Psychiatric disorders can be described on many levels, the most traditional of which are subjective descriptions of the experience of being depressed and the use of rating scales that quantify depressive symptoms. Over the past two decades, research has developed other strategies for describing the biological underpinnings of depression, including volumetric brain measurements using magnetic resonance imaging (MRI) and the patterns of gene expression in white blood cells.

The Encyclopedia of Life (EOL, www.eol.org) continues to expand at a record pace with the addition of new content and partners. At the start of 2012, EOL provides data on nearly half of all described species, with new content in Spanish, rich information about conservation issues from the International Union for the Conservation of Nature (IUCN) and NatureServe, and more images and videos than ever before.

Lithocholic acid (LCA), naturally produced in the liver during digestion, has been seriously underestimated. A study published in the journal Oncotarget shows that LCA can kill several types of cancer cells, such as those found in some brain tumors and breast cancer.

This photo shows the jawfish in association with the mimic octopus -- a case of a fish mimicking an octopus that mimics fish. Nature's game of intimidation and imitation comes full circle in the waters of Indonesia, where scientists have recorded for the first time an association between the black-marble jawfish (Stalix cf. histrio) and the mimic octopus (Thaumoctopus mimicus).