Animal Diversity Web

Ge­o­graphic Range

Het­er­akis gal­li­narum is found world­wide in areas where gal­li­form birds live. (Kauf­mann, 1996)

• Biogeographic Regions
• nearctic
• palearctic
• oriental
• ethiopian
• neotropical
• australian

• Other Geographic Terms
• cosmopolitan

Habi­tat

Het­er­akis gal­li­narum is a par­a­site found in the cecum of nu­mer­ous gal­li­form birds in­clud­ing chick­ens, turkeys, and pheas­ants. The eggs of H. gal­li­narum are passed from the in­testi­nal en­vi­ron­ment of the bird to the soil via the bird's feces. The eggs can sur­vive in the soil for long pe­ri­ods of time, es­pe­cially when a large amount of plant growth is pre­sent. Areas of soil with dense fo­liage bet­ter sup­port the eggs by less­en­ing the chances of dam­age from des­ic­ca­tion, ex­treme tem­per­a­tures, or other or­gan­isms. Earth­worms are often paratenic hosts for the eggs of H. gal­li­narum, with the eggs in­hab­it­ing the gut of the worm. (Kauf­mann, 1996; Lund, 1960)

• Habitat Regions
• temperate
• tropical
• terrestrial

• Terrestrial Biomes
• savanna or grassland

• Other Habitat Features
• urban
• suburban
• agricultural

Phys­i­cal De­scrip­tion

Het­er­akis gal­li­narum has a typ­i­cal round­worm mor­phol­ogy with fea­tures such as a cu­ti­cle, an esoph­a­gus end­ing in a valved bulb, and three papil­lae-lined lips and alae. Alae, which run al­most the en­tire length of the body, are ridges formed by the thick­en­ing of the cu­ti­cle that may act as re­cep­tors for mol­e­cules which stim­u­late re­pro­duc­tion. Adult fe­male and male cecal worms dif­fer in length, with the fe­male (10 to 15 mm) gen­er­ally being larger than the male (7 to 13 mm). Both sexes have a pointed tail, males hav­ing a pre­cloa­cal sucker at the pos­te­rior end. The eggs of H. gal­li­narum are ap­prox­i­mately 65-77 by 35-48 µm, with vis­i­bly thick, smooth shells. (Kauf­mann, 1996; Olsen, 1986)

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry

• Sexual Dimorphism
• female larger

• Range length

  7 to 15 mm

  0.28 to 0.59 in

De­vel­op­ment

Em­bry­onated eggs of H. gal­li­narum are in­gested by their de­fin­i­tive host, a gal­li­form bird, usu­ally by ei­ther di­rect up­take from the soil or by in­ges­tion of an earth­worm or in­sect which has eaten an egg. Within the egg, the lar­vae de­velop to the in­fec­tive sec­ond stage. Once eaten, the egg trav­els through the di­ges­tive sys­tem of the host until it reaches the in­tes­tine where it hatches. The ju­ve­nile then trav­els to the cecum where it molts twice be­fore ma­tur­ing into an adult. The du­ra­tion of time it takes for an egg to molt is de­pen­dent upon the tem­per­a­ture at which the egg is kept; a higher tem­per­a­ture ac­cel­er­ates the process, while a lower tem­per­a­ture in­creases the num­ber of days be­fore the process oc­curs. (An­der­son, 2000; Olsen, 1986)

Re­pro­duc­tion

Like most other ne­ma­tode species, H. gal­li­narum is dioe­cious. Re­pro­duc­tion be­gins in the host's cecum when a male worm coils around a fe­male worm, uti­liz­ing two un­even spicules on his pos­te­rior end to hold the fe­male in place. This act in­volves in­ter­nal fer­til­iza­tion with the male re­leas­ing his ame­boid-like sperm into the fe­male’s gen­i­tal pore. Em­bryos are stored in the fe­male uterus until their re­lease into the host's feces. (Olsen, 1986; Roberts and Janovy, 2008)

Male worms are fully ma­ture 14 days after they have in­fected the host. Fe­males reach sex­ual ma­tu­rity and start to lay eggs some­time be­tween the age of 24 and 36 days. The num­ber of eggs laid by a fe­male cecal worm is de­pen­dent upon the species of bird it in­hab­its, but the av­er­age num­ber of eggs laid is 211. (Lund and Chute, 1972; Lund and Chute, 1974; Olsen, 1986)

• Key Reproductive Features
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
  • internal
• oviparous

• Average number of offspring

  211

• Range age at sexual or reproductive maturity (female)

  24 to 36 days

• Average age at sexual or reproductive maturity (male)

  14 days

There is no parental care after the fe­males lay eggs.

• Parental Investment
• pre-hatching/birth
  • provisioning

Lifes­pan/Longevity

No data are avail­able on the lifes­pan of adult worms, but the eggs of H. gal­li­narum have been ob­served to live up to five years in the soil, al­though this is likely rare. (Lund and Chute, 1974; Lund, 1960)

Be­hav­ior

As in other ne­ma­todes, H. gal­li­narum has lon­gi­tu­di­nal mus­cles which in com­bi­na­tion with the cu­ti­cle and pseudo­coelom form a hy­dro­sta­tic skele­ton. By uti­liz­ing the force that the con­trac­tion of the lon­gi­tu­di­nal mus­cles cre­ates, the cu­ti­cle short­ens on one side then length­ens on the other, cre­at­ing the di­ag­nos­tic S-shaped move­ment of ne­ma­todes.

