In the lead-up to spawning, messmate pipefishes (Corythoichthys haematopterus) engage in a courtship ritual. Females visit a male that is ready to spawn and brood the resulting fertilized eggs. As part of this process, the fish cross their bodies in an X-pattern as seen here. This seems to be integral to pair bonding. The female is in the foreground. Photographed in Kagoshima Prefecture, Japan.