Half male, half female: a unique spider found in Thailand

The unusual specimens were transferred to the Natural History Museum of Chulalongkorn University, where they were carefully studied under a stereomicroscope.

After comparing morphological features with other representatives, the researchers concluded that the found spiders probably belong to the genus Damarchus - a group of migalomorphic spiders known for digging Y-shaped burrows (or "forks") in the ground and waiting in them for prey. Despite morphological similarities, definitive confirmation of genus membership requires molecular data.

The scientists published their work in the scientific journal Zootaxa. One of the most surprising findings was the presence of gynandromorph, a rare form in which the organism consists of halves belonging to different sexes.

In the new species, males and females are very different: the male only reaches a length of about 1.5 cm, while the female grows up to 2.5 cm. Males are covered with a white substance of an unidentified nature and are grey in colour. Females, on the other hand, are bright orange in colour and are devoid of this white coating.

The intersexual specimen found among the specimens is divided symmetrically: one half of the body corresponds to the male (with white colouration) and the other to the female (with orange). This type of gynandromorphism is called bilateral. Unlike hermaphrodites, gynandromorphs have clearly expressed features of both sexes on the sides of the body.

In honour of this unique property, the species was named Damarchus inazuma - after the character Inazume from the manga "One Piece", who can change sex. The scientists noted a visual similarity: in the manga, the left side of the character is coloured orange and the right side is white, which matches the spider's sex characteristics.

This is the first reported case of gynandromorphism in the family Bemmeridae and only the third among mygalomorph spiders. Previously, such features were seen only in the family Theraphosidae (tarantulas).

The reasons for the appearance of gynandromorphs have not been fully elucidated. According to one hypothesis, it may be due to the loss of one or more X chromosomes in the zygote at an early stage of development. Parasitic infections, among others, have been identified as possible factors causing this disorder.