Rare split-sex condition: Researchers find half-male, half-female spider in Thai forest

New Spider Found With Rare Split Sex Traits (Image: Department of Biology, Faculty of Science, Chulalongkorn University's Post)

In a quiet Thai forest, nature offered a fresh surprise to science. A tiny spider sat in its burrow, glowing in two colours. The little creature looked calm but carried an incredible secret. It showed a perfect divide that no one expected.

What makes this spider so unusual?
Researchers found the spider in western Thailand. The team searched for small ambush predators under soft soil. They discovered a new species with two different sides. One side showed orange colours linked with female traits. The other side held grey shades linked with male traits. The researchers saw the split across the whole body structure. They also confirmed that the internal organs matched this clear divide.

How did scientists confirm its split identity?
The spider belonged to the new species Damarchus inazuma. The discovery came from a survey led by Chawakorn Kunsete. He worked with Sarunphat Amuntailkul, Patiphan Chamnanpa and Surin Limrudee. Their report appeared in the journal Zootaxa. The team confirmed bilateral gynandromorphism in this small spider. This meant one side held female organs and the other side did not. The researchers said this condition was extremely rare in spiders. They noted that such cases appear in about one in seventeen thousand spiders. They believed the chance was even lower in burrowing species.

Why does this condition occur in some animals?
Scientists think the condition begins during early growth. They believe errors affect the sex chromosomes during the first cell stages. They say stress, illness or parasites may play a part. Gynandromorphs differ from hermaphrodites across many species. Hermaphrodites naturally use both reproductive systems for normal life cycles. Gynandromorphs do not follow this pattern and stay very rare.

What else do we know about Damarchus inazuma?
This spider belonged to the family Bemmeridae. It was the first known gynandromorph in this family. The name inazuma came from a One Piece character. That figure could shift between two gender forms in the story. The spider lived in a silk burrow shaped like a wishbone. It hunted passing insects with great speed and power. Females grew larger with bright orange legs and dark abdomens. Males stayed smaller with pale grey bodies and white coatings.

How do these spiders behave in the wild?
The survey team saw strong reactions when touching the burrows. The spiders raised their fangs and sometimes released small droplets. Kunsete believed the spiders held venom for stopping tiny prey. He stated the venom likely posed no risk to humans.

Why does this rare spider matter for science?
The researchers said the spider could guide future studies. They hoped it would explain how sex develops in different spiders. They also noted that these processes remain poorly understood today. They believed this one specimen could help uncover hidden biological steps.