Class Branchiopoda in the Christopher B. Smith Preserve

Class Branchiopoda Characteristics: Members of this class include fairy shrimp, clam shrimp, water fleas, and tadpole shrimp. Most are small, feed on plankton and detritus, and live in freshwater. Branchiopods have gills on many of their appendages, including some mouthparts. The class name is derived from the Greek words "brachia" meaning gills and "pous," meaning "foot."

Branchiopods have compound eyes and a carapace (hard shell). In the case of water fleas, the only branchiopod photographed in the Preserve, the carapace is a two-valved shell that encloses the trunk. Since the carapace prevents the use of the trunk limbs for swimming, these animals use their antennae for locomotion. They beat their trunk limbs in a wave-like motion, creating water flow along the midline. This current transports oxygen to its gills and food to its mouth.

Interactions in the Smith Preserve: Branchiopods are an important food source for invertebrates and small vertebrates (amphibians and fish).

Order
Family
Species Name
Common Name
Cladocera
Daphniidae
Daphnia sp.
Water Flea
 

 

Daphnia sp.

Water Flea

Daphnia sp. is a small, planktonic crustacean that lives in ponds and lakes. There are approximately 150 species in the genus. The common name "water flea" is attributed to its jerky swimming motion, that resembles the movement of fleas.

Most are .5 to 1 mm long with a head that points down. The carapace is transparent. As shown in these photographs, many internal organs can be seen through the carapace. The single median eye is compound, consisting of many individual photoreceptor units. A pair of large antennae are used for swimming.

A female is larger than a male and has a brood chamber where eggs are created and carried. The individual shown in these photographs is a female with two developing embryos.

A female can produce thousands of offspring during her two to six month life. Reproduction is both asexual and sexual.

Parthenogenic embryos, like the ones shown in these photographs, are the result of asexual reproduction. These embryos develop from unfertilized eggs. The female releases these young Daphnia into the water when she moults.

During unfavorable weather conditions, females sexually reproduce with males. The resulting eggs, called resting eggs, can withstand time, heat, cold, and drought. The female releases these eggs into the environment when she moults. These eggs have a protective, hardened coat; they hatch when conditions improve.

Daphnia are very sensitive to changes in their environment. In water with low oxygen concentration, an individual increases its hemoglobin production, causing its body to turn red. In the presence of predators, it can develop a large head and tail spine.

Daphnia are filter feeders, eating algae, protists, and bacteria. They are prey of water mites, tadpoles, aquatic insects, and small fish.

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© Photographs and text by Susan Leach Snyder (Conservancy of Southwest Florida Volunteer), unless otherwise credited above.

 

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