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Lagochilascaris minor

By Jennifer Newberry

Geographic Range

The geographic range of Lagochilascaris minor is yet to be specifically identified. It is most frequently found in neotropical areas, with the greatest frequency in South America. (Lanfredi, et al., 1998)

Habitat

There are no free living stages of Lagochilascaris minor, but true definitive hosts are unknown. Migration once inside the host varies. They have been found in the stomach, pharynx, trachea, tonsils, nose and neck of wild cats in South America and the Carribean. Occasionally they will infect humans and one fatality has been reported. (Roberts and Janovy, 2000)

Physical Description

As a nematode, Lagochilascaris minor is cylindrical, has a cuticle with three main outer layers made of collagen and other compounds. The outer layers are non-cellular and are secreted by the epidermis. The cuticle layer protects the nematodes so they can invade the digestive tracts of animals.

Nematodes have longitudinal muscles along the body wall. The muscles are obliquely arranged in bands. Dorsal, ventral and longitudinal nerve cords are connected to the main body of the muscle.

Lagochilascaris minor is stout with tapered extremities. Males are smaller (6 mm) than the females (15 mm). The anterior end of both is domed shaped. This is formed by three wide lips that are separated from the rest of the body by a deep groove. The three lips center around the oral opening. There is a dorsal lip that has two sub-dorsal papilla, and a sub-ventral lip that has one ventral papillae. Near the anterior end resides the excretory pore, interrupting the cuticular striations.

Females have a long straight tail with the anus at the posterior end. The vulvar opening is located near the middle of the body. The posterior end of the males is ventrally curved. There are 22-28 pairs of preocloacal papillae which are sessile, button-like, and arranged in two lateroventral rows.

As a nematode in the group Secernentea, Lagochilascaris minor has a specialized tubular excretory system with three canals. The canals are arranged to form an “H”. (Barnes, 1987; Lanfredi, et al., 1998; Roberts and Janovy, 2000)

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently
  • Range length
    6 to 15 mm
    0.24 to 0.59 in

Development

Research supports that L. minor is heteroxenous with the eggs usually hatching in water. Once exposed to air the eggs molt into a second stage larva within eight days. The larva has an aboring tooth for burrowing and a knobbed tail. The second stage larva then moults into a third stage larva. From this point on L. minor follows typical ascaridoid development. (Lanfredi, et al., 1998; Sprent, 1971; Volcan, et al., 1992)

Reproduction

This species is dioceious, but exact mating behavior is still unknown. 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. (Barnes, 1987; Roberts and Janovy, 2000)

  • Parental Investment
  • pre-fertilization
    • provisioning

Behavior

Nematodes such as Lagochilascaris minor can swim intermittently. The worms are usually only able to move effectively when the pseudocoel is filled with fluid and hypertonic to to the surrounding media. (Barnes, 1987; Roberts and Janovy, 2000)

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). (Barnes, 1987; Roberts and Janovy, 2000)

Food Habits

Adults are found in the upper digestive tract of the host, particularly in the crypts of the tonsils and the pharyngeal region. Lagochilascaris minor burrows into the mucosal lining and there resides, eventually forming abscesses in the host. Other biology concerning food habits is still unknown.

In general, nematode pharyngeal glands and intestinal epithelium produce digestive enzymes to feed on the hosts’ body fluids. Extracellular digestion begins within the lumen and is finished intracellularly. (Barnes, 1987; Roberts and Janovy, 2000; Sprent, 1971)

  • Animal Foods
  • body fluids

Predation

Predators are unknown. These parasites are probably not preyed on directly, but are ingested from host to host. Larval mortality is high as most of the parasites do not reach appropriate hosts.

Ecosystem Roles

There is little host specficity. Normally it is found in various cat species in South America, but can also parasitize humans, domestic and wild animals. However, the mode of host infection and the natural host remain yet unknown.

Species Used as Host

Economic Importance for Humans: Negative

In humans, Lagochilascaris minor will form abscesses that will contian its offspring. These abscesses can be found in the ear, neck, jaw, orbit, mastoid process, and retropharyngeal tissues. These infections can kill quickly or last years. There have only been eight documented cases. (Sprent, 1971)

Contributors

Renee Sherman Mulcrone (editor).

Jennifer Newberry (author), University of Michigan-Ann Arbor, Teresa Friedrich (editor), University of Michigan-Ann Arbor.

Glossary

Neotropical

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

World Map

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.

carnivore

an animal that mainly eats meat

causes disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

chemical

uses smells or other chemicals to communicate

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.

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

motile

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.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

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.

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

tactile

uses touch to communicate

tropical

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

References

ARFAA, F. 2002. "CHAPTER 4: NEMATODES" (On-line). MEDICAL HELMINTHOLOGY. Accessed September 27, 2004 at http://mywebpages.comcast.net/fredarfaa/nematweb.htm#lagochil.

Barnes, R. 1987. Invertebrate Zoology. Orlando, Florida: Dryden Press.

Lanfredi, R., H. Neto, D. Gomes. 1998. Scanning Electron Microscopy of Lagochilascaris minor Leiper, 1909 (Nematoda: Ascarididae). Memorias do Instituto Oswaldo Cruz, 93(3): 327-330.

Machado, P., C. de Oliverira Jayrson Araujo. 1999. Wild Rodents as Experimental Intermediate Hosts Lagochilascaris minor Leiper, 1909. Memorias do Instituto Oswaldo Cruz, 94 (4): 441-449.

Roberts, L., J. Janovy. 2000. Foundations of Parasitology, 6th Edition. USA: The McGraw-Hill Companies, Inc..

Sprent, J. 1971. Speciation and Development in the Genus Lagochilascaris. Parasitology, 62: 71-112.

Volcan, G., C. Medran, G. Payares. 1992. Experimental Heterozenious Cycle of Lagochilascaris minor Leiper, 1909 (Nematoda: Ascarididae) in White Mice and Cats. Memorias do Instituto Oswaldo Cruz, 87: 525-532.

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