David Fleetham / Ring-tailed cardinalfish (Ostorhinchus aureus), male protecting and incubating eggs in mouth, Philippines.

Tony Wu / Spotnape cardinalfish (Ostorhinchus notatus) pair, male taking cluster of fertilised eggs into mouth to brood. Shizuoka Prefecture, Honshu, Japan. June.

Tony Wu / Spotnape cardinalfish (Ostorhinchus notatus) pair, male taking cluster of fertilised eggs into mouth to brood. Shizuoka Prefecture, Honshu, Japan. June.

Tony Wu / Spotnape cardinalfish (Ostorhinchus notatus) pair side by side before spawning, female in foreground. Shizuoka Prefecture, Honshu, Japan. June.

Tony Wu / Spotnape cardinalfish (Ostorhinchus notatus) pair spawning. Female, on right has released eggs, male fertilising eggs. Shizuoka Prefecture, Honshu, Japan. June.

Tony Wu / Spotnape cardinalfish (Ostorhinchus notatus) pair spawning. Male has taken fertilised eggs into mouth to brood, female chasing male in an apparent attempt to steal eggs. Shizuoka Prefecture, Honshu, J...

Tony Wu / Spotnape cardinalfish (Ostorhinchus notatus) pair spawning. Male taking fertilised eggs into mouth to brood. Shizuoka Prefecture, Honshu, Japan. June.

Pascal Kobeh / Ring-tailed / Golden cardinalfish (Ostorhinchus aureus) male incubating its eggs in its mouth, Sulu sea, Philippines

Linda Pitkin / Kupang cardinalfish (Ostorhinchus wassinki), Triton Bay, near Kaimana, West Papua, Indonesia

Linda Pitkin / Ring-tailed cardinalfish (Ostorhinchus aureus), Triton Bay, near Kaimana, West Papua, Indonesia

Richard Robinson / Striped Cardinalfish (Ostorhinchus angustatus) at Walpole Island, New Caledonia.

Franco Banfi / Yellow-striped cardinalfish (Ostorhinchus / Apogon cyanosoma) and Narrow-lined cardinalfish (Archamia fucata) shoal amongst Sea urchins (Echinothrix diadema) spines, Lazi Pier, Dumaguete, East Negros...