To investigate the embryonic and larval developmental characteristics of Leiocassis longirostris (L. longirostris) and determine the Point of No Return (PNR) of starved larvae, fertilized eggs were cultured in a recirculating glass aquarium maintained at a water temperature of (24.5 ± 0.5) ℃. Respectively, the chronological characteristics of embryonic and larval development were observed under a microscope, and starvation experiments were conducted on newly hatched larvae to study their morphological development, growth traits, and feeding capacity. The results indicated that the fertilized eggs of L. longirostris reached a diameter of (3.46 ± 0.16) mm after water absorption and swelling, and the embryonic incubation period was 68-70 h. Embryonic development was observed to progress through eight consecutive stages: fertilized egg, cleavage, blastula, gastrula, neurula, organogenesis, pre-hatching, and hatching. Subsequently, we observed that newly hatched larvae undergo three distinct developmental phases before initial feeding: the appearance of body pigments, the formation of the intestinal tract, and the first coiling of the intestinal tube. Thereafter, results from the larval starvation experiment indicated that L. longirostris larvae relied on endogenous nutrition within the first 4 days post-hatching (dph). Initial feeding occurred at 5 dph, with a feeding rate of (63.33 ± 2.89)%, marking the onset of the mixed nutritional stage. By 9 dph, the yolk sac was fully absorbed, and the larvae transitioned to exclusive exogenous nutrition. Moreover, the feeding rate remained at 100% from 8 to 11 dph, followed by a decline. The PNR was identified at 16 dph. Subsequently, complete starvation-induced mortality occurred between 16 and 17 dph. Thus, the optimal initial feeding time for L. longirostris larvae is recommended to be 5 dph. In summary, the findings of this study provide fundamental data on the early developmental stages of L. longirostris, which has significant practical implications for improving larval rearing efficiency in aquaculture.
A Wed, study studied this question.