Biology of Finfish and Shellfish (2+1)

Leiognathidae

• There are three distinct morphs of leiognathid larvae, differing in pigmentation, head spination, and relative length of second dorsal and anal spine.
• Larvae are moderate to deep, strongly compressed laterally, and have 23-25 myomeres(5-11+12-20).
• The moderate to large head is initially deeply ovate with a steep, blunt, concave snout.
• The mouth is small and reaches to about the anterior edge of the eye. The mouth is extremely protrusible and a large, conspicuous ascending premaxillary process develops by the flexion stage (by 2.6-3.5mm).
• The moderate to large eye is round. At 1.8mm, the preopercular spines and serrate supraoccipital crest are present.
• By 2.2-2.8mm, a prominent posteriorly directed spine on the crest also develops, and is either smooth, serrate or multipronged, depending on species.
• The preopercular spines are either smooth, finely serrate or strongly serrate, depending on species.
• The spine at the preopercular angle is long during the preflexion stage. A supraocular ridge develops by 2.2mm and is serrate prior to flexion.
• It becomes smaller following flexion and reduces to a low, smooth ridge at about 12mm.
• A small spine separates from the supraocular ridge anteriorly in postflexion larvae larger than 6mm, and is retained in adults as the antero-orbital spine.
• Pelvic fin buds begin to form in postflexion larvae by 4.5-5.7mm.
• Full development of the pectoral fin is attained by 7.9-10.5mm. the lateral line is present from about 12mm.
• Leiognathid larvae are relatively lightly pigmented.
• Preflexion leiognathids have characteristic ventral pigment along the midline of the tail that consists of vertically elongate embedded melanophores with one to three melanophores per myomere.
• Melanophores are also present on the finfold anterior to the anus, over the gut and gas bladder.
• Later, pigment appears on the brain, angle of the lower jaw, pectoral-fin base, caudal vertebrae, caudal fin rays and bases, and widely over head, trunk and tail.