Tadpole shrimp

Description:

The Tadpole Shrimp (Triops cancriformis) is native, and the only species of Tadpole Shrimp found in the UK. It is actually the oldest known animal species in the world and is at least 220 million years old! This means it was swimming around in pools when the dinosaurs were roaming our planet.

The Tadpole Shrimp is currently found in only two locations, one is in the New Forest (Hampshire) and the other is in Scotland near the Solway Firth.  The only other record this century is from the Kirkcudbrightshire coast, however it is believed to have been lost in the 1960s as a result of coastal erosion.

Our native species of Tadpole Shrimp is also found across the globe including in countries such as Europe, Russia and the Middle East. However, the Tadpole Shrimp taxonomy needs updating, and it is possible that the British population may be found to be of international significance.

These animals are prehistoric and look it, with a shield shaped carapace; they look like a cross between a Horseshoe Crab and an extinct trilobite.  Lacking modern gills, they breathe with primitive leaf-like extensions on their legs.  In the wild our native Tadpole Shrimp can grow up to 11cm (4.5″) in length (not including the tail). Tadpole shrimps are omnivorous feeders – they will eat small aquatic invertebrates, aquatic plants and sediment.  They are also furious eaters, this is necessary to sustain their fast development; daily they have to eat about 40% of their body mass to sustain their rapid growth rate.

Tadpoles Shrimps live in seasonal brackish (slightly salty) or freshwater pools, which dry out in the summer. When the pools dry out all predators and competitors are killed off however the Tadpole Shrimps have adapted to survive.  Their pools may only last a few weeks before drying out, and then it may be years or even decades before the water returns.  As a result of their short lived habitats Tadpole Shrimps have a very rapid development, maturing from an egg to adulthood in just two to three weeks. Utilising such an inhospitable and difficult habitat is believed to be one of the reasons why this group of animals has been able to survive for so many millions of years.

Tadpole Shrimps are able to survive in temporary pools due to the unique properties of their eggs.  When they are laid a proportion of the eggs hatch, and the rest go into ‘diapause’ – this means the eggs dry out and their development is stopped.  In diapause Tadpole Shrimp eggs are very durable and can survive up to an amazing 27 years. The eggs can also endure extreme temperatures, as well as transportation by winds, and can be eaten and excreted by an animal without harm!  Once these eggs are rehydrated and the environmental conditions are right the diapause will end and the eggs will hatch forming a new generation of Tadpole shrimps.

With a limited distribution there are a number of issues are threatening the existence of our small native population.  These include the introduction of predators, pollution and invasive aquatic plants.  Tadpole Shrimps are especially vulnerable when they are young as they lack mobility, size, as well defence against predators. Consequently if a predator is introduced to habitat containing young Tadpole Shrimps they can easily wipe out a whole generation.  Due to their rarity in the UK our native species (Triops cancriformis) is classified as Endangered and is protected under Schedule 5 of the Wildlife and Countryside Act 1981.

• Size: Up to 11cm in length (not including the tail)
• Life span:  Approximately 90 days as an adult, but eggs in diapause can survive up to 27 years!
• Diet:  Tadpole shrimps are omnivorous feeders – they will eat small aquatic invertebrates, aquatic plants and sediment.
• Reproduction:  Tadpole Shrimps lay eggs. When they are laid a proportion of the eggs hatch, and the rest go into ‘diapause’ – this means the eggs dry out and their development is stopped.  In diapause Tadpole Shrimp eggs are very durable and can survive up to an amazing 27 years. The eggs can also endure extreme temperatures, as well as transportation by winds, and can be eaten and excreted by an animal without harm!  Once these eggs are rehydrated and the environmental conditions are right the diapause will end and the eggs will hatch forming a new generation of Tadpole shrimps.
• When to see:  Adults can be found in seasonal brackish (slightly salty) or freshwater pools; these dry out in the summer months.
• Population Trend:  Unknown – the Tadpole Shrimp is classed as Endangered within the UK and protected under Schedule 5 of the Wildlife and Countryside Act 1981
• Threats:  Loss of habitat through loss of grazing on its ponds, which is essential to maintain the right habitat, and climate change which could make the handful of remaining ponds unsuitable for the tadpole shrimp’s survival. Threat of introduction of non-native predator species.
• Fun Fact:  The Tadpole Shrimp is the oldest known animal species in the world and is at least 220 million years old! This means it was swimming around in pools when the dinosaurs were roaming our planet.
• Additional Fun Fact: One of the UK’s most endangered animals, this species is so rare, and its populations so isolated from each other, that there is a very high risk it will become extinct without our help. They are a protected species and require a licence from Natural England in order to net them, handle them or remove them or their eggs from their natural home.

How you can help: 

Buglife is working to increase awareness of invertebrates and the Tadpole Shrimp through specific projects, such as Species on the Edge, and campaigns, but we need your help!

Do remember that we rely on donations to continue our work.  If you have searched, found and learnt about our incredible invertebrates on our website, please do consider Making a Donation, Becoming a Member or maybe even making a purchase in our shop.  For more ideas on how to support our work find out how to Get Involved.  Thank you 🕷

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