Eutrombicula alfreddugesi

Geographic Range

Eutrombicula alfreddugesi is prevalent across eastern and central North America. There is also evidence of E. alfreddugesi scattered across Central and South America and the Caribbeans. Examples include Argentina, Chile, Brazil, Cuba and Hispanola. (Clopton and Gold, 1993; Cunha-Barros, et al., 2003; Daniel and Stekol'nikov, 2004; Lareschi, et al., 2003; Lareschi, et al., 2007; Rubio and Simonetti, 2009; Zippel, et al., 1996)

Habitat

The larvae of Eutrombicula alfreddugesi are most common in sheltered grasslands. These habitats are ideal for the hosts that the larvae parasitize. These hosts include large vertebrates that are part of Aves, Mammalia, Reptilia classes. Eutrombicula alfreddugesi larvae are also found in forest habitats, but here their populations are much lower than in grasslands and peak earlier in the season. Postlarval chiggers are generally found in habitats of litter and soil, showing preference for decomposing tree trunks. Postlarval chiggers are not found in vertebrate nests or underneath tree-bark and, contrary to mainstream belief, they are not found on Spanish moss.

Evidence suggests that E. alfreddugesi parasitic larva thrives in temperatures between 18 and 38°C, with larval activity being at its maximum at 38°C. The larva also prefers high humidity (85%) over low humidity (35%). The prevalence of E. alfreddugesi steadily decreases north of a latitude of 40°. (Clopton and Gold, 1993; Ewing, 1944; Loomis, 1956; Mallow, et al., 1984; Zippel, et al., 1996)

Physical Description

The body of Eutrombicula alfreddugesi has a gnathosoma and an idiosoma. The gnathosoma consists of chellicerae and pedipalps. In the dorsal view of the idiosoma, a scutum is located anteriorly with one eye located on either side. A pair of sensillae projects from the scutum. In the ventral view of the idiosoma, Claparede's organs are between the coxae of the first and second pairs of legs. The anus is near the posterior end of the idiosoma in the ventral view. Lastly, legs project from the idiosoma (six for larvae, eight for deutonymphs and adults) and setae are visible throughout the idiosoma, both dorsally and ventrally. The larval stage of E. alfreddugesi is usually less than two-fifths of a millimeter (mm) long, while the deutonymphs and adults are much larger. Adults can reach lengths upto one mm. At every stage, E. alfreddugesi is red-colored. (Cunha-Barros, et al., 2003; Ewing, 1944; Janovy, Jr. and Roberts, 2009)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    0.4 to 1 mm
    0.02 to 0.04 in

Development

After fertilization, the female Eutrombicula alfreddugesi lays eggs after about two weeks. These eggs develop one at a time within the female body; however, eggs laid at different times can still develop and hatch together. Eutrombicula alfreddugesi eggs generally hatch two weeks after they are laid. Prelarvae emerge from the eggs and last about as long as the egg stage. The prelarvae then develop into larvae, which is an active, parasitic stage for E. alfreddugesi. The larval stage parasitizes a vertebrate host. The length of this parasitic association can range from two to 48 days and depends on whether the host is warm-blooded or cold-blooded. It takes E. alfreddugesi longer to engorge cold-blooded hosts such as reptiles. After engorging and leaving the host, the larva is active for a few more days before it develops into a protonymph. This protonymph develops inside the cuticle of the engorged larva. The protonymph then develops into an active deutonymph which is a free-living predator. The length of this stage depends on the availability of food and can last anywhere from seven to 32 days. Following the deutonymph is the tritonymph, which is another inactive stage. Similar to the protonymph, the tritonymph also lives and develops with-in the cuticle of its predecessor (i.e., the deutonymph). After five to ten days, the tritonymph gives rise to the adult, which can live as long as 20 months. (Ewing, 1944; Goff, et al., 1982; Janovy, Jr. and Roberts, 2009; Loomis, 1956)

Reproduction

Eutrombicula alfreddugesi adult males travel around their preferred substrate (soil, grass, decomposing tree trunks) and deposit spermatophores along the way. Spermatophores are sperm-containing parcels and in E. alfreddugesi they are stalked. Adult females, upon encountering these spermatophores, insert them into their genital pore. Males have been observed depositing spermatophores onto the substrate without the presence of females. Furthermore, females have been observed inserting these spermatophores into their bodies without the presence of a male. Therefore, sexual reproduction in E. alfreddugesi can occur without the males and the females ever having encountered each other. (Janovy, Jr. and Roberts, 2009; Mallow, et al., 1984; Tuegel and Wrenn, 1998)

Adult Eutrombicula alfreddugesi mate between the months of May and October throughout much of North America. This mating season likely has more to do with temperature and humidity requirements, instead of the actual months of the year. Low temperatures have adverse effects on E. alfreddugesi populations and development. Female E. alfreddugesi have been observed to lay eggs 14 days after fertilization. A complete development cycle (i.e., egg to adult) takes a minimum of 55 days and an average of 68 days, with approximately two to three generations being produced every season. (Loomis, 1956; Tuegel and Wrenn, 1998)

  • Breeding season
    Eutrombicula alfreddugesi reproduces from May to October.

