Embryogenesis and Early Development of the American Eel

The American Eel, Anguilla rostrata, is an ecologically and commercially important species in North America.  It is a fairly well known species found in inland and near shore habitats along the Western Atlantic Ocean.  However, the early life history remains a mystery resulting from the use of a cryptic spawning area in the Sargasso Sea.  With the collection of small larvae being the only circumstantial evidence pinpointing the spawning area, no data on embryogenesis through early larval development is available.  This study was conducted to document the timing of development of the American eel from embryogenesis through the early leptocephalus larval stages.  Eels were artificially matured and in vitro fertilization performed in the laboratory.  Embryos, prolarvae and larvae were maintained at 20°C in petri dishes containing sterile filtered sea water (33 ppt) and antibiotics.  Fertilized eggs were observed and photographed at varying time intervals from day one until day 19 to establish a timeline of development.  Embryological events observed included early 2-32 cell stages, somite development, and hatching.  The timeline of larval jaw, eye and fin development was also observed.  This is the first detailed documentation of the early development of this species.