Induced breeding and embryonic development of Ikan Pipi Merah Systomus rubripinnis (Valenciennes, 1842)

Abstract

The Javaen barb, Systomus rubripinnis (Valenciennes, 1842) or ikan pipi merah in Malay, is a commercially important freshwater cyprinid in Southeast Asia, yet detailed information on its embryonic and early larval development remains limited. This study investigated the efficacy of hormone-induced breeding and characterized the chronological and morphological progression of embryonic development under captive conditions. Sexually mature broodstock were collected from a natural stream at Universiti Putra Malaysia Bintulu Campus, acclimatized, and induced to spawn using salmon gonadotropin-releasing hormone analogue (sGnRHa; Ovaprim®) at 0.5 mL kg⁻¹ for females and 0.25 mL kg⁻¹ for males. Fertilized eggs were examined microscopically at regular intervals to document developmental transitions from fertilization to hatching, followed by larval development during the first 72 h. Fertilized eggs were spherical, demersal, adhesive, translucent to mildly brownish, with an approximate diameter of 0.75 mm. Embryogenesis progressed through six major stages: zygote, cleavage, blastula, gastrula, segmentation, and hatching. Cleavage commenced approximately 45 min after fertilization, the blastula stage occurred at approximately 2 h, gastrulation at 6 h, segmentation at 9 h, and hatching began at approximately 14 h post-fertilization. The embryos exhibited progressive epiboly, germ-layer formation, somite differentiation, tail-bud development, organogenesis, and increasing embryonic motility preceding hatching. Following hatching, pigmentation and ocular differentiation became progressively evident, while the yolk reserve was largely depleted within 72 h, indicating the onset of dependence on exogenous feeding. Overall, the study demonstrates the feasibility of hormone-induced spawning and provides a chronological framework for embryonic and early larval development in S. rubripinnis. These findings provide practical benchmarks for hatchery management, particularly broodstock induction, egg monitoring, hatching management, and determination of the appropriate initiation of first feeding, thereby supporting the development of captive propagation and aquaculture protocols for this species.