Pseudodiplorchis americanus

Geographic Range

Members of the species Pseudodiplorchis americanus parasitize Couch's spadefoot toads ( Scaphiopus couchii ) as their primary host species. Couch's spadefoot toads live the majority of their lives inhabiting burrows deep underground in parts of the southwestern United States and northern Mexico. They can be found in south central Texas, southern Arizona, southern New Mexico, and throughout California. In California, these toads range from the Colorado River westward towards the vicinity of the Algodones Dune, as well as along the United States-Mexico border.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

The habitat for members of the Pseudodiplorchis americanus species changes as they begin development into adulthood. Eggs are laid in temporary pools in desert environs. In the juvenile stages, the freshly hatched parasites leave the pools and invade the skin of their host, Couch's spadefoot toad ( Scaphiopus couchii ), by entering through the nostrils.

As the parasites mature, they move into the lungs. Due to Couch's spadefoot toads living in arid environments, their lungs provide a humid space optimal for parasites to thrive. In the adult stages of the monogenean life cycle, they migrate through the host's body and typically settle in the urinary bladder. They exit the host to return to vernal pools and lay eggs.

• Habitat Regions
• freshwater freshwater

• Terrestrial Biomes
• desert or dune desert or dune

• Aquatic Biomes
• temporary pools

Physical Description

Members of the species Pseudodiplorchis americanus have adult bodies that are typically about 2mm-3mm long. During the oncomiracidium stages, or the larval stage, these parasites are only micrometers long. The 2μm-3μm uterus of an adult parasite holds 50-300 ciliated larvae at a time. During this stage the prohaptor, which is located on the anterior end of the parasite, develops structures that are adhesives which may aid in feeding. Some larvae develop "eye" spots to detect light and swim towards their next hosts. Their body is slim towards the head, widens near the center of the body, and slims again near the prohaptor. Monogeneans practice hermaphroditism, so distinct sexes do not exist.

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Development

Members of the species Pseudodiplorchis americanus go through four major stages of development. In utero, these parasites obtain nutrients directly from the parents’ metabolites. When Couch’s spadefoot toads ( Scaphiopus couchii ) mate they must enter rain pools; parent worms then exit their host’s body and while in the water they lay their eggs. In the second stage ciliated larvae, called oncomiracidium, excrete a thick skin layer known as the tegumental layer to protect them from environmental dangers. Amphibinans absorb water through their skin allowing the parasites entry into their bodies. Monogeneans invade through the nostrils or skin of their new host amphibians. The amphibians may leave the rain pools and expose the parasites to air pre-maturely. To combat this, the oncomiracidia can swim in water for extended periods of time and survive on amphibian skin exposed to air for up to 30 minutes. The tegumental layer of the oncomiracidia can remain for up to 4 hours allowing the parasites to survive or choose different hosts. The oncomiracidia migrate through the buccal chambers into the lungs of host amphibians. The next stage is the juvenile stage. As juveniles, the tegumental layers begins to soften and the parasites return to the mouth of their hosts briefly before going deeper into the intestines and settling in the gallbladders. This is where most of the later development takes place and the monogeneans reach the final stage of their development by fully maturing and reproducing.

Reproduction

During the mating season, Couch's spadefoot toads ( Scaphiopus couchii ) enter water as part of their reproductive cycle. As spadefoot toads absorb water through their skin, the parasitic larvae gain entry into the host's body via cutaneous absorption. Pseudodiplorchis americanus is a hermaphroditic species, possessing both ovaries and testes. This allows for self-fertilization or mating with other individuals.

Members of the species Pseudodiplorchis americanus are hermaphroditic. They contain both sexual organs, and reproduction with other hermaphrodites or self-fertilization are possible. The parasites take 13-21 days to hatch. The intestinal migration of the larvae takes place 26 days after host infection. The juvenile parasites reach sexual maturity in 23-29 days post-hatching. Due to the developmental plasticity of some of Couch’s spadefoot toads ( Scaphiopus couchii ), certain important hormonal indicators are delayed causing parasite migration and even development to be halted until the signal is received. The parasites breed once a year coinciding with the toads' breeding season, April to September. These parasites are ovoviviparous meaning that their eggs hatch inside of them. They lay about 50-400 eggs per season. Mass is not reported for these parasites.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• simultaneous hermaphrodite
• sexual sexual
• ovoviviparous ovoviviparous

For members of the species Pseudodiplorchis americanus , parental involvement is nonexistent. The eggs take nutrients from the parent worms, but they are left to survive on their own after they are released into the water.

