Exposure to light enhances pre-adult fitness in two dark-dwelling sympatric species of ants.
BACKGROUND
In insects, circadian clocks play a key role in enhancing fitness by regulating life history traits such as developmental time and adult lifespan. These clocks use environmental light/dark (LD) cycles to fine-tune a wide range of behavioral and physiological processes. To study the effect of environmental LD conditions on pre-adult fitness components, we used two dark-dwelling sympatric species of ants (the night active Camponotus compressus and the day active Camponotus paria), which normally develop underground and have fairly long pre-adult developmental time.


RESULTS
Our results suggest that ants develop fastest as pre-adults when maintained under constant light (LL), followed closely by 12:12 hr light/dark (LD), and then constant darkness (DD). While light exposure alters developmental rates of almost all stages of development, the overall pre-adult development in LL is speeded-up (relative to DD) by approximately 37% (34 days) in C. compressus and by approximately 35% (31 days) in C. paria. In LD too, development is faster (relative to DD) by approximately 29% (26 days) in C. compressus and by approximately 28% (25 days) in C. paria. Pre-adult viability of both species is also higher under LL and LD compared to DD. While pre-adult development time and viability is enhanced in LL and LD, clutch-size undergoes reduction, at least in C. compressus.


CONCLUSIONS
Exposure to light enhances pre-adult fitness in two dark-dwelling species of Camponotus by speeding-up development and by enhancing viability. This suggests that social ants use environmental light/dark cycles to modulate key life history traits such as pre-adult development time and viability.
Lone
Shahnaz Rahman
SR
Chronobiology Laboratory, Evolutionary and Organismal Biology Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, PO, Box 6436, Jakkur, Bangalore 560 064, Karnataka, India. lone@jncasr.ac.in
Sharma
Vijay Kumar
VK
D000818:Animals; D001000:Ants / Q000254:growth & development* / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D002940:Circadian Rhythm / Q000528:radiation effects; D052284:Clutch Size / Q000528:radiation effects; D003624:Darkness; D007814:Larva / Q000254:growth & development / Q000528:radiation effects; D008027:Light; D010063:Ovum / Q000166:cytology / Q000528:radiation effects; D011679:Pupa / Q000254:growth & development / Q000528:radiation effects; D013045:Species Specificity; D013997:Time Factors