Have you seen this? - Xenopus basking; fertilizing without amplexus?

[findiviglio]

Hello,
The following observations are drawn from my notebooks...the first involves animals in my own collection, the second occurred during my tenure at the Bronx Zoo's Dept. of Herpetology. Any feedback would be most appreciated, thank you.

Many years ago I kept 2 African clawed frogs (Xenopus laevis) that would "bask" on a rock which protruded above the water, directly under an incandescent bulb. This only occurred in winter, when the water temperature in their tank averaged 66 F, so I thought they might be seeking warmth. However, others I’ve kept at that temperature have not left the water, despite being provided with a basking light as well.

The second observation involves a female clawed frog that laid eggs in absence of a male. That in itself is unusual. Odder still, however, was the fact that a male placed in the tank with the eggs (and without the female) on the following day fertilized the eggs. He was in breeding condition, as (“nuptial pads” along his forearms), and perhaps was responding to pheromones in the water, but still should have (according to me, not him, it seems!) required a female to stimulate sperm release. I have spoken with a number of herpetologists about this, and none can recall a similar incident.

These observations date back decades, so I am most anxious for any input!

I have posted a number of articles dealing with the natural history and care of amphibians, reptiles, fishes, invertebrates and birds at:
http://blogs.thatpetplace.com/thatreptileblog
http://blogs.thatpetplace.com/thatavianblog
http://blogs.thatpetplace.com/thatfishblog

Thanks, Frank.

[MegophryidaeMan]

Wow, you don't hear of many frogs basking, but that is a really interesting observation!

[John]

The second observation involves a female clawed frog that laid eggs in absence of a male. That in itself is unusual. Odder still, however, was the fact that a male placed in the tank with the eggs (and without the female) on the following day fertilized the eggs. He was in breeding condition, as (“nuptial pads” along his forearms), and perhaps was responding to pheromones in the water, but still should have (according to me, not him, it seems!) required a female to stimulate sperm release. I have spoken with a number of herpetologists about this, and none can recall a similar incident.

Very interesting observations there Frank. Thank you very much for contributing them. I am particularly curious about this latter observation - perhaps the eggs produced were fertile to begin with and did not require a male? I'm speaking of course about parthenogenicity. What do you think?

[tylototriton]

In regards to the basking, I can't speak for frogs, but I have observed basking behavior in Notophthalmus during winter time. Granted, completely different family, but at least its another amphibian. In regards to the second observation, I racked my brain and could not think of something similar. If I had to hazard a guess I would say pheromones still present in the water, but I have absolutely nothing to back that up. Something to ponder.

Alex

[Jake]

I've had groups of juvenile xenopus attempt to crawl up the corners of their tubs in the winter before, but I use no light. Escaping the cold would be a good explaination because the rest of the year the same age frogs never did this, only when the temps got down to the upper 50's they'd start.

[findiviglio]

Very interesting observations there Frank. Thank you very much for contributing them. I am particularly curious about this latter observation - perhaps the eggs produced were fertile to begin with and did not require a male? I'm speaking of course about parthenogenicity. What do you think?

Interesting thought, so many new surprises in that area lately...a shark just yesterday, a Komodo dragon a few years back...I haven't researched the possibility, worth a try, thanks. Odd that the male would fertilize w/o amplexus, I think...but then again, if any frog would adapt its behavior to the situation, it would be Xenopus!, Frank

[findiviglio]

In regards to the basking, I can't speak for frogs, but I have observed basking behavior in Notophthalmus during winter time. Granted, completely different family, but at least its another amphibian. In regards to the second observation, I racked my brain and could not think of something similar. If I had to hazard a guess I would say pheromones still present in the water, but I have absolutely nothing to back that up. Something to ponder.

Alex

Thanks, Alex...I've run into a few other frogs basking in winter, i.e. an American bullfrog, green frogs fairly regularly, but not salamanders. I was particularly surprised because Xenopus is so poorly adapted for land - they will travel overland on wet nights when ponds are poisoned, i.e. in Californiaduring eradication attempts, and will snatch insects from the shore, but lying out seemed beyond what they "should do".

[findiviglio]

I've had groups of juvenile xenopus attempt to crawl up the corners of their tubs in the winter before, but I use no light. Escaping the cold would be a good explaination because the rest of the year the same age frogs never did this, only when the temps got down to the upper 50's they'd start.

Thanks very much, Jake!...that's the closest I've heard to a similar observation in the 15 years I've had this in mind. They will leave the water when stressed in other ways - drought, poison, etc., so it does follow. I read of a population that lives in the subterranean water supply system of a castle in England (who thought of that introduction!?)..I believe it is in Biology of Xenopus. The water stays cool - 50's I believe...reproduction seems not to occur but marked frogs are 16 or so years of age...need to follow up on that study, thanks for the prompt.

[tylototriton]

So I did some snooping on the thermoregulation observation. I was looking through Kentwood Wells " The Ecology and Behavior of Amphibians," and he has a small section on thermoregulation in aquatic amphibians. The gist of what he says is that it is documented, but most of the studies have been done with larvae and a few with caudates, none (as of the publication of this book) with adult aquatic frogs. The book was published in 2007 so I think its pretty up to date. Its certainly a topic which deserves further study.

In regards to the fertilization after the fact I have found very little. There were a couple papers that mentioned the effects of delayed fertilization, but none that documented its occurrences or causes. This too is a very intriguing topic.

Alex

[findiviglio]

Thanks for your time and trouble, Alex. Barron's will put out a second edition of Newts and Salamanders this spring...I'm not sure of format yet, but if possible I'll include add something re thermoregulation. Best, Frank.