Heat generation, accumulation and dissipation in clusters of the aggregated insects
1Russian Agricultural Correspondence State University
143900 Balashicha, ul. Fuchika, 1
e-mail: ekeskov@yandex.ru
2Chuvash State University
428015 Cheboksary, Moskovskyi pr., 15
e-mail: stoboev@gmail.com
Calorimetric method was used for investigation of the heat generation, accumulation and dissipation by aggregates of the honey bee (Apis mellifera L.) depending on their number and fluctuations of the ambient temperature. The attitude of the bees to the artificial introduction of the heat in aggregates by the use of the thermode (heated up by electric current) was also traced. Temperatures of different zones in the aggregate were measured by means of the thermal microsensors. As judged by distribution of the temperature fields in insect aggregates, the main role in their thermoregulation system belongs to the integral temperature that corresponds to the average level of the heat content of the whole aggregate. The temperature gradients in the latter (characterizing the body heat content) are maintained in optimum temperature range on relative constant level. The temperature decreases from the thermal center to the aggregate upper border approximately 1.5 times, and it decreases to its lower border 3 times. Out of limits of the temperature optimum, these relations vary depending on the ambient temperature fluctuation, bee physiological heating or heat introduction inside of the aggregate, thus being reflected in the heat content of body variation. Its stabilization is achieved probably by means of the interaction of different thermal profiles of the aggregate that stimulate bees (localized in it) depending on the thermal action vector (cooling or heating) to move randomly to the periphery or inside of the aggregate, to maintain the state of the relative rest or to generate the heat. The change of the body heat content is possible also at the expense of the compaction of the aggregate bees in response to their cooling. The most compaction of the bees (corresponding to the cooling rate) at the lower part of the aggregate periphery. Strain degree of the thermoregulation level in the aggregate bees can be described by the heat balance equation qt = qs + Δq, which connects heat production qt, heat dissipation qs, and heat content of body change Δq. At the optimum temperatures range, the aggregate insects tend to retain the relation between qt and qs at which Δq ~ const. Therefore, heat production and heat dissipation in relation to the body heat content play the role of the control action. One can trace more or less expressed convergent similarity in the cold adaptation complex between the bees and the homoiotherms. But the temperature regulation by the aggregate bees is not connected to the presence of the thermoregulation center (setting point) in their aggregate. Aggregate bees operate as simple independent subjects with a low number of effective degrees of freedom. The absence of the setting point (similar to the mammalian hypothalamus) excludes a possibility of integration of the temperature information from different parts of the bees aggregate. Their interaction is provided by the principle of decentralized control in accordance to which numerous subsystems (individual specimens) composing the aggregate operate using only limited local information obtained by their thermoreceptors. As far as only bees localized at the aggregate periphery (especially those that are localized at its lower part) are subjected to cooling, they feel adverse thermal effect to most extent. Therefore, thermal receptors of the bees accidentally appeared in this zone feel largest excitation, and this apparently stimulate their migration inside of the aggregate. These bees penetrate inside of the aggregate and influence by their cold on the specimens contacting with them, which obtain information about decrease of the ambient temperature. In this respect the most cooled part of the bees serve in aggregate as "dynamic cold receptor" and "coolant".
