Insect species discovered with reversed male-female sex organs

Research Press Release | May 01, 2014

  • Neotrogla curvata, one species of Neotrogla, during copulation. The female’s body is approximately three millimeters long. Unlike general insect mating, the female climbs atop the male to copulate.
    Neotrogla curvata, one species of Neotrogla, during copulation. The female’s body is approximately three millimeters long. Unlike general insect mating, the female climbs atop the male to copulate.
  • The female penis (shown in red) of Neotrogla curvata, one species of Neotrogla. The seminal receptacle on the end opens to receive seminal fluid. The spines are used to anchor the male during copulation.
    The female penis (shown in red) of Neotrogla curvata, one species of Neotrogla. The seminal receptacle on the end opens to receive seminal fluid. The spines are used to anchor the male during copulation.
  • The female penis of Neotrogla curvata inserted into the male in a photograph (top) and outline drawing (bottom). The female penis is shown in red.
    The female penis of Neotrogla curvata inserted into the male in a photograph (top) and outline drawing (bottom). The female penis is shown in red.
Press Release – Female penis seen in cave-dwelling Psocoptera insects
Key Points

– We confirmed that female cave-dwelling Neotrogla insects in Brazil (order Psocoptera) possess an erectile penis-like genital organ.

– The female penis functions as an intromittent organ and has complex, diverse forms. In contrast, the male genitalia, which is penetrated by the female, has simple form.

– During copulation, the male transfers seminal fluid and nutrients to the female. It is thought that competition for these nutrients among females facilitated the evolution of the female penis.

– Detailed research on sex reversed animals, for which the female is more choosy for mates, fulfills an important role in verifying the theory of sexual selection and exploring the background of evolution resulting in masculine/feminine characters.

Overview

With few exceptions, for living organisms that perform internal fertilization, the male possesses a penis. We discovered that female Brazilian cave-dwelling insects in the genus Neotrogla (order Psocoptera) have a penis-like intromittent organ, which is inserted into the male during copulation. During copulation, the male Neotrogla transfers capsules containing nutrients to the female together with seminal fluid. Our observations suggest that the female is more competitive than the male regarding copulation for receiving these nutrients, which facilitated the evolution of the female penis. It is expected that detailed research on sex-reversed insects will provide vital hints for exploring the evolutionary background of the origins of differences between sexes.

Inquiries

Associate Professor Kazunori Yoshizawa

Research Faculty of Agriculture, Hokkaido University

TEL: 011-706-2424 FAX: 011-706-2494 E-mail: psocid@res.agr.hokudai.ac.jp

Japanese

Link

 http://www.hokudai.ac.jp/news/140418_pr_agr.pdf

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