tripartite Through-Gut in Ctenophora Has Implications for Metazoan Character Trait Evolution (2016) Did a complete digestive system evolve independently in the Ctenophores and in Bilateria? “Advanced” characters in Ctenophora (compared to sponges) • 1. Through-gut • Nervous system • 3. Muscles • 4. Epithelia Jason S. Presnell, Lauren E. Vandepas, Kaitlyn J. Warren, Billie J. Swalla, Chris T. Amemiya, William E. Browne null, Volume 26, Issue 20, 2016, 2814–2820

10. Other important differences: • A few exceptional bottom-dwelling spp but no polyp phase • Polymorphism unknown in Ctenophores • No Ctenophores are colonial • Colloblast (lasso) cells for feeding • Gastrulation by epiboly or by invagination whereas • cnidarians gastrulate by delamination primarily • Swimming by comb rows under control of apical organ

11. Sense Organs (statolith etc.) and other apical structures in Ctenophores (figure 7.2). The ciliary grooves are agents of nerve impulse conduction……. A nervous system; also consists of a nerve net Pole plates also believed to be sensory in nature

13. Are Ctenophores or Sponges the oldest animals? Oldest known fossils are sponges (600 mya) Cholesterol traces of sponges 650 mya Link between choanoflagellates and sponges Ctenophores have mesoderm, nerves, through- gut & Epithelia But “fronds” present in the preCambrian were Ctenophores and ctenophores are also ancient….

14. Ctenophores are the sister group of all other animals • Genes for mesodermal cells present but lack other animal mesodermal gene components- may be independently evolved Joseph F. Ryan et al

15. Independent origins of a nervous system Leonid Moroz has found that : “…classical neuro-transmitter pathways are absent in Ctenophores; serotonin, dopamine, adrenaline…all absent …is consistent with the idea that the Ctenophore neural system evolved independently. Through gut x x x Through gut Note also independent origin of mesoderm and of a thru digestive system

16. Ctenophora Sister Porifera Sister