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The comparative osmoregulatory ability of two water beetle genera whose species span the fresh-hypersaline gradient in inland waters (Coleoptera: Dytiscidae, Hydrophilidae).

Pallarés S, Arribas P, Bilton DT, Millán A, Velasco J - PLoS ONE (2015)

Bottom Line: Their osmoregulatory strategy (osmoconformity or osmoregulation) was identified and osmotic capacity (the osmotic gradient between the animal's haemolymph and the external medium) was compared between species pairs co-habiting similar salinities in nature.In contrast, the species which inhabit the hypo-hypersaline habitats were effective hyporegulators, maintaining their haemolymph osmolality within narrow limits (ca. 300 mosmol kg(-1)) across a wide range of external concentrations.The hypersaline species N. ceresyi and E. jesusarribasi tolerated conductivities up to 140 and 180 mS cm(-1), respectively, and maintained osmotic gradients over 3500 mosmol kg(-1), comparable to those of the most effective insect osmoregulators known to date.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology and Hydrology, University of Murcia, Murcia, Spain.

ABSTRACT
A better knowledge of the physiological basis of salinity tolerance is essential to understanding the ecology and evolutionary history of organisms that have colonized inland saline waters. Coleoptera are amongst the most diverse macroinvertebrates in inland waters, including saline habitats; however, the osmoregulatory strategies they employ to deal with osmotic stress remain unexplored. Survival and haemolymph osmotic concentration at different salinities were examined in adults of eight aquatic beetle species which inhabit different parts of the fresh-hypersaline gradient. Studied species belong to two unrelated genera which have invaded saline waters independently from freshwater ancestors; Nebrioporus (Dytiscidae) and Enochrus (Hydrophilidae). Their osmoregulatory strategy (osmoconformity or osmoregulation) was identified and osmotic capacity (the osmotic gradient between the animal's haemolymph and the external medium) was compared between species pairs co-habiting similar salinities in nature. We show that osmoregulatory capacity, rather than osmoconformity, has evolved independently in these different lineages. All species hyperegulated their haemolymph osmotic concentration in diluted waters; those living in fresh or low-salinity waters were unable to hyporegulate and survive in hyperosmotic media (> 340 mosmol kg(-1)). In contrast, the species which inhabit the hypo-hypersaline habitats were effective hyporegulators, maintaining their haemolymph osmolality within narrow limits (ca. 300 mosmol kg(-1)) across a wide range of external concentrations. The hypersaline species N. ceresyi and E. jesusarribasi tolerated conductivities up to 140 and 180 mS cm(-1), respectively, and maintained osmotic gradients over 3500 mosmol kg(-1), comparable to those of the most effective insect osmoregulators known to date. Syntopic species of both genera showed similar osmotic capacities and in general, osmotic responses correlated well with upper salinity levels occupied by individual species in nature. Therefore, osmoregulatory capacity may mediate habitat segregation amongst congeners across the salinity gradient.

No MeSH data available.


Relationship between osmotic concentration of the haemolymph and the external medium.Data are expressed as mean ± s.e. (n = 3). The isosmotic line is represented by the discontinuous line. OM: osmolality of external medium, OH: osmolality of haemolymph.
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pone.0124299.g001: Relationship between osmotic concentration of the haemolymph and the external medium.Data are expressed as mean ± s.e. (n = 3). The isosmotic line is represented by the discontinuous line. OM: osmolality of external medium, OH: osmolality of haemolymph.

Mentions: All studied species showed a capacity to hyperegulate in hyposmotic media (from 30 to 340 mosmol kg-1), maintaining haemolymph osmotic concentration within a range of 280–440 mosmol kg−1 (Fig 1). The primarily freshwater Nebrioporus b. cazorlensis, N. clarkii and E. salomonis were unable to hyporegulate in media that reach or exceed their haemolymph osmotic concentration (i.e. over 340 mosmol kg-1), whilst the remaining saline water species (N. baeticus, N. ceresyi, E. politus, E. bicolor and E. jesusarribasi) were effective hyporegulators in hyperosmotic media. In these species, haemolymph concentration values ranged from 250 to 670 mosmol kg−1, across a range of external osmolalities close to lethal levels (Table 2), i.e. until 1580 mosmol kg−1 in E. politus, 2470 mosmol kg−1 in N. baeticus and E. bicolor, 3550 mosmol kg−1 in N. ceresyi and 4280 mosmol kg−1 in E. jesusarribasi (Fig 1).


