Rare intersex spider among new species discovered in Thailand

A new species of spider was recently discovered near a forested area in Nong Rong, Phanom Thuan, Kanchanaburi, western Thailand. The spiders were presented to researchers at the Chulalongkorn University Museum of Natural History, where they were studied further.

After analyzing the samples under a stereomicroscope and comparing them to similar species, the group determined that the spiders were most likely part of the genus Damarchus — a group of mygalomorph, or “Wishbone,” spiders found in South and Southeast Asia. This group of spiders is known for the triangle-shaped burrows they make in the ground, where they wait for prey. Although the characteristics of the new species fit better within the genus Damarchus, molecular data have not yet confirmed this.

The group describes the new species in their paper published in the journal Zootaxa. One of the most striking aspects of the newly discovered species is the striking differences between the male and female spiders.

The male of the species measures only 0.6 inches in length, while the female is usually about an inch in length. Males appear gray in color and are covered with a white substance that remains to be identified. When the male is preserved in alcohol, it appears as a reddish brown color. Females, on the other hand, are a brighter orange color and lack the white coating of unknown substance.

An even more striking discovery was the gynandromorph specimen found throughout. Gynandromorphs are rare organisms that are half male and half female, where each side of the body presents differently, split down the middle. Gynandromorphs are distinct from hermaphrodites in that hermaphroditic organisms still have bilateral symmetry and naturally have both sexual organs. Hermaphroditism is common in some organisms, while gynandromorphism is much rarer.

The gynandromorph specimen shows a distinct division between male and female species characteristics. This gave the species its name.

“The species is named after Inazuma, a character from the Japanese manga ‘One Piece’, known for the ability to change sex between male and female. The inazuma style is characterized by bilateral asymmetry, exhibiting distinct coloration with orange on the left side and white on the right side. This color arrangement closely reflects the sexual dimorphism seen in this species with males exhibiting white colorings and women.

This is the first ever report of a gynandromorph in the family Bemmeridae, to which Damarchus belongs. Only two previous cases of gynandromorphism have been reported in mygalomorph spiders, both in the family Theraphosidae.

“Based on the reported cases, it can be inferred that our gynandromorph specimen corresponds similarly to the first described case, characterized by bilateral asymmetry and the manifestation of both sexes on opposite sides. However, the definitive cause of this gynandic disorder) in the female zygote, potentially induced by various natural factors, including nematode infection,” say the authors.

These new discoveries of not only a new species, but also a gynandromorph in their midst, represent a rare and exciting biological discovery.

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