Biology of Finfish and Shellfish (2+1)

Engraulidae

• Engraulid larvae are very elongate and initially have a cylindrical body that becomes moderately compresses by the end of the flexion stage.
• Subsequently,the body deepens(to at most, elongate) and becomes more compresses as transition is approached.
• There are 39-46 myomeres(21-31+11-20)*. The ratio of preanal to postanal myomeres changes because the anus migrates anteriorly.
• Thus, the tail and particularly the caudal peduncle become relatively longer and the trunk shorter.
• The long, straight gut initially reaches to 74-81% BL.
• The gas bladder is apparent from the flexion stage.
• The head is initially slightly depressed. By 12-15mm, the mouth is moderate to large and the maxilla reaches beyond the eye and may even reach beyond the pectoral fin.
• There is no head spination. Posteriorly-located dorsal-and-anal-fin anlagen appear in preflexion larvae between 3.9 and about 6.0mm.
• The dorsal fin differentiates slightly earlier than the anal fin. Pelvic-fin buds appear just anterior to the gas bladder (at myomere 12-15) between about 10-12mm, and all rays are present by 18mm.
• Engraulid larvae are lightly pigmented but have a remarkably consistent pattern of pigmentation on the gut.
• Initially most of the pigment is located ventally on the trunk and tail: a single row of melanophores on the midline of the isthmus.