Distribution of Procamallanus laevionchus in relation to environmental variables in three tropical African rivers: The role of the host and ecosystem

Abstract

The suitability of parasites for environmental studies has generated a lot of discourses among parasitologists and ecologists in the most recent decades and the major issue of contention is the seeming unpredictability and unrepeatability of parasites’ response to environmental changes. This study was undertaken to evaluate the contribution of the host and ecosystem to the unpredictable response of parasites to environmental changes. We examined the distribution of Procamallanus laevionchus in three tropical rivers using Cichlidae, Mormyridae and Clariidae, natural hosts to the parasite. Fish samples were collected monthly between March 2005 and August 2006 from the Cross, Asu and Ebonyi Rivers, southeastern Nigeria and analysed for parasites. Our studies showed that the parasite-environment correlation was very weak and parasites did not exhibit seasonality despite significant seasonal changes in some water quality variables. However, the ecosystem (F = 5.7, p = 0.005) and the host (F = 3.3, p = 0.04) influenced prevalence significantly, while the host influenced intensity (F = 10.8, p = 0.0001). The interaction between the ecosystem and the host also influenced prevalence (F = 27.0, p = 0.0001) and intensity (F = 27.8, p = 0.005). Therefore, for P. laevionchus (a generalist parasite), the host and local stoichiometry were more important in shaping the population structure of the parasite than seasonal and generalized factors. Based on this, we advise that in environmental studies, parasites should be seldom used alone and when used, results should be interpreted cautiously.

Keywords:

• Procamallanus
• prevalence
• intensity
• environment
• tropical rivers