invasions may impact on zooplankton communities and thereby influence food
webs. Its impacts on, and interactions with, native biota have not been researched
in South Africa.
6.2.4 Nematoda
The only documented alien freshwater nematode is the recently-discovered
Camallanus cotti, a generalist fish parasite native to Asia, and was found on guppies
(P. reticulata) sampled from the Inkomati basin (Tavakol et al. 2017).
6.2.5 Annelida
The aquatic earthworm Eukerria saltensis inhabits the roots of aquatic vegetation,
and is thought to have been introduced from South America, It has been spread
globally and is naturalised throughout the southern hemisphere (Christoffersen
2008). In South Africa, it occurs in variety of moist biotopes along rivers and
impoundments in most of the country.
6.2.6 Mollusca
Molluscs are one of the largest invertebrate groups in South Africa with >5000
species in freshwater, marine and terrestrial environments (Hebert et al. 2011).
Thirteen alien freshwater snails are known to be present in South African fresh
waters, ten of which were introduced via the aquarium and/or ornamental plant trade
(Appleton and Miranda 2015; Lawton et al. 2018). Seven of these species have
naturalised and four—Quilted Melania Tarebia granifera (Fig. 6.3a), Reticulate
Pond Snail Lymnea columella, Sharp Spired Bladder Snail Physa acuta (Fig. 6.3b)
and Slender Bladder Snail Aplexa marmorata—are increasing their ranges (Appleton and Miranda 2015).
Terebia granifera invasions are a particular concern. This freshwater prosobranch
gastropod is native to Southeast Asia, and has invaded aquatic ecosystems in North
America, South America and Africa (Appleton et al. 2009). In South Africa, it was
most likely introduced as a stowaway in aquarium plants. It can reproduce
parthenogenically and its ovoviviparous reproductive strategy allows it to deposit
live young directly into recipient environments (Appleton et al. 2009). This reproductive strategy, coupled with a high salinity tolerance and its competitive feeding
strategy have allowed this species to establish populations in several South African
estuaries (Appleton et al. 2009). In its native range, T. granifera harbours a diverse
and prevalent fauna of trematodes (Appleton et al. 2009) that, as parasitic castrators,
164
O. L. F. Weyl et al.
webs. Its impacts on, and interactions with, native biota have not been researched
in South Africa.
6.2.4 Nematoda
The only documented alien freshwater nematode is the recently-discovered
Camallanus cotti, a generalist fish parasite native to Asia, and was found on guppies
(P. reticulata) sampled from the Inkomati basin (Tavakol et al. 2017).
6.2.5 Annelida
The aquatic earthworm Eukerria saltensis inhabits the roots of aquatic vegetation,
and is thought to have been introduced from South America, It has been spread
globally and is naturalised throughout the southern hemisphere (Christoffersen
2008). In South Africa, it occurs in variety of moist biotopes along rivers and
impoundments in most of the country.
6.2.6 Mollusca
Molluscs are one of the largest invertebrate groups in South Africa with >5000
species in freshwater, marine and terrestrial environments (Hebert et al. 2011).
Thirteen alien freshwater snails are known to be present in South African fresh
waters, ten of which were introduced via the aquarium and/or ornamental plant trade
(Appleton and Miranda 2015; Lawton et al. 2018). Seven of these species have
naturalised and four—Quilted Melania Tarebia granifera (Fig. 6.3a), Reticulate
Pond Snail Lymnea columella, Sharp Spired Bladder Snail Physa acuta (Fig. 6.3b)
and Slender Bladder Snail Aplexa marmorata—are increasing their ranges (Appleton and Miranda 2015).
Terebia granifera invasions are a particular concern. This freshwater prosobranch
gastropod is native to Southeast Asia, and has invaded aquatic ecosystems in North
America, South America and Africa (Appleton et al. 2009). In South Africa, it was
most likely introduced as a stowaway in aquarium plants. It can reproduce
parthenogenically and its ovoviviparous reproductive strategy allows it to deposit
live young directly into recipient environments (Appleton et al. 2009). This reproductive strategy, coupled with a high salinity tolerance and its competitive feeding
strategy have allowed this species to establish populations in several South African
estuaries (Appleton et al. 2009). In its native range, T. granifera harbours a diverse
and prevalent fauna of trematodes (Appleton et al. 2009) that, as parasitic castrators,
164
O. L. F. Weyl et al.