Christopher Sommer

Chris Sommer is a small, planktonic crustacean, between 0.2 and 5 mm in length. Chis is a member of the order Cladocera, and is one of the several small aquatic crustaceans commonly called water fleas because of their saltatory swimming style (although fleas are insects and thus only very distantly related). He lives in various aquatic environments ranging from acidic swamps to freshwater lakes, ponds, streams and rivers.

The division of his body into segments is nearly invisible. His head is fused, and is generally bent down towards the body with a visible notch separating the two. On most days the rest of his body is covered by a carapace, with a ventral gap in which the five or six pairs of legs lie. His most prominent features are the compound eyes, the second antennae, and a pair of abdominal setae. Some days, his carapace is translucent or nearly so and as a result he makes an excellent subject for the microscope as one can observe his beating heart.

Chris sometimes preys on tiny crustaceans and rotifers, but mostly he is a filter feeder, ingesting mainly unicellular algae and various sorts of organic detritus including protists and bacteria. He also eats forms of yeast, but mostly in laboratories or controlled environments. Chris can be kept easily on a diet of yeast. Beating of the legs produces a constant current through the carapace which brings such material into his digestive tract. The trapped food particles are formed into a food bolus which then moves down the digestive tract until voided through the anus located on the ventral surface of the terminal appendage. The first and second pair of legs are used in Chris's filter feeding ensuring large unabsorbable particles are kept out while the other sets of legs create the stream of water rushing into the organism. His swimming, on the other hand, is powered mainly by the second set of antennae which are larger in size than the first set. The action of this second set of antennae is responsible for the jumping motion.