''Karyolysus'' is a genus of coccidia. With the exception of ''K. sonomae'' whose vertebrate host is the yellow-legged frog ('' Rana boylii boylii''), species in this genus only infect lizards of the genus ''

Lacerta Lacerta is one of the 88 modern constellations defined by the International Astronomical Union. Its name is Latin for lizard. A small, faint constellation, it was defined in 1687 by the astronomer Johannes Hevelius. Its brightest stars form a "W" ...

''.

History

The genus was created by Labbe in 1894 for those species of sporozoans that fragmented the host nucleus. Reichenow in 1921 established that this property was of dubious taxonomic value. He proposed a different set of criteria for inclusion in this genus and these are the one currently in use. The type species is ''Karyolysus lacertae'' .

Characteristics of the genus

Schizogeny "Schizogeny" is the ninth episode of the fifth season of the science fiction television series ''The X-Files''. It premiered on the Fox network on January 11, 1998. It was written by Jessica Scott and Mike Wollaeger, directed by Ralph Hemecker, a ...

occurs in the endothelial cells

Gametogony Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism i ...

occurs in the

erythrocyte Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...

s after their penetration by the

merozoite Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism is ...

s. Differentiation from the genus '' Haemogregarina'' may be difficult as in both genera gametocytogenesis occurs in the erythrocytes and have similar morphology. They can be distinguished on the location of schizogony: In ''Karyolysus'' this occurs in the endothelial cells of the visera while in ''Haemogregarina'' schizogony occurs in the bone marrow.

Life cycle

Starting with infected

mite Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear e ...

s which the host lizard ingests the veriform

sporozoite Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism is ...

s are released from the sporocysts. These newly liberated sporozoites bore into the intestinal wall and enter the

lymph Lymph (from Latin, , meaning "water") is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the venous system, is to return fluid from the tissues ...

atic vessels and the

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...

stream. On reaching the viscera and in particular the

liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...

the sporozoites penetrate the endothelial cells. There they form ovoid schizonts within a membranous capsule. They remain in these cells for some time and give rise to 8 to 30 merozoites. The merozoites remain in the cell for some time before rupturing it and entering the blood stream. On entering the blood stream the merozoites penetrate other endothelial cells. There they grow and undergo schizogeny producing a number of small merozoites. These second generation schizonts are smaller than the first generation and lack a discernable

nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom * Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucl ...

. These are also eventually released into the blood stream, this occurs usually day 42 post infection. These small merozoites are actually

gametocyte A gametocyte is a eukaryotic germ cell that divides by mitosis into other gametocytes or by meiosis into gametids during gametogenesis. Male gametocytes are called ''spermatocytes'', and female gametocytes are called ''oocytes''. Development ...

s. These penetrate erythrocytes and differentiate into macrogametoctyes and microgametocytes. Both types are surrounded by a thin membrane. The microgametocytes remain thin and do not develop a nucleus. The macrogametocytes in contrast enlarge and develop a visible nucleus at one end of the nucleus. On ingestion by a female mite (male mites do not require blood) the gametocytes are released from the erythrocytes. Within the gut they associate in spindle like pairs and enter the epithelial cells of the gut. Within the epithelial cell the macrogametocyte increases in size while the microgametocyte shrinks. The microgametocyte divides in two and one of the motile gametes so formed fuses with the macrogametocyte to form a

zygote A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicell ...

. The zygote (or

ookinete Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism i ...

) grows within the cell and undergoes

meiosis Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately r ...

followed by several rounds of mitosis. The ookinte is now known as an oocyst. Within the oocyst the nuclei migrate to the surface of the oocyst and gather cytoplasm around them becoming known as sporoblasts. As they mature become vermicular in shape and are known as sporokinetes. These which are very active. On release from the oocyst the sporokinetes migrate throughout the body of the mite. Some settle in the ovaries and enter the

yolk Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example ...

of the

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...

s. Within the egg they develop a membrane and grow within this. This stage is known as the sporocyst. Within the sporocyst sporogony generates 20 to 30 sporozoites. These invade the developing nymph and enter the endodermal cells of the gut. On feeding some of the sporozoites enter the gut. Some remain within the gut while others exit in the

faeces Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...

. When a lizard swallows the faeces or the mite which may be feeding on it the cycle begins again.

Hypnozoite ''Plasmodium'' is a genus of unicellular eukaryotes that are obligate parasites of vertebrates and insects. The life cycles of ''Plasmodium'' species involve development in a blood-feeding insect host which then injects parasites into a verte ...

s are found in ''Karyolysus lacerate''.

Taxonomy

A study of the 18s rRNA suggests that this genus may overlap with ''

Hepatozoon ''Hepatozoon'' is a genus of Apicomplexa alveolates which incorporates over 300 species obligate intraerythrocytic parasites. Species have been described from all groups of tetrapod vertebrates, as well as a wide range of haematophagous arthropod ...

''.Haklová-Kočíková B, Hižňanová A, Majláth I, Račka K, Harris DJ, Földvári G, Tryjanowski P, Kokošová N, Malčeková B, Majláthová V (2014) Morphological and molecular characterization of Karyolysus--a neglected but common parasite infecting some European lizards. Parasit Vectors 7:555.

Host records

''K. sonomae'' - yellow legged frog ('' Rana boyli boyli'')

Hosts known to be infected but parasite species not reported

Lizard ('' Lacerta raddei nairensis'')

References

{{Taxonbar, from=Q6373871 Apicomplexa genera