Cephalopods can't tolerate fresh water

[Norbert Fnord]

Cephalopods (octopuses, squids, nautilus, etc.) are among the most complex invertebrates. They have been around since before the dinosaurs. Yet, there are none that tolerate fresh water today - perhaps there never have been (I am aware there is one squid in Chesapeake that lives in brackish water). This leads me to wonder about a few things:

1. What is it about this class of molluscs that prevents them from exploiting fresh water environments?
2. Is this why they also have not given rise to any land forms?
3. Is tolerance of fresh water essential to evolution to living on the land?
4. Were the predecessors (e.g. tiktaalik) of the first land vertebrates, fresh water animals?

 

[jim mcnamara]

None are known, that is correct.

Here is a somewhat "layman's version" of why:
http://www.abc.net.au/science/articles/2013/01/16/3670198.htm
Is this why they also have not given rise to any land forms?
No, any larger animals with no kind of skeletal system would have trouble moving, as an example

Is tolerance of fresh water essential to evolution to living on the land?
Were the predecessors (e.g. tiktaalik) of the first land vertebrates, fresh water animals?

The tiktaalik probably was freshwater -
Narkiewicz, Katarzyna; Narkiewicz, Marek (January 2015). "Middle Devonian invertebrate trace fossils from the marginal marine carbonates of the Zachełmie tetrapod tracksite, Holy Cross Mountains, Poland". Lethaia 48 (1): 10–12. doi:10.1111/let.12083.

They likely had primitive lungs.

Please note your questions are good, very good. But they require a multitude of citations. Or a book. There are journals like Lethaia that often have good articles about fossil environments and how animals adapted to new environments.

Try a University library for:
'The Colonisation of Land: Origins and Adaptations of Terrestrial Animals' by Colin Little

 

[Norbert Fnord]

Thank you - for all of that.