New trapdoor spider found living where the sea floods its home in Mauritius
Scientists have formally named a new species of trapdoor spider that lives in a place where no trapdoor spider was expected to survive: coastal rock in Mauritius that is covered by the sea at high tide.
The spider is called the Mauritian tidal trapdoor spider, or Idioctis marevallum. It was formally described in the journal Arachnology by a team led by arachnologist Danniella Sherwood, and announced by the Durrell Wildlife Conservation Trust on 27 October 2026. It lives in the intertidal zone on Ilot Vacoas, a one-hectare island off the south-east coast of Mauritius, where its home is submerged at high tide or battered by waves. It has since also been found on Ile aux Fouquets, another small island nearby.
Instead of digging in soil, it lives in narrow tubes in coralline bedrock, thought to have been made by molluscs and worms thousands of years ago, and seals the entrance with a trapdoor of silk, sand and algae. Its name comes from the Latin for “sea wall”.
The spider was first spotted in 2023, during conservation work on Ilot Vacoas. Entomologist Max Tercel was searching coastal rock by headtorch after dark when he saw a spider’s legs sticking out of a burrow — a sight he had only ever seen before in forests and grassland. He called colleague Nik Cole over. At first the team wondered if they had found Tigidia mauriciana, a trapdoor spider described in 1892 and recorded only once. It proved new to science.
Why it matters
Most trapdoor spiders live on dry land, so one that spends part of every day underwater is remarkable. It is a mygalomorph, the same broad group as tarantulas, yet it survives regular flooding in a tiny patch of coastal rock. The wider study also raised Mauritius’s known spider diversity by more than 25 per cent.
What happens next
Researchers will keep surveying the small islands off south-east Mauritius to learn how far the spider spreads and how it copes with salt water. Conservationists say the find shows even small, overlooked habitats can still hold species new to science.
This article is for general information and education only. It is not legal or financial advice.
Sources
- https://www.durrell.org/news/new-species-of-trapdoor-spider-identified-in-mauritius/ (Durrell Wildlife Conservation Trust, 27 October 2026)
- https://www.discoverwildlife.com/animal-facts/insects-invertebrates/mauritian-tidal-trapdoor-spider (BBC Wildlife / Discover Wildlife, 28 October 2026)
- https://britbrief.co.uk/environment/wildlife/new-spider-species-found-on-tiny-mauritian-island.html (Brit Brief, 29 October 2026)
