Disco clams may also use sulfuric acid to keep predators at bay, the scientists said. Dougherty used calcium chloride, which makes a white precipitate in the presence of sulfuric acid. More tests are needed to verify that disco clams secrete sulfuric acid when threatened, but the defense is a common one among other marine creatures, including some snails and other clams.
The sulfuric acid could be a critical part of the clams' defense strategy. The one-two punch seemed to work wonders on a peacock mantis shrimp. At first, the mantis shrimp struggled to open the disco clam. But then, it suddenly recoiled and became went into a catatonic state, or a state of stupor, leaving the clam alone. It usually takes a mantis shrimp about 45 minutes to crack open a clamshell, so "that is very strange behavior [for the mantis shrimp]," Dougherty said.
It's likely that the clam used sulfuric acid, or another irritating agent, to protect itself, Dougherty said. Preliminary tests also showed that disco clams flash more times a second when prey, such as plankton, are nearby. But it's difficult to test the clam's eating habits in an artificial environment, so Dougherty and her colleagues plan to travel to Indonesia this year to study the disco clams in their natural ecosystem.
Crustaceans include lobsters, crabs and shrimp. Crustaceans are really more related to insects than to clams. Some shellfish or mollusks only have one shell, such as snails. Clams have two shells so they are known as bivalve mollusks. The shells are held together with a hinge. Other bivalves are oysters, cockles, mussels, scallops.
Most bivalves bury themselves in sediment, where they are relatively safe from predation. A sandy sea beach may appear to be devoid of life, but there is often a very large number of bivalves and other invertebrates living beneath the surface of the sand. Others lie on the sea floor or attach themselves to rocks or other hard surfaces.
A few bore into wood, clay or stone and live inside these substances. Some bivalves, such as the scallops, can swim. Clams live in both freshwater and marine habitats, and range in adult size from nearly microscopic to the giant clam, which can weigh lb.
Some clams live only one year, while others live to be over years old. Clams lack heads, but most can react to changes in light and some have eyes. All clams have two shells joined near a hinge structure with a flexible ligament, and all are filter feeders.
Clams also have kidneys, a heart, a mouth, a stomach, a nervous system and an anus. Many have a siphon. There are over 12, clam species found throughout the world in many different habitats. Most bivalves adopt a sedentary lifestyle, often spending their whole lives in the area in which they first settled as juveniles. The majority of bivalves are infaunal, living under the seabed, buried in sand, silt, mud, gravel or coral fragments. When buried in the sediment, they are protected from the pounding of waves, desiccation and overheating during low tide, and variations in salinity caused by rainwater.
They speed up when you scare them or give them food, so anything that excites them will speed up that flashing display. This is fundamentally different from how most other critters in the sea that produce light are going about it. How is this different from bioluminescence? A lot of people actually thought it was bioluminescence initially. The difference is you can see it during the day, and usually bioluminescence isn't bright enough to be seen during the day.
This is based fully on structure within the tissue, whereas bioluminescence is a chemical reaction that actually produces light instead of heat.
Yeah, it's quite different, it's quite unique. And you did a study recently that looked at this match-up between the manta shrimp and the disco clam. What did you find in this study? The most interesting interaction was the disco clam opening mid-attack. When you think about a clam, usually their best line of defense is their shell, right?
They can close very tightly, as anyone who's ever tried to open one knows. The fact that this clam was opening in the middle of an attack to flash at the predator made no sense to us. That's your best line of defense when you're being attacked by this voracious predator. The manta shrimp itself also has a very strange reaction to that red, external tissue.
They actually went into a catatonic state for up to 15 minutes. Given that the manta shrimp goes into this catatonic state, might that open it up to its own predation? That's this weird symptom of the disco clam doing its thing, and then the predator itself gets eaten. There's clearly something going on that the manta shrimp is very unsure of when they encounter this tissue, so that's why we wanted to look at the tissue further and see if we could figure out what was going on that made it so unique and unpalatable.
The manta shrimp is famous for being a voracious predator, it's eating a lot of different things in the sea. Are there any indications that it's off-put by any other potential prey items other than the disco clam? They're not what I would call picky eaters.
I know my PhD P. The fact that we saw this strange interaction with the disco clam fascinated us from a behavioral point of view because there's just not much that will throw off the manta shrimp, especially to the point of going into a catatonic state and cleaning their mouth parts and just clearly being very annoyed at what they were encountering. I think it's also interesting because these are intelligent, as we can define it, creatures that I've seen them actually blow limbs off of crabs and things like that.
They're crafty animals, and it's just interesting to see them fall to pieces when they come across a disco clam. Yeah, so they can be very manipulative with the morphology of any creature that they encounter. I think they have to be in order to get various things open, and avoid getting hurt themselves while they're predating upon something. To see them not only go catatonic, but just seem to be completely lost, I don't know how to deal with this bright red clam that's flashing at me, I don't know what to do with this.
It's a pretty fascinating behavior to encounter. In general, animals usually don't do something unless there's some sort of benefit to them, right?
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