JUMPING SPIDERS | Why do women live longer than men? A spider that suckles its young reveals a secret
In most animal species, females tend to live longer than males.. This seems counterintuitive since, in theory, investments in reproduction, lactation, and offspring care often reduce mothers’ life expectancy. To interpret this paradox, a group of scientists conducted an experiment that yielded surprising results.
Researchers mistook specimens of the species for “guinea pigs.” “feeding” jumping spider, Toxeus Magnuswhich breastfeeds its young for an average of 38 days, and compared the reproductive activity and lifespan of the two sexes.
They found, for example, that while providing “milk” (a nutritional fluid that has four times more protein than cow’s milk) shortens women’s life expectancy, Mothers who breastfed and cared for their offspring lived longer compared to virgins and those who did not care for their offspring..
More conclusions: Copulation increased the lifespan of females but had no effect on males.and although both sexes have comparable developmental durations, The life expectancy of adult females was 2.1 times higher than the life expectancy of males..
The study, published in the journal iScience, suggests that the time it takes for offspring to disperse may act as a key selective force for prolonging female adult life, ultimately leading to longer-lived females in species under maternal care.
Study authors from the Chinese Academy of Sciences compared the life expectancy of adult women who breastfed their young and those who did not, to test the effectiveness overall impact of maternal care interventions on maternal longevity.
Various sex roles
They discovered that Caring for offspring prolongs maternal longevity. Females who care for their young live much longer than those who are responsible only for milk production.
They then compared the reproductive longevity of mothers Toxeus Magnus with the number of egg clutches produced, the number of offspring achieving nutritional independence, and the number of adult stages, and found that The number of offspring does not affect the life expectancy of the mother..
According to the researchers, differences in sex roles in reproduction may drive the evolution of long-lived adult females. Toxeus Magnus. Greater female longevity is only possible in adulthoodand not in the period of development, since there are no significant differences in the time of development of juveniles between the two sexes.
The study suggests that difference in sex role in reproduction (males are involved only in mating, while females also produce eggs, tend them, and provide long-term care for the young) may be the driving force behind the difference in adult lifespan.
While the males Toxeus Magnus may die after mating, mating females require additional time for gestation, egg production, egg care, and maternal care after hatching. On average, adult female spiders lived 95 days longer than adult males.almost the same as the time from the laying of eggs to the settlement of the young.
“To the best of our knowledge, this is the first study to separately test the effects of nutritional provision and non-nutritional care (two major components of offspring care) on female lifespan,” emphasizes Chen Zhanqi, co-author of the study.
Mammal-like care
It was these same researchers who discovered six years ago that this species of jumping spider, which imitates ants, supplies nutrient fluid which they called “milk” and long-term parental care similar to mammals.
This supply of milk in Toxeus Magnus involves a specialized organ over a long period, similar to lactation in mammals. Microscopic observations showed that the droplets emerged from the epigastric groove of the mother, whose young suckled for approximately 38 days.
When spiders are deprived of milk, they simply stop developing and die within 10 days, indicating that This fluid is necessary for the survival of the offspring at the initial stage.. In addition, researchers have proven that caring for the mother and supplying her with milk continues after 20 days, when the offspring can independently obtain food. Mothers continue to constantly maintain the nest, drying out the young and repairing damage.
The presence of the mother after the first 20 days plays a key role in the survival of the offspring and their attainment of a normal adult size.according to the research results.
Another surprising result was that although mothers appeared to treat all youngsters equally, only daughters were allowed to return to the nest after sexual maturity. Adult children are attacked if they try to return. “This may reduce inbreeding depression,” the authors say.
The study showed that The provision of nutrients, as in mammals, and parental care of sexually mature offspring also evolved in invertebrates..
Reference Study: https://www.cell.com/iscience/fulltext/S2589-0042(24)01323-3.
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