Development and Intensity Dependence of Ornithodiplostomum ptychocheilus Metacercariae in Fathead Minnows (Pimephales promelas)

Abstract

Intensity-dependent development of Ornithodiplostomum ptychocheilus metacercariae was studied in fathead minnows (Pimephales promelas) exposed to 0, 20, or 120 cercariae. Subsamples of hosts were necropsied at 2-wk intervals to monitor parasite recruitment, growth, and time to encystment. The complex development of metacercariae within the cranium of minnows involved growth, encystment, and consolidation phases, each of which were affected by intensity. At the end of the growth phase, metacercariae from low-dose fish were 20% longer than those from high-dose fish and the latter took 2-4 wk longer to encyst. At the end of the postencystment consolidation phase (6-8 wk postinfection), the size of metacercariae decreased by approximately 50%. The rate of consolidation was slower in high-dose fish. Our results show that time, intensity, and temperature affect development of O. ptychocheilus. Because metacercariae development and differentiation are linked to infectivity, events occurring in intermediate hosts can potentially impact the structure and size of trematode suprapopulations.

Parasite manipulation of brain monoamines in California killifish ( Fundulus parvipinnis ) by the trematode Euhaplorchis californiensis

“…Briefly, cercariae were stimulated to shed from C. californica by holding snails dry and dark for at least 1 week, followed by immersion in seawater for 2-3 h under an incandescent lamp. Cercariae were then collected, pooled and quantified following procedures described in Sandland & Goater (2000). Fish were exposed to cercariae or sham-exposed to seawater in buckets with 8 l seawater for 2 h. Although E. californiensis metacercariae are infective to definitive hosts after 2 weeks, we allowed 4 weeks for infections to mature before sampling (Martin 1950).…”

The influence of clonal diversity and intensity-dependence on trematode infections in an amphipod

“…Indeed, reductions in metacercariae size with increasing parasite load have been detected in several trematode species (Sandland and Goater, 2000 ;Brown et al 2003 ;Fredensborg and Poulin, 2005). Unlike many trematodes, M. novaezealandensis metacercariae grow and develop substantially during the first few weeks after infection (Poulin and Latham, 2003 ;Fredensborg et al 2004).…”

“…This was most likely due to differences in average room temperature between the two series. Below a certain threshold, the growth rate of metacercariae often increases with increasing temperature (Chubb, 1979 ;Sandland and Goater, 2000). Mean daily temperatures varied significantly between series (series 1 mean temperature¡S.D.= 12 .…”

“…Reductions in trematode growth have been documented when increasing numbers of metacercariae share the same intermediate host (Sandland and Goater, 2000 ;Brown et al 2003). Theoretically, the optimal size that a parasite should reach within its intermediate host also depends on its relatedness to other parasites in the same host (Parker et al 2003).…”

Natal-Host Environmental Effects on Juvenile Size, Transmission Success, and Operational Sex Ratio in the Entomopathogenic NematodeSteinernema carpocapsae

“…Trade-offs between offspring size and number have been seen across parasite species (Loker, 1983;Poulin, 1995), and although rarely examined, within species as well (Herreras et al, 2007). More commonly, density or crowding is seen to reduce the size, fecundity, or both of individuals within a given host (Sandland and Goater, 2000;Ryder and Griffin, 2002;Milonas, 2005). As in free-living species, these competitive effects may affect the sexes differently (Zervos, 1988;Lowrie et al, 2004) or result in sex-ratio shifts (Izraylevich and Gerson, 1996;Lebreton et al, 2010).…”