purposeforporpoise

For love, some would twist the laws of physics. Short of doing that, mantis shrimp communicate with the other sex by spinning light waves, biologists find. The feat seems to be unique to this animal.

Alone in the animal kingdom, mantis shrimp may use the physics phenomenon of circularly polarized light to signal their presence to—and to see—potential mates.
Caldwell

Light is made of electromagnetic waves. These are electric and magnetic fields that wiggle perpendicular to each other and to a light ray's direction. Many invertebrates have sophisticated eyes that can detect wavelengths of light invisible to humans. Some, including bees, can also distinguish linearly polarized light. That's when a light ray's electric field wiggles not in varying directions, but rather in one precise direction that forms a right angle to the ray.

Researchers now show that mantis shrimp—which actually look more like small lobsters—can tell when light is circularly, rather than linearly, polarized. That means that the electric field twists like a corkscrew as the light ray moves. http://louis1j1sheehan.blog.ca/
The corkscrew can twist right or left—or, in biological terms, be right- or left-handed.

Roy Caldwell of the University of California, Berkeley, suspected that one species of mantis shrimp, Odontodactylus cultrifer, might be able to distinguish circular polarizations. Animals in this species, especially adult males, are rare. But 2 years ago, thanks to a tip from a crustacean enthusiast, Caldwell obtained a 4 inch-long adult male originally from Indonesia.

The shrimp had a fin with shades of red that looked more or less intense when seen through filters for right- or left-handed circular polarization. This trait was rare enough, but not unique in the animal kingdom. Caldwell's collaborators at the University of Maryland, Baltimore County (UMBC) and the University of Queensland in Brisbane, Australia also took a closer look at the eyes of O. cultrifer and of two similar species to see whether the animals could distinguish between right- and left-handed polarization.

The researchers found that some of the eyes' light-sensing cells doubled up as filters, explains Tom Cronin of UMBC. The cells have microscopic structures, like bristles of a toothbrush, that slightly slow light with electric fields parallel to the bristles, but not light with fields that are perpendicular. As a result, the twist of a circularly polarized wave will be flattened into a steady, linearly polarized wiggle, which another layer of sensory cells can then detect. Depending on their arrangement, bristled cells will select right- or left-handed polarization. This parsing enables mantis shrimp to distinguish the two types of light.

Meanwhile, the team trained mantis shrimp to feed from one of a few different tubes based on the circular polarization in the tubes' reflected light. Results appear online in Current Biology.

Caldwell says the skill, unknown in other animals, most likely helps the shrimp find mates. "It's the most private communication system imaginable," he says. http://louis1j1sheehan.blog.ca/
"No other animal can see it."

The traditional theory of cetacean evolution was that whales were related to the mesonychids, an extinct order of carnivorous ungulates (hoofed animals), which looked rather like wolves with hooves and were a sister group of artiodactyls. These animals possessed unusual triangular teeth that are similar to those of whales. For this reason, scientists had long believed that whales evolved from a form of mesonychid.

However, since the early 1990s analysis of a wide variety of protein and DNA sequence data consistently indicated that whales should be included among artiodactyls. Most probably they are a sister group of hippopotamids, deeply buried within artiodactyls.^[1] The strong evidence for a clade combining cetaceans and artiodactyls is further http://louis1j1sheehan.blogspot.com/discussed under the entry Cetartiodactyla.

The recent discovery of Pakicetus, the earliest proto-whale (see below) supports the molecular data. The skeletons of Pakicetus demonstrate that whales did not derive directly from mesonychids. Instead, they are a form of artiodactyl (another type of ungulate) that began to take to the water after the artiodactyl family split from the mesonychids. In other words, the proto-whales were early artiodactyls that retained aspects of their mesonychid ancestry (such as the triangular teeth) which modern artiodactyls have since lost. An interesting implication is that the earliest ancestors of all hoofed mammals were probably at least partly carnivorous or scavengers, today's artiodactyls and perissodactyls having switched to a plant diet later in their evolution. Whales, due to the readier availability of animal prey and their need for higher caloric content to live as marine endotherms, naturally retained their carnivorous diet, as did mesonychids, who were however out-competed by better-adapted animals like the Carnivora later on (mesonychids became specialized carnivores when the overall availability of large animal prey was still low; thus their adaptation was likely at a disadvantage when new forms had filled the gaps left by the dinosaurs).

Louis J Sheehan ON THE face of it, John Reader's new biography of the potato seems to have a silly title—“propitious esculent” is just a fancy way to say “helpful food”—and an even sillier subtitle. But that is because the virtues of the world's fourth biggest food crop (after maize, wheat and rice) and its influence on world history are easily overlooked. “I used to take potatoes for granted,” the author writes. His aim is to discourage readers from doing likewise.

The key to the potato's value lies in its high yield and its almost perfect balance of nutrients. Potatoes can produce more energy per unit area per day than any other crop, and it is possible (though tedious) to subsist on a diet of spuds and very little else.

First domesticated in the Andes, the potato was carried to Europe in the 16th century. At first Europeans were suspicious: the potato was variously thought to be an aphrodisiac, to cause leprosy or to be poisonous. http://louis-j-sheehan.net/
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But it slowly caught on as its merits in times of famine and war became apparent (it is more reliable than grain and remains hidden underground until harvested). By the late 18th century it was being hailed as a wonder-food—for the poor, at least. Marie Antoinette promoted potatoes by wearing their flowers in her hair.

People then started to worry that the potato was too popular, and that its abundance was causing an unsustainable increase in population. Exhibit A was Ireland, where the booming population subsisted almost entirely on potatoes. The danger of such dependency was starkly revealed by the Irish potato famine of 1845: at least a million people died, and another million emigrated.

Mr Reader's tale ends with the modern efforts to understand the genetics of the potato, which could lead to more disease-resistant varieties. The propitious esculent, he explains, is likely to feature in the diets of space-farers who will have to grow their own food.

The all-potato diet will not appeal to all readers, but this accessible account embraces the latest scholarship and addresses the failings of previous works on the subject. Indeed the book, like the tuber it describes, fills a void: the spud now has the biography it deserves.