Limits...
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.


Osmotic capacities of Nebrioporus and Enochrus species pairs.Data are expressed as mean ± s.e. (n = 3). Asterisks indicate statistically significant differences between species (P ≤ 0.01) at each conductivity treatment. OC: osmotic capacity.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4401727&req=5

pone.0124299.g002: Osmotic capacities of Nebrioporus and Enochrus species pairs.Data are expressed as mean ± s.e. (n = 3). Asterisks indicate statistically significant differences between species (P ≤ 0.01) at each conductivity treatment. OC: osmotic capacity.

Mentions: Species occupying fresh-subsaline waters (N. b. cazorlensis and E. salomonis), showed similar salinity tolerances (see LC50 values in Table 2) and similar mean hyper-OCs in media up to 90 mosmol kg-1. This was followed by a significant reduction in OC as haemolymph osmolality was closer to the isosmotic point with the external medium, at 180 and 340 mosmol kg-1. OC was significantly lower in E. salomonis at these osmotic concentrations (P < 0.01) (Fig 2A).


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)

Osmotic capacities of Nebrioporus and Enochrus species pairs.Data are expressed as mean ± s.e. (n = 3). Asterisks indicate statistically significant differences between species (P ≤ 0.01) at each conductivity treatment. OC: osmotic capacity.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0124299.g002: Osmotic capacities of Nebrioporus and Enochrus species pairs.Data are expressed as mean ± s.e. (n = 3). Asterisks indicate statistically significant differences between species (P ≤ 0.01) at each conductivity treatment. OC: osmotic capacity.
Mentions: Species occupying fresh-subsaline waters (N. b. cazorlensis and E. salomonis), showed similar salinity tolerances (see LC50 values in Table 2) and similar mean hyper-OCs in media up to 90 mosmol kg-1. This was followed by a significant reduction in OC as haemolymph osmolality was closer to the isosmotic point with the external medium, at 180 and 340 mosmol kg-1. OC was significantly lower in E. salomonis at these osmotic concentrations (P < 0.01) (Fig 2A).

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.