In Eutrombicula alfreddugesi, there is no parental investment made by either males or females. The extent of their investment is sexual reproduction. Eutrombicula alfreddugesi males and females do not even necessarily interact with each other, much less their larval offspring. (Tuegel and Wrenn, 1998)

  • Parental Investment
  • pre-fertilization
    • protecting
      • female

Lifespan/Longevity

Eutrombicula alfreddugesi takes at minimum 55 days and on average 68 days to complete its life cycle. The lifespan of E. alfreddugesi can vary greatly depending on the types of hosts that the larvae parasitize. (Loomis, 1956)

  • Typical lifespan
    Status: wild
    55 to 368 days
  • Average lifespan
    Status: wild
    68 days

Behavior

Eutrombicula alfreddugesi is motile with some life stages being more active than others. For-example, the larval, deutonymph, and adult stages are very active. The larval stage actively seeks out vertebrate hosts to parasitize, moving very rapidly. The deutonymph and adult, similarly, actively seek out prey as they are free-living predators. The protonymph and tritonymph, however, are both inactive as these are pharate life stages. (Goff, et al., 1982; Loomis, 1956; Williams, 1946)

Communication and Perception

Eutrombicula alfreddugesi has a few means of perceiving its environment. In between the coxae of their first and second pairs of legs, E. alfreddugesi has Claparede's organs. These are otherwise known as urstigmata. The function of these organs is to sense humidity levels. Claparede's organs give chigger mites critical information about their surroundings, allowing the chigger mites to seek out environments in which they won't dry out. Additionally, E. alfreddugesi has eyes on the dorsal part of their idiosoma. While it is likely that these eyes aid in visual perception, information about the extent to which chigger mites can "see" could not be found. Eutrombicula alfreddugesi also has sensillae emerging from these scutums. Lastly, E. alfreddugesi is capable of sensing carbon dioxide. This is is how they sense vertebrates approaching. The mechanism by which they sense carbon dioxide, however, is not known. (Goff, et al., 1982; Gold and Clopton, 1992; Janovy, Jr. and Roberts, 2009)

Food Habits

The larvae of Eutrombicula alfreddugesi are temporary ectoparasites. They parasitize reptiles, primarily lizards, and other terrestrial vertebrates such as amphibians, birds, and mammals, including humans. The larvae of E. alfreddugesi are primarily found on a substrate above the soil level. They remain low on the substrate where the temperature is lower and the humidity is higher until they sense a suitable host approaching. The larvae sense approaching hosts by their exhaled carbon dioxide. Upon sensing a host, the larvae move up the substrate and attach on to them. After getting onto a host, the larvae move around very rapidly until they find a fold or another suitably secluded area to begin feeding. Contrary to popular belief, these parasitic larvae do not feed on blood. Instead, they feed on haemolymph or digested host tissue. Eutrombicula alfreddugesi suck this tissue up through a tube that is formed as an immune response by the host to the parasites salivary secretions. This tube is called a stylostome. The postlarval stages of E. alfreddugesi are free-living predators of presumably microarthropods and their eggs. (Ewing, 1944; Gold and Clopton, 1992; Loomis, 1956; Tuegel and Wrenn, 1998; Williams, 1946)

  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles
  • body fluids

Predation

The "snout mites" of the Family Bdellidae are known predators of of E. alfreddugesi larvae. These Bdellidae mites are fast and are able to move backwards as well. They feed on chigger mites by sucking them dry. To resist Bdellidae mites, chigger mites have evolved a useful anti-predator behavior. Once on a vertebrate host, the larvae rapidly run around until they find a fold. They settle in the fold and begin feeding. In such folds, the larvae are protected from predators. In various lizard species, structures called "mite pockets" have even evolved. These are folds in the lizard skin that are ideal for mite habitation. It has been hypothesized that these "mite pockets" evolved to reduce damage to the lizards by concentrating mite populations. This protects the rest of the lizard's body from harm. This hypothesis, however, has not yet been sufficiently tested. (Williams, 1946; de Carvalho, et al., 2006)

Ecosystem Roles

The larvae of Eutrombicula alfreddugesi parasitize a variety of reptile, mammal, and bird hosts. The deutonymph and adult forms of E. alfreduggesi are free-living predators of presumably small arthropods and their eggs. They are found primarily in soil, surface litter, and decomposing tree trunks. Lastly, members of the Family Bdellidae, the "snout-mites", prey on E. alfreddugesi larvae. (Ewing, 1944; Loomis, 1956; Mallow, et al., 1984)

Species Used as Host

Economic Importance for Humans: Positive

Eutrombicula alfreddugesi has no known positive economic importance.

