One day while exploring the web i came across this site:http://www.fantasticmetropolis.com/i/squid/13/

Is there really a freshwater squid, because this is all that i can find on the Mayfly Squid. The article also says that there is a freshwater squid in Brazil somewhere. Whatever. Im dying to know more.

http://zapatopi.net/treeoctopus/

Looks pretty bogus to me.

As far as I'm aware no ceph has made the move to freshwater..........it'd be :cool: if it were true though!

J

The only freshwater squid I have ever come across is the Elephant Squid.

http://i17.photobucket.com/albums/b65/Roadkilldemon/ElephantSquid1.jpg


... But then it was invented by Anthony "Doc" Sheils to explain hte Loch Ness Monster... :lol:



I don't think there is such a thing as a freshwater squid. Leastwise, not one known to science. Plus they are very successful in their existing niches, why would they need to move?

Absolutely hilarious! I love straight-faced B.S. of this magnitude. :lol:

I don't see how they would survive the fresh water environment long enough to adapt, do you?

It is simply a matter of respiration and food.

If you look at the complex of cephalopods living in the oceans (and trees, for those of you with fanciful natures), it is easily seen that the larger species live in deep water...the closer you get inshore (less absorbable oxygen), the smaller.
For a squid, or more likely, an octopus, to adapt to freshwater, it would have to me extremely small...and the food sources in freshwater aren't even close to what is available in the tidal areas.

Doubtful that it will ever happen.

It is simply a matter of respiration and food.

If you look at the complex of cephalopods living in the oceans (and trees, for those of you with fanciful natures), it is easily seen that the larger species live in deep water...the closer you get inshore (less absorbable oxygen), the smaller.
For a squid, or more likely, an octopus, to adapt to freshwater, it would have to me extremely small...and the food sources in freshwater aren't even close to what is available in the tidal areas.

Doubtful that it will ever happen.

I'm with you on food, might add salinity, but I'm not sure I buy the respiration thing: many cephs live in deep, low oxygen conditions, and do just fine; in fact, Gilly's work with Humboldts suggests that they're much better at coping with that than folks had previously thought. Ward's book Out of Thin Air I read recently posits (among many other oxygen-related animal evolution theories) that cephs evolved driven more by advanced respiration, and that jet propulsion and free swimming were side effects of just pushing lots of water over the gills... Although cephs need more oxygen for their active lifestyles, there are plenty of examples of freshwater bivalves and even terrestrial gastropods, so it's demonstrably not inherent in mollusc physiology that they can't survive in low-oxygen environments... and cephs tend to have much better coping mechanisms for low oxygen than other molluscs, like the separate hearts for the gills.

I suspect that vulnerability is an issue, too: cephs don't do well drying out, and they're not well-suited to living in small pools (since we know how much food they require and waste they produce!), and they're vulnerable to predation by birds in shallow freshwater.

This thread was referenced here (http://scienceblogs.com/tetrapodzoology/2007/12/nessie_on_film.php). :cool:

And isn't the whole thing about feeding your ceph freshwater food that it is so low in nutrition they eventually just start to waste away???

This thread was referenced here (http://scienceblogs.com/tetrapodzoology/2007/12/nessie_on_film.php). :cool:

Stone me!:shock: That bloomin' Elephant squid is famous!:mad:

Stone me!:shock: That bloomin' Elephant squid is famous!:mad:
LMAO

And isn't the whole thing about feeding your ceph freshwater food that it is so low in nutrition they eventually just start to waste away???

Kind of. It has to do with fatty acids.

I'm with you on food, might add salinity, but I'm not sure I buy the respiration thing: many cephs live in deep, low oxygen conditions, and do just fine....

Boy, this is one of those questions that really fascinates me... why haven't cephs gone to freshwater (along with why is semelparity adaptive in octos...)
I have to disagree with the not enough food part. While freshwater does have lower bimass overall that marine environments, there are some that have quite high primary production and very high biomass, such as the Amazon river and its tributaries, the Mekong river etc. Even in North America native freshwater mussels can be very abundant, (Margaritifera falcata reaches densities of 39 individuals per square meter , with average individual size about 8cm). These areas are comparable with many tropical marine areas (not coral reefs), which are relatively barren and have low primary productivity. Cephalopods seem to do fine in the deep sea as well, which has a much lower biomass density than many freshwater.
I really don't buy much into the respiration argument either. Nearly all surface waters (down to a 50 m or so), be it freshwater or marine, are oxygen saturated. Saturation level is dictated by water temperature. So really this isn't a problem. Rainbow trout have similar respiratory levels and thrive in freshwater. And it isn't a problem with extraction efficiency, as octopuses can extract up to 76% of the oxygen from their ventilatory stream in normoxic conditions.
I would tend to agree with Monty that it is likely partly a osmoregulation problem. But seriously, there are some cephs that frequent intertidal areas, like O. rubescens, that seem to be fairly resilient to reasonable salinity changes. Additionally, gastropods, the mollusks most closely related to cephs, haven't seemed to have had trouble invading freshwater or terrestrial environments.
I would also say variability in temperature would be another problem in freshwater for cephs, but then again we have cephs that frequent intertidal areas that seem to be fairly resilient to this as well. I will use O. rubescens as an example again, I have seen them go from 11 C to 0 C in the space of three hours, stay down there for about four hours and brought back up to 11 C again over the course of another three hours, and went on to live a long (for an octopus) life. That was as accute change, but O. rubescens occurs from Alaska to the Sea of Cortez, so that suggests that they physiologically can handle a large range of temperatures.
Anyhow, thats my :twocents:. Sorry if that was a bit long, But I find this all really interesting. I have a hunch if some research was to dedicate a descent about of time on the question, they would uncover some really interesting stuff about ceph physiology.

