Priacanthidae: K III B3

Priacanthus hamrur (Forsskal, 1775) *see notes below

Crescent-tail bigeye

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
720-770	1	170-180	clear	Moderate to narrow	bow	44% of NL	23

Egg: The egg (A) often appears slightly asymmetrical, sometimes oval, and the PVS is sometimes moderately wide. The yolk is clear but the surface is rough. The egg is striking, due to the bright amber oil globule, and the heavy black pigment dorsally down the length of the developing embryo. The embryo also has a blotch of black pigment on the nose, often in a ring. (A, white arrow). Heavy black pigment covers the oil globule and is scattered on the yolk around the oil globule. The egg often hatches while the sample is being processed in the evening. Thus incubation is 24-28 hrs in summer, assuming evening spawning (25°C). 

Larva: The newly hatched larva may show the three main pigment patches illustrated in Plates B & C, but more often has a dense line of black pigment dorsally (F). At two days the pigment has consolidated over the gut, and the finfold is rough (G).  At 3 days the eyes are fully pigmented, and there is a fine line of black dots ventrally along the notochord to the tip.  B & C: newly hatched, D: 3 days, E: 4 days (25°C). Included later: F: newly hatched, paler oil globule, G: 2 days.

The barcodes of twenty larvae hatched from these eggs, with oil globules of various shades of pale to dark amber, have matched the sequences of 5 adult Priacanthus hamrur collected locally. Two larvae, from eggs with a dark oil globule, indicate another species of priacanthid, which is Priacanthus sagittarius, according to BOLD, while the barcode of an adult from the Tugela Banks, submitted as P. hamrur, matches Priacanthus fitchi Starnes 1988 (BOLD). A single adult Heteropriacanthus cruentatus has been barcoded, but no eggs have been found to match it. Three hatched larvae, also from eggs with a dark oil globule, submitted as KIIIB3, have matched EIIIB5, which is Pristigenys niphonia, based on sequences in BOLD. This emphasises the need carefully to search for segmentation, in order to separate the latter species from Priacanthus hamrur.

Linked samples	Offshore	Inshore
Eggs	663	423
Hits	76	41

This is a summer and autumn spawner (blue graph). The egg was only seen once in the DHM samples, in January. Apart from an unusual sample in February 1995, this egg has shown no significant trend over the past 25 years (white graph). The Park Rynie linked samples show slightly more (61%) in offshore samples, suggesting spawning around the 35m contour. See Section 7.3 and Table 1 of the Introductory Notes, for more information on the linked samples.