Round 2 - Arthropoda - Branchiopoda
Branchiopoda is a class of small, mainly freshwater crustaceans that feed on plankton and detritus. They are comprised of 9 orders: Anostraca (“Fairy Shrimp”), Anomopoda (“Water Fleas”), Ctenopoda (also “Water Fleas”), Cyclestherida (“Clam Shrimp”), Laevicaudata (also “Clam Shrimp”), Spinicaudata (also “Clam Shrimp”), Haplopoda (“Predatory Water Fleas”), Onychopoda (“Water Fleas” again), and Notostraca (“Tadpole/Shield Shrimp”).
Branchiopods are found mainly in freshwater, including temporary pools and hypersaline lakes, and some in brackish water. Those that live in temporary pools are known for having eggs that can dry out for long periods of time and hatch once they are submerged in water, as an adaptation to drought. Only two families, one in Onychopoda and one in Ctenopoda, contain marine species. Most eat detritus or plankton, catching them in the setae on their appendages. Notostracans are opportunistic omnivores that will feed on algae, bacteria, other branchiopods like Anostracans, and even small fish.
Branchiopods are characterized by the presence of gills on many of the animals’ appendages, including the mouthparts. Most have compound eyes and a carapace. In the Clam Shrimp, the carapace prevents the use of the legs for swimming, so the antennae are used for locomotion instead, as they are in nauplius larvae.
The oldest known branchiopod was Rehbachiella kinnekullensis of the Upper Cambrian. Notostracans in particular have a good fossil record, with the oldest known species being Strudops goldenbergi from the Late Devonian. Notostracans are often described as “Living Fossils” due to their lack of major morphological change over 250 million years.
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