The comparative osmoregulatory ability of two water beetle genera whose species span the fresh-hypersaline gradient in inland waters (Coleoptera: Dytiscidae, Hydrophilidae).

Pallarés S, Arribas P, Bilton DT, Millán A, Velasco J - PLoS ONE (2015)

Relationship between osmotic concentration of the haemolymph and the external medium.Data are expressed as mean ± s.e. (n = 3). The isosmotic line is represented by the discontinuous line. OM: osmolality of external medium, OH: osmolality of haemolymph.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4401727&req=5

pone.0124299.g001: Relationship between osmotic concentration of the haemolymph and the external medium.Data are expressed as mean ± s.e. (n = 3). The isosmotic line is represented by the discontinuous line. OM: osmolality of external medium, OH: osmolality of haemolymph.
Mentions: All studied species showed a capacity to hyperegulate in hyposmotic media (from 30 to 340 mosmol kg-1), maintaining haemolymph osmotic concentration within a range of 280–440 mosmol kg−1 (Fig 1). The primarily freshwater Nebrioporus b. cazorlensis, N. clarkii and E. salomonis were unable to hyporegulate in media that reach or exceed their haemolymph osmotic concentration (i.e. over 340 mosmol kg-1), whilst the remaining saline water species (N. baeticus, N. ceresyi, E. politus, E. bicolor and E. jesusarribasi) were effective hyporegulators in hyperosmotic media. In these species, haemolymph concentration values ranged from 250 to 670 mosmol kg−1, across a range of external osmolalities close to lethal levels (Table 2), i.e. until 1580 mosmol kg−1 in E. politus, 2470 mosmol kg−1 in N. baeticus and E. bicolor, 3550 mosmol kg−1 in N. ceresyi and 4280 mosmol kg−1 in E. jesusarribasi (Fig 1).

Bottom Line: Their osmoregulatory strategy (osmoconformity or osmoregulation) was identified and osmotic capacity (the osmotic gradient between the animal's haemolymph and the external medium) was compared between species pairs co-habiting similar salinities in nature.In contrast, the species which inhabit the hypo-hypersaline habitats were effective hyporegulators, maintaining their haemolymph osmolality within narrow limits (ca. 300 mosmol kg(-1)) across a wide range of external concentrations.The hypersaline species N. ceresyi and E. jesusarribasi tolerated conductivities up to 140 and 180 mS cm(-1), respectively, and maintained osmotic gradients over 3500 mosmol kg(-1), comparable to those of the most effective insect osmoregulators known to date.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology and Hydrology, University of Murcia, Murcia, Spain.

ABSTRACT
A better knowledge of the physiological basis of salinity tolerance is essential to understanding the ecology and evolutionary history of organisms that have colonized inland saline waters. Coleoptera are amongst the most diverse macroinvertebrates in inland waters, including saline habitats; however, the osmoregulatory strategies they employ to deal with osmotic stress remain unexplored. Survival and haemolymph osmotic concentration at different salinities were examined in adults of eight aquatic beetle species which inhabit different parts of the fresh-hypersaline gradient. Studied species belong to two unrelated genera which have invaded saline waters independently from freshwater ancestors; Nebrioporus (Dytiscidae) and Enochrus (Hydrophilidae). Their osmoregulatory strategy (osmoconformity or osmoregulation) was identified and osmotic capacity (the osmotic gradient between the animal's haemolymph and the external medium) was compared between species pairs co-habiting similar salinities in nature. We show that osmoregulatory capacity, rather than osmoconformity, has evolved independently in these different lineages. All species hyperegulated their haemolymph osmotic concentration in diluted waters; those living in fresh or low-salinity waters were unable to hyporegulate and survive in hyperosmotic media (> 340 mosmol kg(-1)). In contrast, the species which inhabit the hypo-hypersaline habitats were effective hyporegulators, maintaining their haemolymph osmolality within narrow limits (ca. 300 mosmol kg(-1)) across a wide range of external concentrations. The hypersaline species N. ceresyi and E. jesusarribasi tolerated conductivities up to 140 and 180 mS cm(-1), respectively, and maintained osmotic gradients over 3500 mosmol kg(-1), comparable to those of the most effective insect osmoregulators known to date. Syntopic species of both genera showed similar osmotic capacities and in general, osmotic responses correlated well with upper salinity levels occupied by individual species in nature. Therefore, osmoregulatory capacity may mediate habitat segregation amongst congeners across the salinity gradient.

No MeSH data available.