September 12, 2019

Adrian Jaimes-Becerra, Ranko Gacesa, Liam B Doonan, Ashlie Hartigan, Antonio C Marques, Beth Okamura, Paul F Long, “Beyond Primary Sequence”—Proteomic Data Reveal Complex Toxins in Cnidarian Venoms, Integrative and Comparative Biology, icz106, https://doi.org/10.1093/icb/icz106

Summary: Cnidarians (corals, sea anemones, sea fans, sea pens, jellyfish, and hydroids) are believed by many evolutionary biologists to be the most ancient lineage of extant venomous animals. Despite being well known for their venomous sting, many cnidarian venoms have never been studied, including from entire clades. This study presents the first protein-based investigation of staurozoan (stalked jellyfish) venom, it expands what we know about hydrozoan and anthozoan (anemones and corals) venom, and compares the diversity and evolution of cnidarian venom to other venomous animals (e.g., snakes and arachnids). The authors found that 75% of toxin protein families are shared between two or more cnidarian classes. They also found that stalked jellyfish did not possess any unique toxin protein families. Notably, anemones and corals have seven unique toxin protein families found in no other classes. The authors also report that venoms appear to group more readily based on function rather than taxonomy. They show this in two ways, first in a table that lists the new toxin peptides identified by their analysis and the toxins that are most similar to those found in other venomous organisms, and, second, in the clustering analysis used to compare and group the approximately 7000 toxin sequences in their database across all venomous animals. The table shows that most newly identified toxins sequenced in this study are more similar to toxins found in unrelated animals, like snakes and spiders, than to toxins from other cnidarians. The clustering analysis suggests that the diversification of toxins across venomous groups is independent of evolutionary time. Taxonomic groups considered older do not necessarily have more diverse venoms than groups considered younger. Cnidarians appeared to have more diverse venoms than amphibians and fish; about the same diversity as insects, gastropods, and elapid snakes; but were not as diverse as vipers or arachnids.

Comment: For many, if not most, creationist scientists, a major question relating to origins is not whether organisms evolve, i.e. change through time, but to what extent and how quickly these changes occur. For example, from most creationist viewpoints, toxins are not expected in the original creation, so it is possible that they would be the result of changes in the venomous species after the Fall. The article by Jaimes-Becerra et al. presents several interesting implications that could be useful to understand the role evolutionary processes played in the alteration of organisms since the Fall. First, it appears that similar toxins are present in a diverse array of animals,[1] which suggests that similar processes might have occurred several times to produce these changes in different kinds of animals. Such changes do not appear to create new structures but modify existing proteins to cause harmful effects in other animals, i.e. a process/mechanism known as co-option. However, the article also suggests that cnidarians share most of their toxin families. This suggests that toxins do not readily change once they have been co-opted in the first place. In summary, if venoms evolved after the Fall, then they appear to have done so many times independently. However, the types of things that are recruited to become toxins appear to be severely limited and once co-opted they remain relatively unchanged. The appearance and diversification of venoms seems to be repeatable but simultaneously limited in scope. It may be that venoms make an excellent model for studying how and to what extent natural processes are capable of altering life since the Fall.

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David Nelsen Ph.D.
Associate Professor of Biology
Southern Adventist University

References

[1] Holford, M., Daly, M., King, G. F., & Norton, R. S. (2018). Venoms to the rescue. Science, 361(6405), 842-844.