Prevalence and pathogenicity of a heterophyid trematode infecting the gills of an endangered fish, the fountain darter, in two central Texas spring-fed rivers
Aj. Mitchell et al., Prevalence and pathogenicity of a heterophyid trematode infecting the gills of an endangered fish, the fountain darter, in two central Texas spring-fed rivers, J AQUAT A H, 12(4), 2000, pp. 283-289
Gills of 194 fountain darters Etheostoma fonticola collected from the Comal
River in Texas from May 1997 through May 1998 were found to be parasitized
with 8-1,524 metacercarial cysts of a heterophyid trematode tentatively id
entified as Centrocestus formosanus. The intensity of infection Varied amon
g three sites on the Comal River. In contrast, of 130 darters from the near
by San Marcos River that were examined, only 4 (3%) were infected, and thes
e had 1-2 cysts per fish. Of 2,279 Melanoides tuberculata snails from the C
omal River that were examined, 139 (6.1%) were infected with the trematode.
Only 1 snail in 2,241 from the San Marcos River that were examined was inf
ected. The presence of metacercariae in darters was associated with flared
opercula, shortened or thickened gill filaments, epithelial hyperplasia, an
d engorged lamellae. The normal cartilage support of the filaments was dist
orted and displaced, leading to severe deformities of filament structure. G
ill damage was severe and possibly life threatening for the darters with mo
re than 800 cysts per fish (9% of examined fish). We suspect that fountain
darter deaths were caused by the parasite in the Comal River during this st
udy.