The effects of temperature on the distribution and establishment ofEchinoparyphium recurvatummetacercariae inLymnaea peregra

Abstract

The establishment and distribution of Echinoparyphium recurvatum metacercariae in the second intermediate host, Lymnaea peregra, were investigated at a temperature range of 5-29 degrees C. Preliminary studies on the survival and infectivity of E. recurvatum cercariae showed that both parameters were temperature dependent. No cercarial transmission occurred at 5 or 10 degrees C. Nevertheless, the transmission efficiency (1/H0) indicated that transmission was temperature independent in the temperature range 17-25 degrees C and was much lower than in previous studies using this host-parasite system. These differences were attributed to low cercarial densities used in this study. The effect of temperature on encystment site choice (mantle cavity, kidney, pericardium) by metacercariae showed that the mantle cavity was the prime site of encystment, followed by the pericardium and the kidney. Temperatures at the lower and upper ranges (14 and 29 degrees C), however, caused a significant reduction in encystment in the mantle cavity but not in the pericardium or kidney. The importance of cercarial densities, the physiological mechanisms influencing metacercarial distribution and their implications for parasite transmission to the definitive host are discussed.

The effects of host size and temperature on the emergence ofEchinoparyphium recurvatumcercariae fromLymnaea peregraunder natural light conditions

“…Therefore the transmission of E. recurvatum is unlikely to increase with elevated temperatures, in contrast to the general conclusions of Poulin (2006) on cercarial emergence under global climate change. Indeed, prolonged high temperatures are likely to result in reduced cercarial emergence (present study) and transmission (Morley et al , 2007). It is possible that other temperate freshwater trematode species may demonstrate a similar thermal response and, consequently, raised temperatures at these latitudes may not result in significant increases in cercarial abundance.…”

“…The stability of E. recurvatum cercarial emergence (present study) and transmission (Morley et al, 2007) in the temperature range 17 -258C may be due to the wide climatic conditions encountered by this species at both temperate latitude and within the shallow freshwater habitats where the snail host is commonly found. Indeed, studies on E. recurvatum metacercarial prevalence and intensity within second intermediate molluscan hosts indicate a gradual accumulation over the summer period, reaching a maximum in September when temperatures are lower than their peak in July (Morley et al, 2004c).…”

“…Indeed, prolonged high temperatures are likely to result in reduced cercarial emergence (present study) and transmission (Morley et al, 2007). It is possible that other temperate freshwater trematode species may demonstrate a similar thermal response and, consequently, raised temperatures at these latitudes may not result in significant increases in cercarial abundance.…”

“…Echinoparyphium recurvatum is a cosmopolitan echinostome of freshwater snails and birds in the UK and has been studied extensively. In particular, laboratory investigations have focused on cercarial transmission into a range of molluscan species, acting as second intermediate host, for elucidating transmission dynamics (Evans & Gordon, 1983a, b; McCarthy, 1990, 1999a, b; Adam & Lewis, 1992; Morley et al , 2007) and the impact of pollutants (Evans, 1982; Morley et al , 2002, 2004a, c). Nevertheless, studies on cercarial emergence have received limited attention.…”

Effect of temperature changes on the cercarial-shedding rate of two trematodes

“…II [3]; Terhune et al, 2002;Tab. II [4]; Morley et al, 2007Morley et al, , 2010, while others exposed the host individuals abruptly to different temperatures (Schmidt & Fried, 1996;Fried et al, 2002;Koprivnikar & Poulin, 2009a;Vignoles et al, 2014;Paull et al, 2015). Despite differences in the expression of results or the protocol for evaluating the effect of temperature, the examples listed in Tab.…”