Sea hares outsmart peckish lobsters with sticky opaline

Mar 27, 2013

Sea hares are not the favourite food choice of many marine inhabitants, and it's easy to see why when you find out about the chemical weapons they employ when provoked – namely, two unpalatable secretions, ink and opaline, which they squirt at unsuspecting peckish predators. However, while much is known about the consequences of purple ink secretion, how the whitish and viscous opaline outsmarts a potential predator remains unknown. Charles Derby from Georgia State University, USA, wondered whether opaline could decrease the activity of a predator's sensory system. Along with his colleagues Tiffany Love-Chezem and Juan Aggio, he set out to test the effect of opaline on spiny lobsters, which occasionally try to snack on sea hares.

The investigating trio find that it is opaline's sticky nature, rather than the chemicals present in the opaline, that is responsible for plugging their sense of smell and published their results in The Journal of Experimental Biology.

To begin, they extracted the water-soluble fraction of opaline, and although this lacks the amino acids and other chemical attractants that make up opaline, it is nonetheless just as sticky and possesses the physical properties of opaline. The team then painted this sticky, water-soluble fraction onto the tips of the lobsters' antennules, which act as the lobster's 'nose' and are important for motivation and ability to feed upon smelling a delicious treat. The trio then presented them with tasty smelling 'shrimp juice' and measured electrical activity in both chemosensory and motor neurons. Unlike lobsters with clean, gunk-free antennules, the shrimp juice failed to whet the appetite of opaline-treated lobsters, with the response of chemosensory and being significantly reduced.

The team next wondered whether the amino acids present in opaline could also dampen neuronal activity. Mixing together the five most prominent amino acids found in opaline, they again painted the antennules and tempted the lobsters with the scent of shrimp juice. This time, however, the neurons fired robustly in reaction to the delicious shrimpy aroma. When the were mixed with the sticky substance carboxymethylcellulose, the neuron reactions were again inhibited. Furthermore, carboxymethylcellulose alone also stopped neurons firing. So, it seems that stickiness is the key to blocking neurons and allowing the sea hare to escape as the lobster preens and cleans itself of the gungy opaline.

Explore further: Orchid named after UC Riverside researcher

More information: Love-Chezem, T., Aggio, J. F. and Derby, C. D. (2013). Defense through sensory inactivation: sea hare ink reduces sensory and motor responses of spiny lobsters to food odors. J. Exp. Biol. 216, 1364-1372. jeb.biologists.org/content/216/8/1364.abstract

add to favorites email to friend print save as pdf

Related Stories

Unusual orange lobster saved from the pot

Aug 06, 2010

What's unusual about this orange lobster? Its alive! Lobsters are usually a brownish-green colour when living and turn orange when they have been cooked. But a rare live reddish-orange coloured specimen has ...

Inside the brain of a crayfish

Sep 01, 2007

Voyage to the bottom of the sea, or simply look along the bottom of a clear stream and you may spy lobsters or crayfish waving their antennae. Look closer, and you will see them feeling around with their legs and flicking ...

Recommended for you

Orchid named after UC Riverside researcher

8 hours ago

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

In sex-reversed cave insects, females have the penises

10 hours ago

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

10 hours ago

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

User comments : 0

More news stories

Deadly human pathogen Cryptococcus fully sequenced

Within each strand of DNA lies the blueprint for building an organism, along with the keys to its evolution and survival. These genetic instructions can give valuable insight into why pathogens like Cryptococcus ne ...

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...

Hackathon team's GoogolPlex gives Siri extra powers

(Phys.org) —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...