Pygmy octopus (Paroctopus cthulu) litter use

When scientists name a new animal species, they need to select one particular specimen. That individual will stand for its whole species, forever, and it is kept carefully in a museum so that in future anyone can come along and see it for comparison with their own finds.

This special individual is called the holotype. It exists as a physical anchor for the newly suggested name, and it doesn’t need to be a particularly fine or complete example of its species (many dinosaurs and other extinct creatures have been named on the basis of little of the original animal). The key is anatomical uniqueness, usually nowadays supported by genetic data.

Precisely how a holotype was found, and its behaviour while alive, are less important. But for today’s post, I wanted to start with a holotype description for a small octopus species first reported in 2021, by Tatiana Leite and her Brazilian colleagues, that does mention behaviour (you’ll soon see why). Here’s the key line from their paper, describing the new Paroctopus cthulu:

Holotype: male (mature) 18.3 mm ML [mantle length] found on sandy bottom next to rocky reefs at a 5-m depth inside an aluminum beer can. Ilha Grande, Rio de Janeiro State (RJ), Brazil.

Yes, inside a beer can.

A rubbish life

Paroctopus cthulu is a pygmy octopus. Its tiny relatives often find shelter in the empty shells left by marine gastropods and bivalves, making use of the enclosed spaces as a refuge. However, as Leite and her team point out:

Natural seashells are becoming increasingly scarce in shallow clear and warm waters due to tourism and collection for craftwork and decoration, while marine debris is increasingly available due to pollution by debris in the oceans.

In fact, all the examples of the new species were found inside some form of human trash. These animals included breeding females, showing that the species was completely adapted to and perhaps dependent on things discarded by people. Here’s a cluster of P. cthulu eggs discovered by the researchers, laid around the rim of a plastic snorkel mouthpiece:

This behaviour raises the possibility that in order to protect the species, there may need to be some form of allowance for human materials to remain in their environment. That beer can habitat of the P. cthulu holotype could be an important clue to how these octopuses will survive and thrive in the Anthropocene.

And this pygmy species is not alone in its attraction to our garbage. As we increasingly pollute the oceans, the ocean’s inhabitants are growing up with plastic, glass, concrete and metal objects as a common part of their backyards and hunting grounds. Octopuses are some of the most naturally curious and flexible members of the undersea community, and so it should not surprise us that they’ve taken to the new materials.

Scrappy behaviour

Earlier this year, Tainah Freitas teamed up with Leite and additional Brazilian and Italian colleagues to investigate just how much of our trash was becoming octopus treasure. Writing in the aptly-named Marine Pollution Bulletin, the group (figuratively) trawled public photo databases, Facebook, Instagram, and the memberships of several dive clubs and professional organisations for any photos or videos of octopuses interacting with human litter. They found 261 examples, of which these are a selection from their paper:

Note that photo (f) in that collage is our little friend P. cthulu. The most common material appropriated by these animals was glass, making up over 40% of the images. Plastic and metal followed. And the most common reason the octopuses were engaged with our litter was shelter, with 68% of the individuals hiding inside a container, or part of one.

Some of the octopuses made use of several items at once, such as the Amphioctopus marginatus or coconut octopus in photo (i) above. It’s tucked into a metal can, and has blocked the entrance with a bivalve shell and other debris for added protection. The researchers were also able to take a first guess at the favourite polluting soft drink for octopuses: Coca-Cola products were used by seven animals, versus only two for Sprite.

This isn’t a behaviour confined to one part of the world, or one group of octopuses. P. cthulu lives off the eastern coast of Brazil, but the scientists found records of rubbish use around the globe, and from shallow scuba-diving depths down to at least 400m off Italy:

Some of these animals are using objects that are fixed into the seabed, and so they are not technically tool-users. But many of them are transporting pieces of glass and other rubbish around their landscape, and using them to shelter when necessary, which is certainly a kind of technology. It’s similar to our use of an umbrella, or a camping tent, although a true analogy would also have to include octopuses first destroying or taking away most of our usual tools, so that all we had for protection was broken things discarded by octopuses.

It may be heartening in a small way to think that some of our tremendous volume of garbage that goes into the ocean helps out a couple of resourceful cephalopods. But the reality is that many animals are going to have to start substituting human trash for the previously abundant natural resources that we’ve now extracted (for gain or pleasure) from their habitats. The truth is, far too often we leave nature carrying the can for our ignorance and apathy.

So here’s my nomination of a new symbol for human wastefulness. It’s 1 minute and 47 seconds of calming music, watching an octopus literally carrying a can:

Sources: Leite, T. et al. (2021) A new species of pygmy Paroctopus Naef, 1923 (Cephalopoda: Octopodidae): the smallest southwestern Atlantic octopod, found in sea debris. Marine Biodiversity 51:68. || Freitas, T. et al. (2022) In an octopus's garden in the shade: Underwater image analysis of litter use by benthic octopuses. Marine Pollution Bulletin 175:113339.

Main image credit: Richard Whitcombe, Lembeh, Indonesia; https://500px.com/p/WhitcombeRD?view=photos || Second image credit: Leite et al. (2021) Figure 7a || Third image credit: Freitas et al. (2022) || Fourth image credit: Freitas et al. (2022) || Video credit: CNN, https://www.youtube.com/watch?v=WsTpv2cTLRc