Merocystis
| Merocystis | |
|---|---|
Scientific classification
| |
| Domain: | Eukaryota |
| Clade: | Diaphoretickes |
| Clade: | SAR |
| Clade: | Alveolata |
| Phylum: | Apicomplexa |
| Class: | Conoidasida |
| Order: | Eucoccidiorida |
| Family: | Aggregatidae |
| Genus: | Merocystis Dakin, 1911 |
| Species: | M. kathae
|
| Binomial name | |
| Merocystis kathae Dakin, 1911
| |
Merocystisis agenusin thephylumApicomplexa.
History
[edit]This genus was created in 1911 by Dakin[1]He discovered this parasite -Merocystis kathae- in the renal organ of the whelk (Buccinum undatum). Its life cycle has been studied in some detail by other workers.[2]
A second species was described -Merocystis tellinovum- by Buchanan in 1979 but this has since been moved to the genusPseudoklossia.
Taxonomy
[edit]There is one species known in this genus.
Description
[edit]Thelife cyclefollows a seasonal course. The earliest stages may appear in thekidneyany time between March and June. Growth proceeds andsexual differentiationtakes place but maturegametesare not found until November, when the first stages of sporogony are first found. Mature spores containing sporozoites are formed in January and become increasingly common up to May. Degenerating stages of spores are common in summer.
The earliest stages within the renal organ are 10μmin diameter.
To the naked eye the later stages of the parasite have the appearance of a rounded milky white dot.
Thetrophozoitesappear opaque and occasionally granular.
Schizogonyoccurs in the host cell.
Morphological sexual differentiation is not detectable until growth is almost complete.
Themicrogametocytedivides into 32nuclei.At this stage cleavage of thecytoplasmbrings about the formation ofuninucleatecytomeres.Nuclear division again occurs within these and these latter divisions form themicrogametes.
The microgamete possesses a dark centre and a lighter ring round the periphery and is released from the host cell.
Fertilizationoccurs within thelumenof the renal organ.
After fertilisation, a thick membrane forms outside thezygote.Thenucleusassumes a characteristicspindleshape and subsequently divides.
Nuclear divisions proceed until numerousconeshaped nuclei are found below the cell membrane. This cell membrane becomes folded and the nuclei sink in (the oocyst stage). Each is surrounded by a portion of cytoplasm to form asporoblast.A single nuclear division then occurs and the two nuclei elongate to form sporozoites each with a small cytoplasmic body.
Theoocysthas numeroussporocystseach with twosporozoites.
References
[edit]- ^Dakin WJ (1911) Notes on a new coccidianMerocystis kathae(n. gen. et sp.,) occurring in the renal organ of the whelk. Arch. Protist XXIII: 1115
- ^Patten, R (1935). "The life history ofMerocystis kathaein the whelk,Buccinum undatum".Parasitology.27(3): 399–430.doi:10.1017/S0031182000015328.