Unicellular maze

Foraminifera are single-celled marine organisms that have inhabited marine or brackish environments from the poles to the equator for more than 500 million years. When alive, they are remarkable bio- indicators of the state of our oceans since they are particularly sensitive to pollution. As fossils, their mineral shells enable palaeontologists to reconstruct past climates. Foraminifera make up one of the most abundant and diverse groups of fossils. This 2 mm-long alveolinid specimen was collected in the Paris Basin, and is over 40 million years old. It testifies to the presence at that time of a warm, shallow sea. When observed under X-rays, it reveals a complex internal organisation, with hundreds of tiny chambers, known as chamberlets, arranged in a spiral. This image is a winner of the 2021 La preuve par l'image (LPPI) competition.