Response of mucous cells of the gills of traíra (Hoplias malabaricus) and jeju (Hoplerythrinus unitaeniatus) (Teleostei: Erythrinidae) to hypo- and hyper-osmotic ion stress

Sandro Estevan Moron,Cássio Arilson De Andrade,Marisa Narciso Fernandes

doi:10.1590/s1679-62252009000300017

Sandro Estevan Moron, Cássio Arilson De Andrade + Show 1 more

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https://doi.org/10.1590/s1679-62252009000300017

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Abstract

The mucous cells (MC) of traíra, Hoplias malabaricus, and jeju, Hoplerythrinus unitaeniatus, two ecologically distinct erythrinid species, were analyzed in fish exposed to deionized (DW) and high ion concentration (NaCl and Ca2+) water (HIW) during 15 days to evaluate the MC responses to ion challenge. MCs are localized in the leading and trailing edge and, interlamellar region of the gill filament epithelium but, in H. unitaeniatus, they are also found in the breathing or lamellar epithelium. MC density is lower in H. malabaricus, the exclusively water-breathing fish, than in H. unitaeniatus, a facultative air-breathing fish. The transference to DW or HIW did not change the MC density and surface area, excepting in H. malabaricus, in the first day of exposure to DW. A single MC containing three types of glycoproteins (neutral, acidic and sulphated) was identified in the gill epithelium of both, H. malabaricus and H. unitaeniatus. The amount (based on the intensity of histochemistry reaction) of these glycoproteins differed between the species and were altered after exposure to DW and HIW showing little adjustments in the amount of mucosubstances in the MC of H. malabaricus and reduction of acidic and sulphated glycoproteins in H. unitaeniatus. The decreasing of these glycoproteins in H. unitaeniatus reduced the mucus protection against desiccation of gill tissue when change the ion concentration in water.

Highlights

Several studies on the teleost gill epithelium have emphasized the pavement cells (PVCs) of the lamellar epithelium which are directly related to gas exchange and the chloride cells (CCs) which are related to the ion regulation as well as the changes of these cells in response to the internal and/or external ionic or acid-base environment (Munshi, 1964; Perry & Laurent, 1993; Goss et al, 1994; Moron & Fernandes, 1996; Fernandes & Perna-Martins, 2001; Moron et al, 2003; Sakuragui et al, 2003)
Mucous cells number is higher in H. unitaeniatus than in H. malabaricus and did not alter after transfer to deionized water and/or water with high ion concentration
Mucus release into water was not quantified but it was more copious in H. unitaeniatus than in H. malabaricus during exposure to deionized water and in ion-rich water

Summary

Introduction

The structure and function of fish gills have been well described by several authors (Munshi, 1960; Hughes, 1966; Hughes & Munshi, 1979; Hughes et al, 1979; Laurent, 1984; Roy & Munshi, 1986; Munshi & Singh, 1992; Fernandes et al 1994; Evans et al, 2005; Moraes et al, 2005; Banerjee, 2007; Fernandes et al 2007). Several studies on the teleost gill epithelium have emphasized the pavement cells (PVCs) of the lamellar epithelium which are directly related to gas exchange and the chloride cells (CCs) which are related to the ion regulation as well as the changes of these cells in response to the internal and/or external ionic or acid-base environment (Munshi, 1964; Perry & Laurent, 1993; Goss et al, 1994; Moron & Fernandes, 1996; Fernandes & Perna-Martins, 2001; Moron et al, 2003; Sakuragui et al, 2003). Changes in the density of the mucous cells of gills and skin (Paul & Banerjee, 1997) have been considered as a response to the changes in the ion concentration in water such as sodium, calcium and chloride (Perry & Wood, 1985; Laurent & Hebibi, 1989) and xenobiotics (Wendelaar Bonga et al, 1989)

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