Aquaculture America 2024

February 18 - 21, 2024

San Antonio, Texas

HISTOLOGICAL AND PHYSIOLOGICAL CHARACTERIZATION OF DIGESTIVE SYSTEM ONTOGENY IN AN ORNAMENTAL WRASSE Halichoeres melanurus

Casey A. Murray*, Grace E. Sowaske,  Sarah W. Hutchins, Matthew A. DiMaggio

 

Tropical Aquaculture Laboratory

Fisheries and Aquatic Sciences

Institute of Food and Agricultural Sciences

University of Florida

Ruskin, FL 33570

casey.murray@ufl.edu



A

 Marine ornamental aquaculture often relies on the production of live feeds  that  are considerably costly to produce, which poses a constraint to the growth of the marine ornamental aquaculture industry. Introducing microdiets during larval development may help reduce the amount of live feeds needed and therefore greatly reduce the cost and labor involved. However,  the digestive tract of m arine larvae is rudimentary in early stages ,  making the digestion  and assimilation  of microdiets difficult. A 25-day trial was conducted to characterize  the  digestive tract ontogeny of Halichoeres melanurus , an ornamental wrasse species not yet commercially cultured, to give insight  into potential  feeding and weaning protocols. Larval  H. melanurus were raised on live feeds , including Parvocalanus crassirostris  copepods, Brachionus plicatilis  rotifers, and  Artemia  sp. nauplii from 3 to 25 days post-hatch (DPH) . Larvae  (n=10 per time point)  were sampled  12 times  throughout the trial to analyze growth, digestive enzyme activity, and  digestive tract  development. The activities of lipase  and trypsin  were quantified using  standard microplate assay s. Histology was used to visualize morphological changes in the digestive system at each sampling time point. Trypsin  (Figure 1A)  and lipase  (Figure 1B)  activities were detectable from 3 DPH and increased more dramatically after 15 DPH, indicating the maturation of the digestive tract . The digestive tract remained agastric and was characterized by a unique pouch-like organ , named the oesogaster, located  posterior to the  esophagus and anterior to the intestine.  Further studies will be conducted to elucidate the function of the oesogaster, which has been found in other species of wrasse. Overall, t hese data  help us better understand the digestive capabilities of  H. melanurus throughout development and will guide future feeding and weaning protocols.