Abby Tabor
As farmland and fresh water become scarcer, and the global population continues to increase, the farming of aquatic species, or aquaculture, may see an expansion of its role in feeding humanity. Important in this will be keeping the cultures disease-free and maximizing their production; highly specialized research in these areas could have a broad impact on countless daily lives. Two scientists recount not only the importance of this work, but the pleasure they take in doing it.
“Are you crazy?” Naim’s friends cried. “You always make the wrong choice!” When she decided to study marine biology, she knew almost nothing about the ocean. She couldn’t even swim properly.
“You went to university for 12 years to become…a shellfish farmer?” people ask Zoë Hilton, clearly perplexed by this path.
The women themselves, both recipients of the 2012 L’Oréal-UNESCO international fellowship for life sciences share a sense of wonder at their own path in aquaculture: “I never would have guessed I’d end up doing this job!” But both are so passionate about their work, and so fully convinced of its promise, that there’s no turning back now. They work on different species—Naim on shrimp and tilapia, Zoë on oysters and other shellfish—but their goal is the same: to better understand the biology of these species in order optimize success in farming them. Aquaculture, they feel strongly, can have a significant positive impact on the environment and on economies, as well as feed the world.
“Shellfish aquaculture makes sense on a global scale,” Dr. Hilton says. “We’re already pretty good at land farming, but we’ve cleared a lot of forest and there’s not much farther we can go. Yet the population is increasing and, as countries develop, people tend to increase the amount of protein they want in their diet. I can’t imagine we’ll be able to meet those demands without having a significant environmental impact.” She sees in aquaculture a truly viable solution. The ability of shellfish to convert food into growth, and thus edible parts, is much more efficient than for terrestrial species. Furthermore, shellfish cultures do not even require feeding, obtaining their nutrients, in the form of plankton, directly from their watery environment. “There’s enormous potential to make really good food.”
Sidrotun Naim, who goes simply by Naim, knows the same desire to help people. She had wanted to become a medical doctor but the tuition proved prohibitive for the family of 11 children. Today, she is on her way to becoming a “shrimp doctor”, instead, via three different Master’s degrees, and a PhD in Environmental Sciences from the University of Arizona. In her native Indonesia, shrimp farming is the main livelihood for coastal populations, involving more than six million people up and down the archipelago. If anything happens to the shrimp—a widespread infection, for instance—the consequences can be huge. From 2006 to 2010, profits lost to a viral disease amounted to $150-200 million; if projected production increases are taken into account, the virus cost Indonesia $500 million. The stakes are high for shrimp health, but, while working for tsunami reconstruction in the devastated Aceh region in 2007, Naim realized there was no one in her country with the specialized knowledge necessary to help.
This is how the mother of one ended up studying at the center of the shrimp pathology world, at the University of Arizona, Tucson. The lab of the field’s expert, Donald Lightner, is located in this desert state, of all places, for two good reasons. With few aquatic ecosystems around, there is little chance of contaminating wild populations with the bacteria and viruses under study. Likewise, their experiments are not at risk of contamination from external sources. Here, under the supervision of Kevin Fitzsimmons, Naim has been working on developing a system of co-culture of shrimp and tilapia fish, which are mutually beneficial and produce even more food from the same space. To maintain good water quality, the fish eat the waste produced by the shrimp, who seem to benefit from the tilapia’s ability to fight off the bacteria Vibrio harveyi – one of the main pathogens affecting shrimp. With her fellowship, Naim will undertake a post-doc at Harvard Medical School to pursue her study of shrimp pathology via the infectious myonecrosis virus (IMNV).
