Carpenter's flasher wrasse 

Paracheilinus carpenteri

Habitat & Distribution:  Western Pacific Ocean

Diet: Small crustaceans, zooplankton, small worms

Size: Up to 8 cm

Lifespan: 3 - 5 Years

Description

Carpenter's Flasher Wrasse possesses a slender, elongated, and laterally compressed fusiform body. One of its most unique anatomical features is its eyes, which have a divided pupil structure—a visual adaptation that allows it to detect small zooplankton while simultaneously keeping watch for approaching predators. Its dorsal fin is equipped with 9 spines and 11 soft rays; in adult males, 2 to 4 of these soft rays are elongated, forming antenna-like filaments. 

Behavior

The behavior that is most iconic—and the source of their name—is "flashing," a unique ritual in which the male swims rapidly, fully extends its fins, and causes its body colors to flare into a brilliant neon glow to attract females or intimidate rivals. As diurnal animals, they are highly active, swimming and hunting for zooplankton during the day; however, they employ a unique nighttime defense mechanism by hiding in crevices within the coral reef and encasing themselves in a thin mucus cocoon to mask their scent from predators.

Reproduction

Spawning occurs via the pelagic spawning method (free spawning within the water column), typically taking place around dusk, and begins with a highly aggressive courtship display by the male. The male darts rapidly around the female, erecting all his filamentous fins and performing "flashing"—intensifying his body coloration until it glows brilliantly like a neon light. If the female is interested and ready to spawn, both fish dart vertically together toward the water's surface (the upper water column) to simultaneously release their eggs and sperm (external fertilization).

Communication & Perception

These fish communicate with and sense their environment primarily through a combination of olfactory signals (scents), specialized vision, and—most likely—lateral line mechanosensation, whereas many coral reef fish rely heavily on bright color displays during the day.

Predator

Groupers, moray eels, and lionfish