Parasitism is increasingly recognized as an important determinant of population dynamics, productivity and community structure in intertidal ecosystems, and yet there is very little known about the effect of parasites on polychaetes, which represent a major component of the benthic fauna. We surveyed 11 polychaete species from a mudflat in Otago Harbour, New Zealand, and found that seven of the...

In the vertebrate-dwelling adults of the digenetic trematodes spermatogenesis and oogenesis are not fundamentally different from these processes in other metazoan groups. The fertilized ovum in the egg develops directly into the miracidium which contains in its body cavity a varying number of germinal cells. After entering the molluscan intermediate host the miracidium metamorphoses into the pr...

The fundamental assumption underpinning the evolution of numerous adaptations shown by parasites with complex life cycles is that huge losses are incurred by infective stages during certain transmission steps. However, the magnitude of transmission losses or changes in the standing crop of parasites passing from upstream (source) to downstream (target) hosts have never been quantified in nature...

A malacological survey of permanent and temporary breeding sites was conducted in the Piedade neighborhood of Jaboatão dos Guararapes, Pernambuco, between November 2006 and November 2007, with the aim of determining the malacological fauna at this locality, along with the potential for Schistosomiasis mansoni transmission. In addition to Biomphalaria glabrata (Say, 1818), the molluscs Drepanotr...

Fishborne zoonotic trematodes (FZT) are widespread in Vietnam and Southeast Asia. It is now recognized that the risk of being infected from eating raw fish dishes applies not only to humans, but also to domestic animals (e.g., cats, dogs, and pigs) and fish-eating birds. The role of ducks and chicken, commonly raised on fish farms, as reservoir hosts, however, has not been adequately investigat...

Anthropogenic stressors such as pollutants can modulate levels of parasitic infections in aquatic animals by suppressing host immunity or through some other mechanisms. One such mechanism could involve increases in either the quantity or quality of infective stages produced by parasites. We investigated the effect of exposure of infected snails, Potamopyrgus antipodarum, to different concentrat...

Although latitudinal gradients in diversity have been well studied, latitudinal variation in the taxonomic composition of communities has received less attention. Here, we use a large dataset including 950 surveys of helminth endoparasite communities in 650 species of vertebrate hosts to test for latitudinal changes in the relative contributions of trematodes, cestodes, nematodes and acanthocep...

1. Variation in life-history strategies among conspecific populations indicates the action of local selective pressures; recently, parasitism has been suggested as one of these local forces. 2. Effects of trematode infections on reproductive effort, juvenile growth, size at maturity and susceptibility were investigated among different natural populations of the marine gastropod Zeacumantus subc...

A field trials were conducted to assess the helminth parasites of 12 marsh frogs (Rana ridibunda ridibunda) in the Anzali, Astara and Aghbaba regions in the north of Iran in May 1994. Experimental results showed that 83.8% of the Anzali marsh frogs were infected by one or two kinds of metacercarian cysts of digenetic trematodes. The helminth parasites were included Skrjabinoeces breviansa, S. s...

A field trials were conducted to assess the helminth parasites of 12 marsh frogs (Rana ridibunda ridibunda) in the Anzali, Astara and Aghbaba regions in the north of Iran in May 1994. Experimental results showed that 83.8% of the Anzali marsh frogs were infected by one or two kinds of metacercarian cysts of digenetic trematodes. The helminth parasites were included Skrjabinoeces breviansa, S. s...