Acclimation of crucian carp and goldfish to temperatures below 15° C causes covering of the gill lamellae by a mass of cells termed the interlamellar cell mass (ILCM). Here we explore the cues underlying gill remodelling (removal or growth of an ILCM) and specifically test the hypotheses that i) depletion of internal O2 stores in the absence of any change in external O2 status, can trigger the removal of the ILCM in goldfish acclimated to 7° C, ii) exposing fish acclimated to 25° C to an abundance of O2 (hyperoxia) can reverse the gill remodelling (i.e. cause the covering of lamellae by an expansion of the ILCM), and iii) neuroepithelial cells (NECs) are involved in signalling the shedding of the ILCM. Hypoxemia induced by phenylhydrazine (anaemia) or 5% CO caused a decrease in the ILCM from 80 to 23 and 35 %, respectively. Hyperoxia exposure at 25° C caused an increase to 67% of total ILCM and a smaller decrease in the size of the ILCM when fish were transferred from 7 to 25° C. Daily sodium cyanide injections were used to stimulate NECs; this treatment led to a significant decrease in the ILCM. Thus, the three major conclusions of this study are i) that gill remodelling can occur during periods of internal hypoxemia, ii) that O2 supply and demand may be a significant driving force shaping gill remodelling in goldfish, and iii) the NECs may play a role in triggering the shedding of the ILCM during hypoxia.
- neuroepithelial cell
- gill remodelling
- carbon monoxide
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