Adult water anole (Anolis aquaticus) from Coto Brus, Costa Rica, with an exhaled – and recycled – air bubble. Photo by Lindsey Swierk.
Over the past few years, I’ve been accumulating evidence that the water anole (Anolis aquaticus) might be a tiny scuba diver in the streams of its home in southern Costa Rica. Anolis aquaticus takes to the water as refuge from predators, swimming and often diving underwater for long periods of time – the record at my study site is currently 16 minutes! To enable these crazy-long dives, it’s possible that anoles may have come up with a scuba-tank method of sorts to “breathe” underwater. I’ve compiled a video of what appears to be underwater respiration of a recycled air bubble that clings to the anole’s head. (A few more details about these observations will be in the upcoming March issue of Herpetological Review.) For now, enjoy the video!
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Sven Vogler
Reminds me of the “physiological lung” of some hemipterid water bug which was used as an example for “underwater breathing” at university.
If it’s a similar adaption there might be special (ultra-?)structures on the head scalation to hold the bubble.
Highly interesting.
Lindsey Swierk
Thanks for the comment! We think this is likely, too – and it’s something we’re currently investigating… I’ll be sure to keep the Anole Annals community up to date with findings!
Sven Vogler
Results may later even be compared with ecologically similar anoles, like Mexican barkeri and Cuban vermiculatus. At least barkeri is able to spend around 15 minutes completely submerged (own observations).
Lindsey Swierk
Cool observation on barkeri – thanks!
Kurt Schwenk
This is fantastic! Great observation. I agree that considering the material properties of the keratin/scales around the nares and front of the snout is important and to do this in a comparative context. Are the water anoles different in any way from related, non-aquatic species? There could be shape differences, as well (as Sven suggested, there is work on diving beetles that looks at these things, including changes in surface polarity in the chitin along the length of the beetle). Also consider, if you haven’t already, the fact that by holding the bubble out there for a bit, particularly in moving water, they are getting some re-oxygenation of the bubble air by diffusion from the water. Finally, I’d be interested in the relationship between aspiratory movement of the ribs and buccal pulsing. Is the respiratory pattern similar to terrestrial breathing or modified (possibly in timing, alone)? Obviously they can’t exhale too much or they pop the bubble (as the lizard does several times at the start of the video). I hope you are not underselling this—it’s very cool. The natural history observations coupled with some of the other investigations is the kind of thing that could fly in PNAS or somewhere…
Lindsey Swierk
Thanks Kurt – those are some fantastic ideas to mull over! We’ve certainly been considering some of them, and I love the idea about re-oxygenation of the air bubble simply by being in gently moving water. How cool would that be?! Thanks for the suggestions, and I’ll be sure to share my progress.
Brian Magnier
Very cool! It reminds me of a video I watched on Star-nosed Moles doing something superficially similar (and using the star-nose to hold the bubble in place!) to supposedly smell underwater to track prey. Very cool convergent behavior for different uses.
Deepti
This is very interesting! Reminds me of diving beetles.
Robert Powell
An observation of very stout claws in A. barkeri some years ago led to an examination of claws in other aquatic species, all of which also had stout claws. This presumably would facilitate hanging on to slick rocks in a strong current. If you follow up on this underwater breathing as a convergent character in aquatics, you might look for other relevant adaptations as well. In light of the adaptive radiation that’s been extensively studied, we shouldn’t be surprised that aquatic anoles exhibit convergence. Be aware, however, that non-aquatic anoles (e.g., A. chlorocyanus) sometimes take to water (even diving on rare occasions), but I suspect their ability to stay submerged pales in comparison.
Lindsey Swierk
Thanks Robert! A great idea – aquaticus’s claws are pretty ‘stout’, I’ll have to look up that paper. And it’s certainly on my list to compare non-aquatic anoles’ abilities to submerge and retain those bubbles… Thanks!
Kurt Schwenk
Brian makes an excellent point. The star-nosed mole nose bubble work was done by Ken Catania. An excellent analog.
Wade C. Sherbrooke
I recall many years ago, in 1971, seeing these diving anoles in Costa Rica. The behavior struck me as very similar to the microteid, Neusticurus ecpleopus, whose reproductive cycle I had been studying in Amazonian Peru. It lives only in small streams and dives from the tiny shore into the water to disappear, holding its breath, using under-edge retreats, or perhaps exiting at a more distant local. The habits, habitats, anti-predator escape behaviors and probably a lot more are similar. It would be very cool if it too used bubbles as well to remain hidden. Biotropica 7:194-207 (1975)
lukemahler
Very cool post! I feel I should chime in and report a “convergence” – my own lab has been working on this phenomenon as well over the last few years, and my student Chris Boccia is wrapping up a paper from his thesis that investigates many of the questions that folks have been suggesting here (e.g., testing other aquatic and non-aquatic species, testing the role of the bubble in respiration, etc.). Suffice it to say, it’s a super cool phenomenon with a lot of neat implications. Lindsey, perhaps we can chat with you about what we’ve been finding! 🙂
Lindsey Swierk
Amazing! That’s fantastic Luke, and I can’t wait to read Chris’ paper and talk with you both more about this. I’m so pleased that Chris is really “diving in” (pun intended) to this topic – it’s certainly needed! Hope this can be grounds for some good collaboration.
