Gynandromorphism

Gynandromorph of the common blue butterfly (*Polyommatus icarus*)

A gynandromorph is an organism that contains both male and female characteristics. The term comes from the Greek γυνή (gynē) 'female', ἀνήρ (anēr) 'male', and μορφή (morphē) 'form', and is used mainly in the field of entomology. Gynandromorphism is most frequently recognized in organisms that have strong sexual dimorphism such as certain butterflies, spiders, and birds, but has been recognized in numerous other types of organisms.

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[Intro] Ever seen a crazy looking butterfly or a bird that looks like two different individuals smashed together? Not like a griffin or a centaur with two different species, but two members of the same species that have different markings. Like a butterfly with two different wing patterns; or a lobster that's red on one side and brown on the other. You probably haven't because they're rare, but they ARE out there. They're know as gynandromorphs. These organisms have both male and female characteristics, often split right down the center of their bodies. The condition can be found in about 1 in 10,000 butterflies and other insects, but also in crustaceans and other arthropods. So: how does such a thing happen? Well, all sexually reproducing animals begin as a single fertilized egg, or zygote, that divides itself again and again through mitosis. One cell turning into two, and two turning into four, and so on, to make a baby animal. Now in mammals, those divided cells differentiate themselves later on in development, so when they first split, they can turn into pretty much any tissue. But in arthropods, all of those early cell divisions are determinate. That means that every cell has a particular inflexible destiny from the very beginning. So, for example, when a butterfly zygote first divides, those first two resulting cells will each determine the left and right sides of the animal. The second division determines what will be the front and the back; and the third assigns top and bottom, and so on. Now, another thing to keep in mind is that before each cell splits, it has two copies of the organism's DNA coiled up in pairs of chromosomes: one set for each new cell. And that information includes the organism's sex- determined by chromosomes we call X and Y. In butterflies, XY is the female, and XX is the male. And yes, that is the opposite of how it is in humans. If there happens to be a mutation in one of these sex chromosomes, usually the information can still be read - like if an animal ends up with just one X and no Y, it'll be female; if it gets three X's, it's male. But if something goes wrong during the earliest stages of mitosis, and the sex chromosomes don't properly separate, one of the new cells may have too many chromosomes, while the other doesn't have enough. So, if this happens during the development of, say, a male Swallowtail butterfly - which would normally be XX - it might end up with one cell only having one X, making it female, and then other cell with three X's, making it male. Then, all the subsequent divisions from those two cells would be all male and all female, and you'd get a bilateral gynandromorph. One that looked like a half male and half female stuck together. Now, if the error occurs in later division, you might end up with a more patchy mix or a mosaic of male and female characteristics. Gynandromorphy is not the same thing as hermaphroditism, which is when an organism has both male and female sex organs. Depending on when the error occurs - and what the anatomy of the animal is like-, gynandromorphs are not necessarily hermaphroditic, although no matter what, it's likely to be sterile. And, as far as we know, gynandromorphy isn't possible in humans or other mammals because our ovaries and testicles release specific hormones that promote either female or male traits. These dominant hormones can actually override abnormalities in our sex chromosomes. Consider it just one more way in which sexual reproduction and just life on Earth in general can be downright weird. Thanks for watching this SciShow Dose, and if you'd like to keep getting smarter with us, all you have to do is go to youtube.com/scishow and subscribe.

Occurrence

Gynandromorphism has been noted in Lepidoptera (butterflies and moths) since the 1700s.^[1]^[2]^[3] It has also been observed in crustaceans, such as lobsters and crabs, in spiders,^[4] ticks,^[5] flies,^[6] locusts,^[7] crickets,^[8] dragonflies,^[9] ants,^[10]^[11] termites,^[12] bees,^[13] lizards,^[14] snakes,^[15] rodents,^[16]^[17] and birds.^[18]^[19]^[20]^[21]^[22] It is generally rare but reporting depends on ease of detecting it (whether a species is strongly sexually dimorphic) and how well-studied a region or organism is. For example, up until 2023 gynandromorphism had been reported in more than 40 bird species, but the vast majority of these are from the Palearctic and Nearctic, indicating that it likely is underreported in parts of the world that are not as biologically well-studied.^[23]

Pattern of distribution of male and female tissues in a single organism

A gynandromorph can have bilateral symmetry—one side female and one side male.^[24] Alternatively, the distribution of male and female tissue can be more haphazard. Bilateral gynandromorphy arises very early in development, typically when the organism has between 8 and 64 cells.^[25] Later stages produce a more random pattern.^{[citation needed]}

A notable example in birds is the zebra finch. These birds have lateralised brain structures in the face of a common steroid signal, providing strong evidence for a non-hormonal primary sex mechanism regulating brain differentiation.^[26]

Normal female of Papilio androgeus
Mosaic gynandromorph of Papilio androgeus
Normal male of Papilio androgeus

