Anguilliformes: D I A1

Gymnothorax sp and Unknown

Eels

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
2330-4020	0	n/a	segmented	wide	n/a	83% of NL	100+

Egg: The massive size, wide perivitelline space, and lack of an oil globule (A & B), set this egg apart from all others found in the area. When fresh the yolk has a light green tint, and measures 45-50% of egg diameter. The developing larva, which expands into the perivitelline space as it develops (B), does not develop any significant pigmentation in the egg (B), but this can vary, with some species having clusters of green or black pigment dotted along the ventral edge of the notochord (D). In my collections the egg hatched within 72 hours, which would indicate an incubation time of 80 hours or more (24°C).

Larva: The 3-day larva is elongate and blade-like, with pigmented eyes, a partly developed mouth, and either no pigment in the body (C), or green to black blotches ventrally on the notochord (D). C: 3 days, D: 4 days PH, E: 8 days PH.

There are clearly several species spawning this type of eel egg without an oil globule. Rearing attempts were frustrated by lack of knowledge of feeding preferences, if indeed these peculiar larvae feed at all. The jaws appear formidable (E), but also ineffectual. Although encountered in plankton samples, no larva has ever been seen with food in the gut. DNA barcoding of these larvae is the surest way to link larva to adult. Four larvae have so far been successfully sequenced, indicating 4 different species.Two suggest the genus Gymnothorax, but neither match adult sequences of G. elegans, G.  nudivomer and G. undulatus, currently available in the BOLD archive.The other two associated with congrids in the cladogram of South African adult material.

This egg is fairly abundant egg in Park Rynie samples (Introductory notes: Section 7, Table 3), with over 400 collected. Due to the solitary nature of eels, the eggs were seldom seen in high numbers in a sample, but the shallow and confined nature of the Durban Harbour mouth, together with the ideal eel habitat it provides, saw individual samples yielding up to 1000 eel eggs. It was the 6^th most common egg seen in the DHM samples (Introductory notes: Section 7, Table 2). The eggs seasonal distribution indicates a summer spawner (blue graph) with an identical seasonal pattern in the DHM samples (green graph). At Park Rynie, the occurrence of these eggs has remained steady (white graph). In the Park Rynie linked samples, the eggs showed a modest offshore majority (62%), suggesting spawning inshore of the two indicator species. See Section 7.3 and Table 1 of the Introductory Notes, for more information on the linked samples.

Linked samples	Offshore	Inshore
Eggs	188	113
Hits	81	56