Species species of the Week week #7 OR Tautonomical IGP!!!
Check it out it's:
Figure 1. Velella Velella in their natural habitat - with sunglasses.
Thanks you guys for giving tautonyms some pop-culture legitimacy!
Ok. No, of course that is the Seattle-ish Electro-pop band Velella Velella (Figure 1). I admit I don't know the story of their name, though I'm sure someone around here does, but I can only assume that the capitalization of the species name is "ironic". In fact, thanks to lack of case-sensitivity, searches for the more gelatinous V. velella are indistinguishable from those searching for the band.
Here is the Velella velella I'm actually talking about:
V. velella emerges as this week's tautonym, you will recall, because it is on the tautonomical menu of the Blue Dragon nudibranch(1). BUT, it is also on the menu for the Baggins snail, Janthina janthina, which is itself on the menu of the nudibranch! Tautononym intraguild predation! Sooo, what? Let me try to explain. No, there is too much, let me sum up (Figure 3).
In addition to sharing the distinction of feeding a sea beastie with excellent grammatical taste, V. velella also shares with J. janthina the peripatetic lifestyle of the pleuston(2). Whereas J. janthina goes the hot air balloon route(3), V. velella is a sailor - hence the common name. They are a type of jelly, so they float around, mostly (see below) passively and distinguish themselves by raising a thin, chitinous(4) plate out of the water - the sail! And if you are, like V. velella, yourself a sailor, you will intuit that V. velella's sail is not parallel to the length of its body, it's offset by a few degrees. This enables it to use its tentacles for stability and to sail off the wind(5). Here is a diagram (Figure 4)!
|Figure 4. There's a caption above and a citation below to give you all the information you need on how PMW ( = Portugese Man O' War. Here they discuss the nearly tautonymic Physalia physalis, which sail similarly to V. velella) sail compared to sailboats.|
Ok, so there is asymmetry, which is pretty cool for lots of reasons, but the other extremely cool thing is that they are not all asymmetrical in the same direction: there are left-sailed and right-sailed V. velella. I'm not sure that folks are yet clear about what determines whether an individual will be right or left-sailed, or at least I haven't found anything that seems clear, but they have tried to understand how this might affect their distribution. This was evidently confounding to ecologists for a long time, because papers on this question date back to the 20's. In Nature in 1959, Robert Bieri explains it thusly(6):
In the northern hemisphere, left-handed specimens of Velella move to the left of the wind direction due to the anticyclonic wind circulation over the ocean. The left-handed specimens are therefore concentrated along the outer edges of the distribution. The right-handed Velella move to the right of the wind direction and are concentrated in the centre of the distribution. Thus one should find the left-handed specimens near shore.And the opposite is true in the southern hemisphere(7). So, all the individuals of one sail type (depending on the hemisphere) might get mass-stranded on the beach or stuck in the Pacific Ocean gyre. This could be a bet-hedging strategy - if you don't know where the food is going to be, send your kids everywhere so some of them make it - AND such a drastic difference in dispersal could have some extremely awesome evolutionary and ecological consequences....blah blah blah <-- Emily drones on and waves her arms a lot here....
As cool as this Velella Velella?
|Figure 5. Velella Velella in SPL-uh.|
I think so, but you'll have to decide for yourself.
References and miscellany:
(1) Well, also because friends (and brother - ever the source of blog post inspiration) kept posting V. velella on my fb page. For the record, I had already written most of this post weeks ago, and just hadn't gotten around to finishing and/or posting it.
(2) Wait, what's the pleuston, again? Well it's like the neuston, only for the big guys.
(3) OHHHH! Speaking of hot air balloons, you should really educate yourself about this mind blowing recent event!
(4) Just ignore that word if it brings back anxiety attacks of your intro bio class. I haven't ever looked into this or even really thought about it, but I'm passively interested (read: pretending to be a science hipster) in the use of calcium carbonate versus chitin in sea creatures to form hard structures.
(5) PS, I clearly don't understand too much about this, and have only a vague notion of why, exactly, one can sail faster than the wind, but for more on the hydrodynamics of the V. velella sail, see this paper.
(6) Yup, I just said "thusly". It even made me gag. Here's the citation for that paper: Bieri (1959) Dimorphism and size distribution in Velella and Physalia. Nature 4695:1333.
(7) Think the Simpsons visit Australia: Why is this only available in Spanish!?