Some were baffled by her desire to study shrimp disease at a medical school, but Naim explains the logic. “Viruses within the same family share similar characteristics, and it’s easier to study human viruses in the animal version [for reasons of safety and ethics].” Similarly, as Naim points out, Bonnie Bassler, the Princeton microbiologist and 2012 L’Oréal-UNESCO laureate, investigated bacterial communication using V. harveyi, which is biochemically similar to the human pathogen causing cholera. Her characterization of the bacteria has now proved relevant to Naim’s work to enhance shrimp farming, too. Next, in the lab of Max Nibert, Naim will undertake molecular studies of IMNV. “In Arizona, I learned to diagnose shrimp disease, but to be a real doctor, you have to know how to treat it, too. At Harvard, I will try to fully understand the virus to know better how to treat it.”
To begin this investigation, Naim explains that they always start from what they see in the field. “We observed cases where replication of the virus was reduced, and we want to know what’s going on at the molecular level. Is it the virus that lost the ability to express certain genes? Or is it because the shrimp developed some form of defense? Right now, it looks more like the virus has lost an ability. What we have observed is that optimum replication takes place at 30°C, not less. In the [natural environment], you can’t control the temperature, but we try to understand the mechanism behind it.”
Unraveling the basic biology of a species and its interaction with the environment provides opportunities to keep it healthy and, in this case, to farm it more effectively. This is also the objective of ecoyphysiologist Zoë Hilton, investigating shellfish cultures on the other side of the world. Dr. Hilton works at the Cawthron Institute in New Zealand, where the focus is on breeding mussels, scallops, abalone, Pacific oysters and flat oysters, with the ultimate goal of selectively breeding stronger, bigger, healthier, or more disease resistant animals.
Dr. Hilton explains that shellfish are such an ancient group that they have evolved great diversity among species. This can be seen in one aspect of their lifestyle that she studies: their reproductive behavior. Some species, like mussels, are broadcast spawners: males and females release their respective sperm and eggs into the aquatic milieu where fertilization occurs. Right from the start, the larvae that hatch from the eggs must fend for themselves. These species are relatively easy to breed in captivity and are very prolific: mussels can spawn every six weeks, producing millions of tiny eggs each time.
At the other extreme are “brooders”, like the New Zealand flat oyster. Hermaphrodites that switch sex throughout the breeding season, they require several months of conditioning, taking up food to nourish themselves and their eggs. The dormant period following conditioning must include a cold snap, mimicking winter, which will induce the oysters to spawn. Compared to mussels, they produce very few eggs – only about 150,000. Most unusual, though, is the fact that these shellfish take their role as parents quite seriously, brooding their offspring within the shell until the larvae metamorphose into spat, or tiny adults, and crawl out.
With her fellowship, Dr. Hilton will work at the Catalan Institute for Food and Agricultural Research and Technology (IRTA) in Tarragona, Spain, studying the European flat oyster (Ostrea edulis). This species is only a partial brooder, retaining its young inside the shell just through the beginning of larval development. What she learns here about the process of spawning and the requirements for larval rearing that lead to metamorphosis will help in understanding the more extreme reproductive process of New Zealand’s oysters (Ostrea chilensis).
Like Naim, arming herself with as much shrimp medical knowledge as she can before returning to Indonesia, Zoë aims to understand more and more about the workings of these species, because of the huge promise for aquaculture. “With land-based agriculture, an enormous amount of fresh water is needed to raise animals and to grow the grains that feed them, while the planet is covered in oceans!” The space available for shellfish farming along the world’s coastlines is significant and its environmental impact relatively small. Zoë says she wouldn’t keep going with her work if she couldn’t see the big picture and the help it can provide. For Naim, although she studies shrimp, her story is really about people. Even if neither scientist ever imagined doing this work, the broader impact of their research is clear to both. “Sometimes,” says Naim “a wrong turn leads to the right path.”
Find out more:
National Oceanic and Atmospheric Administration (NOAA) - Fisheries Service https://www.fisheries.noaa.gov/topic/aquaculture
WWF Aquaculture https://www.worldwildlife.org/industries/farmed-seafood
Fisheries and Oceans Canada – Aquaculture https://www.dfo-mpo.gc.ca/aquaculture/index-eng.htm
