To gain social stature, clownfish can change their size, growth rate, and even their sex.

When a young clownfish gets scooped up by a diver in Disney's new hit, Finding Nemo, his single father sets out through animated oceans on the adventure-filled search of a lifetime. If the story had taken place in actual tropical seas, his journey may have been even more exciting. New research about clownfish and their social structure suggests that after Nemo's mother disappeared, his father would have responded by putting on weight and becoming a female fish.

According to Peter Buston from Cornell University, clownfish live in groups inside sea anemones and must maintain a strict social hierarchy in order to avoid conflict. In each group, the largest fish is always the breeding female, followed by the breeding male and then up to four non-breeders, ranked by size. If the breeding female is removed, each remaining fish moves one rung up the ladder, so the breeding male becomes the breeding female, and the largest non-breeder becomes the breeding male.

Buston's research showed that as you move down the social ranking within a group of clownfish, each fish maintains its size at exactly 80% that of the fish immediately above it. Most other species modify their behavior, rather than their size and sex, to ensure that the group all gets along.

Protected by a thick coat of mucus, clownfish can live unharmed among an anemone's venomous tentacles.
Photo: Rosanna Leveriza, Ocean Views.
Nemo and Marlin, the stars of Disney's new hit, "Finding Nemo", are common clownfish like this one.
Photo: Bart Shepherd, CAS.
Anemone clownfish, genus Amphiprion.
Photo: Zafer Kizilkaya, CAS