Where do Supershrimp come from?

 

 Supershrimp, or Opae ula, as they are called in their native Hawaii, are endemic (= they occur nowhere else) to certain Hawaiian islands, specifically Oahu, Hawaii, Maui, Molokai, and Kahoolawe. They live in so called "anchialine pools", which are basically naturally occuring brackish water pools close to the ocean. Although these pools are usually not directly connected to the ocean, they have indirect connections through the porous lava or limestone rock. In a similar manner, the pools are also connected to groundwater. The mixture of groundwater and ocean water creates the brackish water prevelant in the anchialine pools.

Although other specialized animals live in these pools, the Supershrimp are usually the most abundant creature. Their food consists of algal and bacterial biofilm that grows on the pools’ rocky bottom and side walls. There is no discernable water movement in these pools, which means that the deeper parts are oxygen poor to almost devoid of oxygen. The Supershrimp are, often, the only animal that can live under such extreme conditions. In fact, in pools where predators, usually introduced, are present, the Supershrimp flee to the oxygen poor deeper waters, where their predators cannot follow them.

Anchialine pools are not only connected to the ocean through porous rock, but also to each other. Hence, animals can migrate underground to different nearby pools, so some genetic exchange always happens. The fact that the Hawaiian islands are made up of such porous lava or limestone rock also means that the anchialine pools are only the visible, above ground part of this shrimp’s habitat. The pools provide ample food, and these shrimp like to ascend to these pools due to the ample availability of resources, but a large portion of the Supershrimp population appears to live underground in the dark. Especially ovigerous (egg-carrying or "berried") females appear to prefer staying in the underground parts of their habitats, as such females have never been observed in anchialine pools in the wild. If the anchialine pools provide the only source of food for these shrimp, or if there is some other underground source of food is largely unknown.

Unfortunately, over 90% of anchialine pools on Hawaii have already vanished due to coastal development, and many of the rest have introduced fish and predatory invertebrates (such as Macrobrachium lar) which threaten the survival of this remarkable species. The few natural pools remaining are regularly visited by poachers that collect these shrimp and sell them either as "seahorse food" to pet stores on Hawaii, or to unscrupulous companies that market these wild shrimp in tiny habitats to unassuming customers.