Branchiopoda
Guides
Branchinecta
fairy shrimp
Branchinecta is a genus of fairy shrimp (Anostraca) comprising approximately 50 species distributed across all continents except Australia. The genus includes the largest anostracan, Branchinecta gigas, reaching up to 10 cm in length, and the highest-altitude crustacean, B. brushi, recorded at 5,930 m elevation. Species occupy diverse temporary freshwater habitats from Arctic and Antarctic regions to high-elevation Andean pools. Two species, B. gaini and B. granulosa, have been synonymized based on molecular evidence showing insufficient genetic differentiation.
Cladocera
water fleas
Cladocera is a suborder of small crustaceans commonly known as water fleas, ranging from 0.2–6 mm in size. They are found in freshwater environments worldwide, including rivers, lakes, swamps, and temporary pools, with some species inhabiting brackish water, groundwater, and even leaf axils or caves. These organisms play a central role in freshwater food webs as filter-feeders that consume phytoplankton, bacteria, and organic particles, while serving as essential prey for fish fry and predatory insect larvae. Their sensitivity to environmental changes makes them valuable bioindicators for water quality assessment.
Dendrocephalus
fairy shrimp
Dendrocephalus is a genus of fairy shrimp (Anostraca) in the family Thamnocephalidae, distributed across South and North America. The genus is characterized by a distinctive antenna-like frontal appendage arising between the second antennae and the eyestalks. It comprises approximately 17 species arranged in two subgenera: Dendrocephalus (South American species) and Dendrocephalinus (North American species). Several species have been described recently, with ongoing taxonomic work revealing intra-populational polymorphism in frontal appendage morphology.
Diplostraca
water fleas, clam shrimps
Diplostraca is a superorder of small branchiopod crustaceans encompassing over 1,000 described species, commonly known as water fleas and clam shrimps. Members range from 0.2 to 6.0 mm in length (with Leptodora reaching 18 mm), and are characterized by a folded bivalved carapace covering an unsegmented-appearing body. The group exhibits cyclical parthenogenesis, alternating between asexual and sexual reproduction to produce dormant eggs. While predominantly freshwater, eight species have colonized marine environments—the only branchiopods to do so.
Eurycercus longirostris
Eurycercus longirostris is a Holarctic cladoceran crustacean first described by Hann in 1982. A 2011 taxonomic revision synonymized E. vernalis with E. longirostris due to lack of morphological and genetic justification for their separation. The species has a broader distributional range than previously recognized and belongs to the subgenus Eurycercus (Eurycercus). As a member of the Eurycercidae family, it shares characteristics with other chydorid-like cladocerans including a rounded carapace and specialized feeding appendages.
Lepidurus
tadpole shrimp
Lepidurus is one of two extant genera of tadpole shrimp (order Notostraca), distinguished from Triops by morphological and ecological traits. Species inhabit temporary freshwater pools, vernal pools, and permanent lakes across diverse climates from Arctic tundra to desert regions. The genus exhibits notable life history flexibility, with resting eggs capable of surviving desiccation and freezing for decades. Some species are of conservation concern due to habitat specificity, while others serve as agricultural pests or bioindicators of environmental change.
Macrothricidae
Macrothricidae is a family of small freshwater crustaceans in the order Diplostraca (formerly Anomopoda), commonly known as water fleas. The family comprises approximately 17 genera and at least 80 described species. Macrothricids exhibit diverse ecological specializations and feeding mechanisms, with many species inhabiting littoral zones of lakes and ponds. The family remains among the least studied groups of Cladocera, with ongoing taxonomic revisions revealing previously unrecognized species diversity and biogeographic patterns.
Penilia avirostris
Penilia avirostris is a marine cladoceran crustacean in the family Sididae, distributed across temperate and tropical coastal waters worldwide. It is a holoplanktonic species that exhibits cyclical parthenogenesis, with populations shifting between asexual and sexual reproduction in response to environmental cues. The species has been observed to undergo diel vertical migration and shows strong sensitivity to temperature, with optimal growth around 18°C but tolerance ranging from 12°C to 30°C. Population dynamics are closely tied to seasonal temperature fluctuations, with dramatic increases reported in warming waters.
Podon leuckartii
Podon leuckartii is a small predatory crustacean in the family Podonidae, order Onychopoda. It belongs to the branchiopod group characterized by paired swimming appendages and a bivalved carapace. The species was originally described under the genus Pleopis. Like other onychopods, it is a holoplanktonic predator in freshwater and brackish aquatic systems.
Triops
tadpole shrimp, shield shrimp
Triops is a genus of small branchiopod crustaceans in the order Notostraca, commonly known as tadpole shrimp or shield shrimp. The genus is distinguished by having only a pair of long, thin caudal extensions on the telson, unlike the related genus Lepidurus which bears an additional central platelike process. Some species are frequently sold as aquarium pets in dried egg kits, hatching upon contact with fresh water. In agricultural settings, particularly California rice cultivation, certain species function as early-season pests that damage germinating seedlings.