The Presence of a Functionally Tripartite Through-Gut in Ctenophora Has Implications for Metazoan Character Trait Evolution
Open accessAbstract
The current paradigm of gut evolution assumes that non-bilaterian metazoan lineages either lack a gut (Porifera and Placozoa) or have a sac-like gut (Ctenophora and Cnidaria) and that a through-gut originated within Bilateria [1-8]. An important group for understanding early metazoan evolution is Ctenophora (comb jellies), which diverged very early from the animal stem lineage [9-13]. The perception that ctenophores possess a sac-like blind gut with only one major opening remains a commonly held misconception [4, 5, 7, 14, 15]. Despite descriptions of the ctenophore digestive system dating to Agassiz [16] that identify two openings of the digestive system opposite of the mouth-called "excretory pores" by Chun [17], referred to as an "anus" by Main [18], and coined "anal pores" by Hyman [19]-contradictory reports, particularly prominent in recent literature, posit that waste products are primarily expelled via the mouth [4, 5, 7, 14, 19-23]. Here we demonstrate that ctenophores possess a unidirectional, functionally tripartite through-gut and provide an updated interpretation for the evolution of the metazoan through-gut. Our results resolve lingering questions regarding the functional anatomy of the ctenophore gut and long-standing misconceptions about waste removal in ctenophores. Moreover, our results present an intriguing evolutionary quandary that stands in stark contrast to the current paradigm of gut evolution: either (1) the through-gut has its origins very early in the metazoan stem lineage or (2) the ctenophore lineage has converged on an arrangement of organs functionally similar to the bilaterian through-gut.
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Absorption of both food and ferritin particles into ciliated, epithelial cells of the canal system suggest that both phagocytosis and pinocytosis are active in these cells.
“Absorption of both food and ferritin particles into ciliated, epithelial cells of the canal system suggest that both phagocytosis and pinocytosis are active in these cells (Bumann and Puls 1997; Franc 1972; Presnell et al. 2016).”
From A non-bilaterian perspective on the development and evolution of animal digestive systems (2019) · cites this paper as Presnell et al. 2016
Cites
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- Authors
- Presnell, J. S., Vandepas, L. E., Warren, K. J., Swalla, B. J., Amemiya, C. T., & Browne, W. E.
- Affiliations
- University of Miami (US)
- University of Washington (US)
- Smithsonian Institution (US)
- Corresponding author
- Browne, William E.
- ORCID
- Venue
- Current Biology
- Publisher
- Elsevier BV
- Published
- 2016-10
- Volume
- 26
- Issue
- 20
- Pages
- 2814-2820
- ISSN
- 0960-9822 (ISSN-L)
- OpenAlex
- W2515502041
- Cited by
- 51
- References
- 13
- Citations by year
- 2026: 2 · 2025: 7 · 2024: 7 · 2023: 3 · 2022: 6 · 2021: 5 · 2020: 2 · 2019: 8 · 2018: 7 · 2017: 3 · 2016: 1
- FWCI
- 5.27
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Licence
- Locations
- Current Biology (publishedVersion)
- PubMed (publishedVersion)
- Funders
- National Science Foundation
- University of Miami
- University of Washington
- Topics
- Physical Sciences › Earth and Planetary Sciences › Paleontology › Marine Invertebrate Physiology and Ecology
- Life Sciences › Agricultural and Biological Sciences › Aquatic Science › Echinoderm biology and ecology
- Health Sciences › Medicine › Urology › Comparative Animal Anatomy Studies
- Keywords
- Ctenophora, comb jellies, digestive system anatomy, excretory pore, waste removal
- MeSH terms
- Animals, Biological Evolution, Ctenophora, Gastrointestinal Tract
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