Embryonic and larval development in the freshwater angelfish (Pterophyllum scalare)

The freshwater angelfish, Pterophyllum scalare like many other cichlids show parental care of embryos and larvae. This study was carried out to investigate the embryonic development of P. scalare, which shows biparental care and substrate brooding. During the study adult reproductive behavior and parental care was observed. Once the eggs were fertilized upon spawning, the early and later embryonic stages were observed, documented and various embryo length measurements were analyzed to characterize the developmental pattern in this species. Whole mounts and bone and cartilage measurements of acid free double stained larvae were analyzed to further understand the developmental rates in the hatched larvae. The developmental events were compared with those of other documented cichlid species as well as with the zebrafish, Danio rerio (Family Cyprinidae), which does not show parental care. After fertilization, cleavage division of the P. scalare embryo starts 1.30 hours post fertilization (hpf). On average, cleavage, blastula, gastrula, segmentation and pharyngula periods of embryogenesis are observed for approximately 3 ½, 11 ½, 9 ½, 36 and 12 hours respectively. Ultimately, P. scalare embryos hatched around 72 (hpf). Head Length, dorsal, caudal and anal fins show positive allometric growth while body depth and digestive tract show almost isometric growth. The study highlights that similar to a few other studied cichlids, P. scalare embryogenesis and larval development occur at a slower rate of development compared to D. rerio. In cichlids including P. scalare, parental care may allow these embryos the luxury of developing at a slower rate whereas the lack thereof for D. rerio embryos may necessitate faster development.