Economic Importance for Humans: Negative

The larval form of Eutrombicula alfreddugesi parasitize mammals, including humans. A "bite" by E. alfreddugesi leads to an immune response that results in swelling and a strong itch. Smooth, red marks appear and remain on the skin for up to 21 days. (Gold and Clopton, 1992)

  • Negative Impacts
  • injures humans
    • bites or stings

Conservation Status

Eutrombicula alfreddugesi is common across North, Central, and South America and the Caribbean Islands and does not have any conservation status. (Ewing, 1944; Loomis, 1956)

Contributors

Bhavik Lathia (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.

Glossary

Nearctic

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

Neotropical

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

World Map

carnivore

an animal that mainly eats meat

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

metamorphosis

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.

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

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

radial symmetry

a form of body symmetry in which the parts of an animal are arranged concentrically around a central oral/aboral axis and more than one imaginary plane through this axis results in halves that are mirror-images of each other. Examples are cnidarians (Phylum Cnidaria, jellyfish, anemones, and corals).

seasonal breeding

breeding is confined to a particular season

sexual

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

tactile

uses touch to communicate

temperate

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).

terrestrial

Living on the ground.

tropical

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

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5? N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

Clopton, R., R. Gold. 1993. Distribution and seasonal and diurnal activity patterns of Eutrombicula alfreddugesi (Acari: Trombiculidae) in a forest edge ecosystem. Journal of Medical Entomology, 30/1: 47-53.

Cunha-Barros, M., M. Van Sluys, D. Vrcibradic, C. Galdino, F. Hatano, C. Rocha. 2003. Patterns of infestation by chigger mites in four diurnal lizard species from a Restinga habitat (Jurubatiba) of Southeastern Brazil. Brazilian Journal of Biology, 63/3: 393-399.

Daniel, M., A. Stekol'nikov. 2004. Chigger mites of the genus Eutrombicula Ewing, 1938 (Acari: Trombiculidae) from Cuba, with the description of three new species. Folia Parasitologica, 51/4: 359-366.

Ewing, H. 1944. The trombiculid mites (chigger mites) and their relation to disease. The Journal of Parasitology, 30/6: 339-365.

Goff, M., R. Loomis, W. Welbourn, W. Wrenn. 1982. A glossary of chigger terminology. Journal of Medical Entomology, 19/3: 221-238.

Gold, R., R. Clopton. 1992. Bite-count evaluation of the repellency of N,N-diethyl-3-methylbenzamide to larval Eutrombicula alfreddugesi (Acari: Trombiculidae). Journal of Medical Entomology, 29/5: 858-863.

Janovy, Jr., J., L. Roberts. 2009. Foundations of Parasitology. New York, NY: McGraw-Hill.

Lareschi, M., J. Notarnicola, S. Nava, G. Navone. 2007. Parasite community (arthropods and filarioids) associated with wild rodents from the marshes of La Plata River, Argentina. Comparative Parasitology, 74/1: 141-147.

Lareschi, M., J. Notarnicola, G. Navone, P. Linardi II. 2003. Arthropod and filarioid parasites associated with wild rodents in the northeast marshes of Buenos Aires, Argentina. Memórias do Instituto Oswaldo Cruz, 98/5: 673-677.

Loomis, R. 1956. The chigger mites of Kansas. The University of Kansas Science Bulletin, 37/2: 1259-1279.

Mallow, D., D. Ludwig, M. Hayes, D. Crossley Jr. 1984. Habitat selection of postlarval Eutrombicula alfreddugesi and Eutrombicula splendens from eight microhabitats in Georgia, USA. Journal of Georgia Entomological Society, 19/4: 543-548.

Rubio, A., J. Simonetti. 2009. Ectoparasitism by Eutrombicula alfreddugesi larvae (Acari: Trombiculidae) on Liolaemus tenuis lizard in a Chilean fragmented temperate forest. Journal of Parasitology, 95/6: 244-245.

Tuegel, M., W. Wrenn. 1998. Sexual Dimorphism in Morphology and Development of Pest Chigger, Eutrombicula Cinnabaris. International Journal of Acarology, 24/3: 199-211.

Williams, R. 1946. A contribution to our knowledge of the bionomics of the common North American chigger, Eutrombicula alfreddugesi (Oudemans) with a description of a rapid collection method. American Journal of Tropical Medicine, 26/2: 243-250.

Zippel, K., R. Powell, J. Pamerlee, Jr., A. Lathrop, S. Monks, D. Smith. 1996. The distribution of larval Eutrombicula alfreddugesi infesting Anolis lizards from different habitats in Hispanola. Caribbean Journal of Science, 32/1: 43-49.

de Carvalho, A., A. de Araujo, H. da Silva. 2006. Patterns of parasitism by Eutrombicula alfreddugesi (Oudemans) (Acari, Trombiculidae) in three species of Tropidurus wied (Squamata, Tropiduridae) from Cerrado habitat of Central Brazil. Revista Brasileira de Zoologia, 23/4: 1010-1015.