Synodontidae: H II A4

Saurida undosquamis (Richardson 1848)

Largescale lizardfish

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
1020-1130	0	n/a	clear	narrow	n/a	64% of NL	45-52

Egg: This egg develops no distinguishing features; but always appears bright and glassy, the clear yolk separating it from several clupeiforms (DIIA1 & DIIA2) of similar size (A). The advanced embryo develops a line of fine black pigment spots down the body, only visible on a white background. Incubation is about 50-55 hours; the eggs in Plate A illustrate the 24-hour development difference.

Larva: The early larva has an elongate gut and a myomere count in excess of 45 (B). Four blotches of black pigment, 3 pre-anal and 1 midtail, adorn the 3-4 day larva (C). B: NH, C: 3 days (24°C).

The only synodontid with a smooth-shelled egg listed by both Ikeda & Mito (1988) and Shao et. al. (2001), is S. elongata.  The latter authors list S. undosquamis as having a honeycomb pattern on the egg surface.  Thirteen hatched larvae have been sequenced, all matching the DNA barcode sequence of 5 locally collected adult S. undosquamis (BOLD). Further larvae will be sequenced to establish whether any other local synodontids have eggs with a smooth chorion. S. elongata is not known from South Africa (Heemstra 1986e). The egg can be confused with Thryssa (DIIA2), despite the latter's segmented yolk, so as a precaution, I generally hatch the eggs to confirm identification.

  

At Park Rynie, this egg was common throughout the year, with a small increase in spring and early summer (blue graph). In the DHM samples, the spawning pattern showed a more defined late winter/spring peak, perhaps reflecting a single species (green graph). At Park Rynie, the egg has remained common throughout the study period, but was more common in the first 10 years (white graph). In the Park Rynie linked samples, the eggs were more common offshore (67%), but the low percentage suggests spawning inshore of the two indicator species, ie mostly inside the 40m contour. See Section 7.3 and Table 1 of the Introductory Notes, for more information on the linked samples.

Linked samples	Offshore	Inshore
Eggs	793	390
Hits	248	164