People may associate the concept of the chastity belt with medieval Europe but other parts of the animal kingdom used them long before that.
Male dwarf spiders, for instance, have evolved a mechanical safeguard to ensure their paternity - mating plugs to block off the genital tract of the female they have just mated with. The larger and older the plug, the better the chances are that other males will not make deposits in a female's sperm storage organ, too.
Yes, dwarf spider males (Oedothorax retusus) insert mating plugs into the two copulatory ducts of the females they have mated with.
Ventral view of an Oedothorax retusus female. Red square indicates the position of the genital region (epigyne) that is plugged by the male. Photo Credit: Melanie Witthuhn
Katrin Kunz and co-authors of the Zoological Institute and Museum in Greifswald, Germany, recently studied just how well the mating plugs of the dwarf spider work. They discovered that the material the plugs are made of is transferred in a liquid state from the male to the female and that it needs to harden to a certain degree before it can withstand penetration or removal by a rival male. Remating trials were then staged after females received plugs of different sizes during a first round of copulation. Their effectiveness over periods of time was also tested. The female spiders were then scrutinized under a scanning electron microscope.
Overall, small plugs were found to be less effective than large plugs. This suggests that smaller portions of the translucent plug material can be more easily removed or overcome by a subsequent male that wants to mate. Small plugs are also least effective shortly after they are placed, which suggests that both size and the hardening of the material plays an important role in how well the plug works. Once plugs are older than a day they strongly serve to monopolize access to the duct that leads to the female sperm storage organ.
However, even if subsequent males are able to mate, at least part of their sperm mass remains outside of the female genital tract, confirming the efficacy of the mating plug. Consequently, if a male succeeds in plugging both of the female's copulatory openings, his paternity success is expected to be very high.
"The mating plug in the dwarf spider clearly functions as a mechanical obstacle to rival males," says Kunz. "Mating plugs are a powerful mechanical safeguard whose efficacy varies with plug size and age."
Citation: Kunz, K. et al (2014). Does the size and age of mating plugs alter their efficacy in protecting paternity? Behavioral Ecology and Sociobiology, DOI 10.1007/s00265-014-1742-7
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- Wind Turbine Or Tree? Bats Can't Tell
- Top Mass: CMS Again On Top!
- Epigenetics Of Being Without Electricity For A Few Days
- The Enemy Of Archaeology Is Not People, It's Salt
- Questions a Surface Pro 3 user has about windows 10.
- Science Graduates Are Not Good At Math – But Why?
- Depression Surveys Linked To Unnecessary Antidepressant Prescriptions
- "Everyone over 40 should be taking the Cologuard test recently OKed by the FDA. This is a non-invasive..."
- "From your comment the only conclusion is that you have a basic, rudimentary and even wrong understanding..."
- "I guess when you're held in a dungeon for ransom it can kind of set you on edge when the people..."
- "Thank you for your answer!There's indeed a threshold at about 350 MeV, with a decrease afterwards..."
- "I also infer your existence from the nice picture on the right and the fact that you seem to have..."