Someone made the following comment upon reading the abstract of one of my recently published papers (led by Lucília Souza Miranda): "this claustrum paper just about lost me with its first sentence in the Abstract". It is definitely true that sometimes our scientific papers can be rather esoteric. This is all the more true of an abstract, which is properly meant to be a "retelling" of a paper rather than a summary.
So, let's examine the first sentence of the abstract of the paper in question:
"The claustrum in Cnidaria is a tissue in the gastrovascular cavity delimited by a central layer of mesoglea surrounded by gastrodermis (i.e., gastrodermis-mesoglea-gastrodermis), without communication with epidermis."
In re-reading this sentence, it seems a fair assessment. And indeed, in running the entire abstract through a "Readability Consensus Calculator", the consensus view is pretty clear: VERY DIFFICULT TO READ. Point taken.
So here is an attempt at getting the same information as in our abstract across using alternative language. One caveat: No doubt the language is stereotypical, inaccurate, and/or outdated. I can claim no authenticity for it. But do you get it? Is the alternative more clear than the actual?
Totally gnarly version:
So, like there is this hella cool thing in jellyfish, a piece of gut, yeah? This thing is called claustra and it’s really four different things, each one a claustrum. They grow, like, inside out from walls in the stomach and become totally new walls breaking the stomach into parts. If you zoom in way close, they have jelly-like stuff surrounded by gut tissues on both sides, and they do not connect to the outer skin (your epidermis is showing--jk). And this claustrum's been used to tryna suggest that two different kinds of jellyfishes, the square and hurtful box jellies and the beautifulest stalked ones, are closely related. But it’s totally bogus to accept that box jellies and stalked jellies both have claustra because, like, it's never really been looked at that carefully. But like we did that. Yeah. And the results are whacked. Actually, it’s like hella cool! Only the stalked guys have claustra, and just some of them at that. What some old dudes (gender-neutral) messed up was that box jellies don’t have claustra. They got these holes in their gut, though, near their throat, and that threw the brainiacs off. Cool thing though, stalked jellies also have those holes! I know, right? So, box and stalked jellies don’t share claustra but they do share gut holes. And by the way, it’s just dope to look at a fossil and think you can make out a claustrum in it.
And the real deal:
The claustrum in Cnidaria is a tissue in the gastrovascular cavity delimited by a central layer of mesoglea surrounded by gastrodermis (i.e., gastrodermis-mesoglea-gastrodermis), without communication with epidermis. By dividing the gastrovascular cavity, the four claustra provide an additional level of complexity. The presence of claustra in Cubozoa and Staurozoa has been used as evidence supporting a close relationship between these two cnidarian classes. However, the detailed anatomy of the claustrum has never been comparatively analyzed, rendering the evolution of this character among Cnidaria and its homology in Staurozoa and Cubozoa uncertain. This study provides a comparative investigation of the internal anatomy of the claustrum in Staurozoa and Cubozoa, addressing its evolutionary history based on recent phylogenetic hypotheses for Cnidaria. We conclude that the claustrum is a character exclusive to some species of Staurozoa, with a homoplastic evolution in the class, and that the structure called the “claustrum” in Cubozoa corresponds to the valve of gastric ostium, a structure at the base of the manubrium, which is also present in Staurozoa with and without claustrum. Thus, the claustrum cannot be a synapomorphy of a hypothetical clade uniting Staurozoa and Cubozoa, nor can its hypothetical presence in enigmatic fossils be used to support cubozoan affinities.
And since a picture tells a thousand words (much longer than your typical abstract), here is a diagram that compares species of stalked medusa without and with a claustum. We do not know for certain what the function of the claustrum is, but it does provide a space (pr-principal radial pockets, also known as mesogons or main radial pockets) where the gonads can be separated from the rest of the gut.
And here is what a claustrum looks like in histological transverse section, marked CS:
And here is the bottom line of the paper: Contrary to what has been stated in the past (and repeated by me in some papers), this structure known as a claustrum is not present in box jellyfish (Cubozoa), but is present in some but not all species of stalked jellyfish (Staurozoa). You can read all about in detail in:
Miranda LS, García-Rodríguez J, Collins AG, Morandini A & AC Marques (2017) Anatomy and evolution of the claustrum: a comparative study in Cubozoa and Staurozoa (Cnidaria) reveals that it is exclusive to some species of Staurozoa. Organisms, Diversity & Evolution. https://doi.org/10.1007/s13127-017-0342-6
Or you can contact any of the authors to request a PDF copy of the paper.
