Swimming laps. These computer-enhanced microscope images show how genetic mutations that affect the microstructure of sperm’s flagella, or tails, can affect the cells’ swimming ability. The top sperm follows a normal, linear swimming path, shown by the coloured trails. The middle and bottom sperm carry mutations that affect the structure of their tails, causing them to swim in circles, or diagonally. Both lack enzymes that make important modifications to a protein called tubulin — a major component of the tail core. The findings point to a mechanism underlying certain types of infertility.
Miniature mind. This is a seven-month-old ‘mini-brain’ — a pinhead-sized ball of different types of human brain cell — seen under a confocal microscope. Scientists use mini-brains to study brain development and disease progression. To look inside one, researchers usually have to first cut it into thin slices. But a team at the Geneva School of Engineering, Architecture and Landscape (HEPIA) and the Wyss Center for Bio and Neuroengineering in Geneva, Switzerland, has developed a technique that allows it to produce 3D images of intact mini-brains, revealing the structure and positioning of individual neurons in detail. “Despite advances in growing mini-brains, it has been difficult to understand in detail what is going on inside — until now,” says Adrien Roux, a bioengineer at HEPIA.
Glowing gecko. This baby Namib web-footed gecko (Pachydactylus rangei) fluoresces under ultraviolet light. The intense neon-green and blue glow — among the brightest fluorescence in any vertebrate — is produced by modified pigment cells called iridophores. Why many animals fluoresce is still a mystery — but in this case, the pattern suggests that it helps these social animals to signal to each other across the moonlit desert.