Interesting point about intertidal areas. One thing of note however is that estuarine waters are invariably saline, albeit in fluctuating concentrations. In light of this, it is very likely that cephs in these environments will never actually encounter purely freshwater areas, at least for any length of time. I wonder if osmoregulation, or maybe another problem brought on by salinity levels (bouyancy, possibly?) is to blame? Granted, cephalopods are very similar to gastropods, but given that they fall under the phylum Mollusca, which is more varied than even our own phylum, Chordata, I believe the divide between gastropods and cephalopods is great enough for difference in physiological adaptations.

Of course it could just be entirely down to something as simple as niche allocation. It is entirely possible that any niche the cephalopod could fit in freshwater environments is already taken up by another animal, thus ousting the ceph from filling the niche.

The gastropod bit was a stretch, but in my defense, gastropods and cephalopods are (relatively) closely allied within Mollusca. Obviously, since gastropods have invaded those evironments and cephs haven't, they are enough different to for those differences to be meaningful (is that sentence just as clear as mud?). Physiological, however, gastropods and cephs are very similar and if you want to compare cephs to something else physiologically, gastropods are it. So I think it is informative to look for small differences between the two for this question.

I do like you idea about niche competition, but really off the top of my head it would seem the incredibly higher diversity of forms in marine habitats would mean that niches would be all that more closed in marine than freshwater. Freshwater is filled with a few generalist species occupying a wide range on niches that often are occupied by ten times the number of specialist species in the ocean. Also, freshwater habitats is very ephemeral in the evolutionary sense, rapid changes are often leaving large niches open. Then again these quick changes might be part of the problem with ceph invasion. But that answer just beings us back to our original question: other animals do it, why not cephs.

I have on more idea here. Perhaps it is the lack of diversity in the food base in the freshwater that is the problem. Many octopuses have trouble thriving on a monotypic diet... I am not sure I like that explanation either....

I have on more idea here. Perhaps it is the lack of diversity in the food base in the freshwater that is the problem. Many octopuses have trouble thriving on a monotypic diet... I am not sure I like that explanation either....

Many of us have fed our cephalopods fresh water shrimp, so it is possible for them to prey upon fresh water species.

I am wondering if it has something to do with their high metabolism.

I find it interesting that mammals like the Baikal Seal and the freshwater dolphin species have survived in freshwater environments (although they are now threatened by human pollution...).

I am wondering if it has something to do with their high metabolism.


There are freshwater fishes that have comparably high metabolism. So I don't think that is the case. What you brought up about freshwater dolphins and Baikals seals is very interesting. Being warm-blooded mammals, they have a much higher metabolism per body weight than octopuses, and thus have a higher food requirement as well. However, since there is relatively little water exchanged through the skin with mammals, osmoregulation is going to be wildly different than with most invertebrates such as octos...

Many of us have fed our cephalopods fresh water shrimp, so it is possible for them to prey upon fresh water species.

I am wondering if it has something to do with their high metabolism.

I find it interesting that mammals like the Baikal Seal and the freshwater dolphin species have survived in freshwater environments (although they are now threatened by human pollution...).

I like the re-awakening of this thread!

It seems like marine mammals have a rather different approach to osmotic regulation than many other marine animals, in that they tend to keep the land-evolved systems isolated from the water as much as possible, while gill-using animals tend to, by necessity, have a lot of membrane exposure to salt water directly. I'm not sure how marine mammals get hydrated, though.

The fact that so many octopuses live in intertidal zones sure does fly in the face of most of the arguments for why they have never moved into fresh water... another thing that no one has mentioned recently is that cephs are a very ancient group, and I know that the ocean's salinity is believed to have been appreciably less in the Cambrian, so there's some evidence that early shelled cephs existed in lower salinity conditions.

Has anyone else read Peter Ward's Out of Thin Air book? It's overall about how oxygen levels have been a major and often overlooked driving force for evolution (with many hypotheses that Ward advocates looking at, with appropriate caveats that some may well be wrong... it's a food for thought book.) One of the variants of this story is the hypothesis that cephalopod development of jetting and neutral buoyancy, and hence effective predation, was secondary to development of better respiration: that the mantle inhalation and exhalation through the siphon was to get better circulation of low-oxygen water past the gills, and that had the secondary effect of jet-swimming and higher possible metabolism, which offered an opportunity to prey on the oxygen-starved slower critters in the environment, which nudged the evolution in the direction of free swimming, improved jetting, neutral buoyancy, and tentacles to grab lunch. He also suspects the segmentation of trilobites was more about repeating the body segment that has the gill than anything.

