Friday Squid Blogging: Camouflage in Squid Eyes
Interesting research:
Cephalopods possess a sophisticated array of mechanisms to achieve camouflage in dynamic underwater environments. While active mechanisms such as chromatophore patterning and body posturing are well known, passive mechanisms such as manipulating light with highly evolved reflectors may also play an important role. To explore the contribution of passive mechanisms to cephalopod camouflage, we investigated the optical and biochemical properties of the silver layer covering the eye of the California fishery squid, Loligo opalescens. We discovered a novel nested-spindle geometry whose correlated structure effectively emulates a randomly distributed Bragg reflector (DBR), with a range of spatial frequencies resulting in broadband visible reflectance, making it a nearly ideal passive camouflage material for the depth at which these animals live. We used the transfer-matrix method of optical modelling to investigate specular reflection from the spindle structures, demonstrating that a DBR with widely distributed thickness variations of high refractive index elements is sufficient to yield broadband reflectance over visible wavelengths, and that unlike DBRs with one or a few spatial frequencies, this broadband reflectance occurs from a wide range of viewing angles. The spindle shape of the cells may facilitate self-assembly of a random DBR to achieve smooth spatial distributions in refractive indices. This design lends itself to technological imitation to achieve a DBR with wide range of smoothly varying layer thicknesses in a facile, inexpensive manner.
As usual, you can also use this squid post to talk about the security stories in the news that I haven’t covered.
AlanS • January 17, 2014 4:54 PM
Obama earlier today:
“At the dawn of our Republic, a small, secret surveillance committee borne out of the “The Sons of Liberty” was established in Boston. The group’s members included Paul Revere, and at night they would patrol the streets, reporting back any signs that the British were preparing raids against America’s early Patriots. Throughout American history, intelligence has helped secure our country and our freedoms.”
The President, a Harvard-educated lawyer, educated in Boston no less, and who later taught constitutional law, has a perverse understanding of “The Sons of Liberty”.
At that time the Sons of Liberty were British citizens who were vehemently opposed to their government’s issuing of general search warrants. In 1761 James Otis, who was later one of the Sons of Liberty, gave a rousing argument against Writs of Assistance in the Superior Court of Massachusetts–he lost the case. John Adams, who witnessed the presentation, later wrote: “Every man of an immense crowded audience appeared to me to go away as I did, ready to take arms against writs of assistance. Then and there was the first scene of the first act of opposition to the arbitrary claims of Great Britain. Then and there, the child Independence was born.” Otis’s arguments, along with the decisions in a couple of English cases of the same period, became the bedrock of the 4th Amendment.
It’s a lot easier to make the case for Snowden being the true descendent of the Sons of Liberty than our current intelligence agencies.