Temperature and
developmental plasticity during embryogenesis in the Atlantic cod Gadus morhua L.
T.E. Hall, I.A. Johnston-2003
Marine Biology, 142(5): 833-840
Abstract:
Atlantic cod (Gadus morhua L.) embryos were reared at 4°C, 7°C, and 10°C,
and the relative timing of developmental events was characterized, with
particular reference to myotomal muscle. Embryos started to feed at an
apparently equivalent stage of development, so comparisons were made between
temperature groups on the basis of percentage of time to first feeding and
somite stage. No differences were found in the time of hatching or timing of
appearance of the otic placode, unpaired median fin fold, gut lumen, otic
vesicle, lens of the eye, otoliths, first muscular contractions, swim
bladder, and hindgut, or in the rate of development of somites, myotubes,
myofibrils, and acetylcholinesterase activity over the temperature range
studied. In contrast, closure of the blastopore occurred late with respect
to segmentation at higher temperatures, at the 3-somite, 10-somite, and
12-somite stages at 4°C, 7°C, and 10°C respectively. Muscle cellularity
was also markedly altered in the 10°C group relative to the 4°C and 7°C
groups. Larvae reared at 10°C had significantly more (+14%) deep white
fibers at hatch (P
<0.001), whereas numbers of superficial red fibers remained unchanged. It
is suggested that differences in muscle cellularity might be related to
changes in the relative timing of epiboly, through differential
proliferation of presomitic myogenic cells and/or their relative exposure to
inductive signals.
(Gatty Marine Laboratory, School of Biology,
University of St. Andrews, KY16 8LB, Fife, UK)