For my Bachelor Research Project I did an internship in the Naturalis Biodiversity Center, Leiden, Netherlands, on symbiotic shrimp under the supervision of Charles Fransen, carcinologist and curator of Crustacea. During this internship I illustrated, described and analyzed multiple species of shrimps and actually got to name two of the new species. I would like to introduce all readers to the wonderful world of the symbiotic shrimps, and I hope you will be as shocked as I was when I found out that there’s so much more than the shrimp on your plate.
There are currently around 40 families of shrimp known to science, with the Palaemonidae being the largest family containing around 1,000 known species. All marine shrimp in the family Palaemonidae are what we call symbiotic species. A symbiosis occurs when two organisms live together, whether negatively like a parasite and its host (parasitism), or a win-win situation like a shrimp cleaning the teeth of fish in order to get food (mutualism). This article specifically addresses commensalism: when a tiny shrimp benefits by finding shelter inside or on another animal, while the other organism doesn’t mind it living there. What makes these shrimp so interesting is that each species has its own specific host. It can range from corals and clams to tunicates and sponges, everything is possible for these small shrimp.
Being highly specialized species also means that there are a lot of different adaptations for each one of them. Most species mimic their surroundings in coloration, but some even take it a step further. Take for example shrimp from the genus Dasycaris that live on corals. Their bodies are not only colored like the host, but also mimic the surface by having evolved exaggerated body structures. Another form of adaptation can be found in the genus Odontonia (described by Fransen, 2002). The Odontonia have evolved to live inside small tunicates – a group of invertebrates which resemble a bag with two openings – where they live between the folds of the internal sacs of the tunicates. This means that the shrimp do not have a lot of space, so they developed to be very small and have a smooth body so they do not get stuck inside their host.