(Bleeker)
1. Distinctive characters of early developmental stages
(a) Eggs
Stolephorus tri 1
Pelagic, elliptical and non-pigmented eggs measure 1.41 to 1.73 mm in length and 0.58 to 0.67 mm in breadth, probably the largest among Indo-Pacific species of the genus Stolephorus. The egg has narrow perivitelline space. The yolk is segmented and occupy the entire volume of the egg. A single light brownish or yellowish oil globule with a diameter range of 0.09-0.14 mm is situated at the posterior end of the yolk (Bensam, 1983; Vijayaraghavan, 1957).
(b) Larvae
Stolephorus tri 2
The prolarvae measuring 3.2 mm length immediately after hatching have 29 pre-anal myomeres (PAM). The PAM count reduces to 25 and remains constant up to 16.8 mm length post- larvae. In 20 mm larvae, the PAM count shows further reduction to 24, while in 25 mm larvae, the count reaches the minimum (23) due to slight forward shifting of anus. A few pigment spots (stellate and branching chromatophores ) are present along the alimentary canal in early post larval stage (3.2 to 5 mm size), but totally disappear when the larvae reach 12 mm size. The eyes are silvery. In 5 mm larvae, the anterior part of alimentary canal is straight and narrow, whereas the rectal region is enlarged. In 8-12 mm size, folds appear in the rectal region. In later stages, the rectal folds give rise to vertical muscle strands and intimately from a wall round the rectal region of alimentary canal. In 12 mm larvae, the head region shows concave dorsal profile which almost become convex in early juvenile of 25 mm length (Vijayaraghavan, 1957).
(c) Early juveniles
Stolephorus tri 3
Early juveniles of 25 mm length have 23 pre-anal myomeres. Ventral scutes and ventral fins are not yet fully developed. Dorsal, anal and pectoral fins show same number of rays as in adults. Predorsal spine traceable. Minute scales are present near the caudal region of the body. Silvery lateral band slightly visible in the anterior region of the body (Vijayaraghavan, 1957).
(d) Juveniles and adults
Predorsal spine present; Pungent spine present on the pelvic scute; Posterior margin of preoperculum rounded; Lower gill rakers 23 - 27; (Whitehead, 1972), Ventral fins fully developed when the juveniles attain a size of 30 - 35 mm in length.
2. Distinctive characters of early developmental stages in similar species occurring in the mangrove waterways
(a) Eggs
1) Eggs of Stolephorus buccaneeri
Oil globules absent.
2) Eggs of Stolephorus heterolobus
Yolk occupies two third the length of the egg.
3) Eggs of Stolephorus macrops
Egg length relatively shorter than S. tri ; small vacuole-like structure present above the oil globule.
(b) Larvae
1) Larvae of Stolephorus macrops
Pre-anal myomeres drastically reduce from 29 to 21 as the larva develops. (Pre-anal myomeres almost at a constant count of 25 in most of the larval phase in the case of Stolephorus tri ).
3. Distinctive characters of early developmental stages in similar species from the coastal/off shore waters
(a) Eggs
1) Eggs of Stolephorus bataviensis and Stolephorus commersonii
Elliptical eggs with a distinct terminal knob.
(b) Larvae
1) Larvae of Stolephorus heterolobus
Relatively more number of myomeres (42-43 numbers). (In the case of S. tri the total myomere count is 38 only).
4. Salient biological and ecological information
Laboratory experiments revealed the carnivorous feeding habit of the postlarvae of this species, selectively feeding on planktonic copepods (Vijayaraghavan, 1957). The adults of this species frequently visit the lower reaches of the mangroves where neritic condition prevails.
5. Geographic distribution
East and west coast of India, Indo-Malayan Archipelago and Thailand.