But look at the guy’s fingers… Compared to the lobster that would be about 25cm, and they don’t get much bigger than that. The reason probably as they don’t grow very deep, probably 10 meters down, and the resource is almost depleted. That’s why they are about $35 in a restaurant for one single tail, in comparison with a very descent size steak which would be less than $11. But on the black market which is in every small fishing town on our West Coast you could pick up a whole and mostly alive lobster for about $4.

Pity, but we can wish.

So oxygen doesn’t cause gigantism or huge sizes, I certainly don’t think that you are going to necessarily find giant creatures in every single cold, highly oxygenated environment. Many smaller animals require high oxygen levels too. Like has been mentioned here, there are many factors that can lead to the evolution of gigantism, and depending on ecological stresses, it is not a given that it will occur. But these high oxygen levels could help remove physical oxygen restrictions and be a contributing factor to allowing the organism achieve these large sizes.

Anyway, its amazing finding something like this. but what is much more better are fishes, which btw, never stops growing, like humans do (the more older they are the bigger then get, and thats probably the same w/ crustaceans)

Also, there are certain temperature limits depending on the species of crayfish. I did not say that there were no limits to how cold or how warm they can tolerate. For example, the introduced signal crayfish in Japan can tolerate warmer water temperatures than the native Japanese crayfish, which needs lower temperatures. It depends on the species. For some, like the Japanese crayfish, warmer water can kill them. Of course oxygen level is one of the factors there, I did not say it wasn’t. The lack of oxygen is a quality of the water itself. It does not matter what the reason is, the point is that depending on the species, there are limits to the water temperatures they can tolerate. Saying that it “is the oxygen level rather than the water itself” doesn’t make any difference on this main point.

Besides, we are not talking about Scandinavian crayfish. Perhaps those environments are simply too cold for that large species. As I said, there are limits depending on the species. However, signal crayfish in lake Mashu, Hokkaido, are thriving. The temperatures there are similar to those tolerated by giant cold water crayfish such as the Tasmanian freshwater crayfish. Tasmanian freshwater crayfish need cold water to survive, which is similar to the crayfish that are found in the cold, northernmost parts of Japan. Of course I’m going to consider the possibilities of similar factors at work. Why shouldn’t I based on the argument that they are not found in Scandinavia? There are a lot of reasons why giant crayfish might not be found there. Does that mean I should dismiss all of the possibilities?

However, it is not fully understood what role gigantothermy could play in the deep sea animals that are very large, or exhibit abyssal gigantism, so it is one possibility I leave open.

Thermoregulation is absolutely not the most important factor in size gain, and I can agree that it may have nothing to do with this case. However, whatever the factors in each species may be, just keep in mind that some of the largest aquatic cold blooded animals on Earth are cold water dwelling creatures. The largest invertebrates certainly are. The largest freshwater invertebrate on Earth is a type of crayfish that favors very cold water. So it seems important to me that when considering giant crayfish in this very cold lake, we should look at these examples when trying to figure out what is going on.

Considering the tendency for some cold water animals to be very large, I am trying to examine the possibilities with this crayfish that has been reported. Gigantothermy was merely one, and granted possibly not even the most important, factor.

What I was trying to point out here is that there are many ecological factors at work and I am looking at possibilities. Gigantothermy may be a bonus for some, but not necessarily all. I am not saying that giant squid and salamanders got that way due to gigantothermy, I wish you had read what I said more carefully. I am rather merely pointing out that many aquatic cold blooded animals are some of the largest of their kind due to a variety of reasons that should be considered for these giant Japanese crayfish. I am actually trying to look past gigantothermy here, that’s the point.

Also, the oxygen levels I have already mentioned as a possible factor on many occasions in this discussion, and in the article, but you don’t seem to have listened to me and you mention them here as if it is the first time. Did you not read when I was talking about the role of high oxygen levels?

I have clearly stated here that gigantothermy is little understood, and its exact range of effects is not totally known. It may play a small role or no role at all depending on the type of animal, but it certainly should not be entirely dismissed either. I do understand, and have even said here, that it is not always the sole reason for evolving large sizes.

I will say that as we learn more about the physiology of these animals, the more lines between what is “cold blooded” and “warm blooded” become less clear and less easily defined. It is not always as simple as your arguments make it sound. Our understanding of these terms has changed drastically in recent years, and we are learning more. There are a wide range of thermoregulatory measures, strategies, and adaptations in animals, many that are poorly understood, and it is hard to neatly categorize animals and their thermoregulatory processes. A lot of animals lie somewhere between the two extremes. I would suggest keeping this in mind before make broad generalizations about what “cold blooded” animals or “warm blooded” animals can or can’t do based on these vague definitions.

Shall I go on? The world’s largest salamanders, the Chinese and Japanese giant salamanders, live in cold water. The giant spider crabs which are among the largest of crabs, live in cold water. The giant squid and colossal squid, the largest squid, live in deep, cold water, as do many of the largest octopi and the giant deep sea isopods I mentioned. Many large sharks thrive in cold water environments, and a lot of the largest freshwater fish prefer cold water as well, as well as many large saltwater fish. The tuna you mention actually thrive quite well in cold, oxygen rich waters. I’m actually having trouble of thinking of too many types of warm climate cold blooded animals that are a whole lot larger than their cold water counterparts. Just what exactly do you mean when you say “actually the largest species don’t live in cold climates”? This is simply not true at all. Some of the world’s largest aquatic cold blooded animals live in cold environments. I really don’t see where you are getting your ideas.

You also seem to be denying outright the possibility of gigantothermy in deep sea or cold water organisms, even though it is supported by a good deal of evidence and hypotheses within the scientific community, which you don’t seem to want to hear about. I know about the heat conductive properties of water and the challenges of cold water creatures, perhaps more than you seem to think I do. I am well aware of the physiological reasons for heat loss and heat gain, as well as thermoregulatory strategies and what is needed for cold blooded animals to survive.

I’ve tried to explain how gigantothermy works or might work here. It is not useless to consider, and honestly some of your assumptions about the regulatory processes involved here are not completely accurate. Leatherback turtles for example do not have naturally high metabolisms either, they are not fast moving active animals, but rather are able to generate a high metabolism through heat regulation largely caused by the physics of simply being huge.

You are also making statements such as “large cold blooded creatures lose all of their heat at night,” which is not necessarily true, and without considering that the smaller creatures lose it even faster. Once again I’ll say it, large animals lose their warmth they have accumulated during the day more slowly, which by definition minimizes the heat loss you are talking about and could make large sizes a benefit. Large sizes can help, they certainly aren’t completely useless for thermoregulation.

Also, in cold environments, these animals can burrow or do a variety of other things to further retain the heat. You make it sound as if these reptiles would spend all that time gathering their heat and then go sit in the coldest place they cay find, which is not necessarily what happens. You are using the very most extreme examples of what could happen without looking at how the processes I am explaining could help lessen that negative effect. I stand by what I said, they gain heat and lose heat more slowly, which can have dual benefits.

Anyway, the most important thing here is that indeed many of the largest cold blooded aquatic animals do live in cold environments. This is of importance to the topic of these giant crayfish.