Pempheridae: L II A2

Pempheris schwenkii Bleeker, 1855 and P. adusta Bleeker, 1877.

Black-stripe sweeper and dusky sweeper

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
1285-1460	1	270	clear	narrow	stern	51% of NL	25

Egg: With an incubation period of about 50 hours, my sampling schedule and evening sorting through the sample, meant that the egg was seen either at 24 hours post-spawning (A), or about to hatch, at about 48 hours (B). At 24 hours, the egg has a sticky coating, to which light material such as strands of the blue-green alga Trichodesmium will adhere (A). There are no pigment spots on the yolk, and the clear oil globule is tucked into the tail of the embryo (A). 24-hours later the entire embryo and yolksac are covered in pale yellow pigment spots (B).

Larva: Early larvae (C & D), closely resemble those of  Monodactylus (FIIA9), and another pempherid, MIIA5. By day 5 the rapidly enlarging pelvic fin can be clearly seen (F, black arrow). In Plate G, the pelvic fin is tucked along the gut; in Plate H it is angled up along the body (black arrows). In all these stages (Plates C to H), the posterior portion of the notochord is unpigmented. D: 3days, E: 4 days, F: 5 days, G: 14 days, H: 17 days (22-23°C).

Although reared well past first-feeding (4-5 days), the juvenile was not taken through to postflexion in my rearing tanks. With a little care, and reasonable numbers of eggs, this should, however, not be too difficult. Two species of Pempheris are known from the area, and adults of bothe have been DNA barcoded (BOLD). Eleven larvae have been sequenced, 5 matching 5 adult P. schwenkii, and 4 (2 as MIIA5) matching 4 P. adusta, all adults collected locally. Separation of these two species will be attempted (but see also MIIA5). Curiously the barcodes of the other 2 larvae indicate two further species, associated with pempherids in the barcode cladogram. Further sequences are needed to confirm their presence in the area. Note that the pempherids of the WIO are currently under reviw, and the names given above will almost certainly change (J. Randall pers. comm.).

Linked samples	Offshore	Inshore
Eggs	324	477
Hits	53	186

This species is quite common, and spawns all year round, off Park Rynie (blue graph). The egg was also seen in small numbers in the DHM samples, again without a clear seasonal preference (green graph). The Park Rynie linked samples had slightly more eggs in inshore samples (60%), suggesting spawning occurs close inshore, around the 20m depth contour. See Section 7.3 and Table 1 of the Introductory Notes, for more information on the linked samples.