Age of larvae Length (mm)/
Weight (mg)
0 dph 3.0-4.5/0.8-1.1
(Yolksac Length: 1.4-1.6 mm; Yolksac height: 1.2-1.4 mm)
Larvae look silvery. The eyes are very small and appear like black dot on the anterior part of head. Head is attached to yolksac, hence looks little bent at the anterior portion. Yolksac is round and compact. Mouth or mouth cleft is not distinguishable. Small cleft is visible at the posterior part of yolksac, indicating future anus. A continuous membrane encircled from just behind the yolksac and continues in ventral portion to dorsal side encircling tail region.
1 dph 3.5-4.8/0.9-1.2 (Yolksac Length: 1.2-1.5 mm; Yolksac height: 1.0-1.2 mm) Mouth remains opened and lower jaw shows occasional vibration. Vent is clear. No change of continuous membrane from ventral to dorsal side is marked as also seen in the 0 day old larvae. Barbells are not appeared clearly, but a rudimentary bulging or elevation is marked below the lower jaw. Heart looks transparent, but beats are clear, which were 2-3 times per second.
2 dph 4-5/1.2-1.6
(Yolksac Length: 0.9-1.1 mm; Yolksac height: 0.6-1.0 mm)
Mouth opening increases. Small bristle like structure is visible in lower and upper jaw indicating its teeth. Sometimes lower jaw closes for a while. Barbells of lower jaw extend up to yolksac. Tail fin is broad like a sark tail and appearance of rays noticed. But the continuous membrane over the body persists.
3 dph 6-7/2.4-3.0
(Yolksac Length: 0.4-0.6 mm; Yolksac height: 0.2-0.3 mm)
The yolksac does not show any round shape. The yolk content in the yolksac reduced drastically. The continuous membrane on the dorsal side reduced in size and showed dissolving sign with a gap in the dorsal side of peduncle. Tail looks single without any lobe as found in two days larvae. Fin rays are visible but not prominent. Barbells of upper jaw start developing. The visibility of heart beat is reduced. Dorsal, pectoral and pelvic fins are not originated.
4 dph 7-8/2.7-3.2 Lower jaw is movable but still mouth remains opened. Upper jaw barbell is clearly visible. Degeneration of continuous membrane on the dorsal side noticed and an elevation of fin is observed on the dorsal side nearer to neck indicating the initiation of dorsal fin formation. But the membrane at the ventral portion remains continuous as before. No yolk material is seen and elementary canal is visible. Heart beat is not seen due to increase of thickness of body. Bifurcation of caudal fin is initiated and fin rays appeared.
5 dph 7.5-8.5/3.5-4.2 Lower jaw barbells are longer than the upper jaw barbells. Dorsal side looks uniform without any membrane. Elevation of fin still persists as observed on the dorsal side nearer to the neck. The continuous membrane beyond anus to caudal region persists but a depression is marked just before the tail region on the ventral side of caudal peduncle. Faint rays in ventral fin appeared. Bifurcation of caudal fin is clear with 17 rays. Few pigments appear on the upper surface of head.
6 dph 8-9/4.6-5.1 Eye is prominent, which is 0.2 mm in diameter. The pigments on the head are increased in number. The barbells are 2.8-4.7 mm in length. Caudal fin deeply forked with 17 rays, where the upper lobe is longer than the lower one. Rays appear in ventral fin, which are 15 numbers approximately. 
7 dph 12-13/12.8-13.4 Snout looks round, but mouth remains opened. Elementary canal is coiled and extends up to vent. Pigments on the head surface expand in size. Pigments in less numbers also appear just below the dorsal side and over the belly. Ventral fin clearly demarcated with 17-19 rays. A membrane is visible in both side of operculum indicating future pectoral fin. Adipose tissue clearly visible.
8 dph 10-15/16-21 The visibility of elementary canal in the belly drastically reduced. The pigments on the above portion of belly increased in number. Dorsal fin grows bigger with faint rays, which are not countable. Pectoral fin is clear with 3-4 fin rays. Pelvic fin is not at all clear but two bulged membranous structures are found just before the anus.
9 dph 14-18/22-28 Complete closing of mouth is not found, but lower jaw movement is frequent. The teeth in lower and upper jaw are clearly visible. The pigments on the head fused in many places. Dorsal fin is clear with 5-6 fin rays. The ventral and tail fin possesses25-27 and 17-18 rays respectively.
10 dph 15-19/26-32 Black patch on the head surface and above the belly is observed due to merge of pigments. Few dots are also seen below the base of pectoral fin. Heart beats 50-53 times per minute. Pelvic fin is clear with 3-4 rays. Pectoral fin well developed with 4-5 fin rays.The ventral fin well developed with 23-25 fin rays. Tail fin also possesses 18-20 rays.
11 dph 18-22/26-44 The ventral portion of larvae look silvery and the dorsal portion look deep grey. The dorsal, pectoral, pelvic, ventral and caudal fin possesses 6-7(1+5-6), 6-7, 5-6, 24-25 and 19-20 fin rays.
12 dph 21-28/37-46 The color of the larvae is same as seen at the age of eleven days. Mouth is completely closed with lower jaw movement. Few pigments still persist at the base of pectoral spine. Different morphological parts like fins, adipose tissue, barbells etc are prominent. The dorsal, pectoral, pelvic, ventral and caudal fin possesses 6-7(1+5-6), 6-7 (1+5-6), 6-7, 25-26 and 19-20 fin rays, respectively. It resembles with that of an adult P. pangasius. The larvae at this stage swim actively and accept plankton and compound feed during their rearing in the hatchery.
Table 2: Brief description and summary of morphometrical changes of P. pangasius during its larval development.