Carp Ctenopharyngodon idella to control aquatic plants, and the Mosquitofish
Gambusia affinis to control mosquitoes, have resulted in invasions and impact
(Ellender and Weyl 2014).
6.2 South Africa’s Alien Freshwater Fauna
6.2.1 Protozoa
Current knowledge of alien freshwater protozoa is scant and is restricted to research by
fish parasitologists who have recorded one alien flagellate and eight ciliates introduced
as contaminants of alien fishes (Smit et al. 2017). Some of these have not been reported
from the wild, or information on their distribution is too scant to make any inferences.
For example, the ciliates Trichodina mutabilis, T. reticulata and T. uniforma are only
known from samples taken from C. auratus in captivity (Smit et al. 2017).
Four alien ciliates have been reported from native and alien fish populations in the
wild (Table 6.1). Ichthyophthirius multifiliis, the causative agent for the disease
ichthyophthiriosis or “White-Spot”, is now a common problem in aquaculture and
the pet trade that was most likely introduced together with C. auratus and spill-over to
native Mozambique Tilapia Oreochromis mossambicus, Straightfin Barb Enteromius
paludinosus and African Longfin Eel, Anguilla mossambica is reported (Smit et al.
2017). Apiosoma piscicola (Fig. 6.2a), a parasite that lives on the gills and body surface
of its host, was most likely introduced and spread together with C. carpio but has since
spread to alien M. dolomieu, and to at least eight native fish species in multiple locations
(Table 6.1; Smit et al. 2017). Similarly, infestation of the body surface, gills and fins of
freshwater fish hosts by the ciliates Chilodonella piscicola (Fig. 6.2b) and Chilodonella
hexasticha (Fig. 6.2c) cause chilodonellosis, a disease that has resulted in death of
O. mossambicus under culture conditions (Smit et al. 2017).
6.2.2 Platyhelminthes
All 16 known alien flatworms in freshwater ecosystems in South Africa are parasitic
organisms, either of fishes (Smit et al. 2017) or of crayfishes (Du Preez and Smit 2013).
Although many are widespread, they have strong affinities for the host with which they
were introduced. For example, no spillover to native fishes has been reported for the six
ancyrocephalid monogeneans found on Black Bass (Micropterus spp.), despite the
almost ubiquitous presence of its fish hosts in South African ecosystems (Truter et al.
2017). Others, such as the Asian Tapeworm Schyzocotyle acheilognathi, are not only
widespread, but have also spilled over to several native taxa (Smit et al. 2017).
Schyzocolyte acheilognathi (Fig. 6.2d) is a global invader that is known to be
capable of infecting more than 300 fish species (Smit et al. 2017). In South Africa,
S. acheilognathi was introduced in 1975 with infected C. idella from Malaysia. Its
subsequent spread was facilitated by the release of infected fish into the wild and by
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O. L. F. Weyl et al.
Gambusia affinis to control mosquitoes, have resulted in invasions and impact
(Ellender and Weyl 2014).
6.2 South Africa’s Alien Freshwater Fauna
6.2.1 Protozoa
Current knowledge of alien freshwater protozoa is scant and is restricted to research by
fish parasitologists who have recorded one alien flagellate and eight ciliates introduced
as contaminants of alien fishes (Smit et al. 2017). Some of these have not been reported
from the wild, or information on their distribution is too scant to make any inferences.
For example, the ciliates Trichodina mutabilis, T. reticulata and T. uniforma are only
known from samples taken from C. auratus in captivity (Smit et al. 2017).
Four alien ciliates have been reported from native and alien fish populations in the
wild (Table 6.1). Ichthyophthirius multifiliis, the causative agent for the disease
ichthyophthiriosis or “White-Spot”, is now a common problem in aquaculture and
the pet trade that was most likely introduced together with C. auratus and spill-over to
native Mozambique Tilapia Oreochromis mossambicus, Straightfin Barb Enteromius
paludinosus and African Longfin Eel, Anguilla mossambica is reported (Smit et al.
2017). Apiosoma piscicola (Fig. 6.2a), a parasite that lives on the gills and body surface
of its host, was most likely introduced and spread together with C. carpio but has since
spread to alien M. dolomieu, and to at least eight native fish species in multiple locations
(Table 6.1; Smit et al. 2017). Similarly, infestation of the body surface, gills and fins of
freshwater fish hosts by the ciliates Chilodonella piscicola (Fig. 6.2b) and Chilodonella
hexasticha (Fig. 6.2c) cause chilodonellosis, a disease that has resulted in death of
O. mossambicus under culture conditions (Smit et al. 2017).
6.2.2 Platyhelminthes
All 16 known alien flatworms in freshwater ecosystems in South Africa are parasitic
organisms, either of fishes (Smit et al. 2017) or of crayfishes (Du Preez and Smit 2013).
Although many are widespread, they have strong affinities for the host with which they
were introduced. For example, no spillover to native fishes has been reported for the six
ancyrocephalid monogeneans found on Black Bass (Micropterus spp.), despite the
almost ubiquitous presence of its fish hosts in South African ecosystems (Truter et al.
2017). Others, such as the Asian Tapeworm Schyzocotyle acheilognathi, are not only
widespread, but have also spilled over to several native taxa (Smit et al. 2017).
Schyzocolyte acheilognathi (Fig. 6.2d) is a global invader that is known to be
capable of infecting more than 300 fish species (Smit et al. 2017). In South Africa,
S. acheilognathi was introduced in 1975 with infected C. idella from Malaysia. Its
subsequent spread was facilitated by the release of infected fish into the wild and by
162
O. L. F. Weyl et al.