Circadian Rhythms of Locomotor Activity in Ansell’s mole-rat, Fukomys anselli: are mole-rats clocks ticking? J. L. de Vries M. K. Oosthuizen N. C. Bennett Photographs by J. L. de Vries

Introduction Circadian rhythms → Circadian rhythms are endogenous and self-sustaining → In the absence of external cues (zeitgebers), the rhythm free-runs with a period (tau) of close to 24 hours → Suprachiasmatic nucleus (SCN) – Master clock → Allows animals to anticipate changes → Light most common cue (sun) (Goldman et al. 1995; Reuss 1996)

Introduction Previous studies → Solitary species → Cape mole-rat (Georychus capensis) → Social species → Common mole-rat, Cryptomys hottentotus → Mashona mole-rat, Fukomys darlingi → Damaraland mole-rat, Fukomys damarensis (Lovegrove & Papenfus 1995; Oosthuizen et al 2003; Hart et al. 2004; Vasicek, et al 2005; Schöttner et al. 2006)

Introduction Visual capabilities → Blind mole-rat Spalax ehrenbergi → Subcutaneous, atrophied eyes, but are still able to entrain to light cycles → Suggested that African mole-rats (Bathyergidae) have better visual capabilities → Ansell’s mole-rat Fukomys anselli → Visual system that is involved in coordination of visuomotor reflexes → Subsystems which are involved in perception of photoperiod, form and brightness are well developed (Cooper 1993; Cernuda-Cernuda et al. 2003; Němec et al. 2004) Fukomys anselli

Introduction Temporal activity patterns → Very inconsistent data → G. capensis → Nocturnal → F. damarensis → Diurnal → C. hottentotus → Diurnal and nocturnal (Lovegrove & Papenfus 1995; Hart et al. 2004; Schöttner et al. 2006) Georychus capensis

Introduction Ansell’s mole-rat → Herbivorous African mole-rat that is endemic to the savannas of Zambia → Extensive burrow systems that are completely sealed from the surface → Little chance to be exposed to light → Colonies range in size from 2 to 25 animals, but normally found in colonies of 12 (Bennett, N.C. & Aguilar, G. H. 1995) Fukomys anselli

Aims 1) Determine whether the mole-rats are able to entrain their locomotor activity to light cues. 2) Investigate whether the mole-rats exhibited an endogenous rhythm of locomotory activity in constant darkness.

Materials and Methods Animal capture → West of Lusaka, Zambia → February to April 2007 → Modified Hickman traps → Blocking the tunnel with a hoe Animals care → Housed in plastic containers → Fed on chopped sweet potatoes and apples → Cages cleaned after lighting cycle Experimental room → Light controlled → Kept at 25 ± 1°C → Extractor fan (Hickman 1979)

Materials and Methods Experimental model → Animals kept in darkness for 30 days → Placed under various light regimes lasting 20 days each → 12L: 12 D (08:00 – 20:00 L) → DD → 12L :12D (08:00 – 20:00 L) → 12D :12L (08:00 – 20:00 D) Activity measures → Infrared capture placed above each cage → Activity measures captured by Vital view on a Mini Mitter computer

Materials and Methods Data analysis → Double plotted Actograms → Actiview Biological Rhythm Analyses 1.2 software → Percentages determined for activity during dark phase of all cycles → Microsoft Excel

Results Entraining Arrhythmic LD1 DD DL LD2

Results LD1 cycle DD cycle

Results LD2 cycle DL cycle

Results

Discussion Entrainment of activity → Activity patterns not robust, large variation → Same in three subspies of Cryptomys hottentotus → Same in two species of Fukomys genera → Light not a strong zeitgeber → Other external cues might have more influence (Hart et al. 2004; Oosthuizen et al. 2003; Vasicek et al 2005; Schöttner et al. 2006) Cryptomys hottentotus

Discussion Endogenous circadian rhythms → Social cues → F. damarensis → Castor canadensis → Octodon degus → More beneficial for mole-rat → Variation might be due to weak coupling to pacemaker (Bovet & Oertli 1974; Lovegrove et al. 1993; Goel & Lee 1995) Fukomys damarensis

Discussion Endogenous circadian rhythms → Tested during DD lighting regime → Six individuals had arrhythmic activity patterns → Five individual had weak circadian rhythms close to 24h → Lesotho mole-rat → Little advantage of circadian rhythms in subterranean environment → Aseasonl breeder → Low latitude (Bennett & Aguila 1995; Sharma 2003; Schöttner et al. 2006) Cryptomys hottentotus

Discussion Temporal distribution of activity → Majority display nocturnal activity → Largest part of activity took place in dark phase → Large variations

Conclusion → Entrain to light cues → Able to distinguish between light and dark → Active mainly during dark phase → Weak circadian rhythms → Clocks ticking, but very weakly

Acknowledgements → Alfred Sichilima →