• Parental Investment
• no parental involvement

Lifespan/Longevity

Lifespan for Pseudodiplorchis americanus is reported as 3 years in captivity. There is no reported lifespan for monogeneans in the wild. Only about 3% of the parasites survive from invasion until first reproduction in the wild.

Behavior

Members of the species Pseudodiplorchis americanus have strict behavioral patterns that determine their lifespans. They are not social and do not communicate directly between one another. They receive hormonal cues from their amphibian hosts that determine when they start their migration through the intestines, ultimately determining the start of their adult development.

Due to their brief time in the water and their extended time inside of their host' insides, the parasites are natatorial meaning they are specialized for swimming. The parasites have to swim to survive inside of their host amphibians, so they are mobile. They also remain within their hosts for majority of their lives. Monogeneans are solitary and do not directly communicate with one another.

• Key Behaviors
• natatorial natatorial
• parasite parasite
• motile motile
• sedentary sedentary

Home Range

Because members of the species Pseudodiplorchis americanus are parasites that infect amphibians, their home range is restricted to their host amphibians' bodies. They do not defend a territory.

Communication and Perception

Members of the species Pseudodiplorchis americanus do not directly communicate with one another; instead they hatch with a specific set of behaviors that helps them react to outward stimuli, like chemical cues, to navigate within their hosts. The parasites secrete proteins from the pharynx structure that alter the hormones of their host. Some larvae are able to perceive simple light cues with eye spots after first hatching. The eye spots cease development and disappear after the juvenile stages of their life.

• Communication Channels
• visual visual
• chemical chemical

• Other Communication Modes
• pheromones pheromones

• Perception Channels
• visual visual
• chemical chemical

Food Habits

Members of the species Pseudodiplorchis americanus develop in the respiratory system of their host amphibian, using a living tegmental layer as protection from internal elements. Larvae feed for 3-5 weeks before migrating towards the urinary bladder. As adults, the monogeneans use their prohaptor to hook to epidermal cells, making it easier to feed. Although the prohaptor is developed in the larval stages, it persists into adulthood and occasionally develops into a more complex structure. The parasites get their energy from feeding on blood. The digestive system consists of a pharynx, a muscular tube used to suck in blood, and a branched intestine with no anus.

• Primary Diet
• carnivore carnivore
  • sanguivore sanguivore
  • eats body fluids

• Animal Foods
• blood
• body fluids

Predation

Members of the species Pseudodiplorchis americanus have no predators. Their time spent outside their host amphibian is too brief for predation events.

Ecosystem Roles

Members of the species Pseudodiplorchis americanus are parasites that infect Couch’s spadefoot toads ( Scaphiopus couchii ). They primarily inhabit the toads’ urinary bladder and lungs. The parasites feed on their host amphibians' blood and tissue fluids, causing health issues that include and range from respiratory problems to permanent tissue damage. While they do not have known predators, they can be infected by microsporidian hyperparasites which can be passed down in utero to larvae.

• Ecosystem Impact
• parasite parasite

Economic Importance for Humans: Positive

Members of the species Pseudodiplorchis americanus have no positive effect on humans.

Economic Importance for Humans: Negative

Members of the species Pseudodiplorchis americanus have no negative effect on humans.

Conservation Status

The conservation status for members of the species Pseudodiplorchis americanus has not been evaluated by the IUCN Red List. There is no special status for the amphibian on the US Federal List, CITES, or the list for the state of Michigan.

These parasites have their population closely tied to the health and abundance of their amphibian host, Couch’s spadefoot toad ( Scaphiopus couchii ). The amphibians are listed by the IUCN Red list as "Least Concern" and have no special status.

The parasites have no direct threats. Their hosts, Couch’s spadefoot toads, are threatened by climate change which affects their environment. Both of the organisms are dependent on vernal pools to complete a small portion of their life cycles; this environment is impacted by climate change. The loss of vernal pools directly effects the parasites' ability to successfully reproduce and transfer to new hosts as the process takes place entirely within the pools.

Due to their parasitic nature, no conservation efforts are in place to foster the continued survival of the parasites.

Additional Links

Encyclopedia of Life

Contributors

Kousso Bennett (author), Radford University, Natalie May (editor), Radford University, Alexander McVicker (editor), Radford University, Karen Powers (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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