Setosusin

Climate change is leading to alterations in salinity and carbonate chemistry in arctic/sub-arctic marine ecosystems. We examined three nominal populations of the circumpolar arctic/subarctic amphipod, Gammarus setosus, along a salinity gradient in the Kongsfjorden-Krossfjorden area of Svalbard. Field and laboratory experiments assessed physiological (haemolymph osmolality and gill Na+/K+-ATPase activity, NKA) and energetic responses (metabolic rates, MO2, and Cellular Energy Allocation, CEA). In the field, all populations had similar osmregulatory capacities and MO2, but lower-salinity populations had lower CEA. Reduced salinity (S = 23) and elevated pCO2(~1000 μatm) in the laboratory for one month increased gill NKA activities and reduced CEA in all populations, but increased MO2in the higher-salinity population. Elevated pCO2did not interact with salinity and had no effect on NKA activities or CEA, but reduced MO2in all populations. Reduced CEA in lower-rather than higher-salinity populations may have longer term effects on other energy demanding processes (growth and reproduction).

Grooming in rodents presents an evolutionarily conserved behavioral pattern that may cause water loss since saliva is deposited during washing onto large body surfaces. Trinomys yonenagae and Trinomys setosus are sister species of spiny rats occurring in Brazil, the former inhabiting a paleodesert of fixed dunes in the Caatinga, the latter being found in mesic environments of the Atlantic Forest. Consequently, it is expected that both species evolved under different selective pressures related to water balance, with T. yonenagae presenting mechanisms for dealing with water deprivation not found in T. setosus. Reduction of self-cleaning expression seems to offer a possible way to save water, as previously suggested by studies of the sand-dwelling spiny rat. Therefore, we propose to investigate grooming under four conditions: 'control' (C), a regimen of 'water restriction' (WR), of 'dirt' (D), and the combination of both conflicting stimuli (WR + D), in T. setosus, T. yonenagae, and Rattus norvegicus to compare the behavioral responses of these species. The main differences are observed in the forest dweller: T. setosus expresses a low relative duration of face washing under C, whose value is intermediate between the ones found in the two other species. WR treatment does not alter this pattern, however, the addition of dirt (D, WR + D) significantly increases the relative duration of washing in relation to C. Locomotor activity is decreased both in T. setosus and Wistar rats when they are under WR, a situation that could jeopardize antipredatory performance. T. yonenagae, the sand dweller, maintains a significantly lower expression of washing under C, as previously suggested, and under WR, D and WR + D. In addition, differently from the other two species the sand dweller maintains a normal activity level during all treatments. This study suggests differences in grooming as a strategy alluding to water balance by the two spiny rats inhabiting different ecosystems. A significantly clear pattern that saves water is observed in T. yonenagae, which probably has contributed to his evolution in one of the hottest semiarid areas of the world.

Investigation of aerial parts of Margyricarpus setosus afforded three new aryl glycosides, beta-hydroxyphenylethyl-O-alpha-L-rhamnopyranosyl (1-->6)-beta-D-glucopyranoside, benzyl-O-alpha-L-rhamnopyranosyl (1-->6)-beta-D-glucopyranoside, 4-methoxybenzyl-O-alpha-L-rhamnopyranosyl (1-->6)-beta-D-glucopyranoside, and three new triterpene glycosides, tormentic acid 3 beta-O-beta-D-quinovopyranoside, tormentic acid 3 beta-O-beta-D-fucopyranoside and tormentic acid 3 beta-O-alpha-L-rhamnopyranoside. Twelve known compounds were also found, among them beta-hydroxy-3',4'-dimethoxyphenylethyl glucoside and beta-hydroxy-3',4'-dimethoxyphenylethyl rutinoside, which were obtained previously by partial synthesis, were isolated for the first time from a natural source. The structures of the new compounds were elucidated on the basis of chemical and spectral data.