August 26, 2019
The Hitchhiking Anemone
Posted by: John Cassell
A popular summer activity is seine netting at the beach. A seine net is basically one that hangs vertically in the water, and the bottom has weights to drag it along the sandy seafloor. Sometimes we find unusual specimens, such as this Hitchhiking Anemone (Calliactis tricolor).
This small (0.9-3inch) size anemone, not quite like the familiar ones seen in recent Disney films, occurs in the Gulf of Mexico, the Caribbean, and Atlantic coasts. Like all anemones C. tricolor have tentacles with stinging cells (nematocysts) that capture prey. They can attach onto rocks, but like their common name suggests, hitchhiking anemone can be found attached to mollusks, driftwood, docks, and hermit crab shells. When the hermit crab is also using the shell the two form a symbiotic relationship, wherein the anemone gathers food as the host moves while the crab is protected by its stinging tentacles.
This one caught in our seine net was attached to a discarded shrimp shell, quite the unusual host for this individual. What is also unusual is how this species reproduces. They use what scientists call binary fission, a type of asexual reproduction where a single body separates into two. In binary fission the organism duplicates its DNA then splits into two parts, also called cytokinesis, with each new body getting a copy of DNA.
For a look at anemone splitting, click here
For more on the biology behind this phenomenon, click here