Effects of temperature and salinity on the life cycle of Neobenedenia sp. (Monogenea: Capsalidae) infecting farmed barramundi (Lates calcarifer)
Effective parasite management can be achieved through strategically timed treatments that break the life cycle. We examined the effects of temperature (2 °C increments from 22 to 34 °C) and salinity (0, 11, 22, 35, 40 ‰) on the life cycle (embryonation period, hatching success, oncomiracidia (larvae) longevity, infection success, and time to sexual maturity) of Neobenedenia sp. (Monogenea: Capsalidae), a harmful ectoparasite of farmed marine fishes. Experiments were conducted in controlled conditions in the laboratory. The life cycle was faster in warm, high saline conditions compared to cooler conditions (10–13 days between 26–32 °C, 40 ‰; 15–16 days between 22–24 °C at 40 ‰). Warm seawater and high saline conditions (24–32 °C, 35–40 ‰) improved egg hatching success, reduced time to sexual maturity, and resulted in parasites reaching sexual maturity at a larger size (at 30–32 °C) compared to cooler conditions (22 °C). In contrast, cool, hypersaline conditions (22 °C, 40 ‰) increased oncomiracidia longevity and infection success. Linear and quantile regression models were used to construct an interactive, online parasite management interface to enable strategic treatment of parasites in aquaculture corresponding to observed temperature and salinity variation on farms in the tropics. It was recommended that farmers treat their stock more frequently during summer (27–31 °C) when parasites can complete their life cycle more quickly. Nevertheless, farmers should be aware of the potential for increased Neobenedenia sp. infections during winter months (21–26 °C) due to increased infection success.
KeywordsAquaculture Treatment Asian sea bass Monogenea Neobenedenia Egg hatching
We thank Thane Militz and Alejandro Trujillo-Gonzalez of the Marine Parasitology Laboratory, James Cook University, for their assistance in maintaining the experimental infection. Dr. Jeremy VanDerWal and Daniel Baird provided invaluable assistance in linear and quantile regression modelling and development. Queensland barramundi farms provided parasite and fish specimens for this research. We thank Associate Professor Ian Whittington for his advice in maintaining the laboratory infection. An Australian Society for Parasitology (ASP) Student Travel Award granted to AKB enabled the presentation of this research at the ASP annual conference, 2012. This research was funded by James Cook University, a National Climate Change Adaptation Research Facility (NCCARF) Marine Adaptation Network Honours and Masters Research Support Grant awarded to AKB (NCCARF; project no. NATCLI97) and the Fisheries Research and Development Corporation-Department of Climate Change and Energy Efficiency (FRDC-DCEE project no. 2010/521).
Conflict of interest
The authors declare that there was no conflict of interest that biased the reporting of results in this manuscript.
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