Sillaginidae: F III A7

Sillago cf sihama (Forsskal, 1775)

Sand smelt

Egg diameter in µm	Number of oil globules	Diameter of oil globule in µm	Yolk texture	Perivitelline space	Position of oil globule at hatch	Gut length   at eye- pigment stage	Myomeres
790-865	1	190-215	segmented	narrow	stern	46% of NL	35

Egg description:  This pretty little egg catches the eye with its bright yellow pigment, which is well developed by the time I examine the samples in the late afternoon or evening. Some eggs appear a bit patchy in pigment distribution on the embryo (A), others more evenly spread (A1). The yolk is heavily segmented. Incubation time is about 30 hours (24°C).

Larval description:  The larva is easily identified by the size, pigment pattern, oil globule position, segmented yolk, and the high myomere count.  By day 4, the yellow pigment has almost disappeared (F). B: 1 day, C: 2 days, D: 3 days, E & F: 4 days (23°C).

The egg was not successfully reared. Six larvae have been sequenced for DNA barcoding. All 6 matched, and confirm that the genus is Sillago. Barcoding of adults has however, indicated there are 4 cryptic species on the KZN coast (see also FIIIA4B), all of which currently key out to S. sihama (BOLD, and key in Smith & Heemstra 1986). One of these 4 species matches the 6 larvae, but is represented by only a single specimen, collected at Vetch's Pier on the Durban beachfrront. Three wild collected larvae, caught in my plamkton net while sampling for eggs, have also barcoded to this species (BOLD).

The egg was found in autumn and spring at Park Rynie (blue graph). They were fairly common, but were not seen in the DHM samples. (Another of the 4 cryptic species mentioned above, was collected in the DHM samples, see FIIIA4B). The annual trends graph shows a scattered presence, but more consistent in recent years(white graph). In the Park Rynie linked samples, the egg showed an inshore dominance (57%), indicating spawning close inshore, in the 20-30m water depth range. See Section 7.3 and Table 1 of the Introductory Notes, for more information on the linked samples.

Linked samples	Offshore	Inshore
Eggs	51	68
Hits	21	39