I had already been thinking that the presence of so many cephs in deep, low-oxygen water makes many of the "traditional views" of hemocyanin as inferior to haemoglobin is vertebrate arrogance, particularly in light of Gilly's lab's demonstrations of active, fast, huge humbodts spending a lot of time in the anoxic layer, and reports of nautilus having a good ability to survive low-oxygen and even out-of-water conditions. Ward's book, however, really got me thinking a lot more about the inconsistencies of things I'd read, like "the teleost fishes were able to drive the cephalopods to deeper water because their metabolism was much more effective due to haemoglobin and better oxygen storage in tissues." I'm sure this is true up to a point, but the fact that the cephs are the ones who were more successful in the low-oxygen depths suggests that rather than being metabolically challenged, the cephs outcompete vertebrates more readily at low oxygen levels, so the vertebrate respiratory and metabolic systems may be more tuned to current atmospheric oxygen levels rather than universally "better."

I suspect that cephs' mechanisms for handling low oxygen levels are more in the domain of "less well understood" than vertebrates' systems, and there's a tendency to assume "not understood" is "inferior." I'm not sure how osmotic regulation occurs in any mollusc, or how freshwater bivalves and gastropods differ from their marine counterparts in mechanisms for maintaining homeostasis in freshwater environments, and likewise for terrestrial gastropods. I note that table salt is lethal for slugs, snails, and leeches. Is vastly over-salted water lethal to marine molluscs in a similar way? How about freshwater molluscs in marine salinity levels?

Asking why there are no freshwater cephs seems to also just be a reminder of the huge gaps in our understanding of the history of the modern cephs: the almost complete lack of soft body fossils, and consequently our lack of understanding of the prevalence of non-shelled cephs at various points in their evolutionary history-- which raises a question of whether it's easier, harder, or the same for a shelled ceph to migrate to freshwater (where the pumps in the siphuncle and chamber fluid composition might be impacted) or for a coleoid (where it's harder to be neutrally buoyant in freshwater than denser salt water, although octos, for example, seem happy enough to be negatively buoyant.)

I'm not really buying the "all the niches were occupied" argument as an absolute argument, although it may be sort of a "luck of the draw" argument... It seems like cephs were dominant predators in the ocean before vertebrates had established themselves anywhere, certainly not on land. I'd assume that plants and arthropods, and maybe gastropods, had to be well established on land well before vertebrates... if anything, all the hungry ammonites probably provided pressure for arthropods to escape to dry land. Anyone know if there's a fossil record of when the first terrestrial or freshwater gastropods emerged?

A related question someone asked me that may appeal to the readers of this thread is "how come the queen/drone/worker/hive arthropod model that's so successful for insects on land doesn't seem to occur in marine arthropods?" unless there are examples in marine arthropods that I'm unaware of...

And as long as we're asking such questions, perhaps considering why there are no terrestrial or freshwater echinoderms would be interesting as well... I'd think a starfish or sea urchin would be at least as good a candidate as a snail for crawling about on dry land and eating plants and lichens and such off of rocks.

Just one of a few good threads on this subject, the following quote from an off topic thread:

Not alot of detail in the following reference, but it does infer that they are rethinking ammonoid habitat and including superhaline, subhaline, and even brackish (surface) water environments. Still not fresh, but ammonoids could have been headed up stream until their demise at the end of the Cretaceous.


(Reference)
Westermann G.E.G., 1996. Ammonoid Life and Habitat. IN Landman, Neil H., Kazushige Tanabe, and Richard Arnold Davis, editors. Ammonoid paleobiology. Plenum Press, New York [ISBN: 0-306-45222-7]

:ammonite:

Also Fresh Water (http://www.tonmo.com/forums/showthread.php?t=3673) a very similar thread

and a Poll: Are fresh water octos just a hoax? (http://www.tonmo.com/forums/showthread.php?t=3787)

WOO HOO. I love all this sort of discussion...


And as long as we're asking such questions, perhaps considering why there are no terrestrial or freshwater echinoderms would be interesting as well... I'd think a starfish or sea urchin would be at least as good a candidate as a snail for crawling about on dry land and eating plants and lichens and such off of rocks.

As for echinoderms I have a feeling that this is closely tied to their water-vascular system. One of the very basic parts of their lifestyle is this system that keeps a reservoir of water inside them for movement, and this is constantly taking in water from the surroundings at a high volume and leaking water out. On land this would be impossible to maintain (sea star out of water gradually lose the ability to move). This might be feasible in freshwater, but with such a large volume of environmental water inside of you, your osmoregulation problems have gotten to be much much much harder. That is my thoughts on that part..


Has anyone else read Peter Ward's Out of Thin Air book?...I had already been thinking that the presence of so many cephs in deep, low-oxygen water makes many of the "traditional views" of hemocyanin as inferior to haemoglobin is vertebrate arrogance.

