Aquaculture America 2023

February 23 - 26, 2023

New Orleans, Louisiana USA

EXAMINING THE DIGESTIVE PHYSIOLOGY OF LARVAL Betta splendens TO IMPROVE LARVAL CULTURE PROTOCOLS

Casey A. Murray*, Olivia I. Markham, Eva Domas, Matthew A. DiMaggio

 

Tropical Aquaculture Lab

Fisheries and Aquatic Sciences

Institute of Food and Agricultural Sciences

University of Florida

Ruskin, FL 33570

casey.murray@ufl.edu

 



Betta splendens, also known as the Siamese fighting fish, is an anabantoid native to Southeast Asia and is among the top ten freshwater ornamental fish species imported into the USA for the aquarium trade. This fish is popular in the aquarium trade due to its ornate appearance, variety of color morphs, and ability to withstand suboptimal water quality conditions. Although B. splendens is a staple in the ornamental aquaculture industry, little peer-reviewed research has been conducted on larval digestive physiology and weaning. These data could be used to minimize the reliance on costly live feeds during the larval production process by indicating when larvae can transition to an inert microdiet (MD). Using the timing of the development of a functional stomach to guide MD introduction can help reduce live feed use while maintaining survival and growth. A 30-day trial was conducted to examine the digestive enzyme ontogeny, developmental milestones, and digestive morphology of B. splendens to determine the timing of the maturation of the digestive tract. At 1-day post-hatch (DPH), larvae measured 3.11 ± 0.06 mm (TL) with a large yolk sac, unopened mouth, and non-functional eyes. Mouth opening and first feeding occurred at 2 DPH, with subsequent swim bladder inflation occurring at 3 DPH. Flexion began at 6 DPH and completed at 13 DPH. Larvae were fully developed by 40 DPH, where the swim bladder extended to the caudal peduncle and fin coloration was present. Trypsin and lipase (Fig. 1) activities were quantified using standard microplate assays from 1-30 DPH. Both trypsin and lipase were detectable from 1 DPH and increased steadily throughout the larval period. Acid protease activity from 1-30 DPH was also quantified, but the results from this assay did not reveal a clear trend. Results from ongoing histological investigations will confirm the timing of gastric gland development and stomach functionality. Together, these data will be used to design a weaning trial to determine the earliest timepoint at which B. splendens larvae can be weaned from live feeds to MD without affecting larval growth or survival.