After having shown that the workers of the ant Myrmica sabuleti can associate amounts of elements with their time periods of occurrence and knowing that these ants do not take into account the characteristics of elements when counting but take them into account when adding the elements, we wondered if, when associating amounts with their time periods of occurrence, these ants take or do not take account of the characteristics of the elements. Working on six colonies and using three kinds of visual cues during training and these three cues modified as for their size (small, large), color (blue, yellow) or shape (triangle, star) during testing, we revealed that, when associating amounts of elements with their time periods of occurrence, the ants take into account the characteristics of the elements. We checked if, without changing the elements characteristics, the ants effectively associated the perceived amounts (1 – 3, 2 – 4, 3 -5) of elements (squares, blue circles, triangles) with their time periods of occurrence (8 – 19 o’clock, 20 – 7 o’clock), and they did. We also made a complementary experiment on newly collected colonies using a slightly different protocol, and we obtained identical results which leaded to the same conclusion. So, the present work confirmed our previous results and solved the last asked question on the subject.
Myrmica sabuleti ants have a mental number line on which numbers (non-symbolic displayed amounts) are ranked, the smaller on the left and the larger on the right. Here we try to know if the difference between two successive numbers is identically estimated all along this line or is less and less well estimated with increasing number magnitude. Ants were trained to distinguish two successive numbers differing by one unit (1 vs 2, 2 vs 3, …, 6 vs 7) during 72 hours and tested after 7, 24, 31, 48, 55 and 72 h. The ants responded less well for larger numbers (e.g. their response to 6 vs 7 was weaker than that to 1 vs 2). The relation between the ants' ability in discriminating two successive numbers according to their relative difference was best described by a non-linear function, a logarithmic function providing a higher fit than a power function. A linear function could only significantly better fit the data when the ratio or the mean of the two numbers was taken into account, particularly in the case of the mean when large fluctuations in the ants' discrimination score appeared in the course of increasing training time. In fact, mean and ratio do not express the relative difference between numbers. Second-order polynomial functions could provide higher fitting, but generally non-significant. The ants' mental positioning of numerosity on their number line appears thus to be compressed along a non-linear scale, most likely according to a logarithmic function.
The overactive bladder syndrome (OAB) affects the quality of life. It is most often treated with anticholinergic drugs, but at the cost of many unwanted effects. In the last decade to date, mirabegron, an adrenergic receptor agonist drug used to relieve OAB has appeared in the pharmacopoeia. It works through a different mechanism than antimuscarinic drugs, with apparently fewer side effects. In the same way that we have examined the adverse effects of the anticholinergic oxybutynin on the ant Myrmica sabuleti used as a biological model, here we examine the side effects of mirabegron. Unlike oxybutynin, mirabegron had no adverse effect on ants, except that it increased their meat consumption, reduced their sugar water intake and decreased their general activity. No adaptation was observed for this last- mentioned effect, which may correspond to the tiredness reported in humans. The ants did not become dependent on the consumption of mirabegron, whose effect on general activity decreased very slowly and disappeared about 52 hours after weaning. Patients are advised to take mirabegron daily though its elimination half-life is 50 hours, and fatigue is one of the side effects of the treatment. In the event that patients under mirabegron medication show a decrease in activity over their treatment, it would be careful to space out the medication or to add an appropriate stimulant or to alternate mirabegron with an anticholinergic drug that does not affect the patient’s level of activity. The kind of antimuscarinic drug that could be used together with mirabegron, the respective dosage and the timing of each drug should be defined depending on their combined efficacy and side effects, and taking into account their elimination time.
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