The sophisticated sex lives of sea squirts

August 26, 2008
Styela plicata larvae. Image courtesy of Bronwyn Galletly

( -- It may not be pretty, but the humble sea squirt could well be the envy of many: the marine organism never has to worry about contraceptives or IVF.

A UQ study, which is today published in prestigious US journal Proceedings of the National Academy of Sciences, has revealed that sea squirts have a natural ability to control their reproductive cycle, becoming more or less fertile as required.

Lead researcher and PhD student with UQ's School of Integrative Biology, Angela Crean, said the marine organisms could tailor their reproductive cells depending on the level of competition in the sea.

“When there are lots of competing males trying to fertilise the eggs of females, males produce larger, more competitive sperm that live for longer,” Ms Crean said.

“Similarly, when females detect that there are too many males competing for her eggs (too many sperm can kill the eggs of some organisms) the females ‘play hard to get' producing smaller eggs that are harder for searching sperm to find.

“These changes make sense if you're stuck to a rock like sea-squirts are.

“If you can't run away from a highly competitive environment, you must therefore make your gametes more competitive in order to get a higher chance of successfully reproducing.”

The fact that sea squirts don't move made it possible for the majority of the investigation to be conducted in the Moreton Bay field environment.

In a Big Brother-style approach, the primary experiment involved placing a large number of sea squirts in a confined space for an extended period.

“We manipulated adult densities in the field by placing either one (low density) or 15 (high density) sea squirts in a cage for one month,” Ms Crean said.

“This research tells us a little as to how sex evolved in the first place.

“Specifically, it gives us some insight into why sperm are so tiny and males make millions of them whereas female eggs are much larger and are produced in fewer numbers.

“Because these organisms reproduce by the ancestral mode of reproduction, it gives us an indication as to how competition between males led to all sorts of reproductive strategies including the one used by humans: internal fertilisation.”

This research forms part of Ms Crean's PhD, which she hopes to complete by the end of 2009.

Provided by University of Queensland

Explore further: Penguins wander far, but come home to mates: study

Related Stories

Polar bears may survive ice melt, with or without seals

September 4, 2015

As climate change accelerates ice melt in the Arctic, polar bears may find caribou and snow geese replacing seals as an important food source, shows a recent study published in the journal PLOS ONE. The research, by Linda ...

Five bizarre fossil discoveries that got scientists excited

July 20, 2015

From trilobites to tyrannosaurs, most fossils are of creatures with hard shells or bones. These materials don't easily biodegrade and sediment has time to build up around them and turn them into a record of the creature that ...

Recommended for you

Horn of Africa drying ever faster as climate warms

October 9, 2015

The Horn of Africa has become increasingly arid in sync with the global and regional warming of the last century and at a rate unprecedented in the last 2,000 years, according to new research led by a University of Arizona ...

What are white holes?

October 9, 2015

Black holes are created when stars die catastrophically in a supernova. So what in the universe is a white hole?

Could 'The Day After Tomorrow' happen?

October 9, 2015

A researcher from the University of Southampton has produced a scientific study of the climate scenario featured in the disaster movie 'The Day After Tomorrow'.

A mission to a metal world—The Psyche mission

October 9, 2015

In their drive to set exploration goals for the future, NASA's Discovery Program put out the call for proposals for their thirteenth Discovery mission in February 2014. After reviewing the 27 initial proposals, a panel of ...

Scientists paint quantum electronics with beams of light

October 9, 2015

A team of scientists from the University of Chicago and the Pennsylvania State University have accidentally discovered a new way of using light to draw and erase quantum-mechanical circuits in a unique class of materials ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.