Tag Archives: jumping spider

Baby jumping spiders sucking milk from their mother's birth cannal. Credit: Rui-Chang Quan.

Spider milk is a thing, and it’s 4 times more nutritious than cow’s milk

Baby jumping spiders sucking milk from their mother's birth cannal. Credit: Rui-Chang Quan.

Baby jumping spiders sucking milk from their mother’s birth canal. Credit: Rui-Chang Quan.

One summer evening, Chinese researchers were minding their own business in their lab in Yunnan, China, when they came across a peculiar sight. Inside a nest, they saw a juvenile jumping spider attached to its mother like a baby mammal sucking milk from a mamma’s teat. Strikingly, investigations showed that the young spiders really were sucking milk — spider milk! It’s the first time that milk production has been reported in arachnids or any invertebrate, for that matter. It’s very nutritious, too. Researchers reported that the jumping spider’s milk contains 4 times the protein, fat, and sugar typically found in cow’s milk.

The one-of-a-kind findings could help researchers piece together the evolutionary origins of very complex parental care, such as mammalian nursing. Given that we’re talking about a jumping spider (Toxeus magnus), a long-standing hypothesis that prolonged mothering requires complex brain power could be turned on its head.

What’s remarkable is not only the fact that a spider can produce milk but also how long it provides it to its young. Once the female spider’s eggs hatch, the mother deposits milky droplets around the nest, which the babies sip gladly for a couple of days. After the droplets are exhausted, the young spiders line up at the mother’s birth canal to suckle more milk. At the ripe old age of 20 days, the young start to hunt outside the nest, but they will still consume their mother’s milk until they become sexually mature, another 20 days later. Other spider species may hang around their young a couple of days after they hatch, but they never feed them.

When the researchers cut off the juveniles’ milk supply by painting the mother’s birth canal, all spiders younger than 20 days died. When the mother was removed from the nest, older spiders that were still being nursed grew slower, left the nest sooner, and were more likely to die before reaching adulthood, as reported in the journal Science.

The milk-like secretion could actually be liquefied eggs, wrote the authors of the new study, who work at the Chinese Academy of Sciences’ Center for Integrative Conservation in Menglunzhen. Previously, researchers have described other non-mammals producing milk-like substances, such as pigeons or cockroaches. However, a cockroach’s milk-like secretion is absorbed passively through the eggshell of the embryos and is not part of the hatchlings’ diet.

Extended maternal care was thought to be a behavior evolved by only a couple of long-lived social vertebrates, such as humans or elephants. However, the new study shows that invertebrates have also evolved this ability.  The study’s authors do not explain why the spiders nurse their young for so long or why other species of spiders do not produce milk. Nevertheless, the findings provide a reminder that spiders aren’t necessarily cold and harsh creatures.

What scientists learned after they trained spiders to jump on demand

Visual comparison of body attitude and leg arrangement at the start and end of the jumping tasks.

Visual comparison of body attitude and leg arrangement at the start and end of the jumping tasks.

British researchers have trained a spider to jump on demand for the first time. In doing so, they learned what enables the arachnids to jump different distances and over huge heights relative to their size.

“Spiders represent a unique class of natural jumping insects — they offer exemplary jumping behavior at the small scale with evidence of intelligence in assessing surroundings and planning prey capture. Our results suggest that the form of jumping within spiders is rather different from those seen in other insects, and reflects the specialisations for short-range high speed jumps,” Dr. Mostafa Nabawy, a researcher at the University of Manchester and lead author of the new study, told ZME Science.

Nabawy and colleagues worked with regal jumping spiders (Phidippus regius), which they trained to jump between two platforms in a laboratory setup. This was rather challenging since the spiders were reluctant to jump at the whim of some humans. Out of the four jumping spiders recruited for the study, “only one was happy to jump as required,” Nabawy told me.

Researchers recorded the spider, nicknamed Kim, as it jumped different heights and distances on a man-made platform using ultra-high-speed cameras. Micro CT scans were also performed to create a 3D model of the spider’s legs and body structure.

The morphology of the jumping spider Phidippus regius as seen here in CT scans. Credit: Dr Mostafa Nabawy, The University of Manchester.

The morphology of the jumping spider Phidippus regius as seen here in CT scans. Credit: Dr Mostafa Nabawy, The University of Manchester.

The analysis revealed that this particular species of spider employs various strategies to jump over an obstacle, depending on the magnitude of the challenge. When it had to jump over shorter, close-range distances, Kim took a faster, lower trajectory which consumes more energy but minimizes the jump time. Although it uses up more energy this way, the spider makes up for it in accuracy, increasing its odds of capturing prey. However, when Kim had to jump across longer distances or higher on an elevated platform, the spider reduced the amount of energy it used.

Scientists have been aware for more than 50 years that spiders use internal hydraulic pressure to extend their legs. Up until now, however, it wasn’t clear whether this hydraulic pressure is actively used to enhance or replace muscle during the jump. When the University of Manchester team compared the performance of the jumping spider to that of insects, they learned that the estimated muscle power is sufficient on its own to power the jump. This suggests that the additional power from hydraulics is not essential.

The aim of this study was to investigate the jumping spider anatomy and its behavior. The insights that the researchers gained could now be used to design a new class of hyper-agile micro-robots. Jumping spiders can leap up to six times their body length from a standing start, while the best a human can achieve is only 1.5 body lengths. What’s more, the force they used to propel themselves can be up to 5 times the weight of the arachnid.

“Spiders represent a unique class of natural jumping insects – they offer exemplary jumping behavior at small scale with evidence of intelligence in assessing surroundings and planning prey capture. Our results suggest that the form of jumping within spiders is rather different from those seen in other insects, and reflects the specializations for short-range high-speed jumps,” Nabawy said.

“There are still more questions to answer mainly related to the in-depth understanding of the control strategies employed by jumping spiders as well as detailed characterization of legs actuation forces within the jump,” the researcher added.

Scientific reference:  ‘Energy and time optimal trajectories in exploratory jumps of the spider Phidippus regius’ is being published in the journal Nature Scientific Reports by Mostafa R. A. Nabawy, Girupakaran Sivalingam1, Russell J. Garwood, William J. Crowther & William I. Sellers DOI:10.1038/s41598-018-25227-9.