Mesokaryotic cell is the intermediate cell of prokaryotic cell and eukaryotic cell. Dodge has first used the term mesokaryotic in 1966 for the cell that contains an intermediate nucleus (both eukaryotic and prokaryotic characters are present). Although Dougherty (1957) has divided cells into two types – prokaryotic cell and eukaryotic cell.
The name Mesokaryotic is derived from the Greek words Meso and Karyon.
” Meso = intermediate and karyon = nucleus “
Mesokaryotic cell contains a membrane-bound organized nucleus (a characteristic feature of eukaryotes) but performs nuclear division by amitotic method without disintegration of the nuclear membrane (like a prokaryotic cell). The nucleus of mesokaryotic cells resembles both prokaryotic and eukaryotic nuclei. The cells are medium-sized and having membrane-bound cell organelles like – mitochondria, plastids, endoplasmic reticulum, etc. The organisms having mesokaryotic cells are called mesokaryotes.
The cells having organized nucleus containing chromosomes with membrane-bound cell organelles (mitochondria, plastids, endoplasmic reticulum, etc.) and its nucleus divided through amitosis process without disintegration of the nuclear membrane are called mesokaryotic cells.
Characteristic features of Mesokaryotic cell:
Mesokaryotic cells resemble both prokaryotes and eukaryotes. Their major characteristic features are as follows –
1. The cells are medium-sized and the size of the cell is in between prokaryotic cells and eukaryotic cells.
2. They do not have a cell wall but instead have a pellicle or theca.
3. Cell membrane is present.
4. The nucleus is well-organized and surrounded by the membrane.
5. Membrane-bound cell organelles (like- mitochondria, plastids, endoplasmic reticulum) are present in the cytoplasm.
6. The ribosomes in the cytoplasm are 80s type.
7. The histone protein is completely absent in the cell.
8. Chromosome is present and which is formed with the help of acidic proteins.
9. Centrosome is absent in the cytoplasm. So, the mitotic apparatus is not formed during cell division.
10. Cell division occurs through the method of amitosis without disintegration of the nuclear membrane.
11. Flagella are present and consist of filaments.
12. Presence of chloroplast in the cell and contains photosynthetic pigments.
13. Respiratory enzymes are present in the cytoplasm or mitochondria.
Some mesokaryotes are Peridinium and Gymnodinium of algal group Pyrophyta and Noctiluca of protozoa