Lethrinidae: K III B3A

Gymnocranius griseus (Schlegel, 1844)

Grey barenose

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
625-720	1	145-190	clear	narrow	midway-bow	35% of NL	24

Egg: This egg has no outstanding features, and needs to be hatched to gain further clues to its identity. The oil globule is light pink to amber. The developing embryo has some pale yellow pigment which is difficult to see. The midway positioning of the oil globule, and summer spawning period are other clues. These eggs often hatch during the sample separation process, indicating that incubation is 24-28 hours in summer, assuming evening spawning. 

Larva: The early larva can be confused with the pale form of Secutor (LIIIF5), which can be avoided only by rearing to the 2-4 day stage, when the lack of yellow pigment, and lack of a line of “pimples” in the finfolds ( see LIIIF5), assist in separating the two. B: NH, C: 1 day, D: 2 days, E: 4 days (25°C).

This egg (and subsequent larva) is also similar to EIIIB8, but does not have a segmented yolk, and lack the black spot on the snout of the early larva. The similarity to Secutor has probably resulted in undercounting of this egg, as it is not seen often, and spawns at the same time of the year. Seventeen larvae have been barcoded, of which 13, as 1 species, have matched 6 adult Gymnocranius griseus collected locally (BOLD reference). See KIIIA10 for further notes on this species. Another 6 larvae, grouped as another species, have not found a match. While Smith (1986), lists both G. griseus and G. grandoculus (as robinsoni) as occurring on the east coast of South Africa, more recent publications (Carpenter, 2001; Heemstra and Heemstra, 2004) state that G . griseus does not occur on the east coast of Africa. Barcoding of adult material from the KZN coast and Mozambique, has however revealed two species (my adult material, and specimens submitted to BOLD by SAIAB; M Mwale pers. comm.). Whether the KZN G. griseus is identical to G. griseus from northern Australia and Malaysia, requires investigation.

Linked samples	Offshore	Inshore
Eggs	142	10
Hits	65	10

The limited data suggests this species is a summer spawner (blue graph). The Park Rynie linked samples show 95% of these eggs in the offshore samples, evidently spawning outside the geelbek (LIIA6) spawning grounds. See Section 7.3 and Table 1 of the Introductory Notes, for more information on the linked samples.