The sophisticated sex lives of sea squirts

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

(PhysOrg.com) -- 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: Most sea turtles now female in north Great Barrier Reef

Related Stories

Most sea turtles now female in north Great Barrier Reef

January 8, 2018

The vast majority of green sea turtles in the northern Great Barrier Reef are now female because of warmer temperatures due to climate change, which influences their sex during incubation, researchers said Monday.

Emperor penguins may shorten record fast by snacking

January 9, 2018

The endurance of emperor penguins, trudging through the perpetual Antarctic night to their breeding colonies, is legendary. Many trek more than 100 km from their ocean feeding grounds to rookeries at inland locations in preparation ...

Recommended for you

Cells lacking nuclei struggle to move in 3-D environments

January 20, 2018

University of North Carolina Lineberger Comprehensive Cancer Center researchers have revealed new details of how the physical properties of the nucleus influence how cells can move around different environments - such as ...

Information engine operates with nearly perfect efficiency

January 19, 2018

Physicists have experimentally demonstrated an information engine—a device that converts information into work—with an efficiency that exceeds the conventional second law of thermodynamics. Instead, the engine's efficiency ...

Team takes a deep look at memristors

January 19, 2018

In the race to build a computer that mimics the massive computational power of the human brain, researchers are increasingly turning to memristors, which can vary their electrical resistance based on the memory of past activity. ...

Fast computer control for molecular machines

January 19, 2018

Scientists at the Technical University of Munich (TUM) have developed a novel electric propulsion technology for nanorobots. It allows molecular machines to move a hundred thousand times faster than with the biochemical processes ...

0 comments

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.