Reef shrimp are a varied and biologically diverse species of crustacean, all represented under the genus Lysmata. Various species of these shrimp have been present since the Lower Jurassic period until the present and represent an important element of the reef ecosystem. Reef shrimp and their various representative species are broadly categorized as “cleaner” shrimp, living largely off of the parasites and other materials gleaned in symbiotic relationship with fish. They are known to amass in large groups and, sometimes, to live in sponges.
One of the most studied elements of the reef shrimp’s life cycle is their means of reproduction. It is well known that various species of shrimp undergo a form of sequential hermaphroditic transformation- that is, they switch their gender from either male to female or vice versa. Reef shrimp, however, are unique for what is called protandric simultaneous hermaphroditism. They do not switch genders entirely, but become truly both male and female at the same time. So far, no other species in the world has been observed to do this, and every species within the genus Lysmata, at differing points within their respective lifecycles, has.
Reef shrimp are often found in warm tropical zones and temperate waters. They are aptly named for the reefs upon which they usually live. As mentioned above, their diet usually consists of refuse material and tiny parasites cleaned off of other fish. Reef shrimp are bottom-feeders that eat nearly any organic matter that they come across, including brine, tiny anemones and any dead or necrotic material that may be bothering a fish, coral, or sponge. They tend to gather into separate “cleaning stations” where they perform this duty for any creature that wanders close by.
Reef shrimp occasionally undergo a molting process that allows them to grow beyond the size of their current exoskeleton. It is not unlike the molting performed by various reptiles and insects. Scientifically, the process is believed to be biologically related to the molting process of those creatures through a common ancestor. Often, reef shrimp will leave their molted carcass in plain sight in order to distract potential predators while the creature hides away and waits for the new shell to properly harden. All species of reef shrimp exhibit this behavior, sometimes multiple times per year.