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First published online March 16, 2007
Journal of Experimental Biology 210, 1109-1115 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.002238
Gill morphology of the mangrove killifish (Kryptolebias marmoratus) is plastic and changes in response to terrestrial air exposure
Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
* Author for correspondence (e-mail: patwrigh{at}uoguelph.ca)
Accepted 29 January 2007
Amphibious mangrove killifish, Kryptolebias marmoratus (formerly
Rivulus marmoratus), are frequently exposed to aerial conditions in
their natural environment. We tested the hypothesis that gill structure is
plastic and that metabolic rate is maintained in response to air exposure.
During air exposure, when gills are no longer functional, we predicted that
gill surface area would decrease. In the first experiment, K.
marmoratus were exposed to either water (control) or air for 1 h, 1 day,
1 week, or 1 week followed by a return to water for 1 week (recovery).
Scanning electron micrographs (SEM) and light micrographs of gill sections
were taken, and morphometric analyses of lamellar width, lamellar length and
interlamellar cell mass (ILCM) height were performed. Following 1 week of air
exposure, SEM indicated that there was a decrease in lamellar surface area.
Morphometric analysis of light micrographs revealed that there were
significant changes in the height of the ILCM, but there were no significant
differences in lamellae width and length between any of the treatments.
Following 1 week of recovery in water, the ILCM regressed and gill lamellae
were similar to control fish, indicating that the morphological changes were
reversible. In the second experiment,
CO2 was measured
in fish continuously over a 5-day period in air and compared with previous
measurements of oxygen uptake
(O2) in water.
CO2 varied
between 6 and 10 µmol g–1 h–1 and was
significantly higher on days 3, 4 and 5 relative to days 1 and 2. In contrast
to O2 in water,
CO2 in air
showed no diurnal rhythm over a 24 h period. These findings indicate that
K. marmoratus remodel their gill structures in response to air
exposure and that these changes are completely reversible. Furthermore, over a
similar time frame, changes in
CO2 indicate
that metabolic rate is maintained at a rate comparable to that of fish in
water, underlying the remarkable ability of K. marmoratus to thrive
in both aquatic and terrestrial habitats.
Key words: metabolic rate, CO2 excretion, emersion, gill lamellae, interlamellar cell mass
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