Authors

Discussion

Metacercariae of Diplostomum (Digenea: Diplostomoidea)are well known for their pathogenic effects on their fish intermediate hosts as well as their potential to change host behaviour. In Africa, no published data is available on the effects of Diplostomum metacercariaeon fish behaviour; especially on bottom-feeding fish. Therefore, our study aimed to determine the effects of Diplostomum on the behaviour of the Plain squeaker Synodontis zambezensis Peters, 1852 (Mochokidae). A total of 46 S. zambezensis were collected from the Phongolo River in the Ndumo Game Reserve in the Kwazulu-Natal Province of South Africa. Metacercariae were recovered from the eyes of 26 individuals with an overall intensity of 1–12 metacercariae per fish (Prevalence = 57%). Prior to a second sampling trip, ten S. zambezensis were used in a laboratory-based quantitative behavioural acclimatisation experiment in order to determine baseline values. Thereafter 22 fish were used in two different field simulated predator attack experiments. Statistical analysis revealed significant differences (p< 0.05) in behaviour between infected and uninfected S. zambezensis during acclimation and attacks based on time spent in top and bottom zones, frequency of zone alternations, minimum and maximum acceleration and mobility state (immobile – highly mobile). Our study is the first to show significant effects of Diplostomum on the behaviour of bottom-dwelling fish hosts in Africa.

Keywords: Noldus EthoVision, Swimming behaviour, Synodontis zambezensis, Trematoda,Metacercariae, Fish parasites