given in the following species descriptions of S. altivelis 

 and S. alascanus. 



Sebastolobus altivelis Gilbert, Figure 25 



Literature.— Larvae, pelagic juveniles, and early 

 demersal juveniles are described in Moser (1974). 



Distinguishing features. — Larvae of Sebastolobus 

 hatch and are freed from their floating egg mass at about 

 2.6 mm in length. They have an elliptical yolk sac with a 

 posteriorly positioned oil droplet. When the larvae reach 

 approximately 3.5 mm, the yolk sac has been resorbed 

 and the jaws and feeding apparatus are well formed. 

 Flexion of the notochord begins in larvae about 6.0 mm 

 long and is completed in larvae about 7.5 mm (Table 26). 

 Transformation into the pelagic juvenile stage is in- 

 itiated within the size range of 14.0 to 20.0 mm (Table 

 27). All specimens larger than 20.0 mm have some juve- 

 nile pigmentation. The pelagic juvenile stage of S. altive- 

 lis is highly protracted and may last as long as 20 mo. 

 Transformation into demersal juveniles occurs within the 

 size range of about 42 to 56 mm. 



Larvae larger than 10 mm may be differentiated to 

 species on the basis of body depth and pectoral fin shape. 

 Larvae and transforming specimens of S. altivelis are 

 more robust and deeper-bodied than those of S. alas- 

 canus. Body depth of specimens of S. altivelis in the 10- 

 to 20-mm size range is 36 to 45% of the body length (mean 

 of 41%), whereas in specimens of S. alascanus of compar- 

 able size the range is 33 to 39% with a mean of 35%. The 

 pelagic juveniles of S. altivelis are equally robust; body 

 depth averages 41% of body length in the 20- to 40-mm 

 size range but then decreases gradually to 34% in the 

 largest pelagic juveniles. Pelagic juveniles of S. alascanus 



are less robust; body depth averages 34% with a range of 

 31 to 36%. 



As in other scorpaenid genera, the pectoral fins provide 

 excellent characters for species separation. The pec- 

 torals are longer and have a deeper base in larvae and 

 pelagic juveniles of S. altivelis compared with S. 

 alascanus. In specimens of S. altivelis in the 10- to 20- 

 mm size range, the pectoral fin length averages 34% of 

 the body length (range of 29 to 39%). The pectorals reach 

 their maximum relative length in 20- to 40-mm pelagic 

 juveniles where they average 39% of the body length 

 (range of 35 to 41%). In pelagic juveniles 40 to 50 mm 

 long the average is 35% (range of 32 to 37%). In 10- to 27- 

 mm specimens of S. alascanