The matureis approximately 2.5 to 3.0 mm in length and 1.0 mm wide, and somewhat resembles a miniature conch. A single large ventral sucker, known as an opisthaptor, takes up most of the surface area of its underbelly. The opisthaptor is divided into adhesive depressions (termed loculi) formed by muscular septa, which are useful in classification. has 64-66 loculi, arranged in four longitudinal rows. An exterior longitudinal septum, which is a horizontal flap of muscle, divides the body anteriorly. The function of the septum is unknown.
A wide buccal funnel (mouth) has its opening at the anterior end of a flexible neck-like process. Pharyngeal muscles move food entering the buccal funnel into the intestine. Unlike the related Digenean worms, aspidobothreans have a simple, unbranched digestive tract that ends in the cecum, a digestive sac surrounded by muscle. Wastes are removed by flame cell protonephridia, which channel material through excretory ducts into an excretory bladder, eventually exiting the body through a posteriorly located excretory pore.
usually develops within mollusks, but is a facultative parasite of vertebrates, should their mollusk host be eaten. Their life cycle is still direct, requiring only one host for maturation. Infection occurs through intake of the egg, containing a fully developed larva, by the mollusk's siphon. Upon entering the host, the cotylocidium (larvae) will hatch and immediately begin maturation without further migration. At hatching, the larvae are 13 to 17 micrometers long. Since the cotylocidium does not seek the host as in other trematodes, it is unciliated. Instead, it has a simple posterior sucker lacking loculi. There have been no documented cases of Aspidogaster directly infecting a vertebrate host as a free egg or larva, while they have been found in the intestines of fish, so it is assumed that vertebrates are infected by ingestion of parasitized mollusks.
The large ventral opisthaptor appears to play a major role infeeding behavior. Muscular action mechanically disrupts host tissues while marginal organs within the sucker release secretions for extracorporeal digestion. The predigested material is then sucked in through the buccal funnel.
Aspidogaster infections appear to be most prevalent and intense during the colder months, from November through April. (Bailey and Tompkin, 1971; Halton and Lyness, 1971; Huehner, 1987; Huehner, et al., 1989)
The primary hosts for (Rohde, 1972)are freshwater mollusks, usually mussels. However, as a facultative parasite of vertebrates, it is not restricted to mussels, and will also enter into and develop within freshwater snails, fishes, and turtles while feeding on epithelial tissue.
The aspidobothreans do not hold any economic or medical significance for humans. However, they have several archaic characteristics which suggest that they are an ancient group, and so continue to be studied because they seem to represent a link between parasitic and free-living organisms. Since Aspidogaster has not developed any close associations with particular host species, it has been suggested that it is an archaic species of trematode, similar to the hypothetical ancestor from which the related digenean trematodes have evolved their complex life cycles exploiting multiple hosts. (Rohde, 1972)
Renee Sherman Mulcrone (editor).
Raymond Pahk (author), University of Michigan-Ann Arbor, Solomon David (editor), University of Michigan-Ann Arbor.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
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.
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.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
union of egg and spermatozoan
mainly lives in water that is not salty.
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
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.
reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.
an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death
reproduction that includes combining the genetic contribution of two individuals, a male and a female
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Bailey, H., S. Tompkin. 1971. Ultrastructure of the integument of Aspidogaster conchicola. Journal of Parasitology, 57: 848-854.
Bakker, K., C. Davids. 1973. Notes on the life history of Aspidogaster conchicola Baer (Trematoda; Aspidogastridae). Journal of Helminthology, 47: 269-276.
Halton, D., R. Lyness. 1971. Ultrastructure of the tegument and associated structures of Aspidogaster conchicola (Trematoda; Aspidogastrea). Journal of Parasitology, 57: 1198-1210.
Hathaway, R. 1971. The fine structure of the trematode Aspidogaster conchicola von Baer, 1827. Dissertation Abstracts International, 31B: 7687.
Huehner, M. 1987. Aspidogastrid and digenetic trematode single an double infections in the gastropod Elimia livescens from the Upper Cuyahoga River, Ohio USA. Proceedings of the Helminthological Society of Washington, 54 (2): 200-203.
Huehner, M., F. Etges. 1977. The life cycle and development of Aspidogaster conchicola in the snails, Viviparus malleatus and Goniobasis livescens. Journal of Parasitology, 63: 669-674.
Huehner, M., K. Hannan, M. Garvin. 1989. Feeding habits and marginal organ histochemistry of Aspidogaster conchicola (Trematoda; Aspidogastrea). Journal of Parasitology, 75 (6): 848-852.
Laruelle, F., D. Mollogy. 1996. A Guide to Identifying the Endosymbionts of Dreissena polymorpha. The 6th International Zebra Mussel and Other Aquatic Nuisance Species Conference, Dearborn, Michigan. Accessed November 14, 2003 at http://sgnis.org/publicat/96Laruel.htm.
Roberts, L., J. Janovy Jr.. 2000. Foundations of Parasitology, 6th ed. New York: McGraw Hill.
Rohde, K. 1998. "Aspidogastrea" (On-line). Accessed 11/14/03 at http://ag.arizona.edu/ENTO/tree/eukaryotes/animals/platyhelminthes/aspidogastrea/aspidogastrea.html.
Rohde, K. 1972. The Aspidogastrea, especially Multicotyle purvisi Dawes, 1941. Advances in Parasitology, 10: 77-151.