182
Simon B. Laughlin
economize on energy usage, response dynamics are matched to the spatial and
temporal qualities of images and to behavioral requirements.
9 Comparing Retinal Costs
As we have seen (Sect. 7), electrical coding by photoreceptors and LMCs accounts
for 13% of the blowfly's resting metabolic rate. When the blowfly takes off the
total metabolic rate increases 30-fold and the electrical cost is now <0.4%.
However, in flight the cost of carrying the eye is approximately 3% of total
metabolic rate (the eye is 3% of body weight). Thus signalling costs dominate at
rest and carriage dominates in flight (Laughlin 1995; O'Carroll 1998). Because
signalling and carriage contribute significantly to total metabolic rate, it is
advantageous to maximize efficiency and minimize mass. Dragonflies have the
largest apposition compound eyes and they reduce the mass of the retina with
large air-filled tracheae. In addition to catering for energy supply, these tracheae
are saving energy.
10 Energy, Information and Fitness
The subject of sensory ecology, the contributions made by sense organs to ecology
and behavior (Lythgoe 1979), exists because these contributions have promoted
survival by helping species to compete for, and occupy, favourable niches. As
forcefully argued by Chittka (this Vol.) and by evolutionary physiologists
(Garland and Carter 1994), the ultimate measure of the benefit of a set of
physiological mechanisms is their contribution to fitness (Laughlin 1998). To
establish the relationship between sensation and fitness we must move towards
experiments in which we manipulate sensory function and observe the effects on
lifetime reproductive success. The approach set out in this chapter, the analysis of
costs and benefits in terms of the metabolic energy required to achieve a certain
level of performance, is a useful step. When studying the effects of sensation on
fitness one should manipulate systems in which sensory information is costly, is
sensitive to metabolic investment, and contributes directly to reproductive success.
References
Altringham JD (1996) Bats, Biology and Behaviour. Oxford University Press,
Oxford
Atick JJ (1992) Could information-theory provide an ecological theory of sensory
processing. Network-Computation In Neural Systems 3:213-251
Autrum H (1958) Electrophysiological analysis of the visual systems of insects.
Exp Cell Res Supp1 5: 426-439
Simon B. Laughlin
economize on energy usage, response dynamics are matched to the spatial and
temporal qualities of images and to behavioral requirements.
9 Comparing Retinal Costs
As we have seen (Sect. 7), electrical coding by photoreceptors and LMCs accounts
for 13% of the blowfly's resting metabolic rate. When the blowfly takes off the
total metabolic rate increases 30-fold and the electrical cost is now <0.4%.
However, in flight the cost of carrying the eye is approximately 3% of total
metabolic rate (the eye is 3% of body weight). Thus signalling costs dominate at
rest and carriage dominates in flight (Laughlin 1995; O'Carroll 1998). Because
signalling and carriage contribute significantly to total metabolic rate, it is
advantageous to maximize efficiency and minimize mass. Dragonflies have the
largest apposition compound eyes and they reduce the mass of the retina with
large air-filled tracheae. In addition to catering for energy supply, these tracheae
are saving energy.
10 Energy, Information and Fitness
The subject of sensory ecology, the contributions made by sense organs to ecology
and behavior (Lythgoe 1979), exists because these contributions have promoted
survival by helping species to compete for, and occupy, favourable niches. As
forcefully argued by Chittka (this Vol.) and by evolutionary physiologists
(Garland and Carter 1994), the ultimate measure of the benefit of a set of
physiological mechanisms is their contribution to fitness (Laughlin 1998). To
establish the relationship between sensation and fitness we must move towards
experiments in which we manipulate sensory function and observe the effects on
lifetime reproductive success. The approach set out in this chapter, the analysis of
costs and benefits in terms of the metabolic energy required to achieve a certain
level of performance, is a useful step. When studying the effects of sensation on
fitness one should manipulate systems in which sensory information is costly, is
sensitive to metabolic investment, and contributes directly to reproductive success.
References
Altringham JD (1996) Bats, Biology and Behaviour. Oxford University Press,
Oxford
Atick JJ (1992) Could information-theory provide an ecological theory of sensory
processing. Network-Computation In Neural Systems 3:213-251
Autrum H (1958) Electrophysiological analysis of the visual systems of insects.
Exp Cell Res Supp1 5: 426-439