Uvulifer ambloplitis

Geographic Range

Uvulifer ambloplitis is found in mainly the nearctic and neotropical areas, including the northern tip of South America, Central America, and much of North America. These areas are its three host's ranges. (Olsen, 1986)


This species begins its life as an egg, and is passed in the feces of a piscivorous bird. The egg hatches into a miracidium, which may be ingested by a snail where it transforms into a sporocyst. Snails such as Planorbella trivolvis are their first intermediate host. The snail sheds the parasite in the cercariae form, into the water. The cercariae in the water penetrate beneath the scales and eventually deep into the muscle tissue of a fish, transforming to the metacercariae. Fish, particularly bluegill sunfish, Lepomis macrochirus are intermediate hosts. Typical fish hosts are members of the Centrarchidae. The fish are ingested by their final hosts, birds. In the gut of piscivorous birds (kingfishers, for example), the parasites mature to adults and sexually reproduce. The eggs of the parasite are passed in the feces of the birds and the cycle starts over. Infection of hosts may be seasonal, and fish host infection may be higher at certain times of the year. (Hunter and Hamilton, 1941; Krull, 1934; Lemly and Esch, 1984; Tobler and Schlupp, 2006)

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

Physical Description

The first stage of this parasite is the egg, then a ciliated miracidium, followed by a sporocyst. Next, U. ambloplitis turns into cercaria, a larval fork-tailed form. The cercaria burrows under the scales of the intermediate host, a fish. It changes to the metacercariae deep in the muscles of the fish, causing the host to form a black pigmented cyst around the parasite. Although U. ambloplitis is commonly called the "black-spot flatworm," the fish host acquires the black spots, not the parasite. The cysts are roughly 0.377 mm long and about 0.2 mm in breadth. Within these cysts, the metacercariae have two parts: the fore-body and the hind-body. The fore-body is slim, leaf-like, deeply spoon-shaped, and lacks lateral sucking cups. Spines are on the vental surface. The hind-body is shaped like a cone and separated from the fore-body by a constriction. There is a very mobile, flexible hold-fast organ, covered in spines, about 0.055 mm in diameter. The oral sucker is covered with ridges. Flame cells are part of the excretory system.

Adults are flattened, have cephalization, bilateral symmetry, and well-developed holdfast structures. (Hughes, 1927; Hunter and Hamilton, 1941)


This parasite begins as an egg, and passes through various stages within its three hosts. First, the egg hatches into a miracidium, which matures to a sporocyst and eventually a cercaria. Cercariae are shed from their first intermediate hosts, which are snails. The fork-tailed cercariae burrow into the scales of their fish host. This penetration takes about five or ten minutes, but the actual migration to deeper layers of the fish takes much longer. The cercariae change to metacercariae after penetrating into the muscle bundles, which may take several days. The cyst that forms may appear lemon shaped, and it is especially visible because of its black pigment. Then, the fish is eaten by the definitive hosts of the parasite, birds. In the gut of the birds, the metacercariae mature to adulthood and sexually reproduce. The eggs from this reproduction are then passed out into the feces of the bird. The feces enter the soil, and the cycle begins again. (Hunter and Hamilton, 1941; Krull, 1934)


This flatworm reproduces asexually and sexually. Other trematodes may self- or cross-fertilize, as is likely for U. ambloplitis. Sexual reproduction takes place in the gut of the piscivorous bird, and asexual reproduction happens in the snail. (Hunter and Hamilton, 1941; Krull, 1934; Olsen, 1986)

This flatworm reproduces asexually and sexually. In the gut of the bird, sexual reproduction takes place. Asexual reproduction occurs in the sporocyst generation, which takes place in the snail hosts. (Hunter and Hamilton, 1941; Krull, 1934; Olsen, 1986)

  • Breeding interval
    The breeding interval of this trematode is unknown.
  • Breeding season
    The breeding season of this trematode varies.

There is no known parental investment in this species.

  • Parental Investment
  • no parental involvement


There is little available information about how long this species lives.


This trematode does not exhibit any known complex behaviors. It squirms and uses its holdfast structures when necessary. One interesting behavior is the manner in which the parasite burrows into the muscle tissue of its second intermediate host, a fish. (Olsen, 1986)

  • Average territory size
    unknown cm^2

Home Range

There is nothing known about the home range of the parasite.

