Male spiders also eat females
Among invertebrates, the phenomenon of cannibalism is quite widespread. Similar behavior is found in insects, gastropods, copepods and spiders.
The most frequent cases when a large female black widow (Latrodectus mactans) devours her small partner immediately after mating, and sometimes during, before him.
Recent studies have shown that male Micaria sociabilis, Allocosa brasiliensis, and some crustaceans also not averse to eat their partners. Scientists are trying to figure out is the reason for this behavior.
Despite the fact that similar behavior to the layman it seems very strange, in a biological sense, it is caused by many different factors. “When females are few, and a lot of males, it becomes quite clear that the first devour of the second to restore balance,” says study co-author, biologist Sentence LENCA (Lenka Sentenska) from Masaryk University in the Czech city of Brno.
There is another circumstance. Because females have a lot more power in order to lay eggs than males for the production of sperm, some male individuals voluntarily sacrifice yourself for the sake of posterity.
“Males not always resist their fate. In those cases, when they sacrifice themselves, the mating process lasts much longer than when they try to escape. The duration of mating is important because it partner manages to convey more sperm and therefore increase the likelihood of offspring. Besides, the female who eats the male, gets more nutrients, and a chance for her to give birth to healthy offspring is greatly increased,” — says the researcher.
Thus, the causes eating females males more or less clear. Why the opposite happens, is still unclear. Sentence and her colleagues conducted several experiments with M. sociabilis spiders and recorded a few interesting cases that could unravel this natural mystery.
A small brown M. sociabilis spiders, common in Central Europe, the offspring twice a year: in spring and early summer. Observations have shown that the majority of females born in the spring, summer catch the appearance of the offspring, whereas the number of males is reduced dramatically by may. A shortage of one sex leads to cannibalism, scientists say in a press release. Males can choose between old and young, big and small partners. They can mate with the older females from the spring generation or young of the year.
To understand the basis of cannibalism of the males, the researchers placed a single adult male in one enclosure with a completely different females from small to large. The experiment showed that the larger was a male, the more aggressive he behaved towards females: he pounced on any spider, regardless of its age or size. However, on average, spiders pounced on older females and devoured them, and the offspring produced young. From 44 to 52% of the time arthropods were mating. In 20% of cases the males attacked their partners during intercourse.
“It is believed that in the animal world, the male tries to fertilize the maximum number of females to increase the chance of continuation of their kind. Our research shows that some men can be very picky in their choice, however, this selectivity is expressed in a very radical way: the spiders just kill unwanted potential partners. And although for arthropods, this behavior has its advantages, I would not advise people to use their methods” jokes of Sentence.
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