Unrelated queens coexist in colonies of the termite Macrotermes michaelseni

Relatedness increases the likelihood of cooperation within colonies of social insects. Polygyny, the coexistence of numerous reproductive females (queens) in a colony, is common in mature colonies of the termite Macrotermes michaelseni. In this species, polygyny results from pleometrosis and from several female alates that jointly found a new colony. To explain this phenomenon, it was suggested that only related females cooperate and survive during maturation of colonies. Using multilocus fingerprints as well as microsatellites, we showed that nestmate queens in mature colonies are unrelated. Furthermore, we found that all nestmate queens contributed to the production of steriles. Even in mature colonies, several matrilines of steriles coexist within a colony. Although genetic diversity within colonies may increase the likelihood of conflicts, high genetic diversity may be important for foraging, colony growth, and resistance to disease and parasites.     

High gene flow between populations of Macrotermes michaelseni (Isoptera, Termitidae)

Termite alates are thought to be poor active flyers, and this should lead to considerable genetic differentiation on small spatial scales. However, using four microsatellite loci for the termite Macrotermes michaelseni we found low values of genetic differentiation (F_ST) across a spatial scale of even more than 50 km. Genetic differentiation between populations increased with spatial distance up to 50 km. Furthermore, up to this distance, the scatter around the linear regression of genetic differentiation versus spatial distance increased with spatial distance. This suggests that across such spatial distances gene flow and genetic drift are of about equal importance, and near equilibrium. Using a regional F_ST as well as the distance between populations with non-significant F_ST-values (up to 25 km), gene flow is sufficiently high so that populations may be regarded as panmictic on spatial scales of 25 to 50 km. The apparent contradiction between dispersal distances observed in the field and estimates of gene flow from genetic markers may be due to the masses of swarming alates. Assuming a leptokurtic distribution of dispersal distances, atleast some alates are expected to travel considerable distances, most likely by passive drift. Received 25 January 2005; revised 11 April 2005; accepted 26 April 2005.     

The influence of juvenile hormone analogue on soldier differentiation in the higher termite,Macrotermes michaelseni*

ABSTRACT. The influence of topically-applied or vapour-administered juvenile hormone analogue (ZR-515, methoprene (JHA)), on soldier differentiation in a higher termite species, Macrotermes michaelseni (Sjostedt) (Isoptera; Macro-termitinae) was examined. It was found that even male third larvae, which under natural conditions develop exclusively into major workers, could be induced by JHA to differentiate into presoldiers. Intermediate forms between workers and soldiers were produced from some of the treated individuals. Administered in vapour form, JHA induced a higher proportion of presoldiers and a lower proportion of intermediate forms than it did when administered topically. The rate of presoldier formation was found to be JHA-dose-dependent. Biometric analysis showed that male presoldiers have the largest head capsule size, but the smallest mandibular index. The possible mechanism of soldier induction is discussed.     

Estimation of cardiac output by analysis of respiratory gas exchange.

Cardiac output is estimated by least squares fitting of a model of pulmonary gas exchange to measurements of respiratory gas composition obtained with a mass spectrometer during a rebreathing maneuver. This new technique estimates cardiac output on spontaneously breathing subjects at rest and requires neither central venous nor arterial blood samples. Principal features of the technique are the use of multiple gases simultaneously in the analysis, the use of a mathematical model for breath-to-breath evaluation of gas exchange, and simultaneous estimation of gas exchange and alveolar gas tensions with the same instrumentation. The technique is compared with thermal dilution estimates in dogs before and during hemorrhagic shock. Two-thirds of these estimates were within 20% of one another. The standard deviation of replication was 15%. Shortcomings, possibilities for improvement, and possible applications are discussed.     

The variability of respiratory pattern and gas exchange

It is known, that spectral analysis of heart rate and respiratory variability allows to find out the very low frequency (VLF) rhythm. However it is not known, it is necessary to carry this rhythm to what type of wave processes. The purpose of the present researches was to study the respiratory variability and the variability of gas exchange parameters. 10 healthy subjects have been surveyed. The pneumogramms within 30 minutes spent record, and then a method "breath-by-breath" within 30 minutes registered gas exchange parameters (Ve--lung ventilation, V(O2) -O2 consumption and other parameters). Fast Fourier transform method has found out two groups of the basic peaks. The first--in a range 0.2-0.3 Hz (a time cycle--3-5 s), that corresponds respiratory frequency which size at subjects varied from 12 to 20 per minute. The second--in a range 0.002-0.0075 Hz, that corresponds VLF diapason (a time cycle--1-3.5 minutes). At the analysis pneumogramms rhythms in the same ranges have been established. The carried out researches allow to draw a conclusion on steady character of wave process in a VLF-range. It can be carried to quasi-periodic oscillations type. First oscillator or respiratory frequency it is formed by means of mechanisms of chemoreception. Considering, that V(O2) and V(CO2) are function energy exchange, it is possible to believe, what exactly energy demand define the second oscillator.     

Measurement of respiratory gas exchange during artificial respiration

This paper reports a new system for the continuous measurements of respiratory gas exchange in ventilated subjects. It involves mixing some of the inspired gas with all of the expired gas and withdrawing the mixture at a constant rate through a dry gas meter that measures the flow. The inspired gas and expired gas mixtures are sampled and O2 and CO2 concentrations measured with a paramagnetic gas analyzer and a capnograph, respectively, to an accuracy of 0.01%. Evidence is presented to confirm the necessary stability and sensitivity of these instruments. It is possible to use the system with high inspired O2 concentrations, with ventilators where there is incomplete separation of inspired and expired gas, and in the presence of intermittent mandatory ventilation, positive end-expiratory pressure, and continuous airway pressure. The system was compared with the N2-dilution method and with the collection of expired gas in a Douglas bag in dog experiments and with patients in the intensive therapy unit. Excellent correlation between these methods was found in all circumstances.     

Influence of group size and composition on soldier differentiation in female final larval instars of a higher termite, Macrotermes michaelseni

ABSTRACT. Experiments with Macrotermes michaelseni (Sjöstedt), involving artificial groups of different sizes of final larval instar females, showed that the proportion of presoldiers produced in each group decreased exponentially with increase in the size of the colonies. This relationship was not smooth, however, but stepwise. Increasing the number of workers in a group with larvae improved the chance of the larvae differentiating into presoldiers, although the normal proportion of soldiers for the species was not achieved under these conditions, even at maximum crowding. The inhibitory effect of soldiers in stopping larvae differentiating into more soldiers was established, and evidence obtained for a non-volatile or low volatility pheromone. It is postulated that dominance by larvae which have acquired 'competence' over others, allows them to suppress these others from differentiating into presoldiers through the pheromone acting on specific behavioural elements.     

The underground passages and storage pits used in foraging by a nest of the termite Macrotermes michaelseni in Kajiado, Kenya

Part of the system of underground passages and storage pits used in foraging by a nest of Mucrofermes michaelseni was excavated and is described in detail, and an attempt is made to quantify it. Densities as high as 1.9 m of passage and 21.4 storage pits per m² were recorded in the main foraging zone, which is 10–35 m from the nest. The estimated total for the whole nest was just under 6 km of passage and 72,000 storage pits, in an area of about 8000m²