Echinostoma revolutum

Geographic Range

Echinostoma revolutum can be found in the snail Lymnaea elodes in North America (Serensen et al., 1997) and in other lymnaeid species across Eurasia. It has been reported from Germany, Austria, Poland, Bulgaria, England, Russia, Malaysia, Thailand, India, and Vietnam (Kanev, 1994).

• Biogeographic Regions
• nearctic nearctic
  • native native
• palearctic palearctic
  • native native
• oriental oriental
  • native native

Habitat

Eggs of Echinostoma revolutum are found in fresh water habitats (Kanev, 1994) where waterfowl occur. The subsequent life stages are all found in intermediate or definitive hosts, all of which are found in the same still or slow-moving freshwater habitats. As a miracidium, E. revolutum can be found in the ovotestis or digestive gland of the intermediate host (Kanev, 1994). Studies have shown that Lymnaea stagnalis is a widespread spread and common intermediate host for E. revolutum (Kanev, 1994).

• Habitat Regions
• temperate temperate
• tropical tropical
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• temporary pools

• Wetlands
• marsh marsh
• swamp swamp

Physical Description

E. revolutum is the nominal member of the 37-collar-spined E. revolutum group (Kanev, 1994; Kanev et al., 1995). The group consists of the closely related species: E. revolutum (Froelich, 1802), E. echinatum (Zeder, 1803), E. trivolvis (Cort, 1914), E. jurini (Skvortzov, 1924), E. caproni (Richard, 1964), and E. paraensei (Lie and Basch, 1967). All miracidia in this group have eighteen epidermal plates, showing a common pattern of 6:6:4:2 (anterior to posterior), six body papillae, two eyespots, and two excretory pores (Dimitrov et al., 1999).

At time of initial infection, metacercariae average 240 micrometers long and 0.02 square mm in body area. By day 14 post infection, worms reach an average of 3.5 mm in length and 2.0 square mm in body area (Humphries et al., 1997).

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

Development

Adult E. revolutum use avian species, primarily waterfowl as their definitive hosts. Adults are hermaphrodites and live four to eight weeks, occupying the digestive tract of infected birds (Sorensen and Minchella, 1998). Adults begin to produce and release many self-fertilized eggs ten days after infecting the definitive host (Kanev, 1994).

Eggs: The eggs hatch in fresh water in nine to twelve days. Exposure to light stimulates hatching. Eggs hatch into miracidia (Kanev, 1994).

Miracidium: The swimming larval stage can survive six to eight hours before it finds a primary intermediate host, which must be a snail in the family Lymnaeidae (Kanev, 1994). Once a miracidium successfully infects the ovotestis/digestive gland area of the host, it asexually produces three distinct asexual stages, a mother sporocyst and two subsequent redial stages over the course of a month (Sorensen and Minchella, 1998). The final redial produces infective free living cercaria for 25 to 28 days (Kanev, 1994). The cercaria exits the primary intermediate host and infects a secondary intermediate host.

Cercariae: The initialy free-living form infects an aquatic secondary intermediate host within three to six hours. This host can be various pulmonate and prosobranch snails, freshwater mussels ( Unionidae ), frogs , and freshwater turtles ( Testundines ) (Kanev, 1994). In the host, cercaria asexually produce metacercariae (Sorensen and Minchella, 1998).

Metacercariae: This stage becomes infective within one to two days (Kanev, 1994). It remains in this stage until the secondary intermediate host has been eaten by the definitive vertebrate host, usually a bird. Once ingested, metacercariae develop into hermaphroditic adults (Sorensen and Minchella, 1998).

• Development - Life Cycle
• metamorphosis metamorphosis
• diapause diapause

Reproduction

Adult Echinostoma revolutum are hermaphrodites, and produce both self-fertilized and cross-fertilized eggs once in the definitive host. We have no information on mating behavior or mating systems in this species.

This species reproduces asexually at two stages in its life cycle. Sporocysts and rediae, both produce large numbers of offspring asexually, resulting in hundreds or thousands of cercarie generated from a single parent miracidium infecting a snail. Adults worms are hermaphroditic and self- and cross-fertilize.

'Echinostome Echinostoma parasitism peaks in the late summer and wanes throughout the winter (Sorensen and Minchella, 1998).

The trematode, E. revolutum , has a complex three-host life cycle. Adult E. revolutum use avian species, primarily waterfowl as the definitive host (Sorensen and Minchella, 1998). Adults are hermaphrodites and live four to eight weeks. Adults begin to produce and release many self fertilized eggs ten days after infecting the definitive host (Kanev, 1994). Adults after 14 days contain at least 50 eggs (Humphries et at., 1997). Eggs are passed by feces of the definitive host (Sorensen and Minchella, 1998).

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• simultaneous hermaphrodite
• sexual sexual
• asexual asexual
• fertilization fertilization
  • internal internal
• oviparous oviparous

There is no parental investment beyond the limited provisioning of eggs.

• Parental Investment
• no parental involvement
• pre-fertilization
  • provisioning

Behavior

Miracidia and cercariae are active host-seeking larvae that swim. The other stages of this species can move within their hosts, but do not leave them.

