Table 3.

Detailed information of larval development of stinging catfish in the hapa.

Stage of Larvae	Length (mm)	Characteristics
Hatchling	2.78	Mean length of the newly hatched larvae was 2.78 ± 0.04 mm, body color was transparent to brownish. Body was laterally compressed and head was attached to yolk sac looking a little bent at the anterior portion. Eyes were unpigmented, mouth or mouth cleft was not distinguishable. The pale greenish yolk sac was oval in shape with the diameter of 1.28 ± 0.03 mm. A thin and transparent fin fold surrounded the caudal region which extended up to the yolk sac (Figure 3a). A functional heart was noticed with the heartbeat of 180 times per minute.
4-h old larvae	2.92	The 4 h old larvae were brownish in color and, measured about 2.92 ± 0.02 mm in length. The anal pore position was almost at the mid ventral point and was not opened. The optical cups were visible, but the eyes were unpigmented. The two chambered heart became more distinct with circulation of body fluid around the notochord, brain, and yolk. A tube-like digestive tract was visible which emerged from the posterior-dorsal side of the yolk sac. Barbels were not yet developed, and reddish blood corpuscles represented formation of hemoglobin. Scattered melanophores were observed on the yolk sac and on the unpaired fin.
8-h old larvae	3.07	The average length of 8 h old larvae was about 3.07 ± 0.01 mm. The yolk sac became elongated and some melanophores appeared on the head region, ventral, and dorsal side of the body. Heart and brain of the larvae were distinctly visible. Some pigments were visible on the iris. The larvae became very active and light sensitive at this stage.
24-h old larvae	3.13	The 24 h old larvae became 3.13 ± 0.33 mm in its average length. The yolk sac reduced and dark pigmented eyespot appeared on the anterior part of the head. The upper and lower jaws were formed, and alimentary tract was distinct. The mouth and the anal openings were still closed, and the heart was clearly visible in front of the yolk. The blood circulatory system was fully functional. Melanophores were scattered on the dorsal fin fold and trunk region.
36-h old larvae	4.36	The average length of 36 h old larva attained 4.36 ± 0.3 mm. The eyes were spherical in shape with dark pigmentation. Yolk sac was further reduced. Preanal and postanal length were 2.15 mm and 2.21 mm, respectively. Four pairs of tiny barbels appeared (one pair = maxillary, one pair = nasal, two pair = mandibular). The mouth and the vent just opened (Figure 3c).
48-h old larvae	4.57	The larvae attained 4.57 ± 0.14 mm in length with a postanal length of 2.29 mm and preanal length of 2.28 mm. The dark and prominent eyeball diameter was 232.95 µm. The barbels became elongated and the yolk reserve was further reduced in size. The anal aperture and opercula were distinct. Denser melanophores were visible at the head region compared to the body. The pouch-like stomach and the alimentary canal became distinct. Blood circulation was noticed in the opercula, head, and tail region.
3-d old larvae	5.54	The average length of the 3 d larvae reached 5.54 ± 0.29 mm with a preanal and postanal length of 2.68 mm and 2.86 mm, respectively. The body became brownish in color and the mouth and anus become fully functional. The head was prominent and head length reached 1.33 mm. The nasal, maxillary, and mandibular barbels became 0.817 mm, 1.4 mm, and 1.18 mm in length, respectively. Body pigments were more concentrated in the anterior region, the yolk material was reduced in size.
6-d old larvae	6.44	The 6 d old larval average length reached at 6.44 ± 0.06 mm and weight 4.3 ± 0.3 mg. The yolk material became completely absorved, body color became brownish black and caudal fin rays were clearly noticeable with eight rays. Eyeballs were large and barbels become more elongated.
10-d old larvae	7.36	The average length of 10 d old larvae was 7.36 ± 0.43 mm and weight 6.3 ± 0.9 mg with a preanal and postanal length of 3.30 mm and 4.06 mm, respectively. Dorsal and anal fins were almost separated from the caudal fin, and the caudal fin was clearly seen with eight fin rays. The larvae started frequent surfacing movements and active swimming.
15-d old larvae	8.73	The average length of 15 d old larvae reached at 8.73 ± 0.48 mm with weight 15.0 ± 3.1 mg, preanal length 3.67 mm and post anal length of 5.06 mm. A total of eight caudal fin rays became distinguished, dorsal fin formed, spine of the pectoral fin became distinguished. Due to numerous pigments the body, color of the larvae became opaque.
20-d old post-larvae	11.12	The average length of 20 d old post-larvae reached 11.12 ± 0.28 mm with average weight 22 ± 2.1 mg. Body color of the larvae became darker due to huge pigmentation at this stage. Barbels became more elongated.
25-d old post-larvae	17.39	The mean length was observed 17.39 ± 0.95 mm and the body weight was about 36.30 ± 2.9 mg. The body color of the fish became dark reddish brown at this stage.
30-d old post-larvae		The average length and weight of post-larvae were recorded 32.00 ± 2.00 mm and 115 ± 56.3 mg, respectively. The fish became elongated and was observed to be like an adult with all morphological characters. On the head of the fish, two depressions were formed. The terminal mouth was transverse and wide.