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<html><head><style> body {height: 100%; color:#000000; font-size:12pt; font-family:Times New Roman;}</style></head><body>Marie, I think what you may be experiencing is "suspension" in development possibly due to exposure to low oxygen levels in the rearing dishes (easy to occur esp. if the dishes are covered and the room is warm). Keep the surface area to depth ratio high in your dishes. Developing embryos  will actually rotate w/in the egg towards areas of higher O2 when an egg is partially imbedded in gel! Personally I have not seem this but folks here who are working with micro DO probes have. This "suspended animation" quirk happens w/many fish species, perhaps as a method of "holding on" until environmental conditions improve. I'm preaching to the choir w/this next statement, but making new cells is an extremely aerobic process. No oxygen...things slow down...then die. Good paper on this by Christopher Ton and colleagues "Physiological Genomics" 13:97-106, 2003 good luck! ----- Original Message ----- From: Marie Winandy <mwinandy@ulg.ac.be> To: zbrafish@magpie.bio.indiana.edu Sent: Fri, 5 Jun 2009 10:37:03 -0400 (EDT) Subject: [Zbrafish] delay in development or high mortality Hi all, since a few weeks, some PhD students in our lab have got problems with their wild type, non injected embyos: - some have a delay in development (14 somites instead of 24); - in some dishes, there are 3 or more different developmental stages at 24hpf (while the eggs were collected at the same time, with a 15 minutes interval between each clutch); - some clutches show >50 % mortality at 24hpf. We also have some pairs laying only dead eggs. This occurs in 25-30% of the clutches. At this time, the transgenics eggs don't seem to be affected. It seems that this occurs more frequently with eggs collected in the afternoon. The parent fish are 9-12 months old. Recently, there has been some NH4+/NH3 and NO2 in the system, but now it's decreased. We pay attention to let only 50 eggs in the 8cm petri dishes, change water at least once a day, discard unfertilised eggs at 4hpf. Have you any idea of the possible cause(s) of this? Do you think that the N ions could have influenced individuals at different levels, making some of them produce good eggs and other no? Thank you in advance for any shared idea and help. best regards, Marie -- William N. Mebane Superintendent Aquaculture Engineering Divison Marine Resources Center, Marine Biological Laboratory 7 MBL Street Woods Hole, MA 02543 phone (508) 289-7683 fax (508) 289-7900 MBL website - www.mbl.edu Haiti website http://www.mbl.edu/mrc/outreach/sustainable_aquaculture/index.html</mwinandy@ulg.ac.be></body></html>

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