Cleaner shrimp have a calculating, murderous sex life

We have always known that cleaner shrimp mate in pairs. But scientists uncovered new evidence that suggests it isn't out of love; it's out of jealousy and murder. When groups groups of shrimp are put together, they end up killing each other until there's only two left. The shrimp are hermaphrodites, so they aren't even fighting over a single female.