Mussels give up sex secrets
IN relationships, “chemistry” is usually that “special something”, but Deakin chemists are on the brink of understanding the real chemistry of attraction in mussels.
Surprisingly, this will have implications not only for aquaculture, but for animal husbandry and assisted human reproduction.
With his theory that sexual selection was unlikely to occur between rock-bound creatures like mussels, Charles Darwin underestimated the power of chemistry.
Analytical chemist Associate Professor Xavier Conlan and PhD candidate Jake Penny are adapting nanoscale lab-on-a-chip technology to pin down the chemical signalling processes that allow mussels to sexually select “against the odds”.
Based within Deakin’s School of Life and Environmental Sciences, the two are working with colleagues from the University of Western Australia to investigate the chemical signalling that occurs between mussel sperm and eggs during spawning.
The three-year project is being funded by an Australian Research Council Discovery Award and aims to help protect mussels from climate change, improve aquaculture production and contribute to understandings of the chemical underpinnings of reproduction in all animals.
“Understanding the chemi- cal processes in reproduction for these shellfish is likely to have widespread evolutionary study implications and applications for mammals, fish, amphibians, plants and many marine invertebrates,” Prof Conlan said.
“Much of our current know- ledge about sperm in many animals has come from the study of marine invertebrates like mussels. It was only in the 1980s that, with the help of marine invertebrates, we discovered that most sperm don’t enter the oviduct in mammals. Only a few sperm respond to the chemical call. We call this chemotaxis.”
Prof Conlan said molluscs were “broadcast spawning” organisms like other marine invertebrates such as corals, starfish, sea urchins and sea cucumbers. Their breeding process is useful to scientists because it is less straightforward than mammal reproduction and thus gives access to “many different interactions and useful chemical insights”.
Contrary to Darwin’s view that being rock-bound would make mussels unlikely to be sexually selective, modern scientists have discovered that sexual selection is much more than a matter of behaviour. It can even be influenced after mating by chemical or physiological factors.
The research team is focusing on one of the major breeding challenges faced by mussels — finding the best mate.
They are optimistic that this is the key to improving commercial breeding outcomes and to progressing assisted human reproduction and animal breeding techniques.
“Until now, gaining a chemical understanding of this process has been impossible due to the nature of mussels’ habitat,” said Prof Conlan.
“It is hard to identify components in sea water because of the quantity of salt. But now, with lab-on-a-chip technology, we can research how mussel sperm and eggs select each other in sea water in the laboratory. We can observe one or a few sperm interacting with an egg and gain a mechanistic understanding of how specific sperm are guided to the gametes in broadcast spawners.
“Sexual selection is very much about optimising the egg’s chances of being successful. Some sperm are more applicable to certain eggs.
“Once we know how the egg and sperm interact at the chemical level, we can, hopefully, improve fish and shellfish farming practices, perhaps through synthesising chemicals to replicate conditions in the ocean or developing new ways to achieve fertilisation for commercial production. We are also expecting insights that will help fish breeders adapt to climate change and will build our knowledge of the biochemical process in human reproduction.”