Planktonic Neuroscience

Paired photoreceptors function as an oceanic depth gauge

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Science  22 Jun 2018:
Vol. 360, Issue 6395, pp. 1311-1312
DOI: 10.1126/science.360.6395.1311-c

Two different photoreceptors allow an annelid to choose its depth.

PHOTO: MARTIN GÜHMANN (CC BY-SA 4.0)

Ciliary photoreceptors, which are typical of vertebrates, differ in morphology and in type of opsins from the rhabdomeric photoreceptors characteristic of annelids. Larvae of the marine annelid Platynereis dumerilii have both kinds of photoreceptors. Verasztó et al. worked out the circuits and responses driven by this pairing. The ciliary photoreceptors respond to ultraviolet (UV) light, causing the larvae to swim away from it. The rhabdomeric photoreceptors respond to blue light and drive a phototactic response. At the ocean surface, the UV-avoidance response dominates, driving larvae downward, whereas at greater depths, the phototactic response dominates, driving larvae toward the surface. When the swim-upward signal balances out the swim-downward signal, the larvae have found their favorite depth.

eLife 10.7554/eLife.36440 (2018).

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