Microhabitat Selection and Eyefluke Infection Levels in the Western Mosquitofish (Gambusia affinis)

Abstract

Several trematode species infect the eyes of fish as second intermediate hosts. In most cases the definitive host is a piscivorous bird. Studies of a few species have shown an increase in transmission due to decreased visual acuity of the fish host. However, this may vary depending on trematode microhabitat choice within the eye. Some trematode species are found in the lens, some are found in the vitreous humor, and others have been reported from the retina. Here we report 3 genera of eyeflukes in 3 locations of the eye in the intermediate fish host, Gambusia affinis . Clinostomum metacercariae were found attached to the outer sclera within the eye orbit, and Diplostomum metacercariae were found in the lens. Posthodiplostomum metacercariae were confirmed by histology to reside between the choroid and pigmented retina. Posthodiplostomum metacercariae were found in both eyes of all 20 fish examined and in high intensities (up to 27 metacercariae per eye). High trematode intensities between the choroid and pigmented retina found in this study may disrupt vision in this fish host. Our study is the first to document the microhabitat of all 3 trematode metacercariae within the eye of G. affinis .

Putting infection on the map: Using heatmaps to characterise within- and between-host distributions of trematode metacercariae

“…Additionally, parasite density within specific microhabitats has potential consequences for the host, especially for cases where pathology is a function of infection intensity and location. For instance, aggregation of diplostomatid trematodes within the eyes of fish can disrupt vision and reduce host fitness (Griffin et al 2017; Grobbelaar et al 2015; Seppälä et al 2005). Observations such as these highlight the importance of understanding fine-scale variation in parasites’ use of microhabitats within their hosts.…”

“…Many parasites also show remarkable specificity in their distribution within individual hosts or the microhabitat. We define a parasite microhabitat as a small area or niche region of habitat within the surrounding or larger habitat (e.g., host; Griffin et al 2017;Holmes 1973;Marcogliese 2005;Rohde 1994). Microhabitat preferences may be selected to maximise initial infection success, total growth and reproduction or subsequent transmission (Montgomery and Roloff 2017;Poulin 2005;Sukhdeo and Sukhdeo 1994).…”

Histopathological characterisation of retinal lesions associated to Diplostomum species (Platyhelminthes: Trematoda) infection in polymorphic Arctic charr Salvelinus alpinus

“… Crowden and Broom, 1980 , Shigin, 1986 , Chappell et al, 1994 ). The effects of lens infecting diplostomids have been reported widely, although few histopathological studies of the lens or other infected eye tissues are available ( Williams, 1967 , Chappell, 1967 , Lester and Huizinga, 1977 , Shariff et al, 1980 , Grobbelaar et al, 2015 , Stumbo and Poulin, 2016 , Griffin et al, 2017 ). Typical alterations and lesions documented from eyefluke infection in the lens are exophthalmia, local haemorrhage, lens cataract, thickening or complete destruction of the lens, reduced fish growth, emaciation and deformities of the vertebral column.…”