Ultraviolet irradiation of tilapia spermatozoa and the Hertwig effect: electron microscopic analysis

J. Don, R. R. Avtalion

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Electron microscopic analysis of UV-irradiated tilapia sperm showed that with irradiation dose of 1800 J m-2 min-1, an irradiation duration of 0·5 min caused decondensation of sperm chromatin. This phenomenon of chromatin decondensation reached a peak after 1·5 min of irradiation, where ∼ 15% of the sperm showed total decondensation, and was less apparent after 3 min of irradiation or more. Damage to the cytoplasmic membrane and nuclear envelope could be seen in cells that underwent total decondensation. As the duration of irradiation increased, cytoplasmic membrane and nuclear envelope defects appeared more severe, the mitochondria were affected and appeared as empty capsules, and sperm cells tended to lose their tails. Based on these results and others reported in the literature, we propose an explanation for the 'Hertwig curve' obtained in tilapia using UV irradiation. Sperm cells with decondensed chromatin and damaged cytoplasmic membrane and nuclear envelope, activate the 'developmental switch' when they penetrate the egg, but their pronuclei are subjected to cytoplasmic nuclease digestion. Consequently, the maternal pronucleus is the only functional pronucleus in the zygote, and therefore, only haploid embryos with the exclusive maternal genome are formed. If the paternal pronucleus is not digested, these embryos will die due to improper expression of the paternal genes.

Original languageEnglish
Pages (from-to)1-14
Number of pages14
JournalJournal of Fish Biology
Issue number1
StatePublished - Jan 1993
Externally publishedYes


  • Hertwig effect
  • Ultraviolet irradiation
  • spermatozoa
  • tilapia


Dive into the research topics of 'Ultraviolet irradiation of tilapia spermatozoa and the Hertwig effect: electron microscopic analysis'. Together they form a unique fingerprint.

Cite this