Nerd of All

I think that it is a firebrat, a small hexapod.

It could have been crab then bacteria because a crab is a scavenger and will probably eat anything with meat on it. Or you could do the whole food chain all over again, from crab to octopus, to swordfish to small shark, to great white shark to killer whale and even do the food chain all over again. That would mean there is a 24th consumer.

I found a food chain that has a duodenary consumer in the ocean. Picophytoplankton, flagellates, amoeba, ciliates, amoeba, euphausiids, small fish, crab, octopus, swordfish, a small shark, a bigger shark(namely great white), then killer whale.