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. Voracious planktivores
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
predatory Ctenophore Beroe invades the Black sea and begins to control Mnemiopsis .
Mnemiopsis in the Caspian Sea threatens kilka fishery;Iran’s landings down to 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

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. “Advanced” characters in Ctenophora
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. “Advanced” characters in Ctenophora
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. Pole plates also believed to be sensory in nature
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
Mesoderm lost in Porifera, & Placozoa
Joseph F. Ryan et al

15. Independent origins of a nervous system x x x
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