Adeleorina

Adeleorina is a suborder of Apicomplexa.^[1]

History

This taxon was created by Léger in 1911. The first species identified was Dactylosoma ranarum by Lankester (1871) in a frog in Europe. It was initially called Undulina ranarum, but this was changed in 1882 to Drepanidium ranarum. This species was subsequently moved to the genus Dactylosoma.

Canine hepatozoonosis was first described in India in 1905 by James. The organism was named Leukocytozoon canis. The vector was identified in 1907 by Christopher to be the brown dog tick (Rhipicephalus sanguineus). The genus Hepatozoon was created by Miller in 1908 for a parasite of the white rat (Rattus norvegicus) that underwent merogony in the liver and sporogony in the mite Laelap echidinus. This genus was placed initially in the family Haemogregarinidae by Ledger, but was subsequently removed and placed in the newly created taxon Hepatozoidae by Wenyon in 1926.

Life cycle

All species in this suborder use the syzygy method of gamete formation. This involves the association of often motile gamonts prior to the formation of functional gametes and fertilization.

Their life cycles tend to be complex, involving at least one (and often several) asexual cycles of merogony followed by gametogony, syngamy and sporogony. In many species of the group, the meronts and merozoites have morphologically distinct types: one type of meront produces large merozoites which initiate a further round of merogonic replication; a second produces smaller merozoites which are the progenitors of the gamonts. Microgamonts produce usually only one to four microgametes. Other characteristic features include the absence of endodyogony and the enclosure of sporozoites in a sporocyst.

In haemogregarines with heteroxenous species, conjugation of gamonts and subsequent sporogony usually occurs within an invertebrate (definitive host), which also serves as the vector. Merogonial division usually takes place in the parenchymatous organs of the vertebrate host. This is followed by the formation of infective gametocytes in the erythrocytes. In the genus Hepatozoon, gametocytes are also formed in the leukocytes.

The haemogregarines use two modes of transmission:

• Inoculation — the infectious sporozoites enter the vertebrate host during blood-feeding of the vector (Dactylosoma, Haemogregarina)

• Ingestion — the parasite is transmitted by the ingestion of the infected invertebrate host by the vertebrate host. The mode of transmission may even involve a paratenic host. The next definitive host in the life cycle is infected exclusively through blood feeding. Examples include the genera Karyolysus, Hemolivia and Hepatozoon.

Taxonomy

Adeleorina has about 500 species, which have been organised into seven families and 19 genera. The families have been divided into two groups:

• Adelines — monoxenous coccidians of invertebrates — Adeleidae and Legerellidae

• Haemogregarines — heteroxenous coccidians cycling between blood-sucking invertebrates (definitive hosts) and various vertebrates (intermediate hosts) — Dactylosomatidae, Haemogregarinidae, Hepatozoidae and Karyolysidae

One exception to this classification is known: Klossiella (family Klossiellidae) is a monoxenous coccidium of mammals and reptiles.

The taxonomy is this group may be incorrect as the Hepatozoidae appear to be paraphytic.^[2] The genus Hemolivia appears to lie within the genus Hepatozoon.^[3] The genus Hepatozoon appears to have two subgenera with one in the carnivorous mammals and the other in lower vertebrates and rodents.^[4]

Families and genera

The families in this suborder are:

• Family Adeleidae — taxon created by Mesnil in 1903
  • Genera:
    • Chagasella — taxon created by Machado in 1911
    • Ganapatiella — taxon created by Kalavati in 1977
    • Gibbsia — taxon created by Levine in 1986
    • Klossia — taxon created by Schneiderin in 1875
    • Orcheobius — taxon created by Schuberg & Kunze in 1906
    • Rasajeyna — taxon created by Beesley in 1977
  • Subfamily Ithaniinae
    • Genera
      • Adelea — taxon created by Schneider in 1875
      • Adelina — taxon created by Hesse in 1911
      • Ithania — taxon created by Ludwigin in 1947

• Family Dactylosomatidae — taxon created by Jakowska & Nigrelli in 1955
  • Genera:
    • Babesiosoma — taxon created by Jakowska & Nigrelli in 1956
    • Dactylosoma — taxon created by Labbé in 1894

• Family Haemogregarinidae — taxon created by Neveu-Lemaire in 1901
  • Genera:
    • Cyrilia — taxon created by Lainson in 1981
    • Desseria — taxon created by Siddall in 1995
    • Haemogregarina — taxon created by Danilewsky in 1885

• Family Hepatozoidae — taxon created by Wenyon in 1926
  • Genera:
    • Hepatozoon — taxon created by Miller in 1908

• Family Karyolysidae — taxon created by Wenyon in 1926
  • Genera:
    • Karyolysus — taxon created by Labbe in 1894
    • Hemolivia — taxon created by Petit et al in 1990

• Family Klossiellidae — taxon created by Smith & Johnson in 1902
  • Genera:
    • Klossiella

• Family Legerellidae — taxon created by Minchin in 1903
  • Genera:
    • Legerella — taxon created by Mesnil in 1900

Notes

Karyolysus infects lizards (Lacerta) and possibly scincids. Haemogregarina infects turtles and leeches. Species of the genus Desseria infect fish and lack erythrocytic merogony. The genera in the subfamily Ithaniinae share a number of morphological features and infect the digestive tract of insects.

DNA studies suggest Hemolivia may lie within the Hepatozoon clade.^[3] If this can be confirmed, the taxonomy of this group will need revision.

References