''Heterakis'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...

nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...

s. Members of the genus are minute

roundworm The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (hel ...

s, hardly 1 cm long, infecting different

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of gallinaceous birds, including

chicken The chicken (''Gallus gallus domesticus'') is a domesticated subspecies of the red junglefowl (''Gallus gallus''), originally native to Southeast Asia. It was first domesticated around 8,000 years ago and is now one of the most common and w ...

turkey Turkey, officially the Republic of Türkiye, is a country mainly located in Anatolia in West Asia, with a relatively small part called East Thrace in Southeast Europe. It borders the Black Sea to the north; Georgia (country), Georgia, Armen ...

duck Duck is the common name for numerous species of waterfowl in the family (biology), family Anatidae. Ducks are generally smaller and shorter-necked than swans and goose, geese, which are members of the same family. Divided among several subfam ...

geese A goose (: geese) is a bird of any of several waterfowl species in the family Anatidae. This group comprises the genera '' Anser'' (grey geese and white geese) and ''Branta'' (black geese). Some members of the Tadorninae subfamily (e.g., Egyp ...

grouse Grouse are a group of birds from the order (biology), order Galliformes, in the family (biology), family Phasianidae. Grouse are presently assigned to the Tribe (biology), tribe Tetraonini (formerly the subfamily Tetraoninae and the family Tetr ...

guineafowl Guinea fowl () (or guineahen) are birds of the family Numididae in the order Galliformes. They are endemic to Africa and rank among the oldest of the gallinaceous birds. Phylogenetically, they branched off from the core Galliformes after the C ...

partridge A partridge is a medium-sized Galliformes, galliform bird in any of several genera, with a wide Indigenous (ecology), native distribution throughout parts of Europe, Asia and Africa. Several species have been introduced to the Americas. They ar ...

pheasant Pheasants ( ) are birds of several genera within the family Phasianidae in the order Galliformes. Although they can be found all over the world in introduced (and captive) populations, the pheasant genera's native range is restricted to Eura ...

s, and

quail Quail is a collective name for several genera of mid-sized birds generally placed in the order Galliformes. The collective noun for a group of quail is a flock, covey, or bevy. Old World quail are placed in the family Phasianidae, and New ...

. About 10 species are placed in the genus, but

classification Classification is the activity of assigning objects to some pre-existing classes or categories. This is distinct from the task of establishing the classes themselves (for example through cluster analysis). Examples include diagnostic tests, identif ...

is often ambiguous due to their close resemblance, and a number of

synonym A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

s have arisen. '' H. gallinarum'' Schrank, 1788; ''H. isolonche'' von Linstow, 1906; and ''H. dispar'' Schrank, 1870 are the best understood species in terms of

prevalence In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...

pathogenicity In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term ...

, and

biology Biology is the scientific study of life and living organisms. It is a broad natural science that encompasses a wide range of fields and unifying principles that explain the structure, function, growth, History of life, origin, evolution, and ...

. They inhabit the lumen of the

cecum The cecum ( caecum, ; plural ceca or caeca, ) is a pouch within the peritoneum that is considered to be the beginning of the large intestine. It is typically located on the right side of the body (the same side of the body as the appendix (a ...

of the host. The nematodes are whitish in colour,

cylindrical A cylinder () has traditionally been a Solid geometry, three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a Prism (geometry), prism with a circle as its base. A cylinder may ...

, and with fine longitudinal striations throughout the body. The body covering is a

proteinaceous Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...

layer named

cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

. The anterior end is the mouth with distinct lips, and the

anus In mammals, invertebrates and most fish, the anus (: anuses or ani; from Latin, 'ring' or 'circle') is the external body orifice at the ''exit'' end of the digestive tract (bowel), i.e. the opposite end from the mouth. Its function is to facil ...

opens towards the posterior. They are diecious with marked

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

. Males are shorter and smaller, with straight blunt tails, while females are bigger and longer, with curved tails. They all exhibit direct lifecycles. They cause nodular

typhlitis Neutropenic enterocolitis, also known as typhlitis, is an inflammation of the cecum (part of the large intestine) that may be associated with infection. It is particularly associated with neutropenia, a low level of neutrophil granulocytes (the mos ...

diarrhoea Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...

emaciation Emaciation is defined as the state of extreme thinness from absence of body fat and muscle wasting usually resulting from malnutrition. It is often seen as the opposite of obesity. Characteristics Emaciation manifests physically as thin limbs, pr ...

, and

death Death is the end of life; the irreversible cessation of all biological functions that sustain a living organism. Death eventually and inevitably occurs in all organisms. The remains of a former organism normally begin to decompose sh ...

. ''H. gallinarum'' is the most well-known species, and is most important as it transmits the

protozoa Protozoa (: protozoan or protozoon; alternative plural: protozoans) are a polyphyletic group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic debris. Historically ...

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

, ''Histomonas meleagridis'' in birds.

References

External links

BioLib

ZipcodeZoo

{{Taxonbar, from=Q3719459 Parasitic nematodes of vertebrates Parasites of birds Ascaridomorpha Chromadorea genera Taxa named by Franz von Paula Schrank