The enigmatic blue-green iridescence of Sapphirina ovatolanceolata (Dana, 1849) (Crustacea, Copepoda, Sapphirinidae): a live observation from the Lakshadweep waters

The marine planktonic cyclopoid copepod genus Sapphirina is renowned for its striking iridescence, yet in situ observations of this phenomenon are relatively rare. This structural iridescence arises from the interference and reflection of light by thin, multilayered hexagonal guanine crystal platelets in the integument. The dazzling colors, which range from red to blue or violet, vary among species and are displayed exclusively by males. This feature likely serves as an adaptation for mate recognition, intraspecific communication, and predator avoidance through rapid shifts to transparency. During a field expedition near Kavaratti Island in the Lakshadweep archipelago (India) in January 2020, we observed a distinctive “jeweled” appearance of the seawater surface at about 8:30 AM. Investigation revealed that the phenomenon was caused by a swarm of Sapphirina ovatolanceolata males exhibiting brilliant blue-green iridescence. This short communication documents the occurrence and identification of S. ovatolanceolata from Lakshadweep waters, providing live photographic evidence of its blue-green iridescence in the natural environment.