THE USE OF RECTAL TEMPERATURE FLUCTUATIONS IN THE STUDY OF CIRCADIAN RHYTHM IN THREE ADULT VERTEBRATE SPECIES IN AWKA, NIGERIA

Abstract

Biological clocks allow organisms to assess and respond to the oscillating environmental rhythms that result from the earth’s movements via the generation of biological rhythms. Circadian clocks are also assumed to enhance survival and reproductive fitness in part by promoting optional timing of behaviour and physiology in relation to regular cycles in the environment.  Temperature fluctuations were studied in three different vertebrate species – Sylvilagus floridanus, Rattus norvegicus and Columba livia in relation to the rhythmicity of rectal temperature. Clinical digital thermometer was used to record the core temperature by inserting it 2 – 3 cm deep from the anal sphincter before taking readings 3 minutes after.  The highest recorded mean rectal temperature for R. norvegicu s and S. floridanus were 38.85 ± 0.40 0 C and 39.83 ± 0.32 0 C respectively with the lowest being 36.58 ± 0.74 0 C and 36.63 ± 0.18 0 C respectively. C. livia failed to exhibit core temperature fluctuation. There were not significant differences in the mean rectal temperature for both sexes for S. floridanus in relation to time of day. Differences in the circadian temperature fluctuations were traced to variation among the animals, of preferred temperature arising from differential behavioural and physiological regulation, in relation to environmental cues. It is also possible that daily changes in illumination were secondary to C. livia.  The results also suggest that circadian rhythmicity persists even in artificially imposed selective environment. Rectal temperatures are adequate for monitoring the biorhythms, with each species exhibiting endogenous peculiarities in the various circadian phases.