Category: Invertebrates
These small, spiny, globular animals inhabit all the oceans of the world and can survive in shallow intertidal zones, 5000 meter deep abyssal zones, and nearly anything in between. They move slowly about on their hydraulic tube feet, feeding mostly on algae. Sea urchins are able to adjust their metabolisms to the level of nutrition available in their environment. Many species of animals, including humans, hunt and eat sea urchins. Their internal organs are protected by a hard shell called a “test”, to which their spines are attached via rounded turbercles. The spines serve as protection and are toxic in some species.
https://en.wikipedia.org/wiki/Sea_urchin
Cephalopods: Masterminds of the Ocean.
Octopi, cuttlefish, and squids - all cephalopods - have been observed engaging in amazing feats of intelligence (perhaps unsurprising, as cuttlefish and octopuses have the highest brain-to-body mass of all invertebrates). Their suction-cup covered arms are dexterous, and octopuses have been observed putting them to use throwing rocks, opening screw-top jars, even picking up and gathering coconut shells to build fortresses for themselves. Squids, for their part, have been observed hunting cooperatively and are able to communicate with one another via color changes, patterns, and flashing to one another - sometimes using different sides of their bodies to broadcast different signals to multiple squids! Just how smart are they? As they are typically elusive and so very different from humans, we aren’t sure yet - but we do know the question is not “Are they intelligent?” but “How intelligent are they?”
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