Tarantula coloration

[Transient]

Sorry if this subject has been covered, I tried search but didn't exactly find what I was looking for. "evolution color" did not reel in what I thought it would.

We all know that bright colors in animals can be anything from a mating signal to a "Don't you dare eat me" signal. I've been looking at tarantula evolution threads and I got to thinking, Why are tarantulas colored the way they are? Mating is out, tarantulas have poor eyesight. As is a sign of being poisonous, tarantula venom wouldn't hurt (at least lastingly) a creature large enough to want to eat them. "Just because" doesn't seem like a valid answer either.

So is it camouflage? Mostly I'm interested in P. metallica and GBBs. Both have very different habitats, both bright blue.

I apologize in advance if this post is ridiculous.

 

[Bigboy]

I would imagine their coloring is meant to be a deterrent to birds whose eyesight sees color in ways we cannot to the Nth power. This is speculation though, I do not know of any publications addressing the topic either. You can usually be sure however that if an animal is pretty and flashy it is poisonous, and if it is pretty, flashy and easy to catch it is probably capable of doing horrible things to you.

 

[Fins]

According to TKG, for Pokies at least, the garrish colors are most likely for camouflage.

 

[gumby]

One thing to consider is that many of the brighter Ts tend to burrow or hide via tons of webbing more then many of my brown Ts. take the GBB all of the GBBs ive had have been extream webbers thus covering their bright colors. same with my bright Avics and the small P. metalica I had. they either burrowed or hid under something or made a crazy tube web I couldnt see through.

 

[Transient]

One thing to consider is that many of the brighter Ts tend to burrow or hide via tons of webbing more then many of my brown Ts. take the GBB all of the GBBs ive had have been extream webbers thus covering their bright colors. same with my bright Avics and the small P. metalica I had. they either burrowed or hid under something or made a crazy tube web I couldnt see through.

Interesting. I just had a thought, perhaps in their native habitats there are insects that are attracted to bright colors?

 

[High_Rolling_T]

To go with the camouflage idea, perhaps they are to appear similar to foliage in the area(such as flowers or what not).

 

[Comatose]

One more bit to add - in many animals, males use bright colors or other features to attract mates. While I understand tarantulas to have poor eyesight, it's interesting that mature males in many South American terrestrial species develop stunning iridescence. That said, I'm guessing that most coloration is for either camofage or are 'don't mess with me' colors.

 

[Transient]

It just seems that for the small amount of natural predators they have (at least relative to other inverts) that the needs for warning coloring would be less. Of course I've never been to the natural habitat of a brightly colored T so what do I know hahah

 

[Bigboy]

One more bit to add - in many animals, males use bright colors or other features to attract mates. While I understand tarantulas to have poor eyesight, it's interesting that mature males in many South American terrestrial species develop stunning iridescence. That said, I'm guessing that most coloration is for either camofage or are 'don't mess with me' colors.

This is another reason I would expect these bright colors to be warning colors. The males are the ones doing the most wandering and exposing themselves to predation by visual cue predators. Very bright colors are very likely an adaptation developed to deter predation. Think of a P. metallica's warning display. Sure its bright blue to begin with but when it throws up those legs and shows off both yellow and blue the message is clear "I will ruin you".

 

[Kevinitis]

Don't mean to bring up a long gone thread, but I was thinking about this today and so I did a search and found this thread. In addition to the comments above about aposomatic coloration, there is often cases in nature where harmless species use mimicry to imitate the harmful/bad tasting species. Take for example the monarch butterfly, which is either distastful or down right toxic. It's bright orange and black color warns potential predators. On the other hand Then you have the viceroy butterfly which looks almost identical to the monarch but is harmless.

So thinking about T's, you have the Brachypelma's such as Smithi, boehmei, auretum and emilia who all look similar (ie some shade of red/orange/pink on the legs and black). Then you also have Aphonopelma Bicoloratum that looks almost identical to boehmei. Even A. moderatum looks superficially similar or may be evolutionarily trending towards looking like them. Perhaps a stretch, but A. Chalcodes color distribution is similar to Boehmei as well though blond not orange on the legs. So are all these color similarities of T's from this region because they are related and thus look alike, or are they converging on a certain look because one or all of them avoid some type of predation by having that aposomatic coloration? And which if any are mimicking the others? Clearly, at least boehmei and bicoloratum are mimics.

