A snapping shrimp has the fastest vision of any aquatic animal

Abstract

Animals use their sensory systems to sample information from their environments. The physiological properties of sensory systems differ, leading animals to perceive their environments in different ways. For example, eyes have different temporal sampling rates, with faster-sampling eyes able to resolve faster-moving scenes. Eyes can also have different dynamic ranges. For every eye, there is a light level below which vision is unreliable because of an insufficient signal-to-noise ratio and a light level above which the photoreceptors are saturated. Here, we report that the eyes of the snapping shrimp Alpheus heterochaelis have a temporal sampling rate of at least 160 Hz, making them the fastest-sampling eyes ever described in an aquatic animal. Fast-sampling eyes help flying animals detect objects moving across their retinas at high angular velocities. A. heterochaelis are fast-moving animals that live in turbid, structurally complex oyster reefs and their fast-sampling eyes, like those of flying animals, may help them detect objects moving rapidly across their retinas. We also report that the eyes of A. heterochaelis have a broad dynamic range that spans conditions from late twilight (approx. 1 lux) to direct sunlight (approx. 100 000 lux), a finding consistent with the circatidal activity patterns of this shallow-dwelling species.

Keywords: crustacean; dynamic range; temporal resolution; visual ecology.

Figure 1.

Snapping shrimp have eyes with a broad dynamic range. (a) The big claw snapping shrimp, Alpheus heterochaelis. (b) Response–stimulus intensity (VlogI) function for the eyes of A. heterochaelis (n = 8). The shaded box represents the dynamic range of the eyes, which corresponds to 5–95% of their maximum response magnitude. The error bars represent ± 2 s.e.m.

Figure 2.

The eyes of A. heterochaelis have a temporal sampling rate of at least 160 Hz. (a) The eyes of A. heterochaelis (n = 6) have a CFF_max that exceeds 130 Hz, as indicated by the averaged response powers of eyes to light stimuli flickering at different frequencies. (b) The eyes of A. heterochaelis (n = 8) have a CFF_max of at least 160 Hz. In (a and b), the dashed horizontal lines represent a 5% power threshold and the error bars represent ± 2 s.e.m. Responses above the threshold value indicate eyes are following the flickering stimulus. (c,d) Representative ERG recordings from the eyes of A. heterochaelis in which the top trace shows 20 cycles of the flickering light stimulus and the lower traces show the corresponding responses of an eye. According to our FFT analysis, the eye represented in (c) did not follow light stimuli flickering at 180 or 200 Hz (indicated by the grey box), whereas the eye represented in (d) followed all stimuli.