The volcano mouse Neotomodon alstoni of central Mexico, a biological model in the study of breeding, obesity and circadian rhythms.

The "Mexican volcano mouse" Neotomodon alstoni, is endemic of the Transverse Neovolcanic Ridge in central Mexico. It is considered as least concern species and has been studied as a potential laboratory model from different perspectives. Two lines of research in neuroendocrinology have been addressed: reproduction and parental care, particularly focused on paternal attention and the influence of testosterone, and studies on physiology and behavior of circadian rhythms, focused on the circadian biology of the species, its circadian locomotor activity and daily neuroendocrine regulation of metabolic parameters related to energy balance. Some mice, when captive, spontaneously develop obesity, which allows for comparisons between lean and obese mice of daily changes in neuronal and metabolic parameters associated with changes in food intake and locomotor activity. This review includes studies that consider this species an attractive animal model where the alteration of circadian rhythms influences the pathogenesis of obesity, specifically with the basic regulation of food intake and metabolism and differences related to sex. This study can be considered as a reference to the comparative animal physiology among rodents.

Circadian locomotor activity rhythm during ontogeny in crayfish Procambarus clarkii.

The characteristics of the circadian rhythm of locomotor activity in the crayfish Procambarus clarkii during ontogeny under constant darkness and light-dark (LD 12:12) conditions were studied in 132 juvenile crayfish, aged 10-140 days, divided in four groups. All animals were individually monitored with a motor activity recording system. Activity was quantitatively and qualitatively analyzed. All ages showed a circadian rhythm, although the probability of its appearance increased with age. Period values oscillated between 25.0 h in group I (2-4-week-old animals) and 24.3 h in group IV (16-20-week-old animals with more than 6 molts), but always with a high standard deviation. Groups II (5-10-week-old animals) and IV showed a statistically significant bimodal nonrandom synchrony of phases. The activity/ rest relationship diminishes as development progresses and is most uniform in group IV. We discuss the possibility that the pacemaker system responsible for this rhythm might be present from the moment of eclosion, but the coupling strength of this system with the effectors might change along development. The results presented in this work seem to indicate that the central pacemakers responsible for the activity and the ERG rhythm are not the same.