Then you should ask what is their deterent. A couple of obvious items: urtricating hairs, and venom. Now venom you say isn't it because new world T bites don't harm people much, but I read somewhere recently that, in documented cases where T's bit dogs, it was universally fatal to the dog. Are there other potential avian or mammalian T predators in which T venom is extreamly effective? I will have to dig that up and post a link.

Just some thoughts and probably a lead for some reseach topics.

---------- Post added 06-12-2013 at 06:08 PM ----------

Ok here is that link on T's biting dogs. This is an abstract from a scientific publication. This one is about tarantulas from Australia, so it does not really pertain to the species I mentioned above. Nevertheless, we may not understand all about the effects of T venom in other species.


http://www.sciencedirect.com/science/article/pii/S0041010102003951

---------- Post added 06-12-2013 at 06:10 PM ----------

Ok here is that link on T's biting dogs. This is an abstract from a scientific publication. This one is about tarantulas from Australia, so it does not really pertain to the species I mentioned above. Nevertheless, we may not understand all about the effects of T venom in other species.


http://www.sciencedirect.com/science...41010102003951

 

[845BigRed]

Something I was explaining to a friend of mine recently is that males tend to be brighter colored. While I think part of this is to attract potential mates. I think also the brighter colored females die because they can't hide from predators. Males don't need to live as long specially since once they breed thats generally it for them.
Heres a side of by of P Metallica female and male and you can see the more brown coloring in the female
http://img399.imageshack.us/img399/6425/mfmetdb9.jpg

I dont really have bad hair kickers in my collection but think about in nature, animals are all opportunistic. Even the predators will go after the easy prey. So if you have anything that can deter a predator from attacking you, they will likely go away. Heck I've seen videos of people yelling at bears and thats all it takes for the bear to run off.

As far as dogs there was a thread a little while ago, but what to consider is if the venom disables the insects entirely, and it hurts us, then your dog is gonna fall somewhere in the middle, it might be a little sore, it might need serious vet care.

 

[Poec54]

It just seems that for the small amount of natural predators they have (at least relative to other inverts) that the needs for warning coloring would be less. Of course I've never been to the natural habitat of a brightly colored T so what do I know hahah

You're making many assumptions, and I think you need to look at them again. They have a lot of predators, hence the urticating hairs in most NW's, and the confrontational attitudes and hotter venoms of OW's. Also why so many can stridulate. Dorsal colors probably aren't primarily for warnings, more likely for blending in with foliage and flowers (and red clay soils), but the iridescence of the scopulae and red mouth parts are, as is the banding on the undersides of Poecilotheria's front legs. The show really begins when a tarantula stands up.

Brightly colored males can be seen by female in mating range, but the main reason for the colors may be that only the fittest males can survive with such a handicap, making them better sperm donars. This is true in other types of animals, like birds, and probably has some application in some T species.

Tarantula venoms CAN hurt their predators to varying degrees, even to the point of being lethal in some cases, but their limited vision often keeps them from employing it effectively. A full-dose bite from many OW's is going to have an serious impact on any small animal that sees a T as a potential meal. Check out bite reports on humans, who weigh considerably more. It's just a matter of outmaneouvering the spider before it can use it's weapon.

 

[Kevinitis]

Insightful Poec54! In thinking about the NW species, I would think that it is probably the hair flicking that is their main defense against anything that's not a tarantula hawk. I bet one could test bright colors against propensity to flick hair and perhaps show a relationship. B. Boehmei is known to flick hair more so than smithi for example. I would bet that trying to bite a tarantula would give a mouth full of those hairs, not to mention getting them in the eyes and nose.

 

[Poec54]

I would bet that trying to bite a tarantula would give a mouth full of those hairs, not to mention getting them in the eyes and nose.

A rodent, raccoon, coati, ferret, etc. trying to enter a NW tarantula burrow will get a cloud of hairs that attack the mucous membranes (eyes, nose, mouth); a definite deterrent. It's bad enough for us, imagine a small mammal in a confined space with it's face inches from the spider's abdomen. The fact that almost all NW T's have urticating hairs shows how serious mammalian predation is. It's a great defense that doesn't require physical contact with attacker the way biting does. There's always a greater risk when you have to touch your attacker; do you want to defend yourself with a knife or a gun?

