…with apologies to my former classmate Daniel Garson
So, I was going to spend the afternoon creating a logo for Bloggers Half-Assedly Opining about Peer Reviewed Research Even Though Nobody Asked Them in the First Place (or BH-AOPR2ETNATFP) but I decided to devote the time to making this kick-ass band logo instead!
Of course that’s not going to stop me from posting the latest entry in our occasional series where I hastily comment on a slightly stale arm-waving brevium and then we sit back and wait for Catalogue of Organisms’ own Christopher Taylor to come along and straighten us out.
This week we take on Droser and Gehling (2008). Their brief report “Synchronous Aggregate Growth in an Abundant New Ediacaran Tubular Organism” appeared in Science a few weeks ago although, judging from the popular press accounts at least (which, of course are invariably cut-and-paste jobs from the University PR release) might have been better titled “Ropey Sea-Creatures were Sexing it up 570 million years ago…I swear!” From the press release:
Droser and Gehling observed that Funisia appears as 30 cm-long tubes in the fossils. They also observed that the tubes commonly occur in closely-packed groups of five to fifteen individuals, displaying a pattern of propagation that often accompanies animal sexual reproduction.
“In general, individuals of an organism grow close to each other, in part, to ensure reproductive success,” said Droser, the first author of the research paper and the chair of the Department of Earth Sciences. “In Funisia, we are very likely seeing sexual reproduction in Earth’s early ecosystem – possibly the very first instance of sexual reproduction in animals on our planet.
Um, okay, that’s a pretty freaking bold claim. Well, first off, as Larry Moran notes, bacteria do it, yeast do it, even educated peas do it, so sex itself is certainly a larger, longer, deeper and much slimier affair than might be given by an overly credulous reading of that quote. But even accepting for a moment Dr. Droser’s “animal” caveat lets review the evidence shall we?
Funisia fossils from Droser and Gehling 2008
First, the authors noted the occurrence of dense clusters of this tubular problematicon which they interpret as “spat falls”, e.g. multiple individuals which settled onto a substrate after planktonic larval dispersal around the same time. In modern organisms the formation of these aggregations are sometimes seen as a reproductive strategy. Animals which spend their adult life attached to the bottom improve their chances of finding a matching gamete for the sperm or egg they dump into the sea by being close to a member of the opposite sex.
Then they make a logical leap:
Among living organisms, spat production is almost ubiquitously the result of sexual reproduction but is known to occur rarely in association with asexual reproduction. (Droser and Gehling 2008)
That might be compelling circumstantial evidence, if we had any clue what Funisia was. However, like most other Ediacaran animals Funisia might as well be jam on toast for all we know about it’s ecology, life history or evolutionary relationships. Did that make any sense? Good. The author’s themselves note:
The phylogenetic affinity of F. dorothea is problematic. The morphology is consistent throughout all well-preserved specimens and serial units are a 3D character rather than features of external ornamentation. However, the lack of evidence for polypoid openings or pores in the body wall limits our understanding of its taxonomic affinities. Although it is difficult to place these fossils within Metazoa, the morphology and ecology are suggestive of stem-group cnidarians or poriferans.
Speaking of cnidarians…the first thing I thought of when I read the paper was Anthopleura elegantissima the so called “aggregating anemone.” While Anthopleura is capable of sexual and asexual reproduction it forms dense mats of asexually cloned individuals. Perhaps “spat” like clustering of similarly sized individuals isn’t necessarily linked to sexual reproduction.
At any rate, any insight into the Ediacaran ecosystem, however provisional, is certainly significant. Unfortunately, once again a University PR department eager for novelty and newsworthiness has muddied the water around a thought-provoking paper and fed more fuel to the “those crazy paleontologists what will they prove/disprove next?!” fire.