No I haven't read that book, but I have really been meaning to. I did talk with him briefly about his ideas on this a year or two ago at the American Malacological Society meetings and I must say that I was very interested.
And I agree...I don't think hemocyanin is as inferior as the traditional view suggests. Octopuses are efficient and extracting O2 from their environment, period. Octopus vulgaris has been shown to be able to take 76% of the oxygen out of each "breath" of water, that is better than humans, and I have found that O. rubescens can regulate their oxygen uptake (keep their oxygen uptake rate the same) down to 7 mmHg (for reference, oxygen saturation at this temp, 11 C, is about 156 mmHg). These numbers are actually superior to most vertebrates. Hemocyanin, however, is only half the equation: Biomechanics plays a large part as well. Octopus respiration is such that water flows over the gills through out the entire ventilatory stroke in one direction. Its not a tidal breath like humans perform, its actually unidirectional, which helps alot. This one direction that water flows is countercurrent to the blood flow in the gill capillary bed, so extraction is additionally efficient. The strategy of having three hearts (two before the gills and one post-gill systemic heart), means they have high blood pressure throughout their arterial system, further helping gas exchange. Also, in terms of hemocyanin, from what I understand it is more efficient at carrying oxygen at low O2 levels. Hemoglobin binds oxygen cooperatively, which means that as you bind more oxygen (up to four per tetramer molecule in humans) it can bind the next more efficiently. This means that if you have well-loaded hemoglobin, it is very effiecient, but the opposite is also true, if there isn't much oxygen, you lose cooperativity and it is no longer that efficient at carrying oxygen, and hemocyanin which show no (or atleast much less) cooperativity keep up relatively the same efficiency as at high O2 levels.
Even in many high-oxygenated near-shore environments cephs seem to hold their own pretty well against vertebrates. I don't know of anywhere cephs are really "rare" in near shore environments. Really, ceph respiratory physiology is very very interesting and entirely under studied. Its much sexier to study behavior and intelligence, but really their respiratory physiology is just as head and shoulders above all other inverts.


A related question someone asked me that may appeal to the readers of this thread is "how come the queen/drone/worker/hive arthropod model that's so successful for insects on land doesn't seem to occur in marine arthropods?" unless there are examples in marine arthropods that I'm unaware of....

As far as I know, even in terrestrial arthropods I think the high social strategy is restricted to hexapoda (the insects), which have extremely few, if any, representatives in marine environments. Terrestrial arachnids, crustaceans, and myriapods are just as asocial as their marine relatives, so maybe the better question isn't marine vs. terrestrial but really hexapods vs. the rest arthropods why this hasn't arisen. And since we are asking question, why are insects, who have been insanely successful in terrestrial and freshwater environments not further invaded marine environments. If they arose on land, I think I could go for the niche exclusion argument on that one... but serious, I really don't know.

To address some of the answers also brought up in the other freshwater thread...

And I don't want this to come off as though I am picking on Fujisawas Sake, (s)he simply was the main person proffering ideas, so most of the novel stuff came from them.

Hemocyanin serves as a good transport, but has a low affinity for, oxygen. Freshwater is more dynamic in the O2 and salinity (ionic) changes than seawater. Fish, utilizing the more oxygen-efficient hemoglobin, were able to colonize freshwater first, and therefore were able to keep this niche well-stocked and defended.


But really this hasn't stopped many other animals that use hemocyanin. And really hemocyanin is good for variable oxygen levels because of reduced cooperativity. Hemoglobin is simply much more efficient at high O2 levels.

Fish, utilizing the more oxygen-efficient hemoglobin, were able to colonize freshwater first, and therefore were able to keep this niche well-stocked and defended.


But Cephs were around since the upper Cambrian at least, and fish only since the Devonian, it seems cephs had a huge head start and it should have been up to the fish to fight them out of it.

Maybe a less specialized prey menu might have helped too.

Octopus seem to eat anything that moves, and can get into just about any packaging (clams, finding things in holes and cracks with their arms). Fish tend to be awfully picky eaters, and need soft bodied prey or insects. As for being generally out-competed, it seems an uncomfortable reason for not even seeing a single freshwater ceph anywhere.

Case in point: octos hunt crustaceans mostly. The majority of the crustacea are still marine. There would have been no need to try new hunting grounds if no need presented itself. The behaviour wouldn't change, so no selective pressure, therefore no evolution toward a freshwater existence.

While there is far fewer species of crustacean in freshwater, there isn't much lack in numbers. Amphipods are numerous (which are often used as prey by juvenile octos) and crayfish occur in high numbers nearly every long-term body of freshwater. And again, octos are one of nature's great dietary generalists. They can eat just about anything fleshy in a pinch (stomache contents have revealed sea cucumbers, gulls, other things that we often think of as unpalatable to these critters.
Secondly, from what I can tell, life will expand until something constrains it. “No need” isn't really a good argument for why X animal doesn't occur in Y location.
Life operates by producing more offspring than can survive. Because there always is a struggle for existence, every possible means of survival will be exploited.


Another point; osmoregulation. Cephs don't handle freshwater. They are by their nature isosmotic with the seawater and freshwater would stun and most likely kill a ceph quickly.

Kinda circular reasoning. Essentially any marine organism can't handle freshwater (with a few exceptions). If you tossed a marine snail in freshwater it would die, but there are still freshwater snails.

I like the re-awakening of this thread!

It seems like marine mammals have a rather different approach to osmotic regulation than many other marine animals, in that they tend to keep the land-evolved systems isolated from the water as much as possible, while gill-using animals tend to, by necessity, have a lot of membrane exposure to salt water directly. I'm not sure how marine mammals get hydrated, though.


