Amber Pen Shell
Pinna carnea Gmelin, 1791
Family Pinnidae (Pen Shells or Fan Shells)
Pinna carnea is known as the Razor Shell in the Bahamas, reflecting its typical in situ posture with its fragile yet sharp posterior edges protruding from the sand. If dislodged slightly, pen shells can rebury by expelling water from the buried part of the shell, effectively “fluidizing” the sand to bury deeper. If dislodged completely, though, it cannot rebury. Predators include starfish and carnivorous snails. The shells often support a community of attached organisms, including algae, sponges, and polychaete worms. Commensal pea crabs and shrimps often live in the mantle cavity of the living pen shell.
Evolution on the Half Shell...
The Assembling the Tree of Life: Bivalvia project (BivAToL) is a part of the Assembling the Tree of Life initiative, a large research effort sponsored by the National Science Foundation. Its goal is to reconstruct the evolutionary origins of all living things.
Jetsam & Flotsam
Some of the BivATOL team met in early May at the Mote Marine Laboratory’s Tropical Research Station at Summerland Key, FL for a combined collecting trip and coding workshop. Both activities are essential to our project’s goal of determining the phylogenetic relationships among the bivalve families.
After collection, many of the species’ visible and molecular characteristics must be compared and “coded,” after which the phylogenetic computer analyses will be run to produce the final “tree” from which a hypothesis of relationships can be made. Below is an example of a portion of such a phylogenetic tree. Families that are on nearby branches are more closely related to each other than those further away.