Salt intake in Amazonian ants: too much of a good thing?

Abstract

Although herbivory is widespread among insects, plant tissues rarely provide the optimal balance of nutrients for insect growth and reproduction. As a result, many herbivorous insects forage elsewhere for particular amino acids and minerals. Recent studies have shown that both herbivory and recruitment to sodium are commonplace among tropical rainforest ants, but little is known about how ants regulate their sodium intake at the individual and colony levels. In social insects, foragers may respond not only to their own nutritional deficiencies but also to those of their nestmates, who may have different nutritional requirements depending on their developmental stage, sex, or caste. Here, we investigate how salt stress among rainforest ants affects their preferences for salt and subsequent survival. We found that ants recruited more to salt than to any other bait type tested, confirming the strong preference for salt of ants in this region. Initially, we observed similarly high recruitment to salt among workers of the arboreal, herbivorous/omnivorous ant species Camponotus mirabilis. However, when provided with unrestricted access to high concentrations of salt, C. mirabilis workers suffered significantly higher mortality relative to controls, suggesting that C. mirabilis workers forage for sodium to the point of toxicity. Nonetheless, surviving workers showed reduced preference for salt at the end of the experiment, so some but not all individuals were able to regulate their salt intake beneath lethal dosages. We discuss how salt intake regulation may depend on colony members other than workers.

The biogeography of sodium in Neotropical figs (Moraceae)

“…, Arcila Hernandez et al . ). Similarly, species of phyllostomid bats, ungulates, rodents, primates, birds, and insects in western Amazonia visit sodium‐rich licks to consume sodium‐rich soil or to drink sodium‐rich muddy water from soil depressions made by the excavations of larger geophagous mammals (Bravo et al .…”

Physiological and Molecular Mechanisms of Nutrition in Honey Bees

“…Few research studies have been conducted on the impact of minerals on honey bees, although salt (NaCl) is known to be an important dietary supplement (Horr, 1998). Ants also regulate salt intake according to their colony needs (Hernández et al, 2012). Some of the elements detected in pollen have been potassium (K), phosphorus (P), sulphur (S), calcium (Ca), magnesium (Mg), sodium (Na), iron (Fe), zinc (Zn), manganese (Mn), and copper (Cu) (Somerville and Nicol, 2003).…”

Assessing the effects of sodium on fire ant foraging in the field and colony growth in the laboratory

“…Based on previous work (Kaspari et al, 2008), we predicted that fire ants in inland sites would have stronger preferences for NaCl than fire ants in coastal sites. Because ants have shown affinity to sodium in other studies (Vail et al, 1999;Kaspari et al, 2008Kaspari et al, , 2010O'Donnell et al, 2010;Arcila Hernández et al, 2012;Chavarria Pizarro et al, 2012) we also predicted that supplemental sodium would result in increased colony growth.…”

“…However, there is a gap between behavioural responses to sodium baits and the assumed benefits to ants of increased sodium deposition. While preferential foraging for sodium by ants is extensively documented (Vail et al, 1999;Kaspari et al, 2008Kaspari et al, , 2010O'Donnell et al, 2010;Arcila Hernández et al, 2012;Chavarria Pizarro et al, 2012), the effect of sodium supplementation on ant colony growth is untested.…”