Leucochloridium paradoxum

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Geographic Range

The range of Leucochloridium paradoxum follows that of its host, snails of the genus Succinea that live in Europe and North America. (Dawes, 1946; Rennie, 1992)

Habitat

The worm is both an endoparasite of Succinea snails and of various birds such as crows, jays, sparrows and finches. It encounters these animals in temperate forests of North America and Europe. The egg is the only stage of development that exists outside of a host but it must remain moist to survive. (Dawes, 1946; Rennie, 1992)

Physical Description

The worm has different sizes and shapes throughout its development. The eggs are brown and oval shaped. After hatching, the miracidia or first stage larvae are clear and elongate. After transformation, the miracidia become sack-like objects called sporocysts. The sporocysts cause the eyestalks of their snail hosts to pulsate yellow, green, and red. Some sporocysts then give rise to cercaria, or juveniles, which have tails and a more complex digestive tract. The cercaria have a lined excretory bladder which extends into their tails a bit and the tails also have finfolds on the top and bottom as well as setae on the sides. The cercaria also have two eyespots. Cercaria quickly become an encysted metacercaria from which emerge the adults. The adults are spined, long, dorsally flattened, and have suckers for attachment within their definitive hosts. (Fried and Graczyk, 1997; Roberts and Janovy Jr., 2000)

Development

After a succinid snail ingests the worm's eggs, the sporocysts that arise from the miracidia have one of two destinies. Some sporocysts give rise to cercaria and others asexually produce more daughter sporocysts. When a bird ingests the snail, the remaining sporocysts become cercaria, which eventually develop into adults. The adults are monoecious, or hermaphroditic, although they can cross fertilize when in close proximity. The resulting eggs are released by the worms in the rectum and excreted by the bird host along with its feces. (Erasmus, 1972; Fried and Graczyk, 1997; Roberts and Janovy Jr., 2000)

Reproduction

Leucochloridium paradoxum reproduces asexually. The adults are monoecious, or hermaphroditic, although they can cross fertilize when in close proximity. The resulting eggs are released by the worms in the rectum and excreted by the bird host along with its feces. (Erasmus, 1972; Fried and Graczyk, 1997; Roberts and Janovy Jr., 2000)

There is no parental investment beyond the time eggs are released.

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

Behavior

For Leucochloridium paradoxum to continue development, it must be consumed by a snail of the genus Succinea. Once inside a snail, the eggs hatch into miracidia that then become sporocysts. Sporocysts accumulate in the hepatopancreas of the snail and in a broodsac in the head-foot of the host. Many sporocysts move to the tentacles of the snail. (Brand, 1979; Dawes, 1946; Rennie, 1992; Roberts and Janovy Jr., 2000)

Communication and Perception

Bristles and small spines probably act as tactile receptors, and these animals may have reduced chemoreceptors. (Brusca and Brusca, 2003; Roberts and Janovy Jr., 2000)

Food Habits

Leucochloridium paradoxum is an endoparasite of the rectum of birds as an adult. There it feeds on passing digested matter. It shows little definitive host specificity as it is known to parasitize more than fifteen bird species including crows, jays, sparrows and finches. As a sporocyst, the worm absorbs nutrients through its tegument from its intermediate hosts, Succinea snails. (Dawes, 1946; Roberts and Janovy Jr., 2000)

  • Animal Foods
  • body fluids
  • Other Foods
  • dung

Predation

These animals are probably not preyed on directly but are ingested. Egg and larval mortality are high since the parasites often do not reach appropriate hosts.

Ecosystem Roles

The worm is both an endoparasite of Succinea snails and of various birds such as crows, jays, sparrows and finches. It encounters these animals in temperate forests of North America and Europe. The egg is the only stage of development that exists outside of a host but it must remain moist to survive.

Species Used as Host

Economic Importance for Humans: Positive

Leucochloridium paradoxum presents no known benefits to humans.

Economic Importance for Humans: Negative

The parasitism of Leucochloridium paradoxum on succinid snails has no effect on humans. In their definitive bird hosts, they inhabit the rectum where they essentially feed on waste that is about to be excreted so their pathogenic effects on their hosts and ultimately on humans are negligible.

Conservation Status

Other Comments

Two visible changes in the snail occur as a result of the accumulation of sporocysts. First, the snail's tentacles enlarge and pulse in vivid colors. Secondly, the instinctively photophobic snail becomes photophylic and climbs to the tops of trees and grasses. This conspicuous sight looks like a caterpillar to passing birds. The birds swoop down and consume the snail and unknowingly inoculate themselves with Leucochloridium paradoxum. The worm continues its development within the bird's gut and ultimately ends up in the rectum where its eggs are flushed out with waste. Another snail consumes the excreted egg and the cycle continues. How the worm is able to cause such a drastic change in Succinea is still unknown. (Brand, 1979; Dawes, 1946; Rennie, 1992; Roberts and Janovy Jr., 2000)

Contributors

Renee Sherman Mulcrone (editor).

David DeLaCruz (author), University of Michigan-Ann Arbor, Teresa Friedrich (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

agricultural

living in landscapes dominated by human agriculture.

asexual

reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

parasite

an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

terrestrial

Living on the ground.

References

Brand, T. 1979. Biochemistry and Physiology of Endoparasites. Amsterdam: Elsevier/North-Holland Biomedical Press.

Brusca, R., G. Brusca. 2003. Invertebrates. Sunderland, Massachusetts: Sinauer Associates, Inc..

Dawes, B. 1946. The Trematoda. Cambridge, UK: University Press.

Erasmus, D. 1972. The Biology of Trematodes. New York: Crane, Russack, & Company.

Fried, B., T. Graczyk. 1997. Advances in Trematode Biology. Boca Raton, FL: CRC Press.

Rennie, J. 1992. Trends In Parasitology: Living Together. Scientific American, January: 123-33.

Roberts, L., J. Janovy Jr.. 2000. Foundations of Parasitology 6th ed.. Boston: McGraw-Hill.