For the first time, scientists have found a gynandromorph sweat bee, one of a bilateral type. Gynandromorphs are organisms that display male and female phenotypes. Gynandromorphs have already been found in some bees of Megalopta genalis. However, this newly found Megalopta amoena bees is the second one in the family, showing mixed-sex.
This bee species is surprising the scientific world by showing masculine character on its left side and feminine character on its right side. It is entirely different from the sexually diphormic animals that look different either in shape, color, size, etc. according to its gene and hormones. The research team has also analyzed the circadian rhythm(the sleep-wake cycle) of the bees using a Locomotor Activity Monitor (LAM).
Gynandromorphs are organisms that display male and female phenotypes.
Three types of gynandromorphs, based on the position of the sex tissue, are:
- Bilateral Gynanders – It is the distribution of female and male tissues in a single organism with one side male and one side female.
- Anterior-Posterior Gynanders – It is the condition in which the anterior part of the organism’s body displays one sex and the posterior section other sex.
- Sex Piebalds – In sex piebalds, the body of the organism will consist of female tissues with spots of male tissues as irregular scattering.
The phenomenon gynandromorphism was found earlier in some organisms like the half-female leopard lacewing butterfly and gynandromorph tiger swallowtail. The study of a gynandromorph hen helped the researchers understand that each cell in birds has a significant role in determining sex differences. Gynandromorphs was found in 140 species of bees, making only 0.7 percent of its species.
Anatomy of Megalopta Amoena
The gynandromorph bees were usually noticed long after their death. Hence, further study of their physiology and behavior was a puzzling task. Here, this ‘sweat bee’ represents the second gynandromorph in the entire genus of Megalopta. This one was found alive as a larva enclosed in a brood cell. The researchers recognized it as a gynandromorph when it turned an adult.
The sweat bee, which is native to Central and South America, was found in Barro Colorado Island in Panama. The bee’s anatomy attracted the research assistant Erin Krichilsky of the Smithsonian Tropical Research Institute (STRI). Its two halves lengthwise showed two different genders.
Anatomical differences between the halves of Megalopta amoena’s body are astonishing.
|Body Part||Male Side of Body (Left)||Female Side of Body (Right)|
|Flagellomeres in Antenna||*11 flagellomeres|
*0.34 mm length
*0.71 mm scape length
*0.23 mm length
*1.33 mm scape length
*Bidentate with supplementary teeth
|Gena||*Not enlarged||*Enlarged in order to accommodate the larger mandibular musculature characteristic of females|
|Clypeal Punctures||*Continuous, moderately dense, and separated by approximately one puncture width||*Continuous, moderately dense, and separated by approximately one puncture width|
|Posterior Upper Margin of the Metepisternum||*Conspicuously large process covered with Velvety Pilosity||*Conspicuously large process covered with Velvety Pilosity|
*Slender Femur and Tibia
*Straight Apical Spines on the Femur
*Robust Femur and Tibia
*Curved Apical Spines on the Femur
|Metasoma||*Has few ventral abdominal hairs|
*S3 is mostly flat
*Lacks mid longitudinal sulcus
|*Has metasomal scopa hairs on three fourth of the surface used for pollen collection|
|Face||*Delicate, feathery features||*Stout, tugged jawline|
How did Gynandromorphes in Megalopta Amoena emerge?
Honey bees are haplodiploid insects. Therefore, female bees arise from fertilized eggs, containing one set of chromosomes from each parent, while male ones result from unfertilized eggs and carry only one set of chromosomes. As bees are polyspermic, more than one sperm can enter each egg. Bees are born as the result of the combination of a diploid (female) zygote and a haploid (male) tissue originating from a second sperm. It results in the birth of gynandromorphs when a second or even a third sperm enters a fertilized egg and develops to produce male tissue alongside female tissue.
What Researchers Say
There are several questions regarding the circadian rhythm and behavior of these. Will they express masculine, feminine, or a mixed character?
The forager behavior of this bee is different from the normal bees. As we know, the normal ones are active at day time while the gynandromorph was out of the nest at the dark hours of mornings.
Just one specimen does not determine the characters. “Maybe it’s weird because it’s a gynandromorph. Or it’s just weird because it’s weird,” Adam Smith, a biologist at George Washington University, says about the night duty behavior of the gynandromorph Megalopta amoena.
“More studies need to be done to understand better if there is a difference in circadian rhythm based on sex in this species, and to distinguish what the deviant activity pattern of the gynandromorph results from,” the researchers pointed out.
However, the researchers of the University of Sydney say that the gynandromorphs offer no merits to the species, and the development of these creatures may be due to genetic errors.
“This sort of sexual fluidity probably happens more often than we’re aware of,” Krichilsky says. She also added that there were some niches occupied by a more typically female or male. Maybe some individuals can occupy something in between, or both—or become a whole new organism.
“Unusual though they are, gynandromorphs are still bees, just like other bees,” she says. “And we can learn a lot from them.”
Krichilsky E, Vega-Hidalgo Á, Hunter K, Kingwell C, Ritner C, Wcislo W, Smith A (2020) The first gynandromorph of the Neotropical bee Megalopta amoena (Spinola, 1853) (Halictidae) with notes on its circadian rhythm. Journal of Hymenoptera Research 75: 97-108. https://doi.org/10.3897/jhr.75.47828