Glass Cardinalfish
Ambassis sp. (often Ambassis jacksoniensis or similar)
Type: reef fish, saltwater
Physical Characteristics
Small, elongated, and highly transparent body where the vertebral column and internal organs are visible. Large eyes relative to head size, two distinct dorsal fins, and a deeply forked tail. Often possesses a silvery or yellowish tint along the midline. Scales are thin and cycloid.
Habitat & Distribution
Inhabits coastal waters, estuaries, and sheltered lagoons. Often found in mangroves and seagrass beds in the Indo-Pacific and Australian regions, preferring depths of 0 to 5 meters.
Size & Weight
Typically reaches 4 to 10 cm in length. Weight is negligible, usually only a few grams.
Similar Looking Species
Glass Perchlets (Ambassidae) look similar but can be distinguished by their deep bodies and spine counts. Other transparent cardinalfish (Apogonidae) may have different fin positioning and dorsal spine lengths.
Ecological Role
Acts as a vital link in the food web, serving as primary prey for larger carnivorous fish, wading birds, and sea snakes. Help transfer energy from zooplankton to higher trophic levels.
Diet
Opportunistic carnivore and planktivore. Feeds mainly on zooplankton, small crustaceans (like copepods), and tiny aquatic insect larvae.
Behavior
Highly social and gregarious; typically found in large, dense schools during the day to avoid predation. They are mainly nocturnal or crepuscular feeders.
Reproduction
External spawners; females release eggs into the water column or near vegetation where they are fertilized by males. They have a relatively short life cycle with rapid development from larvae to juvenile.
Conservation Status
Least Concern (IUCN); widespread with stable populations in many regions, though susceptible to habitat loss in mangroves.
Identification Tips
Look for the extreme transparency of the body, a silver-lined gut cavity, and the divided dorsal fin. In lagoons, they are often seen hovering in shimmering groups near structures or roots.
Interesting Facts
Members of this genus are often called 'Glassies' due to their see-through nature. Their transparency is a form of camouflage called crypsis, making them difficult for predators to spot in the water column.
User Notes
From lagoon
Identified on: 5/20/2026
Mode: Standard