Getting a grip on a parasitic algae

Tshililo enjoying the sights of Louisiana
Tshililo enjoying the sights of Louisiana

Tshililo Mphephu is a PhD student in the Centre for Biological Control (CBC) and recently spent two months in the USA as part of his studies. His research is focused on gaining an understanding of the effects and implications of a parasitic algal infection on the weevil, Cyrtobagous salviniae. The weevil Cyrtobagous salviniae was released in South Africa in 1985 for the control of the invasive floating weed, Salvinia molesta. In recent years, there has been a decrease in the number of Cyrtobagous salviniae weevils reared at the CBC mass rearing facility. This is thought to be due to a parasitic algal infection in the culture. The alga, Helicosporidium sp., was first detected from field-collected adults of C. salviniae in South Africa, in 2007. Tshililo's time in the US was spent conducting various experiments to understand the effects of Helicosporidium sp. He reports on his experiences as follows:

“As part of my Ph.D. project, I was granted the incredible opportunity to conduct some of my experiments at Louisiana State University (LSU). I was further placed under an international visiting research scholarship program of the university. Specifically, my visit at LSU aimed at determining the role of Helicosporidium sp. infection that is widely distributed in the field populations of Crytobagous salviniae in South Africa. This research follows the work reported the first detection of Helicosporidium sp. infection in Crytobagous salviniae in South Africa by S.E White, Philip W. Tipping and James J. Becnel in 2007. These researchers are based in the United States of America, USDA/ARS.

When I arrived in Louisiana, I was warmly welcomed by many researchers and students of LSU. Dr Rodrigo Diaz hosted me to run my experiments in his lab and mentored me through the process. He made it feel like home which I am extremely grateful for his generosity. Megan Mulchy (Ph.D. candidate at LSU and former Rhodes University MSc graduate) went out of her way to make sure that I enjoyed my time in Lousiana. An MSc student, Giovana Matos Franco, research assistant, Rachel Watson both made sure that my experiments ran smoothly which contributed to the results that I obtained.

Apart from my specific experiments, I was given the opportunity to participate in a big project which is currently receiving a lot of attention in Louisiana. This project involves the biological control of invasive reed, Phragmites australis, which is attacking native and dominant coastal plants in the Mississippi River and is led by Professor James T. Cronin. Additionally, I was introduced to the use of genetics to identify parasites or infectious species in insect body tissues by Dr Vinson Doyle and his lab assistants. I also attended LSU entomology internal symposium and MidSouth Aquatic Plant Management Society 38th Annual Meeting in Hilton Baton Rouge Capital Center, Lousiana.

Most importantly, the results of my experiments indicated that Helicosporidium sp. infections reduce the biomass impact and reproductive output of Crytobagous salviniae on Salvinia molesta. The mobility of Crytobagous salviniae was also affected by the presence of the infection. These conclusions were drawn from a comparison of the performance of the infected (in South Africa) and healthy adults (In Louisiana, United States of America) of Crytobagous salviniae. Therefore, these results call for a further step to subject the infected adults in South Africa to an effective treatment to establish a new and healthy colony for field releases.

This trip was very productive for my PhD research progress and I have grown as a researcher through this experience. Since my return, I have started working towards disinfecting Crytobagous salviniae from Helicosporidium sp. to restore the effectiveness of this weevil against Salvinia molesta in South Africa and elsewhere."


Tshililo attending the MidSouth Aquatic Plant Management Society 38th Annual Meeting in Hilton Baton Rouge Capital Center, Louisiana (left) and collecting some Cyrtobagous salviniae weevils in Baton Rouge with Seth Spinner (right)

Source:  Tshililo Mphephu and CBC Staff

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