Half-male, half-female blue crab found in Maryland Bay is ‘true cellular abnormality’

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An unusual crustacean is the new star attraction at a Maryland science museum: a Chesapeake blue crab that’s half male, half female.

This crab, which has an extremely rare condition known as bilateral gynandromorphism, is about 4 and a half inches long and estimated to be in its third year, has both blue and red tipped claws and an apron that is split all the way down the middle.

A gynandromorphic crab has not been reported on the east coast for at least 15 years.

Typical male blue crabs have blue claw tips and a T-shaped apron, or underbelly, while females have red claw tips and a broad apron.

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A blue crab with bilateral gynandromorphism, or both male and female features, was recently discovered in Maryland

A blue crab with bilateral gynandromorphism, or both male and female features, was recently discovered in Maryland

Aquarius Jerry Smith caught the latest, Chesapeake Bay Magazine reported.

Instead of throwing it into his catch, Smith, a scraper for more than four decades, donated it to the… Delmarva Discovery Museum, where it can now laze around in its own 70-gallon tank.

In a male blue crab, or “Jimmy,” the apron is pointed “like the Washington Monument,” according to the Virginia Institute of Marine Science (VIMS), while the claws are a deep blue.

On a woman, or “sook,” the pincers are pink and the apron is rounded, “like the dome of the Capitol.”

The unnamed crab, which is in its third year, now has its own tank at the Delmarva Discovery Museum in Pocomoke City, Maryland

The unnamed crab, which is in its third year, now has its own tank at the Delmarva Discovery Museum in Pocomoke City, Maryland

“The male claw is much bluer and the female claw is less blue and tipped with red,” September Meagher, a livestock expert at the Delmarva Discovery Museum, told DailyMail.com. “Our crab’s claws don’t show this as clearly, but we notice it more and more every day as it settles in its new habitat and is fed nutrient-rich meals.”

Bilateral gynandromorphism, when the distribution of features is split in the middle, usually arises very early in an organism’s development, when it has between 8 and 64 cells.

“This condition is a cellular abnormality that is believed to occur when the crab is still in egg form,” Meagher said.

Waterman Jerry Smith (pictured) caught the crab and donated it to the Delmarva Discovery Museum

Waterman Jerry Smith (pictured) caught the crab and donated it to the Delmarva Discovery Museum

The crab's apron is split in the middle, between the male 'T' shape and the female 'U' shape

The crab’s apron is split in the middle, between the male ‘T’ shape and the female ‘U’ shape

At some point, a cell doesn’t split its sex chromosomes in the typical way, leading to a non-uniform distribution of sex characteristics, from color to reproductive organs.

It is different from ‘hermaphroditism’, when only the genitals are affected.

Bilateral gynandromorphism does not occur in mammals but has been observed in lobsters, crabs, snakes, butterflies, bees, chickens and other birds. It can potentially be affected by the water temperature or hormone levels in the mother’s uterus.

According to Meagher, VIMS marine biologists are investigating the rare genetic disorder to better understand breeding and sexual development in blue crabs.

The crabs were once a major economic engine in the region, but their numbers have declined due to overfishing and pollution.

The male blue crab is distinguished by its blue claw points and T-shaped apron

The female blue crab is distinguishable by her red tipped claws and the unique inverted U or V shape on the lower abdomen as seen in this image

A female blue crab (right) can be distinguished by her red-tipped claws and the unique inverted U or V shape on her apron or underbelly. The male blue crab has blue claw tips and a T-shaped apron

“It is believed that they cannot reproduce with themselves, as a hermaphrodite sometimes can, but that they can be a viable partner for another crab,” she said.

The museum has not yet named the crab, but Meagher said, “We have a suggestion box and encourage the public to come meet the crab in person and submit their suggestion.”

VIMS reported the discovery of a bilateral gynandromorph crab pulled from the bay in 2005 by Aquarians David Johnson and Robert Watson.

Neither sailor had reported ever seen one before in their 25 years on the water.

That crab, on display in an aquarium in the VIMS visitor center, had a red and a blue claw.

Before that, Smith caught another gynandromorph blue crab in 1979.

In 2020, conservationists at Powdermill Nature Reserve described finding a rose-breasted grosbeak with bilateral gynandromorphism, such as 'seeing a unicorn'

In 2020, conservationists at Powdermill Nature Reserve described finding a rose-breasted grosbeak with bilateral gynandromorphism, such as ‘seeing a unicorn’

In October 2020, researchers at the Powdermill Nature Reserve outside of Pittsburgh reported finding a rose-breasted grosbeak exhibiting bilateral gynandromorphism.

One side of the bird’s chest showed the red wing pits that indicate male beaks, while the other half was yellow, like that of a female.

WHAT IS A GYNANDROMORPH?

Gynandromorphs are rare in the wild, although the coloring or markings of some species make the results more striking than others.

A gynandromorph lobster with yellow (male) color on one side and brown (female) on the other

A gynandromorph lobster with yellow (male) color on one side and brown (female) on the other

A gynandromorph is an organism that has both male and female features – or a male-female chimera.

It is commonly seen in insects, although gynandromorphic birds, snakes, lobsters and other animals have also been observed.

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