Ju­ve­niles of H. gal­li­narum nor­mally re­side in the lumen, but on oc­ca­sion will travel to and enter ei­ther the cecal wall or cecal glands. (An­der­son, 2000; Olsen, 1986; Roberts and Janovy, 2008)

• Key Behaviors
• parasite
• motile

Com­mu­ni­ca­tion and Per­cep­tion

Ne­ma­todes, in­clud­ing H. gal­li­narum, have chemosen­sory or­gans called am­phids. Lo­cated an­te­ri­orly, these in­vagi­na­tions of the cu­ti­cle are made of many neu­rons which in­ter­pret and trans­mit in­com­ing chem­i­cal sig­nals. Het­er­akis gal­li­narum also has papil­lae, which are sen­sory struc­tures sur­round­ing the lip re­gion. Be­hind the lip re­gion are peg-like sen­sory struc­tures which func­tion both as chemore­cep­tors to de­tect chem­i­cals, as well as mechanore­cep­tors to de­tect mo­tion. Chemore­cep­tors are likely used in find­ing a mate, and sex­ual pheromones have been iden­ti­fied for over 40 ne­ma­tode species. (Roberts and Janovy, 2008; Wright and Hui, 1976; Wright, 1977)

• Communication Channels
• tactile
• chemical

• Perception Channels
• tactile
• chemical

Food Habits

Het­er­akis gal­li­narum feeds on the cecal con­tents of the bird in which it re­sides. (An­der­son, 2000)

• Primary Diet
• carnivore
  • eats body fluids

• Animal Foods
• body fluids

Pre­da­tion

Het­er­akis gal­li­narum is not di­rectly preyed upon, but eggs which have been re­leased into the soil can be eaten by other bird species, earth­worms, and in­sects such as flies and grasshop­pers. Often times, the eggs are brought to the sur­face of the soil by the move­ment of earth­worms and other soil in­hab­i­tants, thus mak­ing them more sus­cep­ti­ble to in­ges­tion by those an­i­mals listed above. (An­der­son, 2000; Lund, 1960)

Ecosys­tem Roles

Het­er­akis gal­li­narum is a par­a­site of gal­li­form birds, feed­ing upon their cecal con­tents. Earth­worms can serve as paratenic hosts for ju­ve­niles, al­low­ing them to move from the soil to a bird's gut. Eggs of H. gal­li­narum can be a car­rier of the dis­ease caus­ing pro­to­zoan His­tomonas me­lea­gridis. Birds can in­gest in­fected H. gal­li­narum eggs and ac­quire H. me­lea­gridis, re­sult­ing in black­head dis­ease. Black­head dis­ease af­fects mainly the liver and cecum of in­fected birds, caus­ing le­sions and ul­cers that are even­tu­ally fatal. (Kauf­mann, 1996; Olsen, 1986)

• Ecosystem Impact
• parasite

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

There are no known pos­i­tive ef­fects of Het­er­akis gal­li­narum on hu­mans.

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Het­er­akis gal­li­narum is eco­nom­i­cally im­por­tant be­cause it acts as a host for the pro­to­zoan H. me­lea­gridis. His­tomonas me­lea­gridis causes his­tomo­ni­a­sis, more com­monly known as black­head dis­ease, in turkeys that have in­gested H. gal­li­narum eggs with the par­a­site. Black­head dis­ease af­fects the liver and cecum of in­fected birds, caus­ing enough dam­age to be fatal if left un­treated. If many birds on turkey farms be­come in­fected and sub­se­quently die, sig­nif­i­cant loss of profit can re­sult for farm­ers. (Kauf­mann, 1996; Olsen, 1986)

• Negative Impacts
• causes or carries domestic animal disease

Con­ser­va­tion Sta­tus

• IUCN Red List

  Not Evaluated

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Con­trib­u­tors

Jackie Car­ron (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.

Ref­er­ences

An­der­son, R. 2000. Ne­ma­tode Par­a­sites of Verete­brates: Their De­vel­op­ment and Trans­mis­sion. UK: CABI Pub­lish­ing.

Kauf­mann, J. 1996. Par­a­sitic In­fec­tions of Do­mes­tic An­i­mals: A Di­ag­nos­tic Man­ual. Boston: Birkhauser.

Lund, E. 1960. Fac­tors in­flu­enc­ing the sur­vival of Het­er­akis and His­tomonas on soil. Jour­nal of Par­a­sitol­ogy, 46 (38): 38.

Lund, E., A. Chute. 1972. Het­er­akis and His­tomonas in­fec­tions in young peafowl, com­pared to such in­fec­tions in pheas­ants, chick­ens, and turkeys. Jour­nal of Wildlife Dis­eases, 8: 352-358.

Lund, E., A. Chute. 1974. The re­pro­duc­tive po­ten­tial of Het­er­akis gal­li­narum in var­i­ous species of gal­li­form birds: Im­pli­ca­tions for sur­vival of H. gal­li­narum and His­tomonas me­lea­gridis to re­cent times. In­ter­na­tional Jour­nal for Par­a­sitol­ogy, 4 (5): 455-461.

Olsen, O. 1986. An­i­mal Par­a­sites: Their Life Cy­cles and Ecol­ogy. New York: Dover Pub­li­ca­tions.

Roberts, L., J. Janovy. 2008. Foun­da­tions of Par­a­sitol­ogy: 8th Edi­tion. New York: Mc­Graw-Hill.

Wright, K. 1977. Labial sense or­gans of the ne­ma­tode, Het­er­akis gal­li­narum. The Jour­nal of Par­a­sitol­ogy, 63 (3): 528-539.

Wright, K., N. Hui. 1976. Post-labial sen­sory struc­tures on the cecal worm, Het­er­akis gal­li­narum. Jour­nal of Par­a­sitol­ogy, 62 (4): 579-584.