Creatures that stalk across the seabed on thin, long legs – the sight of giant isopod spiders makes many people shudder. A research team has now managed to unravel a previously unsolved mystery: why the animals have never been seen with offspring.
As numerous isopod spiders of the Colossendeis species can be on the seabed of Antarctica, their reproduction has been a mystery for more than 140 years, explains the research trio from the University of Hawaii in Manoa in the specialist journal “Ecology”.
Contrary to what their name suggests, isopod spiders are not arachnids; they are a separate, purely marine group of animals. Most species are only a few centimeters tall, but some Antarctic species measure more than 30 centimeters from the tip of one leg to the opposite. 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 childcare
“In most woodlice spiders, the male parent cares for the babies by carrying them around as they develop,” explained study leader Amy Moran. Despite descriptions of the animals going back over 140 years, no one has ever seen Colossendeis megalonyx incubating young animals.
Moran’s group had collected such isopod spiders that appeared to be mating by hand during dives and brought them into pools for observation. The animals laid thousands of tiny eggs measuring only about 100 micrometers – but didn’t carry them around. Instead, one parent – probably the father – spent days sticking the eggs to the rocky ground. They developed there for several months until tiny larvae finally hatched.
“We were very lucky to be able to see this,” said co-author Aaron Toh. Within a few weeks of being laid, the eggs were overgrown with microscopic algae, which provided perfect camouflage – which is probably why they had never been discovered before.
