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Implications of mechanical deformation and formaldehyde preservation for the identification of stage‐specific characteristics of Baltic cod eggs

Implications of mechanical deformation and formaldehyde preservation for the identification of... The identification of developmental stages in fish eggs from plankton samples is often complicated by deformation of the embryos due to mechanical stress during the sampling procedure and by dehydration during formaldehyde fixation. The effects of formaldehyde fixation and mechanical stress on Baltic cod eggs (Gadus morhua callarias L.) were examined separately by visually comparing the morphological features of treated vs. live eggs of identical ontogenetic age. Microphotographs were made concurrently for documentation. In stage IA eggs, mechanical treatment resulted in scattered blastodiscs surrounded by single cells, while in further advanced stages the yolk membrane collapsed entirely, the yolk coagulated and the embryo extending over the yolk shrank. Formaldehyde fixation caused the yolk and the blastodisc or embryo to darken, and in some cases crystalline enclosures occurred. Eggs mechanically deformed during handling were clearly distinguishable from those that died prior to catching; however, staging was generally less accurate for formaldehyde‐preserved eggs when compared with living specimens. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Applied Ichthyology Wiley

Implications of mechanical deformation and formaldehyde preservation for the identification of stage‐specific characteristics of Baltic cod eggs

Geldmacher, A.; Wieland, K.
Journal of Applied Ichthyology , Volume 15 (2) – May 1, 1999
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Publisher
Wiley
Copyright
Copyright © 1999 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0175-8659
eISSN
1439-0426
DOI
10.1046/j.1439-0426.1999.00093.x
Publisher site
See Article on Publisher Site

Abstract

The identification of developmental stages in fish eggs from plankton samples is often complicated by deformation of the embryos due to mechanical stress during the sampling procedure and by dehydration during formaldehyde fixation. The effects of formaldehyde fixation and mechanical stress on Baltic cod eggs (Gadus morhua callarias L.) were examined separately by visually comparing the morphological features of treated vs. live eggs of identical ontogenetic age. Microphotographs were made concurrently for documentation. In stage IA eggs, mechanical treatment resulted in scattered blastodiscs surrounded by single cells, while in further advanced stages the yolk membrane collapsed entirely, the yolk coagulated and the embryo extending over the yolk shrank. Formaldehyde fixation caused the yolk and the blastodisc or embryo to darken, and in some cases crystalline enclosures occurred. Eggs mechanically deformed during handling were clearly distinguishable from those that died prior to catching; however, staging was generally less accurate for formaldehyde‐preserved eggs when compared with living specimens.

Journal

Journal of Applied Ichthyology – Wiley

Published: May 1, 1999

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