Tim Herman
There is a lot of interconnected thin bubble persistently covering most of the area on the head. I would guess this is where most of the gas exchange is occurring and the big rostral “bubble” is a quick exchange between this air and the air in the lungs.
Lindsey Swierk
That’s exactly what I was thinking as well!
Siddarth
This is super interesting! Certain insects use a layer of trapped air (called a “plastron”) to breathe underwater. It is known to occur when the skin has some hairy protrusions or other texture combined with a hydrophobic/waxy coating. E.g. Flynn & Bush (2008). “Underwater breathing: The mechanics of plastron respiration”. Journal of Fluid Mechanics, 608, 275-296. doi:10.1017/S0022112008002048
Curious if Anolis aquaticus has evolved something similar!
Andrew
This is totally out of left field, but free divers and surfers (im sure there are other water sports but those are the two that come to mind) which are submerged need to learn to overcome a basic breathing reflex. In the absence of significant gas exchange between the water and the air bubble in between breaths, the bubble trick may be a good way of ‘deceiving’ a breathing reflex in the lizards. Fits closer to the ‘recycled air’, and avoids sucking water into the lungs. Lots of assumptions there, but if a person can ‘quickly’ learn to hold their breath for 5 min, 15 min for a lizard just hanging out underwater should be possible without significant gas exchange.
Stefan K. Hetz
Cool and interesting. Lots of questions from a physiologist. I am looking forward to the issue to read how much the oxygen has dropped in the bubble and figure out if the bubble surface (the most important area for gas exchange) is big enough (the diving bells in water spiders have around the same size – but the spiders are much smaller AND the bubble can not supply the full oxygen. How does the bubble size related to lung volume?) to supply the whole animal with oxygen. Is there a diving response? Does the bubble change its volume due to breathing? There may be alternative explanations and a diving duration of 16 minutes does not seem too long taking into account a dive response, the lower temperature and lower metabolic rates of reptiles and a high anaerobic capacity indicated by lactate accumulation.
Lindsey Swierk
These are fantastic questions, and I know the answers to none of them! Hopefully I’ll be able to dig into these questions in the next few years. I’d be eager to hear more of your thoughts in detail – this is all new ground to me as a non-physiologist.
Bent Christensen
Just a thought for a test here. I guess that the idea is that the gas bubble exchanges oxygen with the surrounding water. However, what is the oxygen concentration in the water? It has to be higher than in the air bubble, which probably is quite unlikely, at least as far as my understanding of oxygen concentrations go. however, if you could measure the different concentrations, that would give you some info. You could probably do that outside of the water for the lizard. An alternative suggestion is that it is lowering the CO2 concentration in its air supply, rather than exchanging oxygen. I am not a physiologist, but I believe that the breathing in humans (mammals?) is affected by CO2 concentrations rather than oxygen concentrations.
Neil Losin
Lindsay, this is really cool (and terrific video to boot). Nate Dappen and I produced a 1-hour broadcast documentary about anoles called “Laws of the Lizard,” which will be premiering December 26 at 8pm on the Smithsonian Channel:
https://www.smithsonianchannel.com/shows/laws-of-the-lizard/0/3459142
We filmed A. oxylophus near Monteverde (indending only to film its anti-predator behavior, e.g. diving into the water and swimming away) and captured similar “re-breathing” behavior on film. Some of that footage made it into our documentary. It’s a pity we didn’t know about your efforts to study this phenomenon with A. aquaticus! It would have been cool to make that part of the story as well.
In any case, I look forward to hearing more about this remarkable biology, both from your work and work in the Mahler lab. Exciting stuff!
Cheers,
Neil Losin (Day’s Edge Productions)
Lindsey Swierk
Thanks Neil! I saw your oxylophus video clip yesterday and LOVED it! How cool – and what amazing footage! It would’ve been great to work together, I agree. Let’s be in touch.
I met Nate last year at Las Cruces, and someone else working with Day’s Edge in LC in 2016. Your team has produced such awesome projects, and I can’t wait to watch Laws of the Lizard over the holidays!
Lindsey Swierk
Thanks Neil! I saw your oxylophus video clip yesterday and LOVED it! How cool – and what amazing footage! It would’ve been great to work together, I agree. Let’s be in touch.
I met Nate last year at Las Cruces, and someone else working with Day’s Edge in LC in 2016. Your team has produced such awesome projects, and I can’t wait to watch Laws of the Lizard over the holidays!
J Burnside
It should be blatantly obvious that the bubble of air adheres to the lizard’s skin because of the electronegativity of oxygen and Van der Waals forces that act as adhesive. Probably not an ionic bond but definitely an adhesion that is charge based.