Freshwater squid?

Graeme

Vampyroteuthis
Registered
Joined
Sep 26, 2005
Messages
352
The only freshwater squid I have ever come across is the Elephant Squid.

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?
 

cthulhu77

TONMO Supporter
Registered
Joined
Mar 15, 2003
Messages
6,638
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.
 

monty

TONMO Supporter
Staff member
Registered
Joined
Mar 8, 2004
Messages
4,884
cthulhu77;98624 said:
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.
 

Spence24

GPO
Registered
Joined
Oct 11, 2007
Messages
123
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???
 

Thales

Colossal Squid
Staff member
Moderator (Staff)
Joined
Jan 22, 2004
Messages
3,027
Spence24;107194 said:
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.
 

Taollan

Vampyroteuthis
Registered
Joined
Aug 17, 2005
Messages
304
monty;98641 said:
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.
 
Top