Yes: their sleep differs, for obvious reasons, and messing with REM sleep could well be why they need more neurons. Specifically, we know that echidna (a terrestrial species that lack REM sleep) has much more neurons than it should given its body mass (and, arguably, behavior), and one hypothesis is there’s a causal link, e.g. REM sleep could be a mean to make neuron use more efficient.
I don’t think whale neurons or the way they are connected are that different, unless you know of some research?
Yes: their sleep differs, for obvious reasons, and messing with REM sleep could well be why they need more neurons. Specifically, we know that echidna (a terrestrial species that lack REM sleep) has much more neurons than it should given its body mass (and, arguably, behavior), and one hypothesis is there’s a causal link, e.g. REM sleep could be a mean to make neuron use more efficient.