Marine mammals get their fluid from the fish/cephalopods that they consume. That being said, when I cared for sick pinnipeds, we would offer them fresh water, and they would readily drink water from a bowl. Also, we would often let them swim in fresh water pools, with no (perceived) ill effect. However, if we were rehabilitating a dolphin or whale, we had to use salt water.

I note that table salt is lethal for slugs, snails, and leeches. Is vastly over-salted water lethal to marine molluscs in a similar way? How about freshwater molluscs in marine salinity levels?


For slugs and land snails, I am pretty sure this has to do with being a land animal and osmosis occurring through their skin.

Asking why there are no freshwater cephs seems to also just be a reminder of the huge gaps in our understanding of the history of the modern cephs: the almost complete lack of soft body fossils, and consequently our lack of understanding of the prevalence of non-shelled cephs at various points in their evolutionary history-- which raises a question of whether it's easier, harder, or the same for a shelled ceph to migrate to freshwater (where the pumps in the siphuncle and chamber fluid composition might be impacted) or for a coleoid (where it's harder to be neutrally buoyant in freshwater than denser salt water, although octos, for example, seem happy enough to be negatively buoyant.)

I am wondering whether buoyancy plays some role in this - although I would guess, if a cephalopod were to make the transition to fresh water, it would be an octopus.

And as long as we're asking such questions, perhaps considering why there are no terrestrial or freshwater echinoderms would be interesting as well... I'd think a starfish or sea urchin would be at least as good a candidate as a snail for crawling about on dry land and eating plants and lichens and such off of rocks.

I can't remember the answer to this, but at one point in my academic career I learned the reason there are no freshwater echinoderms, but I think it has something to do with their water vascular system.


Another point; osmoregulation. Cephs don't handle freshwater. They are by their nature isosmotic with the seawater and freshwater would stun and most likely kill a ceph quickly. Their metanephridia are no where near as hardy as our kidneys, which are pretty fragile. Fish are better at taking the extremes of freshwater by highly developed kidneys. Very few molluscs are freshwater, and those that are show signs of having returned to the water from a land-based life (pulmonate gastropods).

John brings up a good point about cephalopod "kidneys" - their metanephridia may not be capable of handling osmoregulation in fresh water.

For an interesting discussion on the origin of Baikal seals, see this...
http://darrennaish.blogspot.com/2006/12/most-inconvenient-seal_12.html


This is a great discussion, if I weren't so sleep deprived, I would be able to respond more intelligently...

I note that table salt is lethal for slugs, snails, and leeches. Is vastly over-salted water lethal to marine molluscs in a similar way? How about freshwater molluscs in marine salinity levels?

Yes and yes. Essentially all aquatic animals (with the exception of some estuarine critter) are sensitive to salinity. Maintaining osmotic balance is about as proximal of a need for animals as breathing is. Nearly all aquatic animals exchange essentially all of their fluids through the skin, and changes in salinity royally screw with maintaining that balance. Even the most euryhaline (saline change tolerant) freshwater fish can't survive in marine environments for more than a few minutes, and visa versa. Anadromous fish spend days in estuaries retooling their osmotic physiology before they can make the transition.
Marine mammals are kinda the exception. Having come from land mammals, they retain the water-proof skin, they they are largely resilient to such changes. Every year the in Columbia River sea lions venture far up the river foraging on the migrating salmon, much to the dismay of fisherman and fisheries managers.
So that was a long winded answer to yes, over-salted water will kill just about anything aquatic, including mollusks.

But ... Some "guppies" /"mollies" (brackish water fish) CAN and DO survive being simply thrown into salt/fresh water. Granted, a higher success can be achieved by slowly raising/lowering the salinity but survival can occur often enough that any aquarist can accomplish this with long term success without slow acclaimation (acclimitiz(s)ation ;>). Have studies been done on the makeup of the gill "material" of brackish water animals ois there a "pump" difference that would explain the effect?

In case you are interested in osmoregulation in marine mammals (and have a lot of spare time...), here is an interesting article.

I had forgotten about manatees and otters, which have both salt and fresh water species...

http://jeb.biologists.org/cgi/content/full/204/11/1831

But ... Some "guppies" /"mollies" (brackish water fish) CAN and DO survive being simply thrown into salt/fresh water.

Essentially all aquatic animals (with the exception of some estuarine critters) are sensitive to salinity.

Yes, mollies are pretty euryhaline, and can survive in fresh or saltwater because they are a estuarine species. If you have a pretty salinity tolerant animal, adapted to living in estuaries, where salinity is variably on a daily basis, then they are generally somewhat adapted to these changes. Hardy animals like this can generally survive a saline change of about +- 15-17 ppt and survive. So generally anything from 32 ppt (slightly lower than oceanic except Pacific) to 0 ppt is generally tolerated well by estuarine species. That being said, you can kill mollies pretty quickly if you stick them in a stiff brine of 60 ppt or so, and that gets back to my main point of the post:
over-salted water will kill just about anything aquatic, including mollusks.
P.S.: I have also found that goldfish are surprisingly tolerant of fairly radical changes in salinity. I have thrown them into 35 ppt saltwater straight from freshwater and had them survive for a couple days. Given, this isn't as good as mollies, but still amazingly good for a non-estuarine fish.

