Gerreidae: E III B8

Gerres longirostris Lacepede 1801 (=acinaces Bleeker, 1854

Smallscale pursemouth

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








37% of NL


Egg: As the egg develops, two lines of black pigment dots appear laterally on the embryo. These move dorsally and coalesce, and the oil globule becomes dark as black pigment intensifies ventrally (B). Yolk segmentation is mostly around the edge, and can take on the appearance of concentric rings. The oil globule sometimes has a light amber tint. Eggs hatch in about 24 hours.

Larva: This larva was usually identified by the black pigment on the nose, that developed by day 1 (D), but had disappeared again by day 3 (E). At 17 days, the larva is in flexion (G); by 23 days flexion was complete (H), but intervening day larvae were not seen and it was almost certainly completed earlier. At 38 days (I) the larva is taking on the appearance of the adult. C: NH, D: 1 day, E: 3 days, F: 5 days, G: 17 days, H: 23 days, I: 38 days, J: 54 days (23-24°C).

No larvae from this egg, have yet been sequenced for DNA barcoding.  Adults of four local Gerres species have been sequenced, including acinaces (BOLD).

Linked samples









Egg collections from Park Rynie do not show a clear spawning season (blue graph), but the DHM samples indicate a summer maximum (green graph). The egg was 12th most common in the DHM samples (Introductory Notes: Table 2). The trend in eggs over the years at Park Rynie (white graph), might be reflecting the impact of rainfall on this estuarine dependent species, since the peaks were preceded by the better-than-average rainfall years 1987-88, and 1995-96, and the troughs have coincided with dryer periods. The Park Rynie linked samples show the spread of these eggs about equal (51%), indicating that the species is spawning close inshore.  See Section 7.3 and Table 1 of the Introductory Notes, for more information on the linked samples.