mantis shrimp brain

[Bubbashrimp]

I read through Dr. Caldwell site about stomopods and have a biology question for him or others who might be able to answer it.

When biologists talk about brain size or intellegence do they take into consideration how good a sense is? Since the mantis shrimp brain is small but its vision is the best in the animal kingdom how much more brain would it need to interperate all the data its eyes interperate if it only had "average sight".

[Pea-brain]

It is my understanding that the mantis' eye processes all the data before it reaches the brain.note since we are talking about mantis shrimp biology, would you mind if I tagged my own question on it? I'd like to know how a stomatopods mouthworks. I've never been able to get a good look at mine, and I was wondering what kind of parts it incorporates and how they move. It's just wierd how they grab something, hold onto it, and you can't see it but it is eating bite after bite....

[Bubbashrimp]

Or how about the fact that it is not really a shrimp. So what is its closest relative on the evolutionary tree?


Sorry forgot about the systematics.

[justinl]

I can answer a couple of the questions.

eyes: yes, like pea-brain pointed out, the information is processed before it actually hits the brain. I believe this is done in the eye stalks. Our brains on the other hand gets raw data and must process it.

they're closest realtives are lobsters i belive.

mouth: I assume it's the same mandible kinda mouth as a crab or most other crustaceans.

[Pea-brain]

Actually I don't think a common ancestor has been discovered, meaning that for all we know they are closer to crabs, or even amphipods. However, given their elongated bodies they could be related closer to lobsters than others from the group malacostraca. The current theory is that stomatopods evolved from small crustaceans that sifted through sand looking for tiny food items such like pods. When they stirred up the sand a few of them would escape into the water. That is why we believed they evolved the spearing appendages. When they could catch small prey that floated into the water column they eventually got larger (large enough to take down fish) and then some evolved calcified clubs to smash open clams and such. eventually a group relied on smashing more than spearing...well you can put the rest together. Correct me if i am wrong though....

[Bubbashrimp]

So part of the brain is in the eye? or The eye is complex so the information does not need to be processed?

I doubt that the first one is true. So if the later is true then The eye does the work of the brain. How much work does it do? Don't biologists' need to account for this if they say "something has a small brain". Is this not relative to each individual creature? Would it be better to say "This mantis shrimp has a small brain, but its relative brain size is ---cc because of the complex nature of its eyes"

[Pea-brain]

The mantises eyes are so complex that they literally process all the information before it is fed to the brain. The brain is too small and doesn't have the ability to process the information iteself. I believe however that when they say something has a small brain, it means that its brain is...well small. Doesn't necessarily mean that the creature isn't intelligent nor does it mean the creature isn't capable of processing info. It also doesn't take into account what other parts of the body that do work. In humans almost nothing is done without the brain, so we naturally have large brain. However mantis shrimp do not have the luxury of carrying around a large head. They are streamlined, but they still neeed to be intelligent, so secondary things like processing images would logically need to relocate or be completely removed in order to keep the brain small. They need their eyes so they evolved a way to process the image w/o wasting brain space and power. at least that is my little theory...I'm probly wrong

[Bubbashrimp]

Perhaps I should explain myself, have you ever seen nature shows that discuss an animals intellegence. The dolphin and the chimpanzee seem to be the closest to humans. Is this even a fair comparison? Lets say humans had the eyes of a mantis shrimp and therefore we would not need our occipital lope. Lets say that this put our brain size just below that of dolphins for arguments sake. Would that mean that dolphins are more intellegent than humans? I would not think so, we just would have better adapted eyes,right(if mantis eyes = an occipital lobe)?

I believe the mantis shrimp is intellegent, would it not have to be because of all the posturing it does to avoid fighting.

biologists, I do not believe are as careless as nature show directors to even make this comparison. If they do compare brain sizes would they not need to account for discrepencies due to the overcompensation of some senses.

[Bubbashrimp]

Perhaps I should explain myself, have you ever seen nature shows that discuss an animals intellegence. The dolphin and the chimpanzee seem to be the closest to humans. Is this even a fair comparison? Lets say humans had the eyes of a mantis shrimp and therefore we would not need our occipital lope. Lets say that this put our brain size just below that of dolphins for arguments sake. Would that mean that dolphins are more intellegent than humans? I would not think so, we just would have better adapted eyes,right(if mantis eyes = an occipital lobe)?

I believe the mantis shrimp is intellegent, would it not have to be because of all the posturing it does to avoid fighting.

biologists, I do not believe are as careless as nature show directors to even make this comparison. If they do compare brain sizes would they not need to account for discrepencies due to the overcompensation of some senses.

[justinl]

intelligence is a layman's term. I think biologists ime avoid that word when they can. there is the question of how efficiently the brain is used. does it learn? how good is memory? complex behavioural or social expressions?

it's sorta like asking what the strongest muscle in the body. could be the heart for endurance. could be the togue which is technically a group of muscles. there are other candidates for that particular question.

we cannot compare to anything out there because all other life depends so heavily on physical attributes like opposing thumbs, rapts, streamlined shape, etc etc. humans on the other hand depend almost exclusively on "intelligence." so of course we are the most "intelligent" but it also isolates usfrom everyone else.

[Pea-brain]

wow. very well put and worded.

[Bubbashrimp]

So we are still comparing our selected organ against an organ that selection overlooked in another animal.

