What Tarantula Species Drops Its Limbs Most Often?

[scaledverts]

Hello,

I am looking for some information regarding which available species of tarantula drops its legs most often (as the result of rough handling, injury, etc). We are interested in performing a study on limb loss and locomotion in arachnids but want to make sure we choose a relevant species. Species that are readily produced in captivity are preferred to rarer species.

Thanks in advance for your thoughts and help,

Kyle

 

[happysmile88]

I'll take a guess that G.rosea are probably the most abused Ts that are readily available.
Just my 2 cents though

 

[jayefbe]

I don't think there are any species more likely to drop a limb than others. There are some more likely to experience structural damage due to their morphological characteristics (terrestrial vs arboreal) but it's not specific to limb loss. Furthermore, tarantulas do not drop their limbs as a means of predator avoidance in the same manner as many lizards, if you are planning to apply an adaptive story to this research (ie, species x is more likely to drop a leg due to an evolutionary response to pressures from predation). While there are reports of tarantulas intentionally removing an injured limb, it is only upon injury that it occurs.

I'd recommend conducting this research on a fast growing and common species. Depending on the timeline of your research, length of time between molts will be a severely limiting factor. Lasiodora parahybana seems to me like a great candidate.

 

[grayzone]

there is no proven fact to this, however from over a year of searchin these forums ive seen OBT limb loss more than any other. just an observation. none of my ts have ever lost a limb (knocks on wood)

 

[sjl197]

I'd suggest try and get some tiger-rumps, like those sold in the hobby as C.fasciatum or C.pentalore.

Actually, the ones the legs come of most easily are the closely related species zebratum. But those are quite difficult to get in the hobby now.

Otherwise, something like a redrump 'vagans' or albopilosum are very hardy to loosing limbs.

What sort of study are you doing anyway, how many replicates, what controls are you using? Design is very important, as is trying to get your study individuals as comparable as possible, ie from same eggsac, same age, ideally same stage in moult cycle etc.

Avoid the bigger species, and stick to something new-world and terrestrial (unless you want to compare arborials). Avoid large adults, especially old ones - those are often the most prone to problems or even dying after leg loss. Stick to juveniles if you can, which normally cope well with loosing a leg (or more), and easily regenerate. Oh, definately avoid premoult specimens as they tend to loose alot of haemolymph on legloss and can have problems after, so for example with many new-world terrestrials you can see from the bald patch of urticating hair loss when theyre premoult..

 

[scaledverts]

Thanks for the opinions everybody, anymore out there??

We are more interested the consequences of limb loss on locomotion as opposed to the adaptive type story you mention. If in the wild tarantulas (and other spiders) loose their limbs (for whatever reason), they still have to maintain a high level of performance to capture prey, find mates, etc or face predation/starvation themselves.

My initial thoughts were L. parahybana as I have one myself and I have seen their growth rates! I just wasn't sure if I could get enough slings in the correct size range (1-2") easily.

In terms of study design, you actually do not want the same eggsac. The reason for this is mainly statistical. If the individuals are closely related, it could be argued that your samples are not statistically independent from each other (and therefore violate many of the assumptions of commonly used statistics). For most locomotion (an animal studies in general), the general rule of thumb is 5-10 individuals with multiple replicates of each individual. Obviously, the more the better, but at some point you are not adding any more variation to your data set by simply adding more individuals (i.e. you have already found the species or population average). Don't worry we will get the study design finalized prior to beginning it. :wink: We are just in the planning stages of thinking about research specimens etc.

 

[DaveM]

Just a thought, but locomotion deficits might be seen more easily if that locomotion were vertical. A. avicularia are cheap and fast growing.

 

[sjl197]

If you will take more comments from me.

Lasiodora parahybana are a good choice, especially juveniles. Very hardy.
I agree with DaveM too, arboreal species could give better insights on (linearly-directed) locomotion, though i'd say Psalmo or Taps are going to be tougher.
@Jayefbe. Why do you say they dont drop limbs in response to predators? So what happens when say a scorpion, a bird or an even bigger coati grabs one? While you are probably right that removal of an injured limb (for example damaged by a fall or in a bad moult) is probably much more common than predator damage, its going to far to say they dont do it as predator avoidance - especially when it comes to scorpions.

