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What Speed Sperm Should a Sea Squirt Squirt?

Sea Squirt

Sea squirts reproduce by broadcast spawning, where eggs and sperm are released into the ocean and the sperm have to swim around to find an egg to fertilise.

By Angela Crean

Sea squirt sperm is revealing how a male’s environment affects his sperm’s quality, with implications for the health of offspring that could also improve the success of human IVF procedures.

The full text of this article can be purchased from Informit.

A sperm’s job is to swim to an egg and deliver the male DNA. So, sperm have essentially been likened to a car – the speed or quality of the sperm can influence its chances of successfully reaching an egg but, once the cargo is dropped off, the sperm’s quality is not expected to have any further influence on the development or health of the offspring.

The humble sea squirt suggests this assumption is wrong, and what we’ve learned from sea squirt fertilisation could be applied to make IVF more efficient.

Sea squirts (ascidians) may not appear to have any similarities with humans, but they are our very ancient ancestors, belonging to the same Phylum (Chordata). Sea squirts get their name from their feeding structures: they have an inhalant and exhalent siphon for filtering food, which ‘squirt’ water when exposed to air. However, it is not always just water that they squirt!

Sea squirts reproduce by broadcast spawning; both eggs and sperm are released into the ocean, where sperm have to swim around to find an egg to fertilise. This unusual reproductive strategy makes them an ideal species in which to test for links between sperm and offspring quality. We can easily manipulate fertilisation in the laboratory – controlling which sperm have access to eggs while still roughly mimicking the natural process of fertilisation.

To test whether differences...

The full text of this article can be purchased from Informit.