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Cleaner Eurypterid

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In an earlier drawing (see "Cleaner Placoderm" [link]), I introduced the idea that many of the ecological interactions we see in living species - such as cleaning mutualism - may have also existed in the past. Such behavioural interaction are rarely preserved in the fossil record. Indeed even with living species, if they were observed outside of their natural setting, or just as a preserved specimen in a jar, we would never have suspected that a relatively nondescript little fish like a cleaner wrasse would have such a specialised ecological role in their environment.

While most people are familiar with cleaner fishes which pick parasites off their "client fish", fish are not the only players in the cleaning mutualism game. On the Great Barrier Reef and other coral reef systems around the world, living alongside the cleaner fish are cleaner shrimps ([link]) which perform the same role. Like cleaner fish, they advertise to potential clients by performing a little dance to indicate that they are open for business ([link]).

In this drawing I further explore the idea of such cleaning relationships in the ancient past. While in the previous drawing ("Cleaner Placoderms" [link]), I've cast placoderms in the role of the cleaners, there is no real reason why other organisms could not have also evolved to fill the same niche. Playing the cleaner role in this setting is a species of specialised eurypterid (sea scorpion). As well as being conspicuously coloured, it has a pair of brightly patterned paddles with which it advertises its service to potential clients. Its other limbs end in fine, forcep-like pincers which allows it to dig or pull out stubborn ectoparasites. Here it is attending to a Cephalaspis (an osteostracan jawless fish) which has a small group of parasitic trilobites (see this drawing for explanation [link]) attached near the edge of its head shield.
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PeteriDish's avatar
Such a great concept and so well illustrated as well!
PeteriDish's avatar
You are welcome!

The picture really caught my eye because the color scheme reminded me of peacock jumping spiders. :)
t-subgenius's avatar
Remembering one of my invertebrate biology teachers comparing eurypterid limbs to that of some of the cleaner shrimp and postulating that they may have preformed a similar function. Much like parasitic trilobites, given how widespread they were it seems likely that some may have served that function.
The-Episiarch's avatar
Yes, it's a shame we may never definitively if such interactions actually took place. As I said with the cleaner fish as an example, even with living species, if you can't observe them in their natural setting, you would never know that they have such a specialised niche (this equally applies to cleaner shrimps). If you have just scooped up a cleaner fish or a cleaner shrimp with a net, here's nothing about them which would indicate that they do what they do.