Differentiation and development of the gill in <I>Trachinotus ovatus</I> during larval and juvenile development

Abstract

We documented the differentiation and development of the gill and the relationship between gill struc-ture and function in Trachinotus ovatus using histology and scanning electron microscopy.Development of the gill was divided into three stages in the larvae and juveniles.Stage I included organ-primordium formation between 0–3 days after hatching(DAH).During this stage,gill-primordia were present but undifferentiated,there were no gill rakers,and respiration occurred primarily via the finfold,skin,and the microvascular surface of the yolk-sac.Stage II occurred between 4–17 DAH and was characterized by differentiation and development of gill filaments.Gill arches,filaments,secondary gill lamella,and gill rakers developed gradually and the basic structure and morphology of the gill were established.Stage III was initiated at 18 DAH,at which time the gill organs(e.g.,arches,filaments,secondary gill lamella,and rakers) resembled the adult in terms of morphology and function.The total number of gill filaments increased with the increasing body weight and body length in larvae and juve-niles.Thus,the single secondary gill lamella area and total respiratory area also increased with an increase of body weight.The differentiation and development of the gill was in accordance with growth,development,and function in larval and juvenile T.ovatus.