Box jellyfish stable-eyes vision to hunt prey

Ernst Haeckel’s Kunstformen der Natur (Artforms of Nature) was a landmark in biological illustration. Published in 1904, it was lavishly illustrated with 100 exquisitely detailed lithographic plates, including the one above, showing different species of cubomedusae, or box jellyfish. Since around the time that Haeckel’s masterpiece was published, we’ve known that box jellyfish have a unique visual system which is more sophisticated than that of other jellyfish species. They boast an impressive set of 24 eyes of four different types, which are clustered within bizarre sensory appendages that dangle from the cube-shaped umbrella.

The known light-guided behaviours of these organisms are, however, relatively simple, so exactly why they possess such an elaborate array of eyes was somewhat puzzling. A group of Scandinavian researchers working in the Caribbean now report that one of the box jelly’s eye types is highly specialized to peer up towards the water surface at all times, so that it can use terrestrial landmarks to navigate towards its prey.

Continue reading

Advertisements

‘Wasabi receptor’ is snake’s infrared sensor

SNAKES have a unique sensory system for detecting infrared radiation, with which they can visualize temperature changes within their immediate environment. Using this special sense, they can image the body heat radiating from warm-blooded animals nearby. This enables them to track their prey quickly and with great accuracy, even in the dark, and to target the most vulnerable parts of the prey’s body when they strike. It also warns them of the presence of predators, and may be used to find appropriate locations for building dens.

Infrared detection is known to be mediated by a specialized sensory apparatus called the pit organ, but several important questions about the detection mechanisms remain. It is still unclear, for example, where in the pit organ the infrared sensor is located, and whether it detects light particles directly, in a similar way to the eye, or heat energy. These questions have now been answered by a group of researchers from the University of California in San Francisco. In an advance online publication in the journal Nature, they report the identification of the sensor: it is an ancient protein called TRPA1, which has been adapted for this purpose in snakes, but not in other vertebrates.

Continue reading