Clipmark

Tiny mussel-like creatures living 100 million years ago made giant sperm longer than their own bodies, proving size has always mattered for some animals when it comes to sex

Giant sperm are still around today. A human sperm, for example, would have to be 40 meters long to measure up against a fruit fly's. The insect is only a few millimeters in size but can produce 6 cm-long (2.5 inch) coiled sperm

Now the discovery that ostracodes, an extinct ancient class of arthropods, displayed the same trait shows that making giant sperm is a long-standing and evolutionarily successful reproduction strategy.

In most animals, including humans, reproductive success depends on males producing a large number of tiny spermatozoa, while females invest in a few large eggs.

But in some cases where sperm have to compete inside a female's body, the chance of successful fertilization can be improved by increasing the size of the sperm cell.