Home > Papers from 2011 > A jellyfish with dedicated navigation eyes.

A jellyfish with dedicated navigation eyes.

The visual systems of jellyfish are particularly interesting, with box jellyfish having an eye-watering [!] 24 eyes of different types. Along with the many eyes, the nervous systems of jellyfish are also distributed affairs. Garm et al investigate one type of eye (the upper lens eye) of the box jellyfish and suggest that the eye is designed to look through the water surface and detect the direction to the mangrove edge, which is their preferred feeding habitat. This suggests that in jellyfish, individual eyes ( with their associated small neural ganglion ) may be at the service of dedicated behaviours – in this case navigation by terrestrial cues.

The upper lens eyes have 2 specific adaptations that suggest they peer this through the surface. Firstly, they are suspended flexibly and have a crystalline weight such that they maintain an orientation relative to the surface, irrespective of the orientation of the jellyfish. Secondly, the field of view is tuned to the size of Snell’s window, i.e. the 97degrees within which the whole terrestrial field is compressed owing to refraction. As a follow-up, Garm et al modelled the input to these eyes for various distances away from the mangrove, this modelling suggested that the eyes would be sufficient to detect the mangrove edge at distances up to 8 m. This matched perfectly with behavioural data which show jellyfish orienting toward the mangrove edge at 8 m but not at 12 m.

This is a lovely paper, showing how understanding of function depends on understanding the interaction between optics, behaviour and environment.

Anders Garm, Magnus Oskarsson, and Dan-Eric Nilsson (2011) Box Jellyfish Use Terrestrial Visual Cues for Navigation. Current Biology 10.1016/j.cub.2011.03.054

Categories: Papers from 2011
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