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Fishery Bulletin 107(2) 
crease on the head until the entire area was nearly cov- 
ered with small melanophores (Fig. 2D). Gut pigment 
was less visible. The first and second lateral pigment 
bands were fully developed. The third lateral pigment 
band developed directly beneath the posterior portion 
of the second dorsal fin approximately between fin rays 
11 and 13. Pigment in the fourth band was located on 
the caudal peduncle and extended posteriorly onto the 
caudal fin. Pigment was also scattered mediolaterally, 
giving the appearance of a horizontal bar posterior to 
the second band. Pigment developed on the caudal-fin 
rays. 
At the beginning of the juvenile stage, lateral bands 
were well defined by dark pigment (Fig. 2E). Larval pig- 
mentation (e.g., PVMs) was still present until at least 
24.9 mm, but by 33.0 mm no residual larval pigment 
remained. Scattered melanophores on the mediolateral 
part of the body between the second and fourth bands 
were retained and looked like small pigment blotches. 
Table 2 
Total postanal ventral melanophores (PVMs) of larvae 
and juveniles of northern sculpin ( Icelinus borealis). 
Specimens between dotted lines ( ) are undergoing 
notochord flexion; specimens between lines ( ) are 
in transformation stage. Abbreviation; SL = standard 
length. 
Body length 
(mm SL) Postanal ventral melanophores 
7.4 
— 
7.9 
9 
8.8 
9 
10.2 
4 
11.6 
9 
13.4 
14 
14.3 
9 
14.8 
9 
14.9 
7 
15.1 
11 
15.8 
9 
16.0 
8 
16.3 
10 
17.9 
7 
19.6 
5 
22.7 
3 
24.1 
3 
24.9 
7 
32.1 
0 
41.7 
0 
43.2 
0 
45.1 
0 
45.9 
0 
51.7 
0 
Cirri 
Cirri developed during the postflexion stage. Supra- 
ocular cirri were first to develop. Supraocular cirri are 
typically bifid or trifid, but occasionally have more than 
three terminal filaments. The development of nasal 
and postorbital cirri followed supraocular cirri. During 
transformation into the juvenile stage, cirri developed 
posterodorsally on the maxilla. By 25.0 mm, one small 
cirrus was present both anteriorly and posteriorly of the 
parietal and nuchal spines, and more than one opercu- 
lar cirrus may develop per side (two cirri were present 
dorsally on each opercle of a 46.0-mm specimen). A full 
complement of supraocular, nasal, postorbital, maxillary, 
occipital, and opercular cirri was present in juveniles. 
Meristic features 
Except for the dorsal-fin spines and rays and the supe- 
rior procurrent caudal-fin rays, fins ossified by 14.3 mm 
(Table 3). Dorsal-fin spines and rays were completely 
ossified at 15.8 mm, as were the superior procurrent 
caudal-fin rays. Vertebral centra (9-11 abdominal + 
24-27 caudal) ossified at 14.3-15.8 mm. By 15.0 mm, 
lateral line scales began to develop; by 15.8 mm, two 
dorsal scale rows began to develop immediately beneath 
the dorsal fins. Lateral line scales and the two dorsal 
scale rows were ossified by 24.0 mm. Pterygiophores 
of the dorsal and anal fins ossified by 24.1 mm. Adult 
radiographs resulted in vertebral counts of 35-36. 
Spination 
Head spines developed during flexion. At 8.8 mm, pari- 
etal spines were minute but ossified. Four preopercular 
spines were present; the dorsalmost spine was most 
pronounced. At 11.6 mm, small nuchal spines, approxi- 
mately half the size of the parietals, were present. By 
14.3 mm, nasal spines were ossified. Parietal and nuchal 
spines fused together at their tips to form parietal sen- 
sory canals. By 16.0 mm, the dorsalmost preopercular 
spine was bent upward and the ventralmost spine down- 
ward and forward. The fused parietal and nuchal spines 
were less prominent. Nasal spines were well developed 
and slightly curved posteriorly by 22.7 mm. At approxi- 
mately 24.0 mm, the dorsalmost preopercular spine 
was very large and bifurcate; the dorsalmost spine may 
become trifurcate by the juvenile stage. 
Caudal skeleton 
The caudal skeleton consisted of one ural centrum, preu- 
ral centra, neural and haemal spines, three epurals, two 
uroneurals, one superior hypural (HY 4 5 ), one inferior 
hypural (HY 13 ), and 25-31 caudal-fin rays (7-11, 6 + 6, 
4—8) (Fig. 3). At 8.8 mm, HY 13 and HY 4 _ 5 were fused 
and all 12 principal caudal-fin rays (6 + 6) were present 
(Fig. 3A). Three epurals formed by 12.0 mm. Each preu- 
ral centrum had one neural and one haemal spine; how- 
ever, in some specimens the first preural centrum had 
