The term spermatid refers to the haploid male germ cell that results from secondary spermatocyte division. As a result of meiosis, each spermatid contains only half of the genetic material present in the original primary spermatocyte. Haploid (meaning simple in Greek) cells have only one copy of each chromosome. ... Gametes (in Greek: γαμέτες) —also known as sex cells, germ cells, or spores—are the specialized cells that come together during fertilization (conception) in organisms that reproduce sexually. ... Spermatogenesis refers to the creation, or genesis, of sperm cells, which occurs in the male gonads or testes. ... For the article on the figure of speech, see meiosis (figure of speech). ...
Spermatids are connected together by cytoplasmic material and have superfluous cytoplasmic material around their nuclei.
When formed, early round spermatids must undergo further maturational events in order to develop into spermatozoa, a process termed spermiogenesis (also termed spermeteliosis). The spermatids begin to grow a tail, develop a thickened mid-piece where the mitochondria become localised and form an acrosome. Spermatid DNA also undergoes packaging, becoming highly condensed. The DNA is packaged firstly with specific nuclear basic proteins, which are subsequently replaced with protamines during spermatid elongation. The resultant tightly packed chromatin is transcriptionally inactive. Schematic diagram of a sperm cell, showing the (1) acrosome, (2) cell membrane, (3) nucleus, (4) mitochondria, and (5) flagellum (tail) A sperm cell, or spermatozoon ( spermatozoa) (in Greek: sperm = semen and zoon = alive), is the haploid cell that is the male gamete. ... In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ... In sperm cells of many higher animals, the acrosome develops over the anterior half of its head. ... Chromatin is the substance of a chromosome and consists of a complex of DNA and protein in eukaryotic cells. ...
In no cases were round spermatids found in the absence of elongated spermatozoa, and maturation arrest was found always to be a failure of progression beyond meiosis (not at maturation from round spermatid to mature elongated spermatid).
Recently the possibility has been investigated of using 'round spermatids', or 'round cells', derived from testicular tissue (or even from the ejaculate), that are presumably early spermatids, to inject for ICSI for such cases when no elongated spermatozoa are recoverable.
Their successful pregnancy resulted from injection of a spermatid retrieved from the testicle, rather than the ejaculate, but these were not to round spermatids.