THE SILK SPINNING SHRIMP

 

The ability for animals to spin silk has been marvelled at by biologists and comic book fans alike for many years. However, the phenomena may not be limited to as few creatures as previously thought. Researchers have recently discovered a species of shrimp that uses a silk-spinning technique to build its very own sand house.

Crassicorophium bonellii,a tidal dwelling crustacean, has the ability to produce a sticky fibrous material through ducts on its legs in order to generate a functional thread. This similar technique to spiders of extrusion spinning is used to produce ‘gossamer threads’, which have the added property of being salt-water resistance. The fibres are then used to combine sand, vegetation, algae and its own faeces to provide a shelter.

Although Professor Fritz Vollrath and his team from University of Oxford noted the ability of the shrimp to spin silk underwater, much of the properties of the material remain unknown. It is thought to have evolved independently to the production of silk within spiders and as such may provide further insights into convergent evolution- the development of similar characteristics in unrelated species.

Further exploration into the novel material may also provide the basis for future adhesive products or silk production. For example, the barnacle cement biology involved in fibre production may provide a breakthrough in marine glues or barnacle-resistant coatings for boat hulls. The costs of drag in the shipping industry therefore would be minimized.

Currently the silk industry worldwide has an approximate value of $200-$500 million, although much of it is now produced artificially. Genetically modified spider silk was created from worms and goats in Utah State University to produce extra strong fibres which have the ability to stop reduced speed bullets. More advances such as this may be possible as nature reveals more secrets in the form of the shrimp.

By Sophie Meyjes

Squid and Octopus Camouflage Specialists

Recent discoveries by scientists have shed light on how a species of octopus and squid are able to switch their colours from transparent to reddish brown in an attempt to cope with changing light conditions in the depths of the ocean.

Sarah Zylinski and Sonke Johnsen, the lead researchers of the study from Duke University in North Carolina, US, found that the skins of octopus and squid respond to light that deep sea predators produce to illuminate their prey. The switch in the camouflage of these creatures is thought to assist in concealing themselves from the ubiquitous number of predators found in this gloomy environment.    

Sunlight that diffuses through the water also passes through transparent animals, rendering them almost invisible. However if light is shone directly on these transparent tissues they actually become highly visible.

Professor Michael Land, a biologist from the University of Sussex explained that at a depth of 600m light tends to fizzle out, making hiding a difficult issue to overcome in prey species such as the octopus Japetella heathi and the squid Onychoteuthis banksii that ordinarily are transparent. In the gloom of the deep sea, predatory fish tend to be equipped with light producing organs that function as biological headlamps. These lights are designed to attract unwitting prey as well as illuminate others such as J. heathi and O. banksii. With transparency being such a danger in this environment, both these creatures switch to a much darker colour which significantly improves their ability to avoid being seen.

Both J. heathi and O. banksii contain light sensitive cells called chromatophores which contain pigments. When these cells detected the blue light of a bioluminescent predator, they immediately expanded, “dyeing” the animal a deep brown colour.  It was found through experimentation that the change in colour in these creatures was almost instantaneous therefore showing its importance “in a habitat where there is nowhere to hide” said Dr Zylinski.

The ability for cephalopods such as J. heathi and O. banksii to switch between the two colours and optimise optical conditions is vital for their survival in an environment that is extremely hostile.

By Anthony Kubale