Diet and Metabolism: The Process of Nutrition in Photeros annecohenae

     Photeros annecohenae are scavengers. They feed on dead animals and begin to decompose this decaying organic matter. Because of this, they are classified as detritivores, or detritus feeders. Photeros annecohenae feed on decaying fish, shrimp and other invertebrates (even other ostracods) of the tropical seagrass beds in which they reside (Gerrish and Morin 2008). (It has not been observed that these ostracods consume decaying plant matter, only that of animals (Gerrish Personal Communication).) Because of this, they are attracted to carrion, or fish carcasses (Torres and Morin 2007), and this has been helpful in their obtainment for research studies. These scavenging ostracods are night-feeders; they forage at night. The high densities of Photeros annecohenae found in their grassbed habitats indicates that their scavenging is successful (They are able to find enough food.) and that they have a large impact on the environment around them (Gerrish Personal Communication).

     Ostracods use a pair of appendages, their first antennae, to sense the environment, including food sources. They then use a second pair of appendages, their second antennae, to move to their food by means of swimming, burrowing and/or crawling. (This pair of antennae is also responsible for allowing them to distinguish food sources from other matter they intercept.) Because of the fact that ostracods must move to their dead food sources, water velocity strongly affects their ability to acquire nutrients. Fewer juveniles and adults are found foraging when the water velocity is high (Gerrish 2009); this occurs because the ostracod’s ability to swim as well as grasp food is hindered by strong currents. During times of strong currents, the ostracods remain protected in their habitat to avoid being swept away. A strong water current also decreases Photeros annecohenae's efficiency in detecting food since the current carries away chemical cues that the ostracod would typically detect. It appears that feeding behavior corresponds with reproductive behavior in the fact that both are not as prominent during times of strong water velocity (overall inactivity during these periods) (Gerrish 2009). Both also occur at night.  

      After taking in the dead animal material, it is grinded up and moves through a straight-through digestive system that runs from their mouth to their anus. The nutrients absorbed are then circulated to their tissues via an open circulatory system. Food is stored as glycogen.

     Although Photeros annecohenae is not a known parasite for any organisms, it is a victim of parasitism and serves as a host for copepods, an ectoparasite in the family Nicothoidae, which may be found in the valves of the organism's carapace (Gerrish Personal Communication). This parasite is found in the brood of a female ostracod and feeds off her eggs, replacing them with its own. The female releases these eggs into the environment when it comes time for her to release what she thinks are her own juveniles.

To learn more about this parasite and how Photeros annecohenae interacts with other organisms, click here!