Morphological development of halibut (Hippoglossus hippoglossus) larvae with special reference to mouth development and metamorphosis

Abstract

Halibut (Hippoglossus hippoglossus) larvae were raised from hatching to beyond metamorphosis in 11.5 m3 plastic bags with a temperature stable around 6°C. Standard length, myotome height, eye diameter and yolk sac length were measured on live or freshly preserved material. Mouth development and functionality, pectoral and pelvic fin development, intestinal development and the initiation of peristaltic contractions, and eye pigmentation and migration were observed from live material. The gape of the jaws was limited by an oral membrane which appeared coincident with the developing mouth and which persisted in either full or remnant form up to around the time of first feeding. The phenomena of yolk sac vesicles and the Non-reducing Yolk Sac Syndrome are discussed.