Next time we have a student wanting to do research on octopuses, someone remember to point to this thread. Specifically, I am thinking about longevity and hydrating diet ...

I do like you idea about niche competition, but really off the top of my head it would seem the incredibly higher diversity of forms in marine habitats would mean that niches would be all that more closed in marine than freshwater. Freshwater is filled with a few generalist species occupying a wide range on niches that often are occupied by ten times the number of specialist species in the ocean. Also, freshwater habitats is very ephemeral in the evolutionary sense, rapid changes are often leaving large niches open. Then again these quick changes might be part of the problem with ceph invasion. But that answer just beings us back to our original question: other animals do it, why not cephs.


Why? Because cephs are a pre-Cambrian Class. Compared to other contemporary marine animals, I'd say they've been pretty successful, and quite comfortably sat in their niches, able to outcompete other animals that would perform a similar role. Really, cephs have always been quite a strong Class in natural history, and so probably never needed to migrate because they do the best job they can already. In fact, would it be too much to even suggest that migration to freshwater might have been because cephs filled their niches so well? That's maybe going a bit too far...

Then again, it might be something very simple such as they don't like constantly flowing water that they would most likely have to tackle first. True there are currents in the ocean, but they can move between water columns, thus escaping the flowing water. In a fast flowing river, you really have nowhere to hide from the current. Lotic waters are noted for being harsh environments, and maybe cephs just couldn't tackle this, either because of the conditions (given their very soft bodies) or because what little niches there were had already been swiped. Also, the first hurdle is possibly the most significant- estuarine environments are well-known for their turbulent waters. Marine water flowing up, freshwater flowing down generating strange currents. The varying conditions from intense stratification right up to "salt wedge" conditions. Estuaries are quite hazardous environments, even for hardy animals.

I couldn't see a migration from the sea to a lake as plausable- the animals would surely have to migrate up river systems.

Why? Because cephs are a pre-Cambrian Class.

They are a Cambrian, the earliest mollusk that can be called a cephalopod is Plectronoceras from the upper Cambrian.

Then again, it might be something very simple such as they don't like constantly flowing water that they would most likely have to tackle first. True there are currents in the ocean, but they can move between water columns, thus escaping the flowing water. In a fast flowing river, you really have nowhere to hide from the current.

Well, A lot of the best places I have found giant Pacific octopuses are high-flow areas, such as a couple sites just outside Deception Pass in Washington. I don't know that it bothers them all that much. However, even so, some of the river that would most likely be first colonized by invading cephs would be very large, eutrophic rivers with a high biomass such as the amazon. The flow in much of the amazon is very gentle, almost lake-like.

Also, the first hurdle is possibly the most significant- estuarine environments are well-known for their turbulent waters. Marine water flowing up, freshwater flowing down generating strange currents. The varying conditions from intense stratification right up to "salt wedge" conditions. Estuaries are quite hazardous environments, even for hardy animals.

Graeme, I do believe you're brilliant and onto something great here. I really think we are asking the wrong question: "Why haven't cephs invaded freshwater", it should be "why haven't cephs taken on estuaries" Any migration to freshwater will have to go through estuaries. Not only do they physically separate freshwater environments and marine ones, but no animals is going to go from marine to freshwater in a single generation, there will be a series of (many) hypohaline tolerant animals before a true freshwater animal. So, why haven't octopuses taken on estuaries?

They are a Cambrian, the earliest mollusk that can be called a cephalopod is Plectronoceras from the upper Cambrian.

consults sciency stuff. Ahh poo, you're absolutely right. My apologies; I feel quite foolish now :lol:


Well, A lot of the best places I have found giant Pacific octopuses are high-flow areas, such as a couple sites just outside Deception Pass in Washington. I don't know that it bothers them all that much. However, even so, some of the river that would most likely be first colonized by invading cephs would be very large, eutrophic rivers with a high biomass such as the amazon. The flow in much of the amazon is very gentle, almost lake-like.

Interesting. I've never heard of such behaviour. Are they resident to these areas, or perhaps just visiting? Would the sites serve as good feeding grounds? I wonder if they just brave the conditions, as it were, to get a chance at some good eating. Most invertebrate animals that live in flowing water are either extrememly flat and tend to be benthic, burrow or have tough exoskeletons or shells; or a conbination of these. Cephs have none of these adaptations. I'm not too sure as to the physical hardiness of cephs, but I'm guessing that they are quite fragile. I know quite well that octopuses have a high tenacity in their suckers to allow them to cling to substrata (ommitting squids and cuttles as their suckers are only good for one thing- prey capture), but would this result in the octopus losing its arm? I'd also have to consult my old scribblings on the subject- I can't recall the correlation between octopus suckers and pressure (I think it goes that increased pressure reduces the risk of cavitation), and am unsure if there is enough water pressure in a shallow, fast-flowing river to allow completely successful adherence. It would be interesting to see if marine vs fresh water has any impact on the ability of the sucker. If only I was still at uni, I could have went one step further and studied this!



