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)
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)
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)
There is no parental investment beyond the time eggs are released.
For 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)to continue development, it must be consumed by a snail of the genus
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.
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.
presents no known benefits to humans.
The parasitism of 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.on
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 Succinea is still unknown. (Brand, 1979; Dawes, 1946; Rennie, 1992; Roberts and Janovy Jr., 2000). 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
Renee Sherman Mulcrone (editor).
David DeLaCruz (author), University of Michigan-Ann Arbor, Teresa Friedrich (editor), University of Michigan-Ann Arbor.
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.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
living in landscapes dominated by human agriculture.
reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents
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.
an animal that mainly eats meat
uses smells or other chemicals to communicate
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
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.
fertilization takes place within the female's body
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
Living on the ground.
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.