Lacking defensive hairs, OW's tend to make up for it in attitude. Many require little provocation to stand and strike. Some of those terrestrials are also incredbly fast, such as Usambaras and many Asians. Since a higher percentage of OW's have stronger venoms, and that overall both OW and NW eat similar prey in the wild, it seems logical that OW's venoms have evolved to also improve their chances of survival in encounters with predators. I suspect that the hammock egg sacs of many east and southern African species is at least partially due to the heavy predation by baboons; if the mother is snatched and eaten, she's not holding the sac and her unhatched brood can survive on their own. Interestingly, Psalmopoeus lack urticating hairs and also have venoms that produce more painful reactions in mammals (humans included); maybe this isn't a coincidence.

---------- Post added 06-13-2013 at 08:26 AM ----------

there is often cases in nature where harmless species use mimicry to imitate the harmful/bad tasting species. Take for example the monarch butterfly, which is either distastful or down right toxic. It's bright orange and black color warns potential predators. On the other hand Then you have the viceroy butterfly which looks almost identical to the monarch but is harmless.

So thinking about T's, you have the Brachypelma's such as Smithi, boehmei, auretum and emilia who all look similar (ie some shade of red/orange/pink on the legs and black). Then you also have Aphonopelma Bicoloratum that looks almost identical to boehmei. Even A. moderatum looks superficially similar or may be evolutionarily trending towards looking like them. Perhaps a stretch, but A. Chalcodes color distribution is similar to Boehmei as well though blond not orange on the legs. So are all these color similarities of T's from this region because they are related and thus look alike, or are they converging on a certain look because one or all of them avoid some type of predation by having that aposomatic coloration?

The dorsal coloring of some species could be warning colors, but it could just as likely be to help them blend in with their background. There are many places in the world with soils that contain a high iron content which gives them a rusty, reddish color. The fact that certain species have similar colors and patterns isn't always an indication of close genetic relationships, it can also be convergent evolution to similar types of habitats.

 

[845BigRed]

Interestingly, Psalmopoeus lack urticating hairs and also have venoms that produce more painful reactions in mammals such as humans; maybe this isn't a coincidence.

I think if I got a face full of poo though I wouldn't want to eat. I know they aren't the only poop throwers but they are well known for it.

 

[Poec54]

I think if I got a face full of poo though I wouldn't want to eat. I know they aren't the only poop throwers but they are well known for it.

Another great defensive strategy! Not the classiest, but effective.

 

[Alltheworld601]

Aint nature grand? Every shortcoming is made up for by a strength to bring balance to it.

I see it in every living thing, but tarantulas are a great representation because those who keep them get to see the differences first hand, all in one place.

 

[Poec54]

Aint nature grand? Every shortcoming is made up for by a strength to bring balance to it.

I see it in every living thing, but tarantulas are a great representation because those who keep them get to see the differences first hand, all in one place.

+1. What a great hobby. We can bring these fascinating exotic animals into our homes and have glimpses into world's that few people know exist.

 

[Stan Schultz]

How about a couple alternate hypotheses?

1) Way back in Zoology 101 in university one of many phenomena that were repeatedly drummed into our skulls was that the presence of any given characteristic (e.g., color) DOES NOT NECESSARILY REQUIRE A REASON TO EXIST! Mutations and reshuffling of genes occur at random, and this introduces great potential for the development of all sorts of weird and varied characteristics. And, this is the basis for the development of new varieties and species in nature. In the vast scheme of things, which ones will be passed on to the offspring? Which ones will prove to be evolutionary dead ends? Food for thought. And indeed, further discussion.

As an example, albino creatures are rare in nature. Of all the possible reasons for this, the most probable seems to be that an albino tends to be far more visible to predators. But what about other colors? Why do we have gray wolves in Canada of three of four different colors? And, there is a reddish colored wolf native to the extreme southwest of the USA and Mexico. The answer is simple: Their coloring is largely irrelevant. There is no selection AGAINST any of those colors so they not only exist, but persist and even flourish!

So, my hypothesis is that the coloring of tarantulas is largely irrelevant to their survival. Those colors and patterns exit because of accident, and persist because there's nothing to weed them out! After all, what would you expect in a creature that spends 90% of its time in a burrow, completely out of sight? And, seldom comes out of its burrow except during the evening hours? And, creatures whose keenest eyesight is in the green and ultraviolet? (Yeah. We're going to find a lot of ultraviolet light at 3:00 AM in the desert, right? Why even bother? Except that it's illogical, irrational, and accidental.)

So, now we at least have presented that for discussion.

