Sea squirts in sperm warfare

March 21, 2000

Life under the waves can get pretty crowded when you are a sea squirt vying for space on the rocks. But these sea creatures have a novel weapon-they use their sperm to sabotage the eggs of other kinds of sea squirt. According to a marine biologist in California, this may be the first example of sperm competition between species.

Sea squirts spend most of their life clinging on to rocks, and many are broadcast spawners: females and males release eggs and sperm into the water, where they mix and fertilise. Any egg that is fertilised by more than one sperm will not develop properly, so, like other animals, sea squirts have evolved ways to prevent this happening. Once a sperm binds to an egg, the egg releases an enzyme that alters its surface, preventing other sperm attaching.

Now Charles Lambert of California State University in Fullerton has found that other species of sea squirts can subvert this mechanism. Lambert studied two species, Ascidia nigra and Ascidia sydneiensis, in the waters around Hawaii and Guam. Although the two cannot cross-fertilise, the sperm of one still triggers the defence mechanism in eggs of the other, preventing the species under attack from being fertilised. "If one species can cause eggs of another species to die without being fertilised, that takes a possible competitor for space out of the game," says Lambert.

This may partly explain why the males produce so many sperm. "One function of the excess sperm may be to make some of the other species' eggs infertile," Lambert says. He believes that germ-cell warfare between species may be more common than anyone realised. "Few people have looked to see if sperm that cannot fertilise an egg can still render that egg incapable of fertilisation," he says.
Reporter: Jon Copley

Source: The Biological Bulletin (vol 198, p 22)

New Scientist issue: 25th March 2000


New Scientist

Related Sperm Articles from Brightsurf:

Nut consumption causes changes in sperm DNA function
Researchers have evaluated for the first time the effect of a short/middle-term consumption of a mixture of tree nuts (almonds, hazelnuts and walnuts) on sperm DNA methylation patterns in healthy individuals reporting eating a Western-style diet.

Collecting sperm from Covid-19 patients
How does Covid-19 affect sperm and thus the next generation┬┤s immune system?

Paleontology -- The oldest known sperm cells
An international team of paleontologists has discovered giant sperm cells in a 100-million year-old female ostracod preserved in a sample of amber.

Research captures how human sperm swim in 3D
Using state-of-the-art 3D microscopy and mathematics, Dr Hermes Gadêlha from the University of Bristol, Dr Gabriel Corkidi and Dr Alberto Darszon from the Universidad Nacional Autonoma de Mexico, have reconstructed the movement of the sperm tail in 3D with high-precision.

Overweight and obesity are associated with a low sperm quality
Researchers from the Rovira i Virgili University in collaboration with researchers from the University of Utah have carried out a systematic review and meta-analysis evaluating the association between adiposity (normal weight, overweight, obesity, and low weight) and the sperm quality.

Diet has rapid effects on sperm quality
Sperm are influenced by diet, and the effects arise rapidly.

Sperm may offer the uterus a 'secret handshake'
Why does it take 200 million sperm to fertilize a single egg?

Long duration of sperm freezing makes no difference to live birth rates in large sperm bank study
Despite a time limit imposed in many countries on the freeze-storage of sperm, a new study from China has found that the long-term cryopreservation of semen in a sperm bank does not affect future clinical outcomes.

An important function of non-nucleated sperm
Some animals form characteristic infertile spermatozoa called parasperm, which differ in size and shape compared to fertile sperm produced by single males.

DNA of sperm taken from testicles of infertile men 'as good as sperm from fertile men'
Scientists have found that sperm DNA from the testicles of many infertile men is as good as that of ejaculated sperm of fertile men.

Read More: Sperm News and Sperm Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to