Toxicity of chlorine to zebrafish embryos.

TitleToxicity of chlorine to zebrafish embryos.
Publication TypeJournal Article
Year of Publication2014
AuthorsKent, ML, Buchner, C, Barton, C, Tanguay, RL
JournalDis Aquat Organ
Date Published2014 Jan 16
KeywordsAnimals, Chlorine, Dose-Response Relationship, Drug, Embryo, Nonmammalian, Zebrafish

Surface disinfection of fertilized fish eggs is widely used in aquaculture to reduce extraovum pathogens that may be released from brood fish during spawning, and this is routinely used in zebrafish Danio rerio research laboratories. Most laboratories use approximately 25 to 50 ppm unbuffered chlorine solution for 5 to 10 min. Treatment of embryos with chlorine has significant germicidal effects for many Gram-negative bacteria, viruses, and trophozoite stages of protozoa, but is less effective against cyst or spore stages of protozoa and certain Mycobacterium spp. Therefore, we evaluated the toxicity of unbuffered and buffered chlorine solutions to embryos exposed at 6 or 24 h post-fertilization (hpf) to determine whether higher concentrations can be used for treating zebrafish embryos. Most of our experiments entailed using an outbred line (5D), with both mortality and malformations as endpoints. We found that 6 hpf embryos consistently were more resistant than 24 hpf embryos to the toxic effects of chlorine. Chlorine is more toxic and germicidal at lower pH, and chlorine causes elevated pH. Consistent with this, we found that unbuffered chlorine solutions (pH ca. 8-9) were less toxic at corresponding concentrations than solutions buffered to pH 7. Based on our findings here, we recommend treating 6 hpf embryos for 10 min and 24 hpf embryos for 5 min with unbuffered chlorine solution at 100 ppm.

Alternate JournalDis. Aquat. Org.
PubMed ID24429474
PubMed Central IDPMC4133985
Grant ListP30ES000210 / ES / NIEHS NIH HHS / United States
R24 RR017386 / RR / NCRR NIH HHS / United States
5R24RR017386-02 / RR / NCRR NIH HHS / United States
RC4 ES019764 / ES / NIEHS NIH HHS / United States
RC4ES019764 / ES / NIEHS NIH HHS / United States
P30 ES000210 / ES / NIEHS NIH HHS / United States