Sparidae: L III C1
Diplodus capensis (Smith, 1844).
Blacktail
|
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 |
|
890-940 |
1 |
190-200 |
clear |
narrow |
stern |
40% of NL |
24 |
Egg: Blacktail eggs are often seen fresh, at which stage the oil globule is pink and the egg has a yellow hue. As the eggs develop the oil globule becomes light amber, and the embryo is marked by about 6 batches of orange/yellow pigment, the most conspicuous of which are the 2 pairs in the head, like the 4 on a dice. Since the egg floats oil globule up, these are highly visible (A). Black dots run the length of the embryo dorsally, less obvious than the yellow pigment. Incubation is 35-40 hours. Egg development when collected, suggests both morning and evening spawning. The egg tends to sink a few hours prior to hatching.
Larva: The 6-7 yellow pigment blotches of the early larva (B & C), are similar to D. hottentotus (LIIB4), but the larger size of the egg and larva of LIIB4 was assumed to separate them, although Brownell (1979) found an overlap in size. The yellow (often orange) mid-tail patch persists to at least day 4 (E). The 15-day larva is undergoing flexion (F), which is complete by 25 days (G). B: NH, C: 2 day, D: 3 days, E: 5 days, F: 15 days, G: 25 days, H: 29 days, I: 50 days (22-23°C).
This species was easy to rear, and many were taken through to 2 months before being preserved as a voucher, or released. The ease with which this species was reared from various batches of eggs, led me to believe I was working with one species. Barcoding has revealed a slightly different picture. Of the 147 LIIIC1 larvae sequenced so far, 91 were D. capensis (some under the name D. sargus in BOLD), 10 were D. hottentotus (some under the name D. cervinus in BOLD), 29 were Pachymetopon aeneum (LIIIC1B), 8 were Pagellus natalensis, 3 were Porcostoma dentata, 2 were Sparodon durbanensis (LIIIC1C), 2 Lithognathus mormyrus (LIIID1), and 1 each of Pachymetopon grande (LIIIB10), and Chrysoblephus anglicus. While the latter three were probably mistakes, P. aeneum eggs in particular, are difficult to separate from those of D. capensis.
This was the 8th most common egg off Park Rynie (Table 3: Introductory Notes). Winter and spring were the main spawning seasons (blue graph). It was also the 8th most common egg in the DHM samples (green graph and Table 2: Introductory Notes). Annual catch of the eggs off Park Rynie has remained fairly steady, after a poor start from 1987-1992 (white graph). The Park Rynie linked samples had marginally more eggs inshore (52%), indicating most
| Linked samples | Offshore | Inshore |
| Eggs | 14049 | 14992 |
| Hits | 164 | 374 |
spawning occurs inshore of the 30m depth contour. This fish is abundant on the Aliwal Sloal, 5km offshore and 5km north of Park Rynie, but is also common on inshore reefs. See Section 7.3 and Table 1 of the Introductory Notes, for more information on the linked samples.