Proteocephalus pinguis

Geographic Range

Proteocephalus pinguis is native to North America and uses northern pike, Esox lucius and the chain pickerel, Esox reticulatus as hosts. Proteocephalus pinguis is currently found in Maine, Michigan, Wisconsin and various parts of Manitoba, Canada. Its range may expand as the ranges of its two host pike species expands. The northern pike and chain pickerel range from Alaska south to the upper Mississippi valley, east of the Rockies to the Potomac and east and south of the Allegheny Mountains to Louisiana and Arkansas. (Larue, 1914)


Adult forms of Proteocephalus pinguis are found in the intestine and villi of pike. Eggs survive in freshwater systems and are ingested by its first intermediate host, a copepod. Within the copepod the egg hatches and forms a procercoid. The copepod is typically eaten by a second intermediate host, such as frogs, crawfish and fish. Once inside the second intermediate host the procercoid develops into a plerocercoid. (Larue, 1914; Scholz, 1999)

  • Aquatic Biomes
  • rivers and streams

Physical Description

Proteocephalus pinguis has a maximum length of 90 mm and a breadth maximum of 1.24 mm. The length of each proglottid varies depending on its developmental stage. Immature proglottids are smaller than gravid proglottids. Proteocephalus pinguis has four suckers on the scolex that help hold onto the host and a fifth sucker that is referred to as the rostellum. The scolex is an apical organ that attaches P. pinguis to the host and the rostellum is a modification of the scolex that has spines used to hook it onto the host. The head of P. pinguis is typically conical and is flattened dorso-ventrally as is the rest of the body. The body is made up of proglottids that are separated by shallow intersegumental furrows. (Larue, 1914; "Cestode glossary", 2011)

  • Range length
    90 (high) mm
    3.54 (high) in


Proteocephalus pinguis begins as a floating egg in the water and is ingested by a copepod. Once ingested the egg hatches and forms a procercoid, a metacestode that has not formed a scolex. When the copepod is eaten by a second intermediate host, typically a small fish, the procercoid develops into a plerocercoid, a metacestode that has a retracted scolex. The second intermediate host is then eaten by a pike, the definitive host and the plerocercoid attaches to the intestine or villi where it develops into the adult cestode. (Larue, 1914; Scholz, 1999; "Cestode glossary", 2011)

As the plerocercoid becomes the adult cestode it will first develop immature proglottids that later become mature proglottids. In mature proglottids, the reproductive organs are easily seen and defined as testes and ovaries with a genital pore and vitellaria as supporting mechanisms. In this stage, the eggs will be fertilized and the mature proglottids will become gravid. Once gravid, they can be released by segments in the host feces. Once released into the water the proglottid will swell up and burst, releasing the eggs into the water to be ingested by a copepod. (Larue, 1914; Scholz, 1999)


Proteocephalus pinguis does not have distinct males and females, however the proglottids can be male or female specific. This does not mean that they are asexual, but are typically fertilized by a neighboring P. pinguis. It is unknown whether fertilization is by one or multiple mates. (Bush, et al., 2001; Larue, 1914)

Once the proglottids of P. pinguis have developed into mature proglottids they can be fertilized. Most flatworms including P. pinguis can reproduce asexually but P. pinguis typically will not because in each proglottid there are male and female reproductive organs and they mature at different rates. The eggs are fertilized inside the proglottids and when this happens the mature proglottid develops into a gravid proglottid which can then be released with the host feces and can begin the cycle again. (Larue, 1914; Scholz, 1999)

Since little is known about the lifespan, the breeding habits (i.e. what time of year they reproduce, signals that are made, etc.) of P. pinguis are not really known.

There is no known parental investment for Proteocephalus pinguis.

  • Parental Investment
  • no parental involvement


There is no known information on the lifespan of P. pinguis.


Cestodes in general can move around with muscular undulations of the body. These parasites stay fixed to the host with microtriches (folds in the body wall), and the scolex. (Brusca and Brusca, 2003)

Communication and Perception

Although there is no specific information on Proteocephalus pinguis, cestodes in general have a nerve ring in the scolex with ganglia (nerve cells). Tactile receptors are attached to organs and are associated with attachment to the host. (Brusca and Brusca, 2003)

Food Habits

Proteocephalus pinguis has no way to process food once it has been taken in and relies heavily on the host for this process. Like other members of class Cestoda, P. pinguis absorbs the nutrients it needs through the tegument by active transport, mediated diffusion and simple diffusion. These nutrients are needed for P. pinguis to survive and reproduce. Proteocephalus pinguis can partially process the nutrients taken in to transform them into the amino acid lactate or into ATP. (Bush, et al., 2001)

  • Animal Foods
  • body fluids


There is no known predator that actively preys on P. pinguis.

Ecosystem Roles

Proteocephalus pinguis infects two species of pike. The prevalence of infection in pike is 96.2% and the intensity of the infections is 70.38%. (Watson and Dick, 1980)

Species Used as Host
  • northern pike, Esox lucius
  • chain pickerel, Esox reticulatus

Economic Importance for Humans: Positive

There are no known beneficial effects of Proteocephalus pinguis to humans.

Economic Importance for Humans: Negative

There are no known adverse effects of Proteocephalus pinguis on humans.

Conservation Status

This species does not have any conservation status.


Danielle Lare (author), Radford University, Renee Mulcrone (editor), Special Projects.



living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

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


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.

internal fertilization

fertilization takes place within the female's body


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.


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


condition of hermaphroditic animals (and plants) in which the male organs and their products appear before the female organs and their products


condition of hermaphroditic animals (and plants) in which the female organs and their products appear before the male organs and their products


remains in the same area


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 Natural History Museum. 2011. "Cestode glossary" (On-line). Accessed January 19, 2013 at

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

Bush, A., J. Fernandez, G. Esch, J. Seed. 2001. Parasitism the diversity and ecology of animal parasites. New York: Cambridge University Press.

Larue, G. 1914. A revision of the cestode family: Proteocephalidae, Volume 1. Chicago, IL: University of Illinois.

Scholz, T. 1999. Life cycles of species of Proteocephalus, parasites of fishes in the Palearctic region: a review. Journal of helminthology, 73/1: 1-19.

Watson, R., T. Dick. 1980. Metazoan parasites of pike, Esox lucius Linnaeus, from Southern Indian Lake, Manitoba, Canada. Journal of Fish Biology, 17: 255-261.