GoKawiilThree hearts; blue blood; no skeleton; arms like tongues. These are just some of the alien features of octopuses, squid and cuttlefish — members of the cephalopod family. The outlandish list continues. Cephalopod skin can taste chemicals, sense light and change colour and texture rapidly. In many species, the sucker-covered arms can even regenerate.
Cephalopods deserve higher welfare standards in research
These invertebrates have evolved independently from the vertebrate lineage for more than 600 million years. Their last common ancestor was probably a worm-like creature with a rudimentary nervous system and eye-like patches of light-sensitive cells. Despite this evolutionary gulf, vertebrates and these highly specialized molluscs share strange similarities. Their eyes, for example. “It’s eerie how similar they ended up,” says Cristopher Niell, a neuroscientist at the University of Oregon in Eugene. “The convergent evolution of the eye still blows my mind.”
Now, one similarity is spurring a boom in cephalopod neuroscience. Around 400 million years ago, cuttlefish, squid and octopuses diverged from the only other living cephalopods — the nautiluses. They then lost their protective shells and evolved brains that are uniquely large among invertebrates. These brains bestow the soft-bodied cephalopods with high intelligence. Cuttlefish, squid and octopuses have excellent memories, use tools and are adept problem-solvers; they have a concept of time and are capable of delayed gratification.
Cephalopods are the only non-vertebrate animals that have big, smart brains, says Cliff Ragsdale, a comparative neuroscientist at the University of Chicago in Illinois. And that presents a unique opportunity. Neuroscientists have gained a wealth of knowledge about how vertebrate brains work, but are increasingly looking to cephalopods for insights into ways to build large, high-functioning nervous systems.
“It is incredibly exciting for those of us who are interested in figuring out the rules of how brains work,” says Carrie Albertin, a cephalopod researcher at Harvard University in Cambridge, Massachusetts. “This is very clearly an elaborate brain driving elaborate behaviours.”
But a set of ethical challenges accompany the study of those powerful brains. Vertebrates used in scientific research have strong legal protections, but that is not always the case for invertebrates. Even the best efforts to provide gold-standard care are constrained — limited options for pain relief exist for cephalopods, for instance.
Nonetheless, over the past decade and, especially, the past several years, neuroscientists have been refashioning the tools of modern neuroscience and molecular genetics — developed mainly in mice and other model animals — for use in these enigmatic invertebrates. “There are so many biological questions that have not been explored with a modern cellular and molecular approach,” Ragsdale says.
Building a brain
A rudimentary look at the cephalopod nervous system reveals that there is more than one way to construct a large, smart brain. For starters, cephalopod brains are doughnut-shaped organs built around the oesophagus (see ‘Unusual anatomy’). Moreover, a large number of a cephalopod’s neurons — more than half in the case of octopuses — are located in the eight nerve cords, or minibrains, that control the arms.
... continue reading