Graeme, I do believe you're brilliant and onto something great here. I really think we are asking the wrong question: "Why haven't cephs invaded freshwater", it should be "why haven't cephs taken on estuaries" Any migration to freshwater will have to go through estuaries. Not only do they physically separate freshwater environments and marine ones, but no animals is going to go from marine to freshwater in a single generation, there will be a series of (many) hypohaline tolerant animals before a true freshwater animal. So, why haven't octopuses taken on estuaries?

Thanks Taollan. I dunno about the first bit, but I might agree with you on the second bit there :lol: We probably are trying to think too many steps ahead, instead of focussing on the initial steps which are the most important.
Maybe we should all bang our heads together and get a book published on the matter; just interesting arguements towards the case :lol: I can see it now... TONMO's first book: "What happened to the freshwater octopuses?" :lol:

(ommitting squids and cuttles as their suckers are only good for one thing - prey capture)

Not necessarily; I have a few spent/mated female onychoteuthid specimens covered in sucker marks. Plus, in at least one genus, the tentacular hooks (modified suckers) are thought to make cuts on the mantle into which spermatophores are implanted.
Not to be pedantic, of course, and not to hijack the thread... :roll:

Ok, First of all, sorry about my absence for the last couple of days. Walla Walla was hammered by a wind storm and I have been without power since friday. (http://www.king5.com/localnews/stories/NW_010408WXN_easternwa_wind_storm_LJ.d0a 3c96.html if you're at all interested)

Anyhow: to respond


Interesting. I've never heard of such behaviour. Are they resident to these areas, or perhaps just visiting? Would the sites serve as good feeding grounds? I wonder if they just brave the conditions, as it were, to get a chance at some good eating. Most invertebrate animals that live in flowing water are either extrememly flat and tend to be benthic, burrow or have tough exoskeletons or shells; or a conbination of these. Cephs have none of these adaptations. I'm not too sure as to the physical hardiness of cephs, but I'm guessing that they are quite fragile. I know quite well that octopuses have a high tenacity in their suckers to allow them to cling to substrata (ommitting squids and cuttles as their suckers are only good for one thing- prey capture), but would this result in the octopus losing its arm? I'd also have to consult my old scribblings on the subject- I can't recall the correlation between octopus suckers and pressure (I think it goes that increased pressure reduces the risk of cavitation), and am unsure if there is enough water pressure in a shallow, fast-flowing river to allow completely successful adherence.

These GPOs are resident in the area for about three months at a time before moving on. They have dens in the area and can be regularly visited, and sometimes seen out and about. The reason they may be there is the abundance of Pacific spiny scallops, Chlamys hastata, which are filter feeders and seem to like high flow areas. The octopuses in this area eat more scallops than red rock crabs, their second-most consumed prey item in the area.
Really I think that you are underestimating the toughness of octopuses. I really doubt an octopus would have a problem of flow up to 7 knots or so. In my younger and foolish days I was known to pull on the arm of a GPO with all my might, and there was no detatchment of the arm. In fact, even a small 10 pound individual seemed to be little more than annoyed. Later in my octopus experiences I have had 70 gram O. rubescens latch on to my hand with 4 arms, and onto their artificial den (with a one liter volume) with the other four. In an attempt to get the octopus to let go, I pulled my hand, him attached to it, and him attached to the den full of water, all out of the water and he held for about 10 seconds. Octopuses are incredibly strong for their size, and I seriously think even a stiff current would be little more than an annoyance, If it got too bad, octopuses are pretty good at flattening themselves out.

Taollan,
But for how long? There are many very fast animals in the wild but their speed (and possibly the octo's strength) is only for short bursts (I am particularly thinking of the Cheetah but there are numerous others). You mentioned your rubescens held on for 10 seconds but not 10 minutes. IF flow is a factor, endurance would be key.

PS Hope your tanks are OK with the power outage!

How well do cephs cope with temperature changes and extremes? I'm trying to think through the differences (apart from straight salinity) between sea and freshwater environments and one of them would be the (comparitively) rapid and extreme temperature changes that you would get in freshwater environments (except for large lakes and such).

In:kiwiflag: the eels would get any ceph which tried it, much like they go through just about anything else that takes thier fancy :wink:

Rapid temperature change (or gradients) knock squid out almost immediately. It's never been pressure that has caused me problems (with cephs having a partially closed circulatory system - less prone to embolism), but the thermocline.

Power seems to be restored back to Walla Walla in full now. Luckily the WWU campus never lost power, so the octopuses were safe. It did make me very nervous though and I had battery powered aerators and bags of ice on stand-by (the added harzards of keeping cold-water cephs).
Anyhow, you are right, endurance could be a problem, but I was trying to illustrate that the integrity of an octo's body won't be compromised by the forces caused by flow.
but would this result in the octopus losing its arm?
I still don't think flow would be a barrier to freshwater invasion. Like I have mentioned earlier, there are some very low flow freshwater systems with high biomass (lower Amazon, Mississippi, Mekong, most very large rivers), and some octos seem to handle tidal currents well (admittedly these are intermittent).
As for temperature, like SOS mentioned about squid, my experience has been that strictly subtidal species have a hard time with temperature changes. That being said, octopuses that frequent intertidal areas seems to be relatively tolerant. Again, that being said, my experiences have been with octopuses exposed to acute changes (on the order of 11-12C temperature change for the period of 6 hours) and not chronic like you would have seasonally in a temperate lotic system (say same temp range, but over 4 or 5 months). But again those same river systems that have low flow and high biomass have also fairly constant temperatures, especially the tropical ones such as the amazon.
As I think about this more, the more I think the question is: Why are there cephs in the intertidal but not estuaries?

