Development of the digestive tract in first feeding larvae ofBetta splendensRegan, 1910

Abstract

Summary The aim of this study was to analyse the development of the digestive tract of Siamese fighting fish larvae (Betta splendens Regan, 1910), from hatching to 92 hours post‐hatching (hph) at 28.0°C, in order to determine the most appropriate time to begin exogenous feeding (live feed) and to investigate the digestive tract and its function during larval development. At hatching (29 hours post‐fertilization), the digestive tract was a simple and straight undifferentiated tube lined by a single layer of columnar epithelial cells; the mouth and anus were closed. At 18 hph, the mouth was open. At 32 hph, the tongue was located in the depression of the buccopharyngeal cavity floor and supported by basal cartilage. Goblet cells were present in the epithelium lining the pharynx and oesophagus. At 56 hph, the midgut had four distinct layers: the mucosa with typical villi, the submucosa, the smooth muscle layer, and the serosa. Histological analysis revealed that the larvae retained endogenous yolk reserves until 74 hph. Lipid accumulation was observed in the liver, which coincided with complete yolk absorption. At this time, the digestive tract was fully open and functional. Thus, it can be concluded that live feed should be given to B. splendens larvae from 74 hph onward, when the larvae are able to consume the food provided. This study also provides useful data for the improvement of husbandry techniques and for the formulation of diets specific to ornamental fish larvae.

Using digestive physiology to develop larval culture protocols for the Blackbanded Sunfish, a threatened centrarchid native to the United States

“…This endogenous period is shorter than that of Largemouth Bass, which rely on yolk reserves for 5-7 dph at 22-24°C (Coyle et al 2020), and is more similar to that of Gulf Coast Pygmy Sunfish Elassoma gilberti, which have an endogenous period of 3 dph at 24.40°C (Lipscomb et al 2020a). Early developmental milestones, such as mouth opening and swim bladder inflation (2 dph) and first feeding (3 dph), were consistent with those of several other altricial ornamental species, such as the Gulf Coast Pygmy Sunfish (Lipscomb et al 2020b), Serpae Tetra Hyphessobrycon eques (Çelik and Cirik 2020), and Siamese Fighting Fish (Silva et al 2016), for which these milestones occur within the first 4 dph. However, other stages of development, such as flexion, occurred much later for Blackbanded Sunfish (16-32 dph) than for these other species, in which flexion is usually complete within the first 2 weeks posthatch.…”

Ontogeny of the digestive tract of Brycon amazonicus (Teleostei, Bryconidae) under culture conditions: from hatching to juvenile stage

“…Most newly hatched fish larvae commonly exhibit a rudimentary digestive tract that undergoes several transformations until adulthood and, therefore, the larvae are less efficient in obtaining nutrients (Gisbert et al, 2014;Nakauth et al, 2016;Silva et al, 2016;Alveal et al, 2019).…”

“…Characteristics such as dilatation in the proximal region of the midgut and the presence of mucosal folds at the beginning of development (25 hPH) allowed better food retention with increased absorption and digestion efficiency (Maciel et al, 2010;Faustino et al, 2018b). The presence of large supranuclear vacuoles occupying the cytoplasm of cells in the midgut after initiation of exogenous feeding is associated with the absorption and accumulation of lipids, which after luminal digestion are absorbed as fatty acids by enterocytes, in which are resynthesized and then directed to other parts of the body (Silva et al, 2016;Marques et al, 2017). Peña et al (2003) related the presence of supranuclear vacuoles of the midgut to the storage of lipids, which after luminal digestion are absorbed as fatty acids by enterocytes, in which they are resynthesized and directed to other sites in the organism.…”

“…Upon hatching, fish larvae nutrition occurs through absorption from the yolk sac and, generally, their organic systems are simple and incomplete. Throughout this time, the larvae will acquire transitory structures that are adaptations related to the individual development stage, for example the intestinal bag that develops first and is subsequently replaced by the stomach (Nakauth et al, 2016;Silva et al, 2016;Marques et al, 2017).…”

Microverme da aveia como estratégia alimentar na larvicultura do Betta splendens

“…O inicio do período experimental, 3 dias após eclosão, foi definido levando em consideração a funcionalidade do intestino e capacidade de ingestão de alimento. Segundo Silva et al (2016) larvas da espécie Betta splendens apresentam trato digestivo aberto (boca e ânus), absorção total do vitelo e plena capacidade de consumir alimentos 74 horas após eclosão.…”