|Image by Aviva Rossi|
Distantly related to triops and sea monkeys (actually brine shrimp), which you can buy at any decent science shop, the tadpole shrimp share their ability to breathe through their 35 or so phyllopoda (leaf-feet) which also act as paddles. They grow up to a whopping 2 inches in length, eat organic matter smaller than them, and get eaten by everything that normally eats benthic macroinvertebrates: other invertebrates, amphibians, fish, and some birds.
The vernal pool tadpole shrimp hangs its small, strangely shaped hat in ephemeral pools in the San Fransisco bay area that dry out every summer. It survives these dry spells by laying drought-resistant eggs, which will hatch once the pools fill up again.
There are no big surprises with why these are endangered. Habitat destruction is always a problem when your habitat is a big wet spot, and someone says, "Hey, this looks like the perfect place for a shopping mall." Suddenly, your big wet spot is under a ton and a half of concrete. Agricultural and urban runoff, overgrazing, and invasive plants are also having an effect on the tadpole shrimp. Hope exists for them in the form of programs to save wetlands, which are being put into effect all over the United States.