There's a frog in my tadpole

Sometimes a photograph can instantly give you a whole lot more information on a topic than you ever knew. 

This is a cropped close-up of a picture that I showed on the blog a few weeks back (see here). At the time that I took the picture, and later when I selected it for the blog post, I had completely failed to spot this metamorphosing frog in the image. I had never fully appreciated how the new frog in a metamorphosing tadpole was formed. Perhaps because of the colour of this Xenopus laevis frog from an invasive population in Tucson, Arizona, is so stark, you can clearly see through the transparent tadpole flesh the form of the frog coming through.

Note how the head of the tadpole and head of the frog appear to be completely different, yet the sensory organs (eyes, nares, etc.) are functioning on the tadpole and joined by nerves to those same sites on the frog head. Note also the way in which the fore-limbs (that always appeared to come at an odd place on the tadpole) are perfectly situated in relation to the frog head. 

Over the next week or so, the tadpole head will regress in size and the tail will start to shrink as the final stages of metamorphosis take place. Sensory organs will relocate into the frog head. 

Laurie presents at the 22nd European Congress of Herpetology

The 22nd European Congress of Herpetology took place in Wolverhampton UK and Laurie Araspin presented her PhD work on Xenopus acclimation:

Locomotion and physiology depending on temperature in Xenopus laevis native and invasive populations
Araspin, L., Measey, J. & Herrel, A.

Ectothermic species are dependent on temperature, which drives many aspects of their physiology. The distribution of native and invasive populations of the frog Xenopus laevis is characterised by an exceptional latitudinal and altitudinal range. Along these gradients, the thermal environment changes and populations experience different temperatures. We assessed phenotypes depending on the temperature of individuals coming from six native and one invasive populations. We measured the thermal dependence of locomotor performance in adults given its relevance to dispersal, predator escape, and prey capture. Results show that the thermal performance optimum differs among populations, and the minimum critical temperature varies among populations coming from different altitudes. Then, we compared the standard metabolic
rate (energetic cost of organismal maintenance; SMR) depending on temperature, as locomotor performance strongly relies on metabolic activity. We tested SMR in populations from the native range, inhabiting low (South Africa) and high altitudes (Lesotho), and from the invasive range (France). Regarding the contrasting climatic environments of the studied populations, differences in the SMR depending on temperature are expected. We found that populations exhibit different energetic costs in metabolic activity and that populations show reduced metabolic activity in the temperature range the most encountered in their environment (i.e., in cold temperatures for
populations from colder environments and in hot temperatures for populations from warmer environments). The ability of this species to change its optimal temperature for locomotor performance and its metabolic activity across extremely different climatic environments may help explain its invasive potential. These findings highlight the extraordinary thermal adaptation ability of the species. This ability to cope with a wide range of variation in environmental temperatures suggests that the species may be particularly good at invading novel climatic areas.

A demanding way to spend your weekend

While at the Amphibian Foundation at the end of my trip to the USA, I took advantage of an offer to conduct a snake handling course (level 1) that they offer (see here). I've been in situations that have called for venomous snake handling in the past, and have always felt a little under prepared. Now with the course completed I know how to be safer when faced with a venomous snake on the ground, and a group of people that want it moved away.

Looking a little overgrown (after 2 months in the field without a haircut), I was outfitted with gaiters to prevent fangs going through my trousers. Guided by a set of expert instructors I learned how to handle heavy snakes on hooks (notice the braced position of the hooks under the forearms), and importantly how to safely get the snake into a tied bag and sealed bucket keeping it more than arms length at all times. 

Being in Atlanta, we became familiar with several of the regions most venomous snakes including the Eastern Timber Rattlesnake (Crotalus horridus - above), the Eastern Copperhead (Agkistrodon contortrix), Cottonmouth (Agkistrodon piscivorus), and Eastern Diamondback Rattlesnake (Crotalus adamanteus  - below). 

As you can see, the snakes were all very beautiful and it was a great pleasure working with them. Carefully following each of the steps according to instructions allowed us to bag up the snakes in a very safe manor. Run by the Rattlesnake Conservancy, these courses offer experienced and professional tuition in a relaxed and friendly environment.

As you can see, I gained my certificate of competence and feel a lot more confident about how to tackle venomous snakes in future.

Back catching Xenopus in Tucson, Arizona

In 1995, during my PhD at Bristol University, I visited Tucson Arizona to study the population of African clawed frogs at the Arthur Pack Desert Golf Course. The population is known to have dated to the late 1970's when a local academic seeded many impoundments in southern Arizona with Xenopus hoping that he could pick up breeding animals in the future for selling on. It seems that most of the introductions were failures, but at this one golf course the population took hold.

Back in 1995,  it was really hot when I visited this site, reaching 47 C on one of the days that I was there. That's still the hottest I've ever experienced.

I've long wanted to return to the site, and so I made it a priority on my North American leg of my world Xenopus tour.  

The picture above is from 1995 and is the southernmost lake on the golf course, featuring a canoe which I was allowed to use to paddle around this lake and set traps.

This is the same site now. The willow tree is gone, but you can see the same wall above the lake.

The canoe is still around and once again I was allowed to use it and paddle out to a pole in the deepest part of the northernmost lake to set some temperature loggers.

I remember the last time I sat in that canoe in 1995 a golf ball whizzed passed my ear making me very pleased that I was wearing a hard hat. 

With the help of Becca Cozad and her ARC crew: Karen & Maya, we were able to quickly run through the catch and process all the animals needed from Arizona. We were also joined by Randy Babb who bought his seine net which made really short work of bringing in a lot of tadpoles for sampling.

A special thank you to Brian Stevens and all his staff for making us so welcome at the Crooked Tree Golf Course. They really pulled all of the stops out and went out of their way to make sure that this was a successful mission. Strapping a canoe to the top of a golf cart and driving it across the course was unforgettable. We really are most indebted to them all.  

Terblanche & Measey featured in the Stanford Spectator

This month's copy of the Stanford Spectator features an article about the work that Naas Terblanche conducted and was published in PeerJ last June (see blog post here). The article is actually a printing of the blog post with some edits, and new images by Naas himself. Stanford is rightly proud of what their local man has produced. 

Measey, J. (2023) Stanfordian initiates study on frog communities. Stanford SpectatorSeptember 15.