Ag moeder! This strange spider mom suckles her babies like a mammal
The ant-mimicking jumping spider has turned conventional thinking about lactation on its head
Spiders are not noted for their maternal bonding, with some matricidal spiderlings even devouring their mothers shortly after hatching.
But the ant-mimicking jumping spider is rewriting the natural history books after scientists discovered it produces milk and suckles its young for nearly 40 days.
Much like baby mammals nursing at the teats of their mothers, researchers have recorded the tiny insects gathering to feed on super-nutritious milk produced in an opening from which the eggs are released.
Until now lactation has been considered a purely mammalian trait. Although some non-mammals such as pigeons, flamingos, emperor penguins and cockroaches produce a similar nutritious fluid it is considered fundamentally different to milk both in production and use.
But researchers at the Chinese Academy of Sciences in Beijing said the fluid secreted by the spiders was four times as nutritious as cow’s milk, and could be considered as true milk. They found that feeding continues long after the little arachnids can forage on their own, and probably evolved during a period when food was scarce.
Writing in the journal Science, author Dr Rui-Chang Quan, said: “Extended parental care could have evolved in invertebrates as a response to complex and harsh living environments that require offspring skills to be fully developed before complete independence.
“The mother’s physiology, behaviour and cognition might have changed to adapt to providing milk and prolonged maternal care as in mammals.
“We anticipate that the discoveries presented in this study will encourage a reevaluation of the evolution of lactation and its occurrence across the animal kingdom.”
Scientists chose to study the ant-mimicking jumping spider (Toxeus magnus) because of its strange communal living arrangements in which adult females were often seen cohabiting with juveniles when most other spider young had left the nest.
The researcher speculated that the teenagers were hanging around because they were still receiving care and food from their mother.
After following the spiderlings from hatching, the scientists noticed that for at least 20 days neither mother nor babies left the nest, yet the offspring continued to grow as if they were being fed, more than tripling in size in the period.
Closer observations revealed that the mother provided a seemingly nutritious fluid from her underside.
During the first week the mother deposited milk droplets on the nest’s internal surfaces which the spiderlings came to eat.
But after the first week, milk deposition stopped and the offspring sucked directly from the mother’s epigastric furrow, a grooved opening through which the eggs are deposited.
Although spiderlings sometimes left the nest to forage from about 20 days, milk sucking continued until they reached the sub-adult stage at about 40 days when no more milk was produced. The mother also tended the nest during the 40-day period, making repairs and carrying out dead skin.
Unlike cockroaches, which deposit a nourishing fluid to the brood sac of the growing embryos, the spiders use a specialised organ and continue to suckle their young over an extended period, like mammals.
The researchers believe the milk might be made from unfertilised or failed eggs which are reused to feed the newly emerged offspring. When they blocked up the duct producing the milk, all the spiders died within 10 days, but when allowed to flow 76% made it to adulthood. In other species, such as wolf spiders, only 1% survive.
– © Telegraph Media Company Limited