Table 1.

Quantum catch, Q, in the four eye types under starlight conditions (per receptor and integration time)

D (μm)Δϕ≈Δρ (degrees)l (μm)Δt (ms)QQpoolCpool (%)
AMEs470±2.3 (N=8)2.5*82±0.8 (N=8)56±5.5 (N=12)1.1 (0.5–1.9)102 (45–173)10 (8–15)
ALEs330±2.1 (N=9)2.15±0.03 (N=40)48±0.4 (N=9)63±3.3 (N=12)0.5 (0.3–1.0)47 (23–90)15 (11–21)
PMEs280±1.3 (N=8)3.34±0.06 (N=40)52±0.2 (N=8)48±2.2 (N=16)0.7 (0.4–1.2)67 (33–108)12 (10–18)
PLEs430±2.1 (N=6)2.10±0.03 (N=40)47±0.2 (N=6)56±2.6 (N=12)0.7 (0.5–1.1)67 (41–79)12 (10–16)
  • Calculations (see Appendix 1) are based on the tabulated optical values: D, lens diameter; Δρ, acceptance angle; l, rhabdom length; Δt, integration time; other values are given in Appendix 1 (means ± s.e.m.). Integration time was taken as the half-width of electrophysiologically measured impulse responses. For ALEs (anterior lateral eyes), PMEs (posterior median eyes) and PLEs (posterior lateral eyes), which all have reflecting tapeta, the morphological rhabdom length l was doubled in the calculation. (AMEs, anterior median eyes.) Quantum catch for spatiotemporal pooling, Qpool, assumes groups of 3×3×3 rhabdoms in a hexagonal array, and a 10-fold increase in integration time. The minimum detectable contrast Cpool is calculated as the signal difference that can just overcome quantum noise (square-root of Qpool). For Q and C values the ranges in parentheses are calculated from the measured minimum and maximum values of D, and the upper and lower bounds of standard deviation of Δϕ, l andΔ t. *Calculated from anatomical data (see Materials and methods)