Caridean shrimp like this one carry pollen between male and female sea grass flowers. Image Credit: Enrique Dans via Wikimedia Commons // CC BY-SA 2.0.
Just when you thought nature couldn’t get any more adorable, there’s this. Scientists have discovered that teensy shrimp, jellies, and other sea creatures act as pollinators for underwater plants. They described the sea bees’ activity in the journal Nature Communications.
The sea grass Thalassia testudinum, also known as turtle grass, grows in dense meadows in the shallows of the Caribbean and the Gulf of Mexico. The grass puts out little white and pale pink flowers, some (male flowers) giving off pollen and others (female flowers) accepting it. Scientists have long believed that turtle grass pollinates itself by simply releasing its pollen into the water, which washes it into receptive female flowers.
Those scientists were correct. But the grass also seems to make use of its little visitors, as researchers learned when they trained video cameras on a flowering meadow. They discovered that the meadow was a bustling place frequented by dozens of different species [PDF], from shrimp and crabs to jellies, isopods, and worms.
Analysis of the recordings also revealed an interesting trend: male flowers full of pollen were far more popular with crustacean visitors than those without. The researchers watched as the tiny animals fed from the male flowers and swam away, grains of pollen still stuck to their bodies. The situation looked awfully familiar. Was it possible that the animals serve the same role underwater as bees do on land?
To find out, the researchers carefully collected flowering turtle grass and a sampling of its animal visitors, then brought them all into the lab. They set up a series of trays, each containing a single pollen-rich male and a single female flower, then added the trays to small aquaria teeming with their regular customers. They also ran a second experiment, in which the two flowers were buffeted by different types and strengths of current.
The researchers’ hypothesis was spot-on: The little animals were indeed ferrying grains of pollen from male to female flowers, allowing the flowers to get it on even in the absence of strong currents.
Kelly Darnell of The Water Institute of the Gulf was unaffiliated with the study, but told New Scientist she was excited with its findings.
"That pollination by animals can occur adds an entirely new level of complexity to the system," she said, "and describes a very interesting plant-animal interaction that hasn’t really fully been described before."
Turtle grass can also reproduce asexually, so pollination via shrimp likely represents a pretty small portion of its sex (or sexless) life. But the fact that it happens at all is delightful enough for us.