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).
Communication Channels: tactile ; chemical
Other Communication Modes: pheromones
Perception Channels: tactile ; chemical
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.
There is no known economic importance to humans.
Rhabdias bufonis potentially infects all frogs and toads, however, it is commonly found in Bufo bufo in Canada.
Ecosystem Impact: parasite
Species Used as Host:
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.
Animal Foods: body fluids
Other Foods: dung; microbes
Primary Diet: carnivore (Eats body fluids); coprophage
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.
Biogeographic Regions: nearctic ; palearctic ; oriental ; ethiopian ; neotropical ; australian
Other Geographic Terms: cosmopolitan
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.
Habitat Regions: temperate ; tropical ; terrestrial ; freshwater
Terrestrial Biomes: savanna or grassland ; forest ; rainforest ; scrub forest
Aquatic Biomes: lakes and ponds; rivers and streams; temporary pools
Wetlands: marsh ; swamp ; bog
Other Habitat Features: suburban ; agricultural ; riparian
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.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: female larger; sexes shaped differently
These parasites are probably not preyed on directly. Larval mortality is high as most of the parasites do not reach appropriate hosts.
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.
Key Reproductive Features: simultaneous hermaphrodite; sexual ; fertilization (Internal ); ovoviviparous
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.
Parental Investment: pre-fertilization (Provisioning); pre-hatching/birth (Provisioning: Female)
Rhabdias bufonis is a species of parasitic nematode in the family Rhabdiasidae. It was first described from the lungs of the European common toad (Bufo bufo) but has also been found in a number of other species of frog.[1]
Rhabdias bufonis has a heterogonic lifestyle in which a generation of parasitic individuals is succeeded by a free-living generation. This is advantageous to the parasite as it allows reproduction for one or more generations in the absence of the host. The free-living male and female worms mate and produce eggs which hatch inside the mother. They feed on her internal organs and moult twice before they leave her body. They are now infective larvae and can penetrate the skin of a frog. Once inside, they can migrate to the lungs and further develop there, feeding on the lung tissue. The adult parasitic worm is a hermaphrodite and grows to be about ten times the length of the free-living form. The eggs it produces are coughed into the frog's mouth, are swallowed and develop in its intestine. They are passed in the feces and develop into free-living forms. In the soil, the worms feed on bacteria and other organic matter. The female may produce a pheromone to attract a male.[2]
Rhabdias bufonis is found in the parts of Europe and Asia in which its host frogs are found. Besides the common toad from which this roundworm was first described, it has been found in the common spadefoot toad (Pelobates fuscus), the common frog (Rana temporaria), the moor frog (Rana arvalis), the agile frog (Rana dalmatina), the European fire-bellied toad (Bombina bombina), the yellow-bellied toad (Bombina variegata), water frogs (Pelophylax spp.) and the European green toad (Bufo viridis).
Juvenile frogs are often infected and a heavy worm burden can seriously restrict their growth. In a study, some of the infected juveniles were only half as heavy as controls with no worms. The parasite-induced anorexia caused a decrease in food intake and some of the young host frogs died.[3]
Rhabdias bufonis is a species of parasitic nematode in the family Rhabdiasidae. It was first described from the lungs of the European common toad (Bufo bufo) but has also been found in a number of other species of frog.
