Larval Development of Penguin Tetra (Thayeria boehlkei): Morphological Observations

In this study, the larval development stage of the penguin tetra fish (Thayeria boehlkei), a popular species in the freshwater aquarium fish industry, was investigated. For this purpose, penguin tetra larvae were morphologically observed from time to hatching until they reached the juvenile stage. Throughout the larval development phase, samples were randomly taken daily and captured on a camera using a stereomicroscope. Larval development stages were categorized into four periods: (I) Yolk-sac larva, (II) Pre-flexion larva, (III) Flexion larva, and (IV) Post-flexion larva. Larvae were fed with Artemia nauplii until they reached the juvenile stage for the entire research. Morphological changes, including the state of the yolk sac from hatching, mouth opening, changes in body shape and color, and fin formation processes, were recorded daily. According to the findings, the mouth opened on the 5th day, and external feeding also started on the 5th and 6th days. At the same time, free swimming movements were observed in the larvae, and it was determined that the yolk sacs were consumed. The flexion larva stage occurred on the 15-16th days. The larval development process of the penguin tetra fish was completed within 25 days after hatching. After this stage, the juveniles became morphologically identical to their parents.