• Key Behaviors
• natatorial natatorial
• parasite parasite
• motile motile
• sedentary sedentary

Communication and Perception

Miracidium are are positively phototactic. Cercariae are negatively phototactic (Kanev, 1994).

• Perception Channels
• visual visual
• chemical chemical

Food Habits

Sporocysts lack ambulatory musculature and absorb primary intermediate host nutrients via their tegument. Rediae have a muscular pharynx and primitive gut. Rediae actively consume and digest primary intermediate host tissues while moving throughout the infected host (Sorensen and Minchella, 1998).

Predation

We have no information on particular predators of this species. It is likely that the host-seeking stages (miracidia, cercariae) are consumed by predators that eat zooplankton. This species depends on predation of its intermediate host to enter its definitive avian hosts.

Ecosystem Roles

Infection of Lymnaea elodes by E. revolutum significantly affects growth, fecundity, and survival rates (Sorensen and Minchella, 1998). Snail mortality between zero and four weeks post infection can be attributed to an increase in energetic demands and starvation, while snails four to seven weeks post infection die from tissue degredation (Sorensen and Minchella, 1998).

At five weeks post infection E. revolutum pathology involves destruction of the digestive gland and ovotestis (Sorensen and Minchella, 1998). This type of parasitic castration along with reduced nutrients results in a reduction in snail egg production. It is proposed by Sousa (1983) that gigantism will occur in trematode infected mollusc species because excess host energy reserves are made available via parasitic castration.

Brown et al. (1988) and Sorensen and Minchella (1998) both demonstrate a correlation between increased snail size and trematode infection. E. revolutum infection tends to cause gigantism in lymnaea species. In 1975, Baudoin presented hypotheses to explain the correlation between host size and prevalence of infection. These hypotheses included three basic mechanisms including increased host growth rates, host mortality rates, and host size-specific preferences of parasites. It is proposed that a combination of multiple hypotheses will result in gigantism of the host (Sorensen and Minchella, 1998).

Economic Importance for Humans: Positive

In Indonesia, Suhardono et al. (2006) have shown that E. revolutum will act competitively to infect Lymnaea rubiginosa . L. rubiginosa is more commonly infected by Fasciola gigantica . L. rubiginosa infected with F. gigantica causes fasciolosis in cattle stocks feeding on harvested rice crop infested with the snails. E. revolutum will compete with F. gigantica , and when successful, prevents F. gigantica from infecting L. rubiginosa (a necessary stage in its life cycle). Inhibition of F. gigantica prevents further life stages and consequently prevents parasitic infection of cattle. E. revolutum will occupy the intermediate host ( L. rubiginosa ) but will not infect the cattle feeding on the rice crop.

Economic Importance for Humans: Negative

Worms in the genus Echinostoma have been known to infect humans who have eaten raw snails or other molluscs.

• Negative Impacts
• injures humans
  • causes disease in humans causes disease in humans

Conservation Status

The world-wide population size of this species is unknown. It has not been considered for conservation status by any agency.

Additional Links

Encyclopedia of Life

Contributors

Michael Kortbawi (author), Rutgers University, Rosiane Lesperence (author), Rutgers University, Natasha Lloyd (author), Rutgers University, Alexa Martinez (author), Rutgers University, David V. Howe (editor), Rutgers University, George Hammond (editor), Animal Diversity Web Staff.

References

Baudoin, M. 1975. Host castration as a parasitic strategy. Evolution , 29: 335-352.

Brown, K., B. Leathers, D. Minchella. 1988. Trematode prevalence and the population dynamics of freshwater pond snails. American Midland Naturalist , 120: 289-301.

Dimitrov, V., I. Kanev, R. Sorensen, M. Alxexiev, M. Nestorov, V. Radev. 1999. Studies on the argentophilic structures of two populations of Echinostoma revolutum (Frolich, 1802) (Trematoda:Echinostomatidae) miracidia. Experimental Pathology and Parasitology , 3: 3-6.

Humphries, J., A. Reddy, B. Fried. 1997. Infectivity and Growth of Echinostoma revolutum (Froelich, 1802) in the Domestic Chick. International Journal for Parasitology , 27/1: 129-130.

Kanev, I., B. Fried, V. Dimitrov, V. Radev. 1995. Redescription of Echinostoma trivolvis (Cort, 1914) with a discussion on its identity. Systematic Parasitology , 32: 61-71.

Kanev, I. 1994. Life-cycle, delimitation and redescription of Echinostoma revolutum (Froelich, 1802) (Trematoda: Echinostomatidae). Systematic Parasitology , 28: 125-144.

Sorensen, R., I. Kanev, B. Fried, D. Minchella. 1997. The occurrence and identification of Echinostoma revolutum from North American Lymnaea elodes snails. Journal of Parasitology , 83(1): 169-170.

Sorensen, R., D. Minchella. 1998. Parasite influences on host life history: Echinostoma revolutum parasitism of Lymnaea elodes snails. Oecologia , 115: 188-195.

Suhardono, , J. Roberts, D. Copeman. 2006. Biological control of Fasciola gigantica with Echinostoma revolutum . Veterinary Parasitology , 140: 166-170.