Meiofauna

Part of speech: noun

Definitions

1. Microscopic and very small invertebrate animals that live in the spaces between grains of sand and mud on the seabed or lake bottom
2. Tiny aquatic creatures that dwell among the particles of marine or freshwater sediments, too small to be caught by ordinary nets
3. The community of minute animals inhabiting the gaps between sand and silt particles in aquatic bottom habitats

Etymology: "Meiofauna" is a compound built from two parts. The second, "fauna," is the familiar Latin word for animal life, the same root that gives us "fauna" in its general sense of all the animals of a region. The first part, "meio-," comes from Ancient Greek "meîon," meaning "less." The name therefore describes these creatures by size: they are animals smaller than the ones ecologists usually count, living in the spaces between sand and mud grains on the seabed. The coinage works by contrast. Scientists studying the seafloor had long collected larger animals such as worms and molluscs, while the tiniest organisms were tallied separately. Adding "meio-" to "fauna" marked out an intermediate size class, a deliberate scientific label rather than an ancient term. Because the word was built from classical parts, it looks old, but it belongs to modern marine biology.