Susceptibility of gametes and embryos of the eastern oyster

To help get a better idea of the workings of the biological world, researchers pay special attention to the interactions that occur among organisms in the same ecosystems. These relationships are defined by mutual circumstances, but the effects that organisms have on each other is not always mutually beneficial. There are times when a certain species can benefit another without receiving any benefit itself and there are other times when one species harms, either intentionally or unintentionally, another species. Understanding how this happens and what can explain it can go a long way to understanding how organisms interact with one another and the effect they can have on each other. A study by Rolton et al. on the eastern oyster does just that. They wanted to look at the effects of harmful algal blooms (HABs) on the gametes and embryos of this bivalve species. HABs can affect co-occurring species by producing toxins, physical contact or increased biomass. Recent studies indicate that HABs can affect fertility, growth, development and the ultimate survival of bivalve larvae.

In the Gulf of Mexico, the primary HAB species is Karenia brevis and it occurs in this body of water on a near annual basis. This is of particular interest to researchers since its blooming period corresponds almost exactly to the spawning of the Crassostrea virginica oyster that populates the eastern waters of the Gulf of Mexico. This leaves gametes and larvae extremely vulnerable to the effects of K. brevis. Previous studies had shown effects on larvae size and an increase in larval abnormalities, but no attention has been paid to the effect on gametes, which could have additional negative effects on larvae. However, the question that has arisen from all these previous research is: what other harmful, chemically uncharacterized compounds are also associated with the observed effects? Essentially, Rolton and her colleagues were trying to isolate the cause of the effects to determine if K. brevis can be blamed for what was observed.

What they found is that indeed K. brevis can be held responsible. By examining several different properties, such as mitochondrial membrane potential, researchers were able to isolate extracellular brevetoxins as the primary cause of gamete and larvae abnormalities. To obtain these results Rolton and her team used the JC-10™ indicator to track changes in mitochondrial membrane potential. The varying colors emitted depending on excitation help to facilitate this. As excitation increases, the color emitted from the indicator switches from green to orange-green. This helps to clearly indicate the activity and allows for easy interpretation. Also, JC-10™ has improved solubility and is therefore less likely to precipitate in aqueous solutions. This is particularly useful in a study like this involving marine organisms as it allows researchers to trust that the results they obtained were not tainted by any external conditions. Being able to confidently defend your results is a key component to a successful study and is facilitated with quality materials such as the JC-10™ indicator.

References

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1. Rolton, Anne, et al. "Susceptibility of gametes and embryos of the eastern oyster, Crassostrea virginica, to Karenia brevis and its toxins." Toxicon 99 (2015): 6-15.