Killer sperm means worms that mate with wrong species are doomed

31 July 2014 - 13:34 By Times LIVE
subscribe Just R20 for the first month. Support independent journalism by subscribing to our digital news package.
Subscribe now
C. nigoni male treated with maternal Cni-fog-3(RNAi). Oocytes (o) develop instead of sperm, while the somatic testis, including the glandular vas deferens (vd), remain unaffected.
C. nigoni male treated with maternal Cni-fog-3(RNAi). Oocytes (o) develop instead of sperm, while the somatic testis, including the glandular vas deferens (vd), remain unaffected.
Image: PloS One.

Caenorhabditis worms of different species have a novel way of maintaining their differences - killer sperm.

According to a statement, scientists figured this out when they tried to mate different species - and noticed that the females tended to either die, or end up infertile.

The scientists then decided to try putting the worms under a microscope using a fluorescent stain, to try and figure out what was going on.

It turns out that the sperm from other species of nematode isn't terribly friendly, it was breaking through the sphincter of the worm's uterus and invaded the ovaries.

Once there it destroyed the eggs, sterilising it.

After this, the sperm would go on to invade the rest of the worm's body, destroying tissue and eventually killing it.

"Our findings were quite surprising because females typically just select sperm from males of their own species during fertilisation, an action that does not lead to long-term consequences because there is no gene flow between the species," said one of the researchers, Asher Cutter,  who is an associate professor of ecology and evolutionary biology at the University of Toronto.

So why is it like this? Well the researchers believe that the way these nemotode worms mate has caused their sperm to become very aggressive.

"Caenorhabditis females commonly mate with multiple males, and sperm competition selects for more aggressive sperm within species," the researchers said in their study, published on PloS One.

The females of the species develop resistances that help them cope with this vicious sperm, but when it ends up in the female of the wrong species, those resistances aren't present.

"It remains to be tested whether heterospecific sterilization by sperm could also be co-opted as a weapon in inter-species resource competition when multipleCaenorhabditis species inhabit the same resource patch,"  the researchers said.

subscribe Just R20 for the first month. Support independent journalism by subscribing to our digital news package.
Subscribe now