Once again I claim to know nothing about squid. I'm thankful for the answers I got to my post. The only other comment that makes sense pertaining to what I saw is the threadfin shad doing some some sort of mating ritual. The backwaters where I fish have an abundance of these shad. The main times I see these shad is when bass are schooling on them so obvioulsy the only ritual they would be practicing then is escape. The thing that still bothers me is how close that fictional article sounded (including where these creatures would be found and the surrounding habitat cypress trees, crayfish, polluted waters). It very well could have been shad, but I still believe this should be investigated further because I knew nothing about this fictional article until after I had that experience. To anyone who is interested, there is documented proof of a bull shark being caught in a town called Simmesport, Louisiana some 2 years ago. From a North/South standpoint, that is as North as where I am fishing, just on the other side of the Mississippi River. If that guy wouldn't have caught that shark, no one would believe it could have gotten there. Ironically, the only other country to have documented bull sharks in freshwater is Brazil (in the Amazon). At least the only other country I know of.

Once again I claim to know nothing about squid. I'm thankful for the answers I got to my post. The only other comment that makes sense pertaining to what I saw is the threadfin shad doing some some sort of mating ritual. The backwaters where I fish have an abundance of these shad. The main times I see these shad is when bass are schooling on them so obvioulsy the only ritual they would be practicing then is escape. The thing that still bothers me is how close that fictional article sounded (including where these creatures would be found and the surrounding habitat cypress trees, crayfish, polluted waters). It very well could have been shad, but I still believe this should be investigated further because I knew nothing about this fictional article until after I had that experience. To anyone who is interested, there is documented proof of a bull shark being caught in a town called Simmesport, Louisiana some 2 years ago. From a North/South standpoint, that is as North as where I am fishing, just on the other side of the Mississippi River. If that guy wouldn't have caught that shark, no one would believe it could have gotten there. Ironically, the only other country to have documented bull sharks in freshwater is Brazil (in the Amazon). At least the only other country I know of.

The shark may have been placed there by an irresponsible hobbyist who couldn't accommodate the animal anymore. There are reports of sharks popping up in strange places. Apparently they are surprisingly tolerant of low salinity conditions.

AM,
It is unlikely that a bull shark was anyone's pet (well, OK, mayby the hound os Tindalos :wink:). However, bulls have been documented up stream on numerous occassions and there was a recent (to my eyes, may have been a repeat) documentary that mentions one that managed to eat a kid or two in Illinois long before I was born. :old: Wikipedia has a reference to the Illinois siting as well as other notes on their freshwater travels.

http://en.wikipedia.org/wiki/Bull_shark

I'm not all that familiar with all the different sharks honestly. All I know is much like crocodiles and alligators, people are dumb enough to think they can keep them, and then when they start growing really big and become uncontrollable they dump them wherever it's convenient.

There was an interesting talk at the NZ marine sciences conference last week about habitat use in bull sharks. Apparently they use the Australia's Gold Coast artificial canal system extensively, with the youngest age class actually preferring salinities of 6-18ppt.

Abstract attached.

if i never mentioned this ur signature is rather hilarious Tintenficsh

This might be in particular reference to a certain someone's singular habit of ordering event horizon inducing breakfasts of undetermined specific gravity at iffy Wellington based breakfast "restaurants".

I would personally never do such a thing :)

Nor would TF ever, EVER add ketchup to the equation...

Ketchup!! :yuck:

My sig was penned by the great Fujisawas_Sake... I can't remember whether he intended it as a haiku or not. But it is. 8-) Also applies equally well to Steve's favorite lineup of morning foods. Did I mention :yuck:

Also applies equally well to Steve's favorite lineup of morning foods. Did I mention :yuck:

Let me guess, would this be some combination of high LDL meats and starches seasoned with butter or lard?

You are SO spot on...

and while we're talking about signatures, urs is very wise, sad and true

My friend found these remains floating in Watch Lake near 100 Mile House in British Columbia. Neither of us are any sort of biologist; however, I couldn't help but notice the suction cup looking parts and traits similar to squid I have seen in pictures. It's hard to tell as the remains are rather decomposed. This is very bizzar to my friend as she was just on vacation and thought she'd found an interesting log, when it was in fact dead flesh of some kind. What do you think it is? Her pics are on Facebook. I'll post the link and hopefully you can see them.

http://www.facebook.com/album.php?aid=50403&id=569472376&ref=nf

.... we have to log in to see those pics (and I'm not big on these things). Can you post the pics without a facebook login?
Thanks

I don't seem to have permission to view them, even when I'm logged in to facebook... would it be possible for you to include them in a post or upload them to the image gallery?

I'm certainly curious, but I expect that it makes more sense to look for a non-cephalopod explanation.

Given the location, this could well be Octopus paxarbolis?

I made a site along time ago to follow along the tree octopus site, you may visit it if you wish and let me know how funny it is to you. It is totally bogus and untrue, but funny still. Make sure you read it all.

www.savethepeal.info