Sneaky Silkmoths

Last spring, the periodical cicadas emerged across eastern North America. Their vast numbers and short above-ground life spans inspired awe and irritation in humans—and made for good meals for birds and small mammals. Such snacks do not come without cost, however: Cicadas emit extremely loud shrieks when captured. Perhaps the pattern of the giant silk moth Citheronia azteca (right) evolved to resemble a cicada as a form of Batesian mimicry—imitation by a nonpoisonous species of a poisonous or unappetizing one. So Philip Howse speculates in Giant Silkmoths: Colour, Mimicry and Camouflage (Papadakis, $40 paper), in which he and photographer Kirby Wolfe showcase these members of the Saturniidae family.

Wolfe offers notes on collecting and raising silk moths. But the book’s wealth of photographs serves as collection enough: Viewing page after page of stunning moths from all over the world, I felt the guilty pleasure of seeing more of these creatures than one would ever normally encounter. Caterpillars are well represented also.

Anna Lena Phillips in American Scientist.Here

The recent discovery of really, really big viruses is changing views about the nature of viruses and the history of life

The common view of viruses, mostly true, is of tiny burglars that sneak into cells, grab the biosynthetic controls and compel the cell to make huge numbers of progeny that break out of the cell and keep the replication cycle going. Viruses are supposed to be diminutive even compared to cells that are just a micrometer (1,000 nanometers) in diameter. They are supposed to travel light, making do with just a few well-adapted genes.

 

In 1992, a new microorganism was isolated from a power-plant cooling tower in Bradford, England, where Timothy Robotham, a microbiologist at Leeds Public Health Laboratory, was seeking the causative agent of a local pneumonia outbreak. His search led to the warm waters of the cooling tower, a known reservoir for bacterial pathogens in the Legionella genus, which are the cause of the pneumonialike Legionnaire’s disease. Particles present in the sample were mistakenly identified as bacteria. Gram positive and visible under the microscope as pathogens within the particle-gobbling amoeba Acanthamoeba polyphaga, the entities surprisingly did not generate any product from the gene-amplifying polymerase chain reaction technique using universal bacterial primers.

Eleven years later, in 2003, the mystery organism received a new identity and a new name, Acanthamoeba polyphaga Mimivirus, for microbe-mimicking virus. Mimivirus is the largest virus ever discovered. Giant viruses had been known for a few years, many of them in a group termed nucleo-cytoplasmic large DNA viruses (NCLDVs). This group features several other virus families, including Poxviridae, which infects vertebrates (for example, smallpox virus) and invertebrates, the aquatic viruses Iridoviridae and Phycodnaviridae, and the vertebrate virus Asfarviridae. Giant viruses are considered to be ones with genomes larger than 300 kilobase pairs and with capsid diameters of about 200 nanometers or more.

James L. Van Etten in American Scientist: Here