Clupeidae: G III A1

Gilchristella aestuaria (Gilchrist 1914)

Estuarine roundherring

Egg diameter in m

Number of oil globules

Diameter of oil globule in m

Yolk texture

Perivitelline space

Position of oil globule at hatch

Gut length at eye- pigment stage

Myomeres

865-890

0-2

50

Segmented

narrow

stern

87% of NL

41-44

Egg: Plates A and B show eggs collected with a surface-skimming plankton net, in October 2003, from the Msimbazi estuary, a small, closed estuary 5km south of the Lovu estuary on the KZN south coast (Figure 2: Introductory Notes). It was marginally oval, and had from 0-2 tiny oil globules. The eggs shown in Plate C, were collected in St Lucia estuary (Connell 1996), measuring 840m, with 2-4 oil globules. The wide PVS is obvious in these latter (C), but was not so in the Msimbazi eggs. Incubation was about 26 hours.

Larva: The newly hatched larva has virtually no pigment (B), except for an indistinct line dorsally on the notochord. Eyes and mouth are undeveloped.

No DNA barcode sequence are available from hatched larvae, because they are not seen offshore at Park Rynie. Sequences are available from 6 adult fishes collected locally (BOLD).

Brownell (1979) referred to an egg described by Gilchrist, from the Knysna lagoon, as probably referable to this species. The egg was 710-720m with a wide perivitelline space (80m), no oil globule and a segmented yolk. Some of the Msimbazi estuary eggs lacked an oil globule, but the PVS was very narrow. This may however depend on the development stage of the egg. The St Lucia eggs had a similar PVS to the Knysna eggs, but also had 2-4 tiny oil globules. Blaber et. al. (1981) described different morphology of Gilchristella aestuaria adults from different estuaries, ascribing this to varying nutrition. Whether this could account for differences in egg morphology is unknown.