Creature Feature: Tadpole Shrimp

Andrew Hosie's blog | Created 9 years ago

Just add water: Tadpole shrimp Triops australiensis (Spencer & Hall, 1895)

Lying in wait in the sun-baked sediments of outback Australia are the tiny eggs of the tadpole shrimp. Once the rainy season starts and they are inundated with water, the developing embryo quickly hatches and then the race is on to grow and reproduce before the pool dries out. Normally the eggs of aquatic animals will quickly die if they become desiccated, but the tadpole shrimp’s eggs enter a state of dormancy known as diapause. This allows them to wait for many years for rain to fill their dried up pool. In fact, the eggs won’t hatch unless they do dry out. The tiny larval stage ends within two days of hatching and within two weeks the tadpole shrimp are mature and begin mating. The females will then release the fertilised eggs on the bottom of the muddy pool. Adults can grow to up to 9 cm long.

The tight timeframe has turned these animals into opportunistic feeders. They feed on almost anything organic in their temporary world, including plants, insects and each other. Included on the menu are mosquito larvae, so there is the potential that tadpole shrimp could be employed as a biological control agent to reduce mosquito numbers and assist in reducing mosquito-borne disease. Since the eggs can be dried out and stored they can be easily delivered to areas where they are required. This ease of storage has also led to them becoming popular in the aquarium trade, marketed as Billabong Bugs or Jurassic Shrimp.

Reaching lengths of 9 cm the tadpole shrimp is a bizarre-looking crustacean, with their large shield-shaped carapace and long abdomen. They even have three eyes, which is how they got their name (tri = three, ops = eye). They belong to an ancient lineage of crustaceans dating back to the Carboniferous period (360–300 million years ago) – predating the dinosaurs.

Three Tadpole Shrimps of different sizes facing one another
Tadpole Shrimp - Triops australiensis
Photo by Andrew Hosie
Image copyright of WA Museum