2) But, I have yet a further hypothesis! If I may be allowed to spin a most unscientific tale believing in predestiny and all that stuff, maybe they have their bizarre coloring in anticipation of some other, quasi-intelligent species evolving that would fancy the tarantulas for their colors or other characteristics. And, this whole thing is a clever plan by some Grand Creator or Master of the Universe to ensure the continuing survival of tarantulas in the face of, and in spite of the Earth's fifth or sixth Great Extinction?

Which brings me around to my closing comments:


Douglas Adams was wrong, by the way. The masters of the universe aren't white mice. They're large, fuzzy spiders!


You may now genuflect to your little 8-legged master!

:roflmao:

 

[Poec54]

How about a couple alternate hypotheses?

1) Way back in Zoology 101 in university one of many phenomena that were repeatedly drummed into our skulls was that the presence of any given characteristic (e.g., color) DOES NOT NECESSARILY REQUIRE A REASON TO EXIST! Mutations and reshuffling of genes occur at random, and this introduces great potential for the development of all sorts of weird and varied characteristics. And, this is the basis for the development of new varieties and species in nature. In the vast scheme of things, which ones will be passed on to the offspring? Which ones will prove to be evolutionary dead ends? Food for thought. And indeed, further discussion.

So, my hypothesis is that the coloring of tarantulas is largely irrelevant to their survival. Those colors and patterns exit because of accident, and persist because there's nothing to weed them out! After all, what would you expect in a creature that spends 90% of its time in a burrow, completely out of sight? And, seldom comes out of its burrow except during the evening hours? And, creatures whose keenest eyesight is in the green and ultraviolet? (Yeah. We're going to find a lot of ultraviolet light at 3:00 AM in the desert, right? Why even bother? Except that it's illogical, irrational, and accidental.)

So, now we at least have presented that for discussion.

I'm of the theory that tarantulas have primarily evolved colors/patterns for reasons that have proved beneficial. Poecs for example: their dorsal patterns blend in very well with tree bark and lichen; the ventral colors on their first two pair of legs (black, yellow, white) are similar to the warning bands on bees. In addition T's have red mouth parts, iridescent scopulae, and many can stridulate; also part of the warning display designed to get an animal's attention.

Many species have a lot of browns & blacks, which blends in with most soils, and orange/red colors work in areas with rusty, red soils and clays. This would be one reason why wolves are reddish in the SW USA as was mentioned, and grey in the north, and white in the extreme north. I think that alone proves that color is important to wolves; it's not a coincidence there's no white wolves in the SW or red wolves in the arctic. Certainly some of tarantula's colors could exist because there's no evolutionary pressure to eliminate them. But considering so many have bright, contrasting colors and patterns, there's likely to be some incentive to have taken it to those levels. It's one thing for evolution to tolerate an unneeded characteristic, it's another when it's taken to the art form we see in many T's. Few of us ever see tropical T's in the wild, and the foliage they live with. There are many flowers competing for polinators. There's a lot going on there with colors, patterns, and shapes, not to mention the profusion of unusual foliage and roots. The pink tarsi of Avicularia and 'lightning slashes' of Psalmopoeus metatarsi could make them look like a small bromeliad (Neoregelia), some of which have pink/red tips on the end of their leaves. The coats of tigers and leopards look very flashy in a cage, but in the wild are difficult to see. Likewise, some T's may look gaudy in a cage, but be perfect camoflauge in their native habitat. Just because we don't see the connection it, doesn't mean it's not there. There are many tropical plants, including orchids, with showy and strangely-shaped flowers. Whether it's for predator or prey, the goal for a T would be to look like anything but a spider. Amidst a background of those diverse and colorful plants, do T's really stand out? One could argue, the more colors and patterns, the less they look like a spider, and the more they look like flowers, leaves, or roots. They've had milleniums to fine tune this.

I think almost everything about them serves to increase their survival, whether it's size, shape, growth rate, eggs per sac, size of hatchlings, sex ratios, colors, patterns, sexual dimorphism, drought tolerence, venoms, etc. There's a tremendous amount of variety in these characteristics in the 900+ T species, little of which is likely to be simply chance. I think all of it combines to make a package that enables a species to best exploit it's niche. For so many brightly colored and patterned T's to exist, something has to be driving that for it to have become so advanced. I don't think it's an evolutionary 'runaway train' that keeps producing increasingly wild colors because nothing can stop it. It takes resources to produce them; there has to be a trade off that makes it worthwhile. We just haven't figured out what most of those are yet.