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Gender beyond male and female: Discovery of an intersex mosquito by UM researchers

An intersex mosquito Culex sitiens was recently discovered by the Universiti Malaya researchers in a mosquito surveillance programme conducted in a rubber plantation area located at Kuala Lipis, Pahang, on July 20, 2019. This the first report of intersexualism or precisely ‘gynandromorphism’ for Culex sitiens worldwide. This unique creature was attracted to a human and first gained attention by conspicuous irregularities of its head part—bushy antenna on the left side, the typical characteristic of a male mosquito. It was an unusual phenomenon because only female mosquitoes are attracted to human to obtain bloodmeal for egg production. This mosquito was then transported back to the laboratory for further examination.

Interestingly, intersexualism was observed in antennae, legs and wings of the specimen, with distinct male characters on the left and female characters on the right. However, this mosquito displays well-developed male genitalia. This species is native to various coastal areas because it uses salt and brackish water as its breeding habitats. The occurrence of this species is unexpected because the collection site—Kuala Lipis is an inland area at least 100 km apart from the east coast and west coast of Peninsular Malaysia. This observation merits further investigation.


Culex sitiens is known to transmit Japanese encephalitis virus. Various mosquito control strategies have been introduced to reduce mosquito populations, including genetic modified mosquitoes. Although the release of genetically modified mosquitoes for disease control is still a good way off, this discovery may provide an opportunity for scientists to better understand the evolution and sexual development of mosquitoes, and to scrutinize the control potential by disrupting the sex determination pathway in mosquitoes. This extraordinary finding was recently published in Acta Tropica, the Netherlands renowned journal for tropical medicine.

Low VL, Wong ML, Liew JWK, Pramasivan S, Jeyaprakasam NK & Vythilingam I. (2019) Gender beyond male and female: Occurrence of a gynandromorph in the Japanese encephalitis vector Culex sitiens (Diptera: Culicidae). Acta Tropica.

Kindly contact our researcher for more info.

Dr Low Van Lun

Email :

Gentle beyond male and female_pages-to-j

Fig. 1. Gynandromorph of Culex sitiens discovered from Kuala Lipis, Pahang on July 20, 2019

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