606 
Fishery Bulletin 99(4) 
Table 2 
Incidence of dorsal midline melanophores at the trunk and tail (%) in Thunnus thynnus. Each melanophore is 
Myomere 
Size range 
(BL; mm) 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
3.50-3.99 
14 
7 
14 
7 
7 
7 
7 
36 
29 
36 
4.00-4.49 
4 
4 
4 
15 
4 
4 
7 
7 
15 
41 
22 
4.50-4.99 
4 
4 
4 
4 
7 
15 
7 
5.00-5.49 
8 
8 
8 
8 
17 
5.50-5.99 
10 
10 
10 
10 
10 
6.00-6.49 
20 
30 
30 
6.50-6.99 
17 
7.00-7.49 
10 
10 
10 
10 
20 
20 
30 
7.50-7.99 
10 
10 
10 
20 
40 
20 
40 
20 
10 
20 
8.00-8.49 
8 
15 
31 
23 
62 
77 
77 
85 
85 
85 
69 
69 
62 
8.50-8.99 
23 
54 
38 
46 
46 
54 
54 
54 
62 
85 
85 
85 
85 
92 
85 
92 
92 
92 
92 
9.00-9.49 
25 
67 
17 
25 
33 
33 
83 
58 
50 
58 
58 
67 
67 
67 
58 
75 
83 
67 
67 
9.50-9.99 
30 
80 
20 
30 
40 
40 
100 
70 
60 
70 
70 
80 
80 
80 
70 
90 
100 
80 
80 
I- 
Table 3 
1 
Incidence of the ventral midline and ventrolateral melanophores of the trunk and tail (%) in 
Thunn 
us thyn 
nus. 
Each melanophore 
not observed on 
the first to sixth myomeres. 
Myomere 
Size range 
(BL; mm) 
6 7 8 9 10 11 12 13 14 15 16 
17 
18 
19 
20 
21 
22 
3.50-3.99 
7 7 7 7 7 14 14 29 
7 
7 
50 
7 
21 
21 
4.00-4.49 
4 4 7 7 22 
22 
11 
15 
7 
19 
4.50-4.99 
10 5 5 0 10 10 
29 
24 
19 
19 
24 
33 
t 
5.00-5.49 
8 
17 
17 
17 
5.50-5.99 
10 
10 
30 
| 
i 
6.00-6.49 
10 
10 
30 
10 
6.50-6.99 
6 
11 
6 
7.00-7.49 
20 
10 
7.50-7.99 
8.00-8.49 
8.50-8.99 
8 
8 
8 
9.00-9.49 
9.50-9.99 
creased as the fish grew; no erythrophores were observed 
in specimens >20 mm BL. 
Head spination 
Major head spines first appeared in specimens at 4—7 mm 
BL. The posterior preopercular angle spine and anterior 
preopercular spine appeared at 4.23 mm BL (Fig. 2D), and 
the posttemporal spine at 6.80 mm BL. The largest speci- 
men lacking anterior and posterior preopercular spines was 
4.48 mm BL, and the largest specimen lacking posttempo- 
ral spines, 7.21 mm BL (Fig. 2E). No other spines or spine- 
lets of the head appeared in later developmental stages. 
The number of anterior and posterior preopercular spines 
increased 2-3 (nine maximum) and 5-7 (nine maximum), 
respectively, in the size range of 5-16 mm BL (Fig. 2, F 
