Question: Cannabalism

[Star]

Just curious, as I have had my little ones housed together from the start (apart from ones that needed a bit more attention) and have never had any cannibalistic issues at all. I know it will vary but I am curious, common sense tells me that keeping them very well fed will reduce any issues by a great deal. Is this correct? Mine are little fatties and quite happily all pile on top of each other or huddle up but I've never seen any snaps and I sit next to them a lot of the time as they are next to my pc.

 

[Johan]

Hi Star,

You might be interrested in this abstract, unfortunately the article itself is not free, but it's abstract is.
Effect of Food and Density on Development of Typical and Cannibalistic Salamander Larvae in Ambystoma tigrinum nebulosum by James P. Collins and James E. Cheek

Here is a little summary:

"Two subspecies of the tiger salamander, Ambystoma tigrinum, have a distinctive polymorphic life history that can include four adult morphs as well as typical and cannibalistic larval morphs. We evaluated the effect of environment on development of larval morphology in two laboratory experiments.

In Experiment I, 180 larvae were raised in individual 3-liter containers and fed one of three food levels. Larvae in Experiment II received one of two levels of food, and were raised at three densities: one larva per 3 liters of water (50 containers), three larvae per 22 liters of water (18 containers), or seven larvae per 22 liters of water (18 containers).

Cannibalistic morphs developed only in nine containers at the highest density, and their occurrence was independent of the two food levels."

Source: Amer. Zool. (1983) 23 (1): 77-84, Effect of Food and Density on Development of Typical and Cannibalistic Salamander Larvae in Ambystoma tigrinum nebulosum; James P. Collins, James E. Cheek.

 

[Star]

Ooh thanks! I'll see if I can get the article free through uni

 

[Johan]

Ooh thanks! I'll see if I can get the article free through uni

No thanks! That would be a very good idea, they can probably get it for you!
From the abstract, I get the impression that space is a somewhat more important factor than food, as cannibalism was observed in the containers with the highest density (seven larvae per 22 liters) and on both food levels.

But it also only occurred in half of the containers (9 out of 18) so there probably are more factors, like genes and/or other environmental factors. They seem to have found cannibalistic morphs in only experiment two though.

By the way, this article is about the tiger salamander (Ambystoma tigrinum), not axolotls, I could not find one for Ambystoma mexicanum, maybe someone else can?

 

[Star]

I shall have a gander for one on A. mexicanum on my uni thing, see what I can find. I guess temperature may be a factor as well. I did keep mine in large containers so they had the space to keep apart nut they have never shown that tendency, always seemed to prefer huddling up Even when feeding, which has surprised me as I figured accidental nips would happen but still had none.

 

[Johan]

That would be great, I would love to know more if you find out! If I find something I'll post it here. Temperature on itself might be a factor, but maybe also (or a combination of) different quick sequential environmental changes?

About tiger salamander larvae, I found another interesting article, in which they describe that the cannibalistic ones can recognize their siblings and are less likely to eat the cannibalistic ones when given a choice. That one is called: Kin recognition and cannibalism in polyphenic salamanders

Quote from abstract:
"When housed with smaller larvae that differed in relatedness, both cannibals and typicals preferentially consumed less-related individuals. Cannibals ate typicals much quicker when the choice was between nonkin and siblings than when the choice was between nonkin and cousins, indicating that cannibals could distinguish different categories of relatives. Cannibals were less likely to eat a larval sibling that was a cannibal morph than a sibling that was a typical morph."

source: Behavioral Ecology (1994) 5 (2): 225-232; Kin recognition and cannibalism in polyphenic salamanders; David W. Pfennig, Paul W. Sherman and James P. Collins

 

[memojo1979]

Did I read something about those with cannibalistice tendancies physically looking different too?.... Gonna have to go look now!

Aha! I have something to add too now (from axolotl.org) -
Cannibalism is a natural tendency, and studies have been carried out on the cannibalistic variants of salamander larvae. If left to cannibalise their siblings, they actually develop different morphology (shape and appearance). This is most noticeable in the shape of the head and the teeth. James Petranka's Book, "Salamanders of the United States and Canada" discusses cannibalism in detail, especially in the case of the Tiger Salamander, with some excellent photography, and William Duellman and Linda Trueb's book, "Biology of Amphibians", contains some excellent diagrams of the head morphology of the different morphs of the tiger salamander, a close relative of the Axolotl (see the Books and Links Page).
In young larvae, particularly melanoid albino larvae like that on the left, you can actually see the liver, heart, stomach and intestines right through the skin. To minimise cannibalism, Peter Scott recommends that the tank is heavily planted and that light levels are lowered. A more reliable method is to reduce the numbers as much as possible in each container, but appetite does seem to decrease in low light

 

[Skilly]

Wow, this is extremely interesting. I would love to read those articles if you guys are able to find them! It is very interesting that they can recognize a sibling when given the choice. I was also talking to my friend, the other day, who is a biologist, and she was telling me that they did some study on axolotls and found that they communicate with each other through bubbles and small "clicking" noises.

I know, not about cannibalism, but cool non-the-less.

Maybe the larvae delegate who gets eaten when they are put together using their clicking noises... "I'm your brother, don't eat me, but you can eat that other guy over there!"

 

[Johan]

Thank you so much, that is very interesting! I'll see if I can get my hands on those books sometime, they sound very informative! May I ask, do you know why melanoid albino larvae have this translucent trait that you talk about? Does this have anything to do with being cannibalistic?

@Grace
Wow that sounds interesting too! Would love to see some scientific articles on that if they exist.
Could it be that they excrete a different substance through their mucous skin, than the others so they can recognize, like they smell alike? So their genes have the most chances of living / reproducing?

 

[Skilly]

Hmmm.... that is a good possibility Johan.

Also the translucent trait is found with other color morphs and not just the melanoid albinos. My golden albinos and leucistics are also quite transparent (especially when they are juveniles). I watched ones heart beat before and can see all of their insides- pretty neat! So I do not think that the translucence is indicative of cannibalism. Morphology usually refers to more permanent physical features such as minute skeletal changes and exact formulation of muscle structure. Traits of this nature, would be linked to cannibalistic induced physical changes but are probably not easily seen with the naked eye.

 

[Johan]

Thank you for your clear answer! Today I've found an article about skull growth in cannibalistic tiger salamanders, it's on the web in pdf format, this is the direct link to save the article.
I still have to read it myself, but thought I would share.