Circadian consequences of social organization in the ant species Camponotus compressus

The locomotor activity rhythm of different castes of the ant species Camponotus compressus was monitored individually under laboratory light/dark (LD) cycles, and under continuous darkness (DD). The colony of this ant species comprises two sexual castes, the queens and the males, and three worker castes, namely the major, media, and minor workers. The virgin males and virgin queens display rhythmic activity patterns, but the mated queens were arrhythmic while laying eggs, with the rhythmicity resuming soon after egg-laying. Under the LD regime, major workers showed nocturnal patterns, while about 75% of the media workers displayed nocturnal patterns and about 25% showed diurnal patterns. Under the DD regime, most major workers exhibited circadian rhythm of activity with a single steady state, whereas media workers displayed two types of activity patterns, with activity patterns changing after 6-9 days in DD (turn-arounds). The pre-turn-around τ of the ants that showed nocturnal activity patterns during LD entrainment was <24 h after release into DD, which then became >24 h, after 6-9 days. On the other hand, the pre-turn-around τ of those ants that exhibited diurnal patterns during LD entrainment was first >24 h after release into DD, and then became <24 h, after 6-9 days. The activity of the minor workers neither entrained to LD cycles nor showed any sign of free-run in DD. It appears that the circadian clocks of the ant species C. compressus are flexible, and may perhaps depend upon the tasks assigned to them in the colony

Visual Deprivation Decreases Somatic GAD65 Puncta Number on Layer 2/3 Pyramidal Neurons in Mouse Visual Cortex

Proper functioning of the visual system depends on maturation of both excitatory and inhibitory synapses within the visual cortex. Considering that perisomatic inhibition is one of the key factors that control the critical period in visual cortex, it is pertinent to understand its regulation by visual experience. To do this, we developed an immunohistochemical method that allows three-dimensional (3D) analysis of the glutamic acid decarboxylase (GAD) 65-positive inhibitory terminals in the visual cortex. Using this method on transgenic mice expressing yellow fluorescence protein (YFP) in a subset of neurons, we found that the number of somatic GAD65-puncta on individual layer 2/3 pyramidal neurons is reduced when mice are dark-reared from birth and reverted to normal levels by re-exposure to light. There was no change in GAD65-puncta volume or intensity. These results support the reorganization of inhibitory circuitry within layer 2/3 of visual cortex in response to changes in visual experience

Clocks for sex: loss of circadian rhythms in ants after mating?

This paper describes experiments on the locomotor activity rhythm of queens of the ant species Camponotus compressus, which were performed to investigate the consequences of mating on circadian clocks. Locomotor activity rhythm of virgin and mated queens was monitored individually under constant conditions of the laboratory. The locomotor activity rhythm of virgin queens entrained to a 24 h (12:12 h) laboratory light/dark (LD) cycle and free-ran under constant dim red light (RR) with a free-running period (τ ) of approximately 24 h. The locomotor activity of the mated queens on the other hand was arrhythmic during the period when they were laying eggs, and robust rhythmicity appeared soon after the egg-laying phase was over. The τ of the locomotor activity rhythm of mated queens was significantly greater than that of virgin queens. These results are contrary to the commonly held belief that the role of circadian clocks in ant queens ceases after mating flights, thus suggesting that circadian clocks of ant queens are adaptively plastic and display activity patterns, perhaps depending on their physiological state and tasks in the colony