Morphological changes of jaw and tooth structure in canibalistic larvae

I was reading through my old axolotl files last night and stumbled across a few pages I had printed out about how the jaw and tooth morphology of axolotls that were allowed to cannibalize siblings were different than those that did not cannibalize siblings as neonates. A few of the pages are missing, and I cannot find the source anymore.

Then after way too many cups of coffee at work I got got to wondering about this. I was hoping someone more knowledgeable could offer insights of links to references I could read on this subject.


So, here's what I was wondering about:

1. Is this true, or is this a bit of misunderstanding on my part?

2. Is this true only in Ambystoma mexicanum, or prevalent through all Ambystomids? Does it happen with other types of newt or salamander?

3. Is this a result of some science fiction like protien assimilation, or digestion of hormones from the devoured siblings, or some other reason I have absolutely no way of imagining?

4.Where would be a good source to find scientific documentation on this subject nowadays? These pages are from circa 2001-3

Re: Morpological changes of jaw and tooth structure in canibalistic larvae

Hi,

What you're asking about is called 'phenotypic plasticity' and this particular type is fairly common among amphibians, including caudates. Phenotypic plasticity is basically the genetically determined ability to alter your phenotype based on your environment (http://en.wikipedia.org/wiki/Phenotypic_plasticity). To answer your specific questions:

1. Yes, it's true
2. I've found several references to it in different species (see below) but not in axolotls specifically.
3. Probably more the result of something like hormones (or other chemical cues) acting on the genes and physiology of the one doing the eating to trigger a predictable change in phenotype (rather than the proteins, say, directly affecting the physiology).

I've found a few articles that might be have you're looking for. You'd need a subscription to see the full articles (so just pm me if you'd like any of them). I'll list a few of the most promising:

Title: Differentiated phenotypic plasticity in larvae of the cannibalistic salamander Hynobius retardatus
Author(s): Michimae, H
Source: BEHAVIORAL ECOLOGY AND SOCIOBIOLOGY Volume: 60 Issue: 2 Pages: 205-211 Published: JUN 2006

Title: Proximate causes of cannibalistic polyphenism in larval tiger salamanders
Author(s): Hoffman, EA; Pfennig, DW
Source: ECOLOGY Volume: 80 Issue: 3 Pages: 1076-1080 Published: APR 1999
Times Cited: 18

MORPHOLOGICAL VARIATION AND CANNIBALISM IN A LARVAL SALAMANDER (AMBYSTOMA-MACRODACTYLUM-COLUMBIANUM)
Author(s): WALLS, SC; BEATTY, JJ; TISSOT, BN, et al.
Source: CANADIAN JOURNAL OF ZOOLOGY-REVUE CANADIENNE DE ZOOLOGIE Volume: 71 Issue: 8 Pages: 1543-1551 Published: AUG 1993
Times Cited: 18

eta: I forgot to add that I can blab on and on about phenotypic plasticity if you want me to or if you have any more specific questions

Re: Morpological changes of jaw and tooth structure in canibalistic larvae

Erin beat me to the punch. Plasticity is absolutely fascinating. To simplify the whole thing; remember that gene expression and phenotype (the characteristics shown) are controlled not only by genotype (the actual genetic code) but also by the environment. Genes can be turned on or off based on the environments or conditions that are present.

Alex

Re: Morpological changes of jaw and tooth structure in canibalistic larvae

Very very interesting...

I am still trying to locate the source file for the Ambystoma mexicanum specific data, but, the ways of the web are fickle to say the least. Thank you very much for the links! Very interesting reading is to be had there. I would love to read those articles, and I think others may too!


And please ramble on about this subject, I find it mind blowingly interesting!


My own experiences with it seemed to show that in fact axolotl neonates allowed to eat their smaller siblings did seem to become larger, healthier adults.

I know this is an old post but im quite interested in it, i have a melanoid axolotl which I selected from 150 axolotls( average size one inch), which i raised for a friend who owns a pet shop and was having problems with cannibalism and overcrowding( they were all in a two foot tank). This melanoid was twice the size of the others and had a slightly different head shape, the mouth was broader and more pointed I witnessed it eating/attacking its siblings on several occasions and was altogether more aggressive, it is now six inches and shares a tank with a similar sized albino which it gets on with. I keep baby guppies in the tank with them and whilst the albino generally ignores them, the melanoid spends all day actively hunting them down and is quite successful , to the extent that ive lost about twenty guppies in the last fortnight. What I would like to know is cases like mine, does the axolotl cannibalize purely because its bigger or is it bigger because it cannibalizes? Was it hatched with a different shaped head or did it develop it because of its diet? Is my melanoid likely to attain a larger size than usual? Is it more of a danger to its tank mates because of its aggressive nature? Would it benefit from a more meat( larger meat items including amphibians) based diet due to its physiological differences to a standard axolotl? I hope somebody can provide me further information or direct me to more source material. Thanks

I have been raising a lot of tigerlarvaes this year from my own tigerbeeding in winter. I have used a lot of plastic tubs in order to have room for them. However, what happens is that when too crowded or offered too little food, some of the animals develope widermouth parts and would soon eat their relatives if they are not constantly sorted after size.
My biggest bigmouth is 14 cm now and it has bigger mouth parts than some of the relatives on 17 cm. It can eat very large foodithems.

