{"id":852136,"date":"2026-08-12T03:06:19","date_gmt":"2026-08-12T03:06:19","guid":{"rendered":"https:\/\/www.newsbeep.com\/au\/852136\/"},"modified":"2026-08-12T03:06:19","modified_gmt":"2026-08-12T03:06:19","slug":"male-redback-spiders-invite-cannibalism-through-a-self-sacrificial-somersault-during-sex-but-why-spiders","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/au\/852136\/","title":{"rendered":"Male redback spiders invite cannibalism through a \u2018self-sacrificial somersault\u2019 during sex \u2013 but why? | Spiders"},"content":{"rendered":"

If you think you\u2019ve had a bad one-night stand, spare a thought for the male redback spider, whose sole reproductive partner eats him after sex.<\/p>\n

Male redbacks appear to invite this cannibalism through a \u201cself-sacrificial somersault\u201d, with new research shedding light on the genetic basis of the behaviour.<\/p>\n

The redback, also known as the Australian black widow, is one of two monogynous widow spider species \u2013 meaning that males typically only mate with a single female.<\/p>\n

During copulation, a male redback uses his pedipalps \u2013 two arm-like appendages \u2013 to transfer sperm to the larger female\u2019s two sperm storage organs. He also somersaults into the jaws of the female.<\/p>\n

\u201cHe\u2019s pumping sperm, he flips his abdomen right over into her mouthparts and then he constricts his abdomen \u2026 to make it hard for the female to get a purchase on his abdomen. That lets him survive the first mating,\u201d said Cor Vink, an associate professor and spider expert at Lincoln University in New Zealand.<\/p>\n

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The self-sacrificial flip is thought to help maximise reproductive success, but the males risk being eaten before they are able to transfer sperm to the female\u2019s second storage organ.<\/p>\n

\u201cIdeally, males should mate with the same female two times because females have two separate sperm storage organs,\u201d said Kardelen \u00d6zg\u00fcn Uludag of the University of Hamburg, the study\u2019s first author.<\/p>\n

\u201cA male needs to inseminate and plug both of them, so that he can sire all of the offspring she produces.<\/p>\n

\u201cIf a male dies after the first mating, another male can mate with the same female and then half of the female\u2019s offspring would be from the second male.\u201d<\/p>\n

To avoid becoming a post-coital meal, previous research<\/a> has found that some males have developed the survival tactic of mating with immature females not yet experienced in eating their partners.<\/p>\n

A female redback. Of the 31 species of widow spider, male sacrificial behaviour is only usually observed in redbacks and brown widows. Photograph: cbstockfoto\/Alamy<\/p>\n

The venomous redback spider is widespread throughout Australia and has been unintentionally introduced to other countries including New Zealand, Japan and the United Arab Emirates.<\/p>\n

Redbacks are closely related to the New Zealand katip\u014d, which do not engage in sexual cannibalism. \u201cIn the katip\u014d, the male inseminates the female and runs off the web \u2013 that\u2019s the same for most widow spiders,\u201d Vink said. \u201cThe term widow is actually a misnomer.\u201d<\/p>\n

Of the 31 species of widow spider, male sacrificial behaviour is only usually observed in redbacks and brown widows.<\/p>\n

In a study published in Biology Letters<\/a> on Wednesday, German researchers investigated the genetic basis for why redback males perform a \u201cself-sacrificial somersault\u201d during mating, but katip\u014d males do not.<\/p>\n

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The katip\u014d (Latrodectus katipo), a spider endemic to New Zealand that is thought to have diverged genetically from redbacks about 100,000 years ago. Photograph: Cor Vink\/Lincoln University<\/p>\n

To do so, they bred female katip\u014d with male redbacks to determine how many offspring inherited the somersaulting behaviour. Close to half of their third-generation offspring also somersaulted, leading the scientists to conclude that the behaviour was linked to a specific location on the spider\u2019s X chromosome.<\/p>\n

\u201cIt is quite remarkable that a highly complex phenotype such as somersaulting, which may lead to partial reproductive isolation, can have such a simple genetic basis,\u201d the researchers noted.<\/p>\n

\u201cOur work shows that this highly complex cannibalistic behaviour can evolve rapidly, with very few genetic changes,\u201d Uludag said.<\/p>\n

In New Zealand, Vink has found evidence that interbreeding between native katip\u014d and invasive redbacks occurs in the wild. \u201cThis is a concern because we could lose our endemic protected species just through hybridisation,\u201d he said.<\/p>\n

Vink, who sourced the katip\u014d spiders for the study but was not otherwise involved in the research, described the work as an \u201celegant paper\u201d that shed light on the redback\u2019s \u201cweird mating behaviour\u201d.<\/p>\n

Katip\u014d are thought to have diverged genetically from redbacks about 100,000 years ago. \u201cIt\u2019s really neat that they\u2019ve lost this behaviour in 100,000 to 200,000 years,\u201d Vink said.<\/p>\n

\u201cThe more we know about the interbreeding, the more we know about what we can do to combat redbacks and katip\u014d interbreeding in New Zealand,\u201d he added.<\/p>\n","protected":false},"excerpt":{"rendered":"If you think you\u2019ve had a bad one-night stand, spare a thought for the male redback spider, whose…\n","protected":false},"author":2,"featured_media":852137,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[64,63,128],"class_list":["post-852136","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-au","tag-australia","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/852136","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/comments?post=852136"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/852136\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media\/852137"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media?parent=852136"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/categories?post=852136"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/tags?post=852136"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}