Spatial and Temporal Variation of Cestode Infection and its Effects on Two Small Barbs (Barbus humilis and B. tanapelagius) in Lake Tana, Ethiopia |
| |
Authors: | Eshete Dejen Jacobus Vijverberg Ferdinand A Sibbing |
| |
Institution: | (1) Experimental Zoology Group, Wageningen Institute of Animal Sciences, Marijkeweg 40, 6709 PG Wageningen, The Netherlands;(2) Netherlands Institute of Ecology (NIOO-KNAW), Centre for Limnology, Rijksstraatweg 6, 3631 AC Nieuwersluis, The Netherlands;(3) Present address: Eshete Dejen, Amhara Region Agricultural Research Institute, P.O. Box 527, Bahir Dar, Ethiopia |
| |
Abstract: | Pseudophyllidean cestodes as Ligula have a complex life cycle with cyclopoid copepods as first intermediate host, zooplanktivorous fish as second, and piscivorous
birds as final host. We studied the effects of diet, season and habitat occupation on the prevalence of plerocercoid larvae
of the tapeworm Ligula intestinalis in two closely related small barbs and the effects of the parasites on the barbs life histories in Lake Tana (Ethiopia) during
1 year. In all affected barbs L. intestinalis caused retardation in gonad development, maturation at reduced size and lower absolute fecundity. Infection rate, averaged
over all habitats was significantly higher in B. tanapelagius (10%) than in B. humilis (6%). Below a threshold of 48 mm the infection rate was zero for both barbs, this coincided with a very low proportion of
copepods in their diets, increasing up to 90 and 55%, respectively, for their largest size class (81–90 mm). The relatively
high infection rate in B. tanapelagius is explained by its obligatory zooplanktivorous feeding behaviour, ingesting a relatively high proportion of infected cyclopoid
copepods. This is in contrast with B. humilis, which is a polyphagous species, feeding both on zooplankton and benthic invertebrates. Significant seasonal effects in infection
rates were observed. In both barb species infection rates were lower during the breeding season. Only for B. tanapelagius a significant negative correlation was observed between rain fall and infection rate, probably caused by an increased turbidity
that decreases feeding efficiency on zooplankton. Habitat type had also a significant effect on infection rate. Barbus humilis showed a much higher infection rate in shallow clear water (10%) than in shallow turbid water (3%), whereas B. tanapelagius showed much higher infection rates in the shallow sublittoral (13%) than in the deeper pelagic (7%). Most likely, birds predate
more efficiently on barbs in shallow clear waters than in shallow turbid and deep waters. |
| |
Keywords: | African lakes habitats parasite pressure reproduction zooplankton piscivorous birds |
本文献已被 SpringerLink 等数据库收录! |
|