Both yours and ours. The most unique tarantula on Earth was born in Uruguay, leaving scientists astonished.

A team from the University of the Republic in Uruguay observed a group of orange baboon tarantulas (Pterinochilus murinus) that had just undergone molting into adult specimens, when they noticed a very special individual, as reported by IFLScience.

The researchers found that one of the tarantulas was quite unusual and had an interesting appearance after shedding its old exoskeleton: its right side was hairier and had thicker limbs, while the left side was more bare and slender. The team studied the individual more closely and discovered that the right side was actually female, while the left side was male.

In nature, this anomaly is known as gynandromorphism — a genetic condition where an organism is born with both male and female characteristics. It is worth noting that this anomaly has been previously documented in many different animal species, from stick insects to bees and various birds; however, scientists believed it to be extremely rare among tarantulas.

Essentially, this genetic condition is not typical for tarantulas, making the individual discovered in 2014 the first documented case observed in a Mygalomorphae tarantula. Initially, it seemed that the genetic condition did not affect the health and life of the tarantula, but later findings suggested otherwise.

According to the study's author and entomologist Fernando Pérez-Miles, the gynandromorphic tarantula walked and fed normally; at least, the scientists did not notice any deviations. However, as the tarantula aged, researchers began to observe some issues.

It is known that male tarantulas do not continue to molt after reaching sexual maturity when their sexual organs — palpal bulbs — develop. Scientists note that this is due to morphological constriction, as the shape of the palpal bulbs makes molting of these organs difficult. In contrast, female tarantulas do not stop molting even after reaching maturity.

Unfortunately, researchers observed that the gynandromorphic tarantula did molt after reaching maturity, resulting in a deformation of its sexual organ. The researchers also noted that the unique individual was more prone to aggression from its peers.

During several experiments, scientists introduced the individual to females; unfortunately, in none of the four cases did the tarantula engage in courtship, and the females showed no sexual activity. Moreover, in one experiment, a female attacked the gynandromorph and injured one of its legs.

Despite all these challenges, the unique individual managed to survive and reach a relatively normal age. It is still unclear what causes gynandromorphism in any species, although it is known to arise from abnormal cell division and segregation of sex chromosomes at an early developmental stage.

Spiders have significantly more complex systems of sex chromosomes with varying compositions among different species. Therefore, scientists previously thought such anomalies to be extremely rare among tarantulas; however, that turned out to be not entirely accurate.