The naked tail of a hermit crab is a flaccid, unsexy, and vulnerable thing. When a snail shell of the right size is nowhere to be found, the hermit crab’s gotta do what’s it gotta do, which in this case is living inside a sea anemone. Hermit crabs will often place anemones on their shells—the anemone’s stinging tentacles keep away predators and it gets to hitch a ride while feeding on food particles the crab misses. That’s probably how this started. But when the crab outgrew its small snail shell, the anemone grew to cover both shell and crab.
Greg Rouse and colleagues found this critter during an expedition off the coast of Costa Rica in 2010. The area is lacking in large snail shells, says Dr. Rouse, and there has been a previous report of this species, Parapagurus foraminosus, covered by an anemone.
Image courtesy of Greg Rouse, Scripps Institution of Oceanography at UC San Diego
Up-close views of Typton carneus‘s shear-like tools.
In Hansel and Gretel, two ravenous children stumble upon a house made entirely of sugary goodness, and begin to chow down with abandon. But the kids’ journey quickly turns sour, as the owner of the house, a wicked witch, tries to cook them for dinner.
While the story seems to be a cautionary tale, it turns out that finding and living in an edible house can actually be pretty sweet—at least in the animal kingdom. Researchers in Prague have now learned that some tiny shrimp in the Belize Barrier Reef dine on fire sponges, their homes, by first tearing off pieces of tissue with claws not unlike those of Edward Scissorhands.
Bluestreak cleaner wrasses servicing a “client.”
Our legal system was built on the idea that different crimes warrant different punishments. Aggravated assault will snag you less jail time then, say, premeditated murder. And with no small degree of hubris, many of us believe that we’re the only animals on the planet to implement such a discerning system. But scientists have now learned that a species of fish also punish delinquents according to the severity of their crimes.
Starting life as females, bluestreak cleaner wrasse band together to clean off parasites and dead tissue from bigger fish, including sharks. At some point, the largest wrasse in a group, which typically has about 16 members, will change sex, become harem master, and reproduce with the others.
Yet while they normally feed on parasites, wrasse females actually prefer something a bit tastier: their clients’ mucus. However, a misplaced mucus nibble can annoy the client and thereby drive off the group’s food source, so males chase and bite any females caught misbehaving. Last year, scientists saw that punished females seem to fall back in line.