Oplegnathidae: E III A2

Oplegnathus robinsoni Regan 1916 

Natal knifejaw

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








45% of NL


Egg: My notes describe the developing embryo in the egg as being lightly covered with lime green/yellow pigment, and the oil globule tinted pale amber. This is one of those species where the oil globule is up front, but not tightly tucked up into the bow (B). Incubation is 35-40 hours (23°C).

Larva: The larva has 6-7 patches of pigment down the body, starting just behind the eyes. Colour is generally more yellow than the orange tint of B. By day 4, black pigment is becoming prominent over the gut (D). By day 5, yellow pigment has almost disappeared from some individuals (E).  B: 1 day, C: 3 days, D: 4 days, E: 5 days (23°C).

Four larvae, hatched from this egg have been sequenced, which matched 4 local adult O. robinsoni, as well as a 5th specimen collected off Pomene in Mozambique, and submitted as O. peaolopesi (BOLD).

This egg is uncommon, having been seen, on average, in only one sample per year. This is surprising, since the adult is not uncommon on the reefs off Park Rynie. The sparse data suggests an early and late summer spawner, though also extending into May (blue graph). The appearance of these eggs off Park Rynie has been eratic during this study (white graph). The Park Rynie linked samples had 68% offshore, indicating spawning in the vicinity of the 30-40m depth contours (although numbers are low). See Section 7.3 and Table 1 of the Introductory Notes, for more information on the linked samples.

Linked samples