[Gonodactylus]

Hey, guys. Interesting discussion. I wish I had a couple of hours to try to wade in on this, but unfortunately I have a ton of work to get through this weekend.

As for the stomatopod eye, it does not have the "best vision", but it certainly has the most complex receptors. Gonodactyloids do see across the broadest spectral range of any known animal - 300 - 700 nm and they have up to 16 different visual pigments (rhodopsins). They also that up to 4 colored filters, three different polarization analyzing systems and a range-finding system that effectively gives them hexnocular vision (compared to binocular vision).

It would not be correct to say that all of the visual processing takes place in the three ganglia in the eyestalk, but certainly more does than in our retina. The brain still must integrate information from the two eyes, determine what is relevant and act on it (or not). In arthropods, much of this processing and integration takes place in areas called mushroom bodies - analogous to to our visual cortex. In flying insects, these structures are very large probably to provide rapid and detailed analysis required during flight. They are much smaller in stomatopods. In neither case does this have a lot to due with complex learning

Octopus have relatively large brains - larger than those of stomaotpods. However, about a fifth of the brain is devoted to the control of the chromatophores and skin muscles that allow the animal to change color and texture. Stomatopods don't need to do that. Furthermore, octopus do not have a hard skeleton. Controlling body movements is much more complex in cephalopods because of the need to coordinate different muscles. If you think about it, to move a leg at a joint in an arthropod or a person required only the control of a few muscles. To do the same task in an octopus arm requires the integration of dozens of muscles. (To know where the arm is also requires a lot more sensory input in an octopus.) I could go on with a similar discussion of dolphins. Their sonar system occupies a considerable portion of their brain. The same is true of weakly electric fish, bats, etc.

As for the phylogenetics of stomatopods, they are all in the superorder Hoplocarida which split from other crustaceans over 400 mya. Most biologists now place them in the Subclass Eumalacostraca and in the Class Malacostraca. There are four superorders in the Eumalacostraca: the Hoplocarida, the Syncarida, the Eucarida and the Peracarida. The Eucarida contain many of the crustaceans that people are familiar with. The order Euphausiacea include Krill and the Order Decapoda that contain the shrimp, crabs, and lobsters.

The Class Malacostraca includes the Eumalacostraca as well as the subclass Phyllocarida - a small group of most suspension feeders. A few classifications place the hoplocarids as a sister group to the Phyllocarids, but I think that is pretty much dead as more molecular evidence comes in.

As for the mandibles, I've attached a photo of a pair of mandibles (moltskin) from a Lysiosquillina maculata. The "L' shaped serrated teeth on the two arms would normally oppose one another. They are effective at cutting and sawing apart chunks of prey. I've even had large lysiosquillids and Hemisquilla chew a hole in a heavy nylon mesh dive bag in a few minutes and escape. If you look at the contents of the stomach, the material is usually completely macerated and unidentifiable.

Roy

[justinl]

wow thanks for the post Dr Roy! great info in there. I love the pic of the L. mac mandibles. i can see that they would be very effective at sawing up food... or dive bags for that matter.

[Gonodactylus]

Forgot the image.

Roy

[Bubbashrimp]

Do biologists use brain size as a measure of intellegence?

[Gonodactylus]

Only the pin-headed ones.

ROy

[Bubbashrimp]

Well what are your views on I.Q. tests then?

[Gonodactylus]

This has nothing to do with stomatopods, so I shouldn't answer it. However, since I do know a bit about the subject, let me say that there is nothing wrong with using "IQ" tests to measure various types of performance as long as those tests are applied within a group with similar experience. As soon as comparisons are made across cultural boundaries, the validity of the tests becomes questionable.

As for brain size and IQ, there is basically no correlation in humans as long as you do not approach the extreme pathological limits. For example, if one included individuals that were considered microcephalic, they would score poorly on an IQ test.

[Bubbashrimp]

Well could you in theory set up an I.Q. test for the Stomatopods ... Much like the Octopus opening a jar to recieve a treat, "Since there is nothing wrong with using "IQ"..."

Maybe there will need be adjustments made for stomotopods of the same spieces but from different regions IF(The big if) they even have a culture.

The reason why I am asking is that like you I am interested in invertabrate behavior. The posturing in mantis shrimp( to avoid war and loss of home) is interesting. Is it learned through experiences it has or is it via instinct. Can we even answer this nature v.s nuture question intellegently in humans? It seems that in humans behavior is a function of intellegence(not always). Is this idea not important in behavioral ecology?

Thank you for all your insites!!!!!!!!!

[Opcn]

If learned components came into the test I would imagine that they would invalidate the test. IQ tests for humans are based on learned behavior, which in a sense invalidates them, since two individuals of equal brain power can have been exposed to different sets of information, thus preparing one individual more than the other for a subjective measure of intelligence.

[Bubbashrimp]

So giving a stomatopod an "IQ" test would have to include not exposing the animal to HOW to accomplish the test. That is in octopus do not do the same IQ test twice or let another octopus see the first octopus open the jar.

I imagine on would have to start with a mantis shrimp egg to eliminate this invalidity.

[rekn]

my peacock i think uses tools. i put cubes of food in front of the powerhead, he used to have to swim after them daily to eat. after a few weeks of this he made a wall out of rubble and the cube hits that and he just walks over to it.

[Bubbashrimp]

Thats awsome, do you have any photos or videos of this wall he made?

Do you think if you take the wall down that he will build it up again?

[rekn]

no i dont but ill try taking apart his wall.