Marie-Claire Cammaerts’s research while affiliated with University Hospital Brussels and other places

Young Myrmica sabuleti worker ants aged at most a few weeks and settled in small single-cohort colonies, were learned, by operant conditioning, to recognize either 2 or 3 dots displayed on a stand. When tested in front of two stands bearing different numbers of dots, one even and the other odd, their response was always higher towards the stand bearing the same parity as the one learned. They thus reacted to the parity corresponding to the number of dots they have learned to associate with the reward. These young ants were sensitive to the parity of a number of dots ranging from 1 to at least 6, but could not discriminate their parity when in front of 5 and 6. They were somewhat more responsive towards an even number than towards an odd number, having learned a number with this parity. A preceding study showed that older workers (experienced foragers) are sensitive to the parity of numbers of dots ranging from 1 to at least 7, and this equally whether the numbers are odd or even. Their limit of parity discrimination of close numbers is in front of 6 and 7. It therefore appears that, although present early on, the sensitivity of young workers to parity of numbers of elements and to number discrimination has to improve over the course of their lives, perhaps through an age-related maturation process, or through acquired experience.

Here we summarize our recent studies on the physiological and behavior effects of five products widely used by humans, using an ant, having received these substances in their usual diet, as a biological model. Nutmeg is a spice which decrease the activity and movement speed of the ants, leading to further motor-linked impairments, but not impairing other behavioral traits as well as learning and memory. Vortioxetine (Brintellix) is an anti-depressant recently appearing reducing obesity and having moderate adverse effects in humans. It negatively affected the ants’ food intake, general activity, tactile sensitivity, state of stress and cognition. Berberine is a supplementary dietary regulating, in humans, glucosemia and several parameters. In ants, food intake, general activity, tactile sensitivity, were also negatively impacted, but not their state of stress and cognition. Cashew nuts and mangoes may have similar allergenic effects in humans. In ants, cashew consumption induces sinuosity of movement, stress and nervousness while mango consumption reduces their general activity and behaviors related to motor activity. The correspondence between dependence to a substance, short duration of its effect after withdrawal and abrupt loss of its effect is discussed.

Worldwide, insects are declining at an alarming rate. Among other causes, the use of pesticides and modern agricultural practices play a major role in this. Cumulative effects of multiple low-dose toxins and the distribution of toxicants in nature have only started to be investigated in a methodical way. Existing research indicates another factor of anthropogenic origin that could have subtle harmful effects: the increasingly frequent use of electromagnetic fields (EMF) from man-made technologies. This systematic review summarizes the results of studies investigating the toxicity of electromagnetic fields in insects. The main objective of this review is to weigh the evidence regarding detrimental effects on insects from the increasing technological infrastructure, with a particular focus on power lines and the cellular network. The next generation of mobile communication technologies, 5G, is being deployed – without having been tested in respect of potential toxic effects. With humanity’s quest for pervasiveness of technology, even modest effects of electromagnetic fields on organisms could eventually reach a saturation level that can no longer be ignored. An overview of reported effects and biological mechanisms of exposure to electromagnetic fields, which addresses new findings in cell biology, is included. Biological effects of non-thermal EMF on insects are clearly proven in the laboratory, but only partly in the field, thus the wider ecological implications are still unknown. There is a need for more field studies, but extrapolating from the laboratory, as is common practice in ecotoxicology, already warrants increasing the threat level of environmental EMF impact on insects.

Categorizing numbers into even and odd is an ability held by humans that has recently been found to be also held by honeybees. We examined whether ants could also make such parity discrimination. Working on the species Myrmica sabuleti, we learned the ants of two colonies to associate 2 black circles with a reward and 5 of these circles with the absence of a reward, as well as learned the ants of two other colonies to associate 3 of these same cues with a reward and 4 of these cues with the absence of a reward. By collectively testing foragers of each colony in a separate tray in front of these cues, it was first verified during three days if they dully learned the ‘correct’ cue. Thereafter, while the ants continued to be trained, foragers of each colony were collectively subjected to nine successive choice tests, each day in front of a pair of cues different from the one used during the learning process. The cues used during these tests differed from those used to train the ants by the number and size of the dots, the cumulative surface of the dots, the perimeter of their area (surfaces and perimeters being maintained equal between the cues) and their layout. A ‘correct’ cue had the same parity (even or odd) as the cue learned during training. The tested ants each time consistently responded to the number that had the same parity as that of the number they learned during conditioning. This sensitivity to the number parity occurred from the number 1 until the number 7. Discrimination between 7 and 8 dots was beyond the ant capability.

Authors studied the cognitive abilities of the ant Myrmica sabuleti Meinert 1861, and in addition to the separate publications of their findings, they also summarized them in until now three papers. Here, the authors summarize their eight last findings, and report similar abilities in humans as well as advices for acquiring and using them. The ants can associate visual cues, numbers of elements, and odors with the time periods of their occurrence, and do so taking into account the characteristics of the elements. Humans should do so for ameliorating their daily life. For adding two numbers, the ants must see them with a time gap not exceeding 8 minutes. The ants discriminate recent and previously perceived events, locating the recent but not the old ones on a ‘time line’. Humans must learn to evaluate the passing time, to have a ‘time line’. The ants’ time perception is underestimated when they are more active. This is true for humans, and must be considered while working, playing or doing nothing (e.g., elderly persons). The ants can navigate using a learned (memorized) sequence of odors. Humans must learn sequences of cues for finding their way. The ants discriminate even and odd numbers until the number 7. Humans are sensitive to numbers’ parity, and this should freely impact their choice. Shortly, the authors revealed four cognitive abilities in ants which should occur in humans, natively or acquired through experiences, at a more precise, complex and extended level, in order to provide them with an as comfortable as possible live.

The ant Myrmica sabuleti uses essentially odors for navigating. It has also several skills which presume that it could learn, memorize a sequence of odors and afterwards use it for navigating. By training (operative conditioning) then testing forager workers, we demonstrate that these ants are able to soon learn and memorize a sequence of four odors, i.e., thyme, lavender, basilica, and orange zest, linearly set during training between the nest entrance and the food site, and a simple additional experiment showed that the trained ants effectively used the learned sequence of odors for moving between the nest and the food. Moreover, as workers of this ant can associate odors with the time of the day during which they perceive them, they should be able to use a memorized sequence of odors at appropriate time periods in order to optimize a safe navigation. As this ant is known to use visual cues, odometry, area marking, and deposition of the trail pheromone to navigate, it is also liable to combine these strategies with that of following odor sequences.

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.