| Karyolysus | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Clade: | Sar |
| Clade: | Alveolata |
| Phylum: | Apicomplexa |
| Class: | Conoidasida |
| Order: | Eucoccidiorida |
| Family: | Karyolysidae |
| Genus: | Karyolysus |
| Species | |
Karyolysus lacazei | |
Karyolysus is a genus of coccidia.[1] With the exception ofK. sonomae whose vertebrate host is the yellow-legged frog (Rana boylii boylii), species in this genus only infect lizards of the genusLacerta.
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 isKaryolysus lacertae[2].
Schizogeny occurs in theendothelial cells
Gametogony occurs in theerythrocytes after their penetration by themerozoites.
Differentiation from the genusHaemogregarina 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: InKaryolysus this occurs in the endothelial cells of the visera while inHaemogregarina schizogony occurs in thebone marrow.
Starting with infectedmites which the hostlizard ingests the veriformsporozoites are released from thesporocysts. These newly liberated sporozoites bore into the intestinal wall and enter thelymphatic vessels and theblood stream. On reaching the viscera and in particular theliver 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 discernablenucleus. These are also eventually released into the blood stream, this occurs usually day 42 post infection.
These small merozoites are actuallygametocytes. These penetrate erythrocytes and differentiate intomacrogametoctyes andmicrogametocytes. 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[clarification needed].
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 azygote.
The zygote (orookinete) grows within the cell and undergoesmeiosis followed by several rounds ofmitosis. 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 assporoblasts. As they mature become vermicular in shape and are known assporokinetes. 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 theyolk of theeggs. 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 theendodermal cells of the gut. On feeding some of the sporozoites enter the gut. Some remain within the gut while others exit in thefaeces. When a lizard swallows the faeces or the mite which may be feeding on it the cycle begins again.
Hypnozoites are found inKaryolysus lacerate.
A study of the 18s rRNA suggests that this genus may overlap withHepatozoon.[3]
K. sonomae - yellow legged frog (Rana boyli boyli)
Lizard (Lacerta raddei nairensis)