Czech scientists discover rare male-less spider species in Prague
Czech scientists have discovered an entirely new species of spider on Petřín Hill in central Prague. What makes this spider truly remarkable is that it reproduces exclusively through parthenogenesis—meaning it does not need males to reproduce. The species has been named the “male-less six-eyed spider” (Dysdera parthenogenetica) and represents the first documented case of its kind in Europe. Radio Prague International spoke with Milan Řezáč, head of the research, and first asked him how they determined that this spider in fact might be a new species.
"We encountered a population of spiders that was very similar to a species called Adythera hungarica, but there were some notable differences. There were no males present, and we observed small differences in morphological features.
"So we formed a hypothesis that this could be a new species. To test this, we brought males of Adythera hungarica from Slovakia and performed a hybridization experiment. In this experiment, the females of the new species were not able to copulate with the males.
"In addition, there were genetic differences. For example, the chromosome structure of the spiders was different, which showed that the species are already well separated."
Can you describe the new spider species so that we can picture what it looks like?
"It's a medium-sized spider with a body length of around one centimetre, and it has a rusty-brown coloration. It is usually active during the night. If you want to find it during the day, you need to turn over stones, where you can find the spiders hiding in their silken retreats."
As its Czech name suggests, the spider can reproduce on its own. How does that work?
"The females lay eggs that are not fertilized by sperm. Inside the eggs, there are different cells: one is the egg cell, and the others are called polar bodies. In this case, a polar body fuses with the egg cell and takes on the role that sperm would normally play. However, these cells all come from the same parent, the mother. As a result, the offspring is genetically identical to the mother."
Does this ability give the spider an advantage, or is it more of a disadvantage?
"There is a major disadvantage to asexual reproduction, which is genetic homogeneity. A population made up of genetically identical individuals is very fragile when it comes to disasters or diseases.
"When a disease appears, it can wipe out the entire population because none of the individuals carries a mutation that might provide resistance. That is why such populations often disappear quite quickly.
"However, there are also significant advantages. Parthenogenetic species can reproduce much faster than sexual populations. In sexual populations, about half of the eggs develop into males. In parthenogenesis, all eggs develop into females, so reproduction is effectively twice as fast."
"It is also much easier for parthenogenetic species to colonize new localities. A single egg can establish a population, whereas in sexual species, at least two individuals must arrive, mature, find each other, copulate, and reproduce."
Where can this spider be found? Is it limited to Prague’s Petřín Hill?
"It has a broader distribution and can also be found, for example, in South Moravia. However, Prague is the locus classicus, meaning it is the type locality of the species. This is the place where the specimens used for the original description were collected, so Prague remains the classic locality of the species."