Communication and Perception

The fluke possesses a cephalized nervous system, which includes a head with sensory organs. Many trematodes with snail hosts are able to sense and get to the host at the miricidial stage, but the mechanisms are unknown. (Olsen, 1986)

Food Habits

The parasite’s nutrients are obtained directly from its hosts, which are snails, fish, and piscivorous birds. (Olsen, 1986)

  • Animal Foods
  • body fluids


There are no direct predators of this species, but in the free-living stages, aquatic filter-feeders may ingest them.

  • Known Predators
    • no known predators

Ecosystem Roles

The flatworm parasitizes fish, including the western mosquitofish, Gambusia affinis. The mosquitofish acquires black spots on its body surface when parasitized, which may reduce the advantage of shoaling with conspecific fish. Highly-parasitized fish may lose a significant amount of body-weight or even die. Uvulifer ambloplites also parasitizes birds and snails, decreasing their fitness. (Krull, 1934; Tobler and Schlupp, 2006)

Species Used as Host
Mutualist Species
  • There are no known mutualists.
Commensal/Parasitic Species
  • This species has no known parasites.

Economic Importance for Humans: Positive

There is little evidence of any positive economic importance to humans.

  • Positive Impacts
  • research and education

Economic Importance for Humans: Negative

Humans may be unlikely to consume fish that are infected with this parasite because of the black spots.

Conservation Status

Other Comments

The species has also been known as Neascus ambloplitis and Crassiphiala ambloplitis.


Mary Hickner (author), University of Michigan-Ann Arbor, Heidi Liere (editor), University of Michigan-Ann Arbor, John Marino (editor), University of Michigan-Ann Arbor, Barry OConnor (editor), University of Michigan-Ann Arbor, Renee Mulcrone (editor), Special Projects.



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


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

World Map


reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents

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.


an animal that mainly eats meat


uses smells or other chemicals to communicate


a period of time when growth or development is suspended in insects and other invertebrates, it can usually only be ended the appropriate environmental stimulus.


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


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.


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


having the capacity to move from one place to another.

native range

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


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


remains in the same area


non-motile; permanently attached at the base.

Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa


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


uses touch to communicate


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).


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


movements of a hard surface that are produced by animals as signals to others


Barger, M., G. Esch. 2001. Downstream changes in the composition of the parasite community of fishes in an Appalachian stream. Journal of Parasitology, 87 (2): 250-255.

Cort, W., S. Brooks. 1928. Studies on the holostome cercariae from Douglas Lake, Michigan. Transactions of the American Microscopical Society, 47 (2): 179-221.

Hughes, R. 1927. Studies on the trematode family Strigeidae (Holostomidae) No. VI. A new metacercaria, Neascus ambloplitis sp. nov. representing a new larval group. Transactions of the American Microscopical Society, 46: 248-267.

Hunter, G., J. Hamilton. 1941. Studies on host-parasite reactions to larval parasites. IV. The cyst of Uvulifer ambloplitis (Hughes). Transactions of the American Microscopical Society, 60 (4): 498-507.

Krull, W. 1934. Cercaria bessiae Cort and Brooks, 1928, an injurious parasite of fish. Copeia, 2: 69-73.

Lane, R., J. Morris. 2000. Biology, prevention, and effects of common grubs (digenetic trematodes) in freshwater fish. Tech Bull Series Iowa State University, 115: 1-6.

Lemly, A., G. Esch. 1984. Population biology of the trematode Uvulifer ambloplitis (Hughes, 1927) in juvenile bluegill sunfish, Lepomis macrochirus, and Largemouth Bass, Micropterus salmoides. Journal of Parasitology, 70 (4): 466-474.

Olsen, O. 1986. Animal parasites: Their life cycles and ecology. Baltimore, MD: Dover Publications.

Spellman, S., A. Johnson. 1987. In vitro encystment of the black spot trematode Uvulifer amploblitis (Trematoda: Diplostomatidae). International Journal of Parasitology, 17: 897-902.

Tobler, M., I. Schlupp. 2006. Influence of black spot disease on shoaling behaviour in female western mosquitofish, Gambusia affinis (Poeciliidae, Teleostei). Environmental Biology of Fishes, 81: 29-34.

Wilson, D., P. Muzzall, T. Ehlinger. 1996. Parasites, morphology, and habitat use in a bluegill sunfish (Lepomis macrochirus) population. Copeia, 2: 348-354.