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Rhabdias bufonis

By Zachary Leonard

Geographic Range

Rhabdias bufonis inhabits all areas of the world where its hosts species of frogs and toads occupy. It has been found in North America, most notably Canada. However, it is most common in the European toad and frog habitats. (Goater and Ward, 1992)

Habitat

Rhabdias bufonis live in any environments that support their host frog and toad species. Common hosts species include Bufo bufo in Canada. They have been found in North America, most notably in Canada. Also, they are the most common in the European toad and frog habitats. However, R. bufonis can occur wherever toad and frog populations are supported. (Goater and Ward, 1992)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • temporary pools

Physical Description

Rhabdias bufonis is characterized by a heterogonic lifestyle in which there is an alteration of free-living and parasitic generations. The adults of the two generations differ drastically in size and appearance. Adult parasitic hermaphrodites are more than 10 times longer than the largest free-living females and the body size of adult hermaphradites containing eggs varies two-fold whereas free-living females containing eggs varies less than 20 percent. The eggs in parasitic mothers that develop into males and females are larger than the eggs of of free-living mothers. The parsitic adults contain about 500 times more intestinal nuclei than free-living adults.

The hypodermis is made of fine subcuticle and four longitudinal cords. The thickness and structure of the subcuticle is uniform throughout the body. The cuticle of this nematode is very thin (.5 to .6 micrometers) and consists of five layers. The fibrils of the subcuticle extend to form a bundle and then fan out to the periphery of the medial cords. Rhabdias bufonis has eight muscle cells visible in a cross section. These cells are uniform throughout the body. The contractile portion of the muscle are myofibrils with supporting fibrils between them. The fibrils within the reticulum form a wide interlaced network. The nucleus is situated in the middle of the cytoplasmic sac and has an elliptical shape containing one nucleolus. The nucleus can be as long as 20 micrometers parallel to the longitudinal axis of the body. Also, the hypodermis consists of five to seven membranes. This nematode has an H-shaped excretetory system with two sub-ventral gland cells and the lateral canals are embedded within the lateral cords. (Bogoyavlenskii, 1982; Lee and Atkinson, 1977; Spieler and Schierenberg, 1995)

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently

Development

Hermaphrodites that are parasitic in the lungs deposit their eggs within the lungs. These eggs are then coughed into the mouth where they are swallowed and then hatched into the first larval stage in the small intestine of the host. The larvae come together in the large intestine and then exit the host via the feces. The larvae remain in the feces and develop there for 3-7 days. These undergo a total of 4 molts before reaching the adult males and females of the free-living generation. The free-living females' progeny hatch within the mother and feed on her internal organs until developed into the 3rd larval stage when they exit the mother. (Goater and Ward, 1992; Roberts and Janovy Jr., 2000)

Reproduction

Females may produce a phermomone to attract males. The male coils around a female with his curved area over the female genital pore. The gubernaculum, made of cuticle tissue, guides spicules which extend through the cloaca and anus. Males use spicules to hold the female during copulation. Nematode sperm are amoeboid-like and lack flagella. The free-living females' progeny hatch within the mother and feed on her internal organs until developed into the 3rd larval stage when they exit the mother. (Goater and Ward, 1992; Roberts and Janovy Jr., 2000)

The free-living females' progeny hatch within the mother and feed on her internal organs until developed into the 3rd larval stage when they exit the mother. (Goater and Ward, 1992)

  • Parental Investment
  • pre-fertilization
    • provisioning
  • pre-hatching/birth
    • provisioning
      • female

Behavior

Rhabdias bufonis has a heterogonic life cycle that alternates between parasitic hermaphroditic generations and free-living generations which have both males and females. (Anderson, 1992)

Communication and Perception

Nematodes within the Secernentea have phasmids, which are unicellular glands. Phasmids likely function as chemoreceptors. Females may produce pheromones to attract males.

Nematodes in general have papillae, setae and amphids as the main sense organs. Setae detect motion (mechanoreceptors), while amphids detect chemicals (chemoreceptors). (Brusca and Brusca, 2003; Roberts and Janovy Jr., 2000)

Food Habits

The parasitic generation feeds on the lung tissue of toads and frogs. The larvae of the non-parasitic generation feed on the feces that they exit the host in to develop into the adult. The non-parasitic adults feed on bacteria and other occupants within the organic material in the soils produced by the decomposition of plants. The pharyngeal glands produce an esterase that passes into the intestine where it functions as a endopeptidase in the breakdown of hemoglobin. A lipase has also found in the intestines that functions to hydrolyze fats. (Lee and Atkinson, 1977; Roberts and Janovy Jr., 2000; Spieler and Schierenberg, 1995)

  • Animal Foods
  • body fluids
  • Other Foods
  • dung
  • microbes

Predation

These parasites are probably not preyed on directly. Larval mortality is high as most of the parasites do not reach appropriate hosts.

Ecosystem Roles

Rhabdias bufonis potentially infects all frogs and toads, however, it is commonly found in Bufo bufo in Canada.

Species Used as Host

Economic Importance for Humans: Positive

There is no known economic importance to humans.

Contributors

Renee Sherman Mulcrone (editor).

Zachary Leonard (author), University of Michigan-Ann Arbor, Barry OConnor (editor), University of Michigan-Ann Arbor.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

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

Neotropical

living in the southern part of the New World. In other words, Central and South America.

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.

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.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coprophage

an animal that mainly eats the dung of other animals

cosmopolitan

having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

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.

freshwater

mainly lives in water that is not salty.

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

marsh

marshes are wetland areas often dominated by grasses and reeds.

motile

having the capacity to move from one place to another.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

ovoviviparous

reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.

parasite

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

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

scrub forest

scrub forests develop in areas that experience dry seasons.

sedentary

remains in the same area

sexual

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

suburban

living in residential areas on the outskirts of large cities or towns.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

Anderson, R. 1992. Nematodes Parasites of Vertebrates: Their Development and Transmission. Cambridge: University Press.

Bogoyavlenskii, Y. 1982. Structure and Function of the Integuments of Parasitic Nematodes. New Delphi: Amerind Publishing Company.

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

Dick, T., L. Graham. unknown. "Rhabdias bufonis" (On-line). WELCOME TO PARASITOLOGY 22.346. Accessed September 28, 2004 at http://www.umanitoba.ca/faculties/science/zoology/faculty/dick/z346/rhabhome.html.

Goater, C., P. Ward. 1992. Negative Effects of Rhabdias bufonis Nematoda on the Growth and Survival of the Toads Bufo-Bufo. Oecologia, 89(2): 161-165.

Lee, D., H. Atkinson. 1977. Physiology of Nematodes Second Edition. New York: Columbia University Press.

Roberts, L., J. Janovy Jr.. 2000. Foundations of Parasitology Sixth Edition. Boston: McGraw-Hill.

Spieler, M., E. Schierenberg. 1995. On the Development of the Alternating Free-Living and Parasitic Generations of the Nematode Rhabdias bufonis. Invertebrate Reproduction and Development, 28(3): 193-203.

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