Science – Solving the mystery: Giant woodlice spiders with special care – Knowledge

Manoa (dpa) – Creatures that roam the seabed on long, thin legs – The sight of giant isopod spiders makes many people shudder. A research team has now managed to unravel a previously unsolved mystery: why have animals never been seen with offspring before?

Because many isopod spiders of the species Colossendeis can be found on the Antarctic seafloor, their reproduction has been a mystery for more than 140 years, a research trio from the University of Hawaii at Mānoa explain in the specialist journal Ecology.

Contrary to what their name suggests, isopods are not arachnids, but rather a separate group of marine animals. Most species are only a few centimeters long, but some Antarctic species measure more than 30 centimeters from the tip of one leg to the other. The researchers explain that it is a case of “polar gigantism”: organisms in polar regions sometimes become much larger than their relatives in warmer climates.

Male woodlouse spider takes care of children

“In most woodlice spiders, the male parent takes care of the babies by carrying them while they grow,” study leader Amy Moran explained. Although descriptions of the animals go back more than 140 years, no one has ever seen Colossendis megalonyx cradling baby animals.

Moran's group collected such isopod spiders that appeared to mate by hand while diving, and brought them to pools for observation. The animals laid thousands of tiny eggs, only about 100 micrometers in size, but did not carry them. Instead, a parent – perhaps the father – spent days gluing the eggs to the rocky ground. They develop there for several months until tiny larvae finally hatch.

“We were very lucky to be able to see this,” said co-author Aaron Toh. Within a few weeks of being laid, microscopic algae bloomed on the eggs, providing perfect camouflage, which is probably why they had not been discovered before.

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