Digest: Subcellular reallocation and the evolution of anisogamy in nematodes

Why has sperm gigantism evolved, and how do subcellular allocations scale with size? Schalkowski & Cutter (2025) addressed these questions with transmission electron microscopy of Caenorhabditis sperm, finding that a species with giant sperm disproportionately invests in mitochondria, consistent with energetic demands of motility and persistence. Here, the results are interpreted through anisogamy theory, highlighting how ecological conditions can favor sperm gigantism, why such costly sperm remain rare, and how new data invite mechanistic models of gamete evolution.