This week I was interested in writing about something wacky in marine systems. Being an ecologist, I tend to discuss organisms and their environment. So as I brainstormed what to write, I thought back to my time as a research technician at the Virginia Institute of Marine Sciences (VIMS) with Dr. Emmett Duffy. While working at VIMS, 99% of my time was focused on seagrass communities. However for that other 1% of the time working in the lab, I helped curate the largest collection of eusocial snapping shrimp currently in existence.
What does eusocial mean?
The word eusocial is defined by Merriam-Webster as “living in a cooperative group in which usually one female and several males are reproductively active and the non-breeding individuals care for the young or protect and provide for the group.”
Certain people may immediately come to the conclusion: BEES! Yes, bees are one organism that is considered eusocial. Many bees have one queen, a few reproductive males, and worker bees called drones that care for the hive. While bees are probably the most recognizable eusocial organisms, there are others found in terrestrial systems (or on land): termites, naked-mole rats (the only mammal), and even some ant species.
Yet in the aquatics systems, there is only one group of animals that are considered eusocial (that we know of): snapping shrimp from the genus Synalpheus.
Synalpheus species typically are found living inside of sponges on coral reefs. They are only a few millimeters to centimeters in size. When they snap their claw it creates a bubble that can reach speeds of 60 miles per hour and the produce a sound that reaches 218 decibels. The pressure from their snap can kill a small fish in it path. Luckily, these shrimp typically only use this as defense mechanism!
The eusocial shrimp live in colonies inside of their host sponge. The can have one or sometimes multiple queens per colony and hundreds of drone-like worker shrimp that excavate the inside of the sponge. When the queen dies an new one (or more) develops to continue the reproduction of the colony.
Disclaimer: Not all species in this genus are eusocial. Some live in colonies with a queen, some live in male-female pairs, while others are completely isolated. In reality out of over 100 species in this clade only 8 are eusocial: S. brooksi, S. chacei, S. elizabethae, S. filidigitus, S. rathbunae, S. regalis, S. microneptunus, and S. duffyi.
Interestingly, eusociality in these species seems to have evolved many different times. It is believed this “life style” arose due to competition for space within the host sponges! From reports it seems that you can rarely find a sponge with out these shrimp living inside. AND it appears that the eusocial species of Synalpheus are out competing their non-eusocial relatives, taking over the sponges with their large colonies. (Talk about hating your relatives!)
Even though these eusocial snapping shrimp are small, they sure are making a big splash!