The cell has vesicles that increase the deposition of silica creating a new valve girdle band. Vegetative cells are diploid, and gametes are the only haploid stages. Sexual reproduction differs in centric and pennates diatoms. Centric diatoms undergo meiosis to form eggs and sperm. Oogonial cells usually produces one egg, which may be released into the water or retained.
Size decreases as mitosis proceeds.
This provides a timing mechanism between sexual reproduction. Centric, antheridial cells meiosis produces 4 sperms or more per cell. Penate are cells not flagellate, gametangial cells pair in muscilage, and each cell undergoes meiosis. In some diatom, vegetative enlargement occurs by release of the protoplast from its surrounding frustule, enlargement, and formation of a new frustule. However, there are some as part of the benthos attached on substrates.