As im sure you all know, in the wild most terrestrial tarantulas are actually burrow dwelling sit and wait predators, so there is often pretty much no locomotion in the wild, except retreating down a burrow again in the day and coming back to the entrance at night. It would be interesting to see if there are differences in detection zone (kill zone) around the spider if you remove one or more front legs especially, which are the legs they place forward to detect prey. The other factor is the speed at which a spider can retreat back into the safety of a deep burrow when a predator threatens, but this is more turn-speed than direct forward movement. Adult males are quite different of course.

Even if you went for say L.parahybana, and tried to get offspring of several eggsacs, then the individuals are still closely related as theyre still the same species, and youve likely no idea of the ancestry of the parents you think are different bloodlines (which for example could easily be from the same eggsac themselves). So claiming that getting young from different breeders to get statistical independence is far from correct. Relatedness is a limitation that many good stats methods can either deal with somehow (ie correction factors etc) or you just have to tolerate relatedness within your assumptions. Having many from the same batch/eggsac should actually be beneficial to reduce some of the unknown variability in your sample, as siblings a priori should be expected to share heritable aspects of fitness, and the environment theyre raised in before the study should be the same (and hence controlled). If you look at health trials with humans, there can be many statistical benefits to running experiments with siblings and even twins specifically.

Of other potential variables, i'd suggest body size (like diagonal leg span) would be important to control, so you should be aiming to have some comparison of individuals of the same moult stage, and try to get metabolic conditioning either the same or different as you prefer (ie either keeping food intake and heating same, or different as you prefer). You should also try to test fitness both before removing legs, while lost, partial regeneration, and after complete regeneration. Id be interested to know if after complete regeneration the fitness is the same as before loosing legs.

So anyway, good luck, and i really just wanted you to consider that your experimental design is likely much more important than the species you choose.
and p.s. I've removed legs from about 600+ tarantulas of about 200 species for my own biological experiments, so when i said C.fasciatum/pentalore are easiest i was answering your question as best i could, though my sample size of most species was just 1-5 individuals. And no, dont go for the african bitey species, simply for your own safety and sanity, nasty ones like those hate to have their limbs pulled off for science...

 

[jayefbe]

My statements were based on the fact that I've never heard of limb loss occurring as a specific predator avoidance mechanism, specifically, a tarantula intentionally removing its own limb to avoid a predator. While I do imagine that tarantulas do lose limbs when a predator grabs one, and it may aid in avoiding predation in such instances, it is not driven by a mechanism developed for the purpose of avoiding predation. Rather, in those cases, I imagine that it's a byproduct of the direct predator-prey interaction and the structural damage that is produced. My intended point wasn't that losing a limb never helps a tarantula avoid a predator, but that the ability to lose and regenerate limbs likely did not arise specifically for the avoidance of predators (as is the case in some lizard species). I only brought it up because it seemed as though the OP might be planning a study from basis of it being an adaptive predator avoidance mechanism. This was due to the fact that he was asking which species dropped limbs most often (which species loses limbs most often and does that confer a fitness advantage due to enhanced predator avoidance...or something like that).

 

[Stan Schultz]

My statements were based on the fact that I've never heard of limb loss occurring as a specific predator avoidance mechanism, specifically, a tarantula intentionally removing its own limb to avoid a predator. ...

As a peripheral comment: I have seen tarantulas (Haplopelma minax and Aphonopelma moderatum. Note: two different subfamilies.) intentionally remove a damaged limb. And eat it!

 

[scaledverts]

If you will take more comments from me.

Lasiodora parahybana are a good choice, especially juveniles. Very hardy.
I agree with DaveM too, arboreal species could give better insights on (linearly-directed) locomotion, though i'd say Psalmo or Taps are going to be tougher.
@Jayefbe. Why do you say they dont drop limbs in response to predators? So what happens when say a scorpion, a bird or an even bigger coati grabs one? While you are probably right that removal of an injured limb (for example damaged by a fall or in a bad moult) is probably much more common than predator damage, its going to far to say they dont do it as predator avoidance - especially when it comes to scorpions.