Martin

Some fish exhibit this same kind of physical change , the brown trout(salmo trutta) sometimes becomes cannibalistic, changing its diet from insects to fish , they then grow a larger head, bigger teeth and grow considerably larger , the common eel(anguila anguila) develops a different head shape depending on the food supply, plenty of invertebrates and it has a pointy nose, fewer invertebrates and it develops a wider mouth to eat fish, at one time they were even thought to be two separate species. I find it amazing that an animals diet/behavior can lead to physiological changes.

My female lecuistic has a huge head / jaws for the reasons you are speaking of. Only got her because the shop i got her from was going to get rid of her because she had a taste for legs. I can put pictures up if anyone is interested. She is massive compared to my wildtypr also and they dont look the same. She is beautiful though and they have bred, does anyone know if the cannibalistic head/jaw trait will show up in my larvae at some stage? Or is it purely a developmental thing not passed through genetics ?

One of my strauchii juvies has a very different jaw structure from his siblings. I've been wondering if it had anything to do with this. I'll try to get some pictures soon once I figure out my camera

I would be great if someone could post pictures showing the difference in jawsize between diets?

As far as stated in Petranka's book, this jaw and tooth differentiation affects larval salamander forms exclusively. In the book a few dozens of Ambystoma species are said to have such different morphological features. But I'm pretty sure it does also occur in other families than Ambystomatidae. In Salamandridae it exists at least on Salamandra salamandra but its much likely to happen in a few other species in other Genera.

I'd like to read Pentranka's book could anyone give me the title or isbn?

Here is a book review with all the info you need.

Update on my cannibal axolotl, the differences in head and jaw structure did not carry on into adulthood, it grew into its head like a puppy grows into its feet. It is 12" very bulky and shows no inclination to attack its tank mates who are of a similar size, it does show increased hunting proficiency and will hunt down any live fish, frog or tadpole which enters its tank before the other axolotls even know they are there. The link shows a new thread about cannibal morphological changes which carried through into adulthood in tiger sals http://www.caudata.org/forum/f1173-...etc/88463-cannibalistic-tiger.html#post361439

I find this morphology facinating.
That the larval stages of several salamander will actually morph to become "top predators" better able to canablize with food source is low is just amazing.

I read that same article you spoke of several years ago, but I also couldnt' find it on the net when I went back to find it. The only ones I found on google scholar were papers on A.tigrinum and a few others, but none specifically on A.mexicanum.

I have personally seen these jaw morphs in some babies at a pet shop at north that pretty much all had no limbs because they were just eating eachother. I was more then shocked to see them for sale!?!?

This thread doesn't seem TOO old.

I was fortunate enough to encounter A wild A.m. Melanostictum Cannibal morph this Tuesday evening, And I included a picture of a Normal looking larvae of similar body size for side-by-side comparison.

You'll notice that the regular morph has an elongated head shape, narrowing sharply to the nose from the gills. Wheras the cannibal has a uniform arc from one side of its head, commencing at the gills, all the way to the other. It also possesses a significantly larger head in proportion to its body and overall length.

It has been said that very large populations trigger this morph. These salamanders were observed in a large temporary body of water, with many spade foot tadpoles and various sizes of insects, most notably "water tiger" beetles which were both feeding on, and being fed upon by tiger salamander larvae, and even some present terrestrial adults swimming about the shallows. The population of tiger salamander larvae this year, was such that, every sweep of the net averaged 2 individuals composed of 2 distinct broods (3 inch, and 1 inch) The size and uniform depth of this body of water suggests tens, maybe hundreds of thousands of salamanders. This number will naturally take a plunge as water tigers, and cannibals mature. The water also may clear, exposing them to predation of birds.

I've never seen this body of water so full for so long. I'm actually worried it might remain so all year and the remaining salamanders will not metamorphose, for this body of water seldom reaches 2 ft in depth and will certainly freeze to the ground. The salamanders in this area are regularly neotenic, and haven't successfully bred in this particular lake for several years due to dry springs.

In deeper lakes, a short drive away, there are healthy, neotenic populations, where branchiated adults can sometimes be observed foraging at night. They aren't the dull-green of many neotenic western tigers, But rather dark, mottled, aged in appearance, and often possess the marking of terrestrial adults. Absent is the flattened tiger-salamander larva head, these tend to appear similar to mature axolotls.

Heres a better shot of two individuals of similar size side-by-side showing both types.

Axolotls - Biology
This is the site I read about the changes that axolotls go through from eating there siblings, also great reading hope it helps

that site is SORTA also this site