Causes

The cause of this phenomenon is typically (but not always) an event in mitosis during early development. While the organism contains only a few cells, one of the dividing cells does not split its sex chromosomes typically. This leads to one of the two cells having sex chromosomes that cause male development and the other cell having chromosomes that cause female development. For example, an XY cell undergoing mitosis duplicates its chromosomes, becoming XXYY. Usually this cell would divide into two XY cells, but in rare occasions the cell may divide into an X cell and an XYY cell. If this happens early in development, then a large portion of the cells are X and a large portion are XYY. Since X and XYY dictate different sexes, the organism has tissue that is female and tissue that is male.^[27]

A developmental network theory of how gynandromorphs develop from a single cell based on a working paper links between parental allelic chromosomes was proposed in 2012.^[28] The major types of gynandromorphs, bilateral, polar and oblique are computationally modeled. Many other possible gynandromorph combinations are computationally modeled, including predicted morphologies yet to be discovered. The article relates gynandromorph developmental control networks to how species may form. The models are based on a computational model of bilateral symmetry.^[29]

As a research tool

Gynandromorphs occasionally afford a powerful tool in genetic, developmental, and behavioral analyses. In Drosophila melanogaster, for instance, they provided evidence that male courtship behavior originates in the brain,^[30] that males can distinguish conspecific females from males by the scent or some other characteristic of the posterior, dorsal, integument of females,^[31]^[32] that the germ cells originate in the posterior-most region of the blastoderm,^[33] and that somatic components of the gonads originate in the mesodermal region of the fourth and fifth abdominal segment.^[34]

References

^ Rudolphi, Karl Asmund (1828). "Beschreibung einer seltenen menschlichen Zwitterbildung nebst vorangeschickten allgemeinen Bemerkungen über Zwitter-Thiere". Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin (in German): 45–69.
^ Packard, Alpheus Spring (1875). "On Gynandromorphism in the Lepidoptera". Memoirs Read Before the Boston Society of Natural History. 2: 409–412.
^ Pavid, Katie. "Beauty of the dual-gender butterfly". Natural History Museum. Retrieved 11 May 2021.
^ Suzuki, Yuya; Kuramitsu, Kazumu; Yokoi, Tomoyuki (2019-06-14). "Morphology and sex-specific behavior of a gynandromorphic Myrmarachne formicaria (Araneae: Salticidae) spider". The Science of Nature. 106 (7): 34. Bibcode:2019SciNa.106...34S. doi:10.1007/s00114-019-1625-x. hdl:2241/00159248. ISSN 1432-1904. PMID 31201570. S2CID 189819156.
^ Labruna, M. B.; Ribeiro, A. F.; Cruz, M. V.; Camargo, L. M A.; Camargo, E. P. (August 2002). "Gynandromorphism in Amblyomma cajennense and Rhipicephalus sanguineus (Acari: Ixodidae)". Journal of Parasitology. 88 (4): 810–811. doi:10.1645/0022-3395(2002)088[0810:GIACAR]2.0.CO;2. PMID 12197141. S2CID 26299983.
^ Morgan, T. H. (1 June 1914). "Mosaics and gynandromorphs in Drosophila". Experimental Biology and Medicine. 11 (6): 171–172. doi:10.3181/00379727-11-105. S2CID 87401593.
^ Maeno, Koutaro; Tanaka, Seiji (September 2007). "Morphological and behavioural characteristics of a gynandromorph of the desert locust, Schistocerca gregaria". Physiological Entomology. 32 (3): 294–299. doi:10.1111/j.1365-3032.2007.00573.x. S2CID 85317122.
^ Taniyama, Katsuya; Onodera, Kaori; Tanaka, Kazuhiro (December 2018). "Sexual identity and sexual attractiveness of a gynandromorph of the lawn ground cricket, Polionemobius mikado (Orthoptera: Trigonidiidae): Gynandromorph of Polionemobius mikado". Entomological Science. 21 (4): 423–427. doi:10.1111/ens.12321. S2CID 91381517.
^ Renjith, R. V.; Chandran, A. Vivek (26 June 2020). "A record of gynandromorphism in the libellulid dragonfly Crocothemis servilia (Insecta: Odonata) from India". Journal of Threatened Taxa. 12 (9): 16183–16186. doi:10.11609/jott.5322.12.9.16183-16186.
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^ Miyaguni, Yasushi; Nozaki, Tomonari; Yashiro, Toshihisa (August 2017). "The first report of gynandromorphy in termites (Isoptera; Kalotermitidae; Neotermes koshunensis)". The Science of Nature. 104 (7–8): 60. Bibcode:2017SciNa.104...60M. doi:10.1007/s00114-017-1478-0. PMID 28676938. S2CID 21170853.
^ Lucia, Mariano; Gonzalez, Victor. H. (1 November 2013). "A New Gynandromorph of Xylocopa frontalis with a Review of Gynandromorphism in Xylocopa (Hymenoptera: Apidae: Xylocopini)". Annals of the Entomological Society of America. 106 (6): 853–856. doi:10.1603/AN13085. hdl:11336/23238. S2CID 84567180.
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- Laura Wright (March 25, 2003). "Unique Bird Sheds Light on Sex Differences in the Brain". Scientific American.
^ Gouldian finch Erythrura gouldiae Gynandromorph Archived 2006-07-16 at the Wayback Machine
^ Powdermill Banding Fall 2004 Archived 2006-12-31 at the Wayback Machine
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