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Tadpole Shrimp cont. they produce. When the vernal pool eventually dries down, these cysts remain dormant and viable for up to ten years while waiting for the next rains to initiate their hatching. These cysts also can withstand the often extremely high temperatures of California summers while embedded in the top layers of the vernal pool soil sediments. A female vernal pool tadpole shrimp may produce thousands of cysts during her lifespan. Some of these cysts hatch out during the same wet season. However, for reasons that still remain unclear, a large portion of these cysts produced in any given wet season will only hatch after the pool dries down and subsequently refills, possibly several years later. The vernal pool tadpole shrimp is different from almost all California fairy shrimp since it is able to produce more than one generation in a single wet season. Another strategy for adapting to the vernal pool environment is reaching sexual maturity rapidly (in as little as three weeks). Rapid sexual maturity allows the vernal pool tadpole shrimp to hatch, mature, and produce numerous drought-resistant cysts quickly after the pools refill, thereby effectively using such a short-lived environment. This temporal isolation (separated by time) allows the vernal pool tadpole shrimp to occupy a harsh environment to which few predator species have adapted. Vernal pool tadpole shrimp differ from the related fairy shrimp by the way they move; vernal pool tadpole shrimp swim or scoot along typically muddy or rocky bottom sediments "right side up," whereas fairy shrimp swim higher up in the water "upside down." Adult vernal pool tadpole shrimp are much larger in body mass than adult fairy shrimp and may reach an inch and a half in length, whereas fairy shrimp are often less than half an inch in length. Fairy shrimp can be whitish or have some orange body parts, but they are almost translucent in comparison to vernal pool tadpole shrimp, which are typically olive or grey colored. This olive or grey coloration is sometimes mottled, and helps provide good camouflage for the vernal pool tadpole shrimp to blend in with aquatic plants or when they burrow horizontally in muddy bottom sediments. Vernal pool tadpole shrimp are often quite hard to spot in the water unless they are seen in motion. |
Last updated:
May 27, 2008
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