(Dutt and Rao)
1. Distinctive characters of early developmental stages
(a) Eggs and prolarvae
Not yet recorded from the mangroves.
(b) Advanced postlarvae (Based on 2.2 mm size)
Coilia korua 1
Body elongate and gradually narrowing towards the tip of the caudal. Free pectoral filaments not yet formed. (In young ones and adults, there are 10 free pectoral filaments). Dorsal fin with 13 rays and small spine before dorsal fin not yet formed. (In young ones and adults, a small spine is present before dorsal fin origin). Pelvic fins with 7 rays. Anal and caudal fins distinguishable at the confluent point. (In juveniles and adults it is difficult to distinguish the caudal from the anal fin). Anal with over 100 soft rays. Myomeres not discernible in advanced postlarvae. Scales and scutes not yet formed. (In young ones and adults, there are 7-10 prepelvic scutes and 8-11 post pelvic scutes). The pigmentation is poor and without any pearly spot on flanks.
2. Distinguishing characters of early developmental stages in similar species of the genus Coilia from brackish water and marine environment
(a) Coilia dussumieri (Largely after Delsman, 1932b)
1) Eggs
Coilia dussumieri egg
Eggs are spherical (oval in the case of Stolephorus , another genus of the engraulid). Perivitelline space narrow, yolk coarsely segmented. Egg contains 8 to 12 colourless oil globules of relatively bigger and uniform size on the ventral side. (No oil globule in Thryssa , another genus of the family Engraulidae and bigger oil globules of assorted size in Setipinna another genus belongs to Engraulidae). Egg size varies according to salinity of the water (about 1 mm in 34 ppt salinity and 1.05 to 1.1 mm in 27 to 30 ppt salinity).
2) Prolarvae
Coilia dussumieri 1
The Prolarvae resemble those of the family clupeidae. However, the bigger sized oil globules occupy the hinder part of the yolk along the alimentary canal as in the case of the closely related genus Setipinna . Pre-anal myomeres are 36 and new myomeres are added as the larvae grow in this species with long tail.
3. Salient biological characteristics
(a) Maximum size
18 cm (from mangroves of southeast India)
(b) Food and feeding
Juveniles and adults of this species feed on benthic crustaceans (tanaids, gammarids, benthic copepods), sergestids, planktonic copepods and mysids from mangrove waterways (Jeyaseelan, 1981).
(c) Reproductive biology
Not yet studied in this recently described species.
4. Salient ecological information
(a) Habitat
Advanced postlarvae occur scarcely in lower reaches of the south east Indian mangroves. Juveniles and adults occur in nearshore and brackish waters, including mangroves.
(b) Geographic distribution
East coast of India.
(c) Behaviour
It is a shoaling species feeding on both benthic and pelagic crustaceans.
5. Evolutionary significance
Among engraulids, members of the genus Coilia have a distinct body shape (with out bifurcated caudal fin, with long tail, free pectoral filaments and long anal fin confluent with caudal fin). This species (Coilia korua ) is placed between C. reynaldi and C. coomansi based on variations in prepelvic scute counts, which are geographically distributed in Myanmar and Indonesia respectively. (Whitehead, 1972)