The branchiopods: arthropods, that is, invertebrates with exoskeletons, whose abdominal legs serve as gills, and are mostly restricted to continental aquatic environments. Likewise, they make up the most primitive class of the large group of crustaceans, who  are especially diverse and abundant in the sea while insects are so on the continents.

“Surprising” is possibly the best word to define the branchiopods, an animal group whose natural history is often an exception and “breaks the rules”. Of course, they attract the attention because of their scarcity, but also for the curiosity of species which seem to survive against common sense.

The group is divided into four orders. A few macroscopic species are much rare but easy to notice in the field and informally coined as the Large Branchiopods. They include the tadpole shrimps, or notostaceans (literally “shell-swimmer”), represented by the genus Triops of really primitive aspect, the clam shrimps, or concostraceans (“crustaceans-clam”) with protective bivalve shell, and the most diverse and defenseless fairy shrimps, or anostaceans (“without-shell”). To complete this picture, add the broader order of water fleas, or cladocerans (“spiny branch”), which are microscopic and highly modified planktonic organisms within the class, are also bivalves and provided with a terminal spine.

Along with amphibians and various atypical ferns (Marsilea, Isoetes), the Large Branchiopods are the true specialists of temporary Mediterranean ponds and lagoons. This habitat, more abundant in arid regions, is highly threatened by changes in land use and currently considered a priority for conservation.

With 15 detected species, Andalusia represents a diversity hotspot for the group in Europe. The Andalusian Fairy Schrimp (Linderiella baetica) is the rarest and most threatened species by far, known from a single peri-urban locality and developing under specific hydrological conditions of low mineralization. Other notable species are the Iberian Clam shrimp (Cyzicus grubei), the Moorish Clam shrimp (Maghrebestheria maroccana), the aggregate of Mediterranean Triops species (Triops mauritanicus aggr.) and the Iberian Fairy Shrimp (Branchippus cortesi). We must also mention the Brine shrimps (Artemia spp) well known to the public and restricted to salt flats and salty lagoons.