As im sure you all know, in the wild most terrestrial tarantulas are actually burrow dwelling sit and wait predators, so there is often pretty much no locomotion in the wild, except retreating down a burrow again in the day and coming back to the entrance at night. It would be interesting to see if there are differences in detection zone (kill zone) around the spider if you remove one or more front legs especially, which are the legs they place forward to detect prey. The other factor is the speed at which a spider can retreat back into the safety of a deep burrow when a predator threatens, but this is more turn-speed than direct forward movement. Adult males are quite different of course.

Even if you went for say L.parahybana, and tried to get offspring of several eggsacs, then the individuals are still closely related as theyre still the same species, and youve likely no idea of the ancestry of the parents you think are different bloodlines (which for example could easily be from the same eggsac themselves). So claiming that getting young from different breeders to get statistical independence is far from correct. Relatedness is a limitation that many good stats methods can either deal with somehow (ie correction factors etc) or you just have to tolerate relatedness within your assumptions. Having many from the same batch/eggsac should actually be beneficial to reduce some of the unknown variability in your sample, as siblings a priori should be expected to share heritable aspects of fitness, and the environment theyre raised in before the study should be the same (and hence controlled). If you look at health trials with humans, there can be many statistical benefits to running experiments with siblings and even twins specifically.

Of other potential variables, i'd suggest body size (like diagonal leg span) would be important to control, so you should be aiming to have some comparison of individuals of the same moult stage, and try to get metabolic conditioning either the same or different as you prefer (ie either keeping food intake and heating same, or different as you prefer). You should also try to test fitness both before removing legs, while lost, partial regeneration, and after complete regeneration. Id be interested to know if after complete regeneration the fitness is the same as before loosing legs.

So anyway, good luck, and i really just wanted you to consider that your experimental design is likely much more important than the species you choose.
and p.s. I've removed legs from about 600+ tarantulas of about 200 species for my own biological experiments, so when i said C.fasciatum/pentalore are easiest i was answering your question as best i could, though my sample size of most species was just 1-5 individuals. And no, dont go for the african bitey species, simply for your own safety and sanity, nasty ones like those hate to have their limbs pulled off for science...

Absolutely, the more comments/discussion the better!

The same species is actually what we want for statistically testing the effects. If we had different species, we would run into problems of comparability among the data. Yes, it is true that non-independence can be controlled for statistically. However, this drastically reduces power and may result in having to switch statistical methods all together (not to mention problems of pseudoreplication). Personally, I would actually rather have more variability in the data set to start with anyway. Sure, this reduces your ability to detect differences between treatments, but the data are much more likely to match species averages. IF the differences performance as the result of leg loss are still significant between treatments even with the increased variability, the broader conclusions that can be discussed are much more interesting.

Also, I would argue that species choice is perhaps the most important part of experimental design if you want your results to mean anything biologically. For example, if we choose a species that NEVER drops its limbs in nature (because of reduced injury rates or whatever) but will drop its limbs in captivity readily, it would be very hard to make any kind of arguments about the evolution of octopodal locomotion or test any of the hypotheses as to why multiple limbs evolved. That's awesome that you have conducted a number of experiments also. We have been looking for experimental studies on limb loss in tarantulas but have not found much (there are some out there for wolf spiders and a few others). So anything that you could point us in the direction of (your own or other's work), would be great!

 

[Stan Schultz]

... I am looking for some information regarding which available species of tarantula drops its legs most often (as the result of rough handling, injury, etc). ...

This may not be the optimal group of people to ask this question because we go out of our way to avoid causing limb loss in our pets. So of course, any comments we make would be heavily biased by that skewed experience.

And, in over 40 years of dealing with literally hundreds of species and thousands of individuals of tarantulas, I have not noticed that any one species is more prone to leg loss that any other. But then again, my experience has been biased as mentioned above.

Having said that, several decades ago, I had noticed that one species, Phormictopus cancerides (Haitian brown tarantula, "PC"), did arrive through the pet industry often missing one or more legs. But, because these bite at every available opportunity, because of their limited distribution in nature, and because this state of affairs lasted for less than a year, my presumption was that this was due to poor handling by one or a very few collectors who were inordinately rough with them, trying very hard not to be bitten!

My own experience with wild North American species (genus Aphonopeloma) is that wild tarantulas lacking one or more limbs are exceedingly rare. Either it never happens, or if it does the victim is put at such a severe disadvantage that it succumbs to predation very quickly. You may be trying to examine a nearly completely artificial, almost irrelevant phenomenon. But then pure science doesn't concern itself with practicality.

Lastly on this topic, those of us who have kept baby tarantulas have noticed that the extremely young (perhaps less than 1" - 2.5 cm diagonal leg span, "DLS") are more prone to molting difficulties and limb loss than the larger individuals. No one has examined the reasons behind this phenomenon in detail, but this might be of interest to you in planning your study. Such young tarantulas certainly would recover more quickly than the larger spiderlings you propose if for no other reason than their rapid molting frequency.

... We are interested in performing a study on limb loss and locomotion in arachnids but want to make sure we choose a relevant species. Species that are readily produced in captivity are preferred to rarer species. ...

Others have suggested using Lasiodora parahybana (Brazilian salmon tarantula, "LP") as research subjects. There are several issues with that species. First, they eat relatively huge amounts of food as they grow, they grow fast, and within a very few years reach truly gargantuan sizes. Thus, they will only be within the size range of your experimental parameters for a brief period of time. And, their size poses some caging and care challenges, especially if you need any number for your study.

The other issue deals with their genetic variability. Long time enthusiasts hold the opinion (probably justified) that virtually all LP in the hobby arose from a very few females (I heard six) that were smuggled out of South America several decades ago. And, because of inbreeding, virtually all such individuals in the hobby are genetically, virtually identical twins. Baring some small genetic variability inherited through their blood lines and the few mutations that have doubtlessly occurred but have not been culled out in captivity, their genetic variability is pretty close to nil.

This lack of genetic variability is accentuated by the fact that a typical eggsac produced by one female in captivity releases something on the order of 2,000 babies! Thus, one breeding per year pretty much swamps the market for at least a year. As a result, successful breedings are not numerous, and the probability of you acquiring research subjects from more than one or two eggsacs is slim.

If you're looking for the arachnid version of inbred lab rats, LP is your choice. If variability is key to your study, maybe not so much.

Given that leg loss does not vary appreciably between the different species of tarantulas in captivity, and that you want as much genetic diversity within your test population as possible, I would suggest using any of the species that

1> Have been imported in large numbers. (Increases the probability of greater genetic diversity among the original, source population.)

2> Are bred often in captivity. (Increases the probability of acquiring relatively non-closely related individuals.)

Two species immediately come to mind: Brachypelma smithi (Mexican redknee tarantula, "BS") and Brachypelma albopilosum (curlyhair tarantula, "BA").

During the 1970s and early 1980s BS were imported into the pet industry in truly remarkable numbers. Upon their listing in Appendix II of the CITES treaty in 1985 that importation ceased, but because of the vast numbers in captivity and their high demand as pets concerted efforts were made to breed them in captivity, and they are now regularly available in the industry in relatively large numbers. And, because of their long generation time inbreeding has been minimal. Thus, they are available in number, and their genetic diversity is still relatively high. They also grow slowly so the individual research animals will remain within your specified size range for a longer period than with LP. Lastly, as adults they are not small tarantulas, but are neither gargantuan by any means, making caging and care a little less onerous.

Much the same may be said for BA, although they were imported in significantly smaller numbers. The individuals of BA, however, were imported from several Central American countries, possibly increasing genetic diversity, and are very easy to breed and therefore usually readily available.

Some have mentioned Grammostola rosea (Chilean rose tarantula, "GR"). This species is currently being imported into the pet industry in huge numbers, and these individuals are readily available in pet shops around the world. If your study would allow the use of wild caught individuals these might be an option. Also, many of the females that are imported have been impregnated in the wild and subsequently produce eggsacs and babies in captivity. So, it is not too difficult to acquire baby GR. Their biggest disadvantage is that they are a rather slow growing species and obtaining individuals of appropriate size may be problematic.

I hope this helps you in finding your research subjects. Whatever happens, keep us posted on the progress and outcome. Best of luck! :smile: