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Traumatic insemination, also known as hypodermic insemination, is the mating practice in some species of invertebrates in which the male pierces the female's abdomen with his penis and injects his sperm through the wound into her abdominal cavity (hemocoel). The sperm diffuse through the female's hemolymph, reaching the ovaries and resulting in fertilization. The process is detrimental to the female's health. It creates an open wound which impairs the female until it heals, and is susceptible to infection. The injection of sperm and ejaculatory fluids into the hemocoel can also trigger an immune reaction in the female. Bed bugs, which reproduce solely by traumatic insemination, have evolved a pair of sperm-receptacles, known as the spermalege. It has been suggested that the spermalege reduces the direct damage to the female bed bug during traumatic insemination. However, statistical experiments showed no conclusive evidence for that hypothesis; hygienic protection against bacteria being the preferred explanation for that organ.〔 The evolutionary origins of traumatic insemination are disputed. Although it evolved independently in many invertebrate species, traumatic insemination is most highly adapted and thoroughly studied in bed bugs, particularly ''Cimex lectularius''.〔 Traumatic insemination is not limited to male-female couplings, or even couplings of the same species. Both homosexual and inter-species traumatic inseminations have been observed. ==Mechanics== In humans and other complex life forms, blood and lymph circulate in two different systems, the circulatory system and lymphatic system, which are enclosed by systems of capillaries, veins, arteries, and nodes. This is known as a closed circulatory system. Insects, however, have an open circulatory system in which blood and lymph circulate unenclosed, and mix to form a substance called hemolymph. All organs of the insect are bathed in hemolymph, which provides oxygen and nutrients to all of the insect's organs. Following traumatic insemination, sperm can migrate through the hemolymph to the female's ovaries, resulting in fertilization. The exact mechanics vary from taxon to taxon. In some orders of insects, the male genitalia (paramere) enters the female's genital tract, and a spine at its tip pierces the wall of the female's bursa copulatrix. In others, the male penetrates the outer body wall. In either case, following penetration, the male ejaculates into the female. The sperm and ejaculatory fluids diffuse through the female's hemolymph. The insemination is successful if the sperm reach the ovaries and fertilize an ovum.〔 Female resistance to traumatic insemination varies from one species to another. Females from some genera, including ''Cimex'', are passive prior to and during traumatic insemination.〔Arnqvist, citing A.D. Stutt, ''Reproductive Strategies and Sexual Conflict in the Bed Bug''. PhD thesis. University of Sheffield, England.〕 Females in other genera resist mating and attempt to escape.〔Arnqvist 89, citing personal observations and ''Monograph of Cimicidae''〕 This resistance may not be an aversion to pain caused by the insemination, as observational evidence suggests that insects do not feel pain. Research into the paternity of offspring produced by traumatic insemination has found "significant" last-sperm precedence. That is, the last male to traumatically inseminate a female tends to sire most of the offspring from that female. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Traumatic insemination」の詳細全文を読む スポンサード リンク
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