Zanclidae: L III D8

Zanclus canescens (Linnaeus, 1758)

Moorish idol

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
790-815	1	190	clear	narrow	stern	59% of NL	23

Egg: This egg has not been photographed, as it has not been recognised as different at the egg stage. My notes record no pigment in the egg stage.  The oil globule is clear. Thus it is likely to be confused with serranid eggs (LIIIB4, LIIID2, LIIID4), but early development of yellow chromatophores oin thefinfold edge of the larva will distinguish it from all but KIIIA4. This latter egg has a much smaller oil globule, and the oil globule is anteriorly placed in the early larva.

Larva: The pattern of yellow pigment in the 1 & 2-day larvae, around the finfold edge, is distinctive, keeping in mind the position of the oil globule, and clear yolk. By day 4, a large brown blotch has appeared above the anus (E). Note also the serrated finfold edge that develops at this stage (E1, arrows). The larva is developing a protruding jaw, which is even more pronounced at day 5 (F), when outer finfold pigment persists.  B: NH, C: 1 day, D: 2 days, E: 4 days, F: 5 days (26°C).

This egg was initially listed as an acanthurid, due to the small, early protruding mouth, but a larva listed as KIIIA4 has yielded a barcode match with Zanclus, (BOLD), causing my confusion, since these two larvae are similar in appearance soon after hatching, apart from the position of the oil globule. The larva was however, not collected off Park Rynie, but off Pomene in Mozambique, in November 2008. Barcodes from larvae collected locally are needed to confirm the identification.

The presence of a serrated finfold edge, is shared with two other larvae which develop an early protruding mouth (LIIIE7 & LIIIG4), both acanthurids. Note however that a serrated finfold edge is not exclusive to these three species. It is also well developed in labrids and bothids, among others.

The rare collections made of this egg point to summer spawning season (blue graph). The egg was not seen in the DHM samples.