Swimming with dolphins is an effective treatment for mild to moderate depression, say researchers in this week's BMJ.

Canadian scientists have developed some clever molecular trickery that is helping to reduce the drug cravings of addicted rats. One of the problems in addiction is that neurons in some parts of the brain lose glutamate receptors from the cell surface, and those receptors are important for communication between neurons. The researchers have sidestepped this problem by crafting a peptide that mimics a portion of the tail of the glutamate receptor and, once inside a neuron, serves as a decoy to prevent the loss of glutamate receptors.

Using a tiny flatworm best known for its extraordinary ability to regenerate lost tissue, researchers have identified a gene that controls the ability of stem cells to differentiate into specialized cells. The gene encodes a protein that is most similar to the protein PIWI, an important regulator of stem cells in organisms ranging from plants to humans.

Species evolve at very different rates, and the evolutionary line that produced humans seems to be among the slowest. The result, according to a new study by scientists at the European Molecular Biology Laboratory (EMBL), is that our species has retained characteristics of a very ancient ancestor that have been lost in more quickly-evolving animals. This overturns a commonly-held view of the nature of genes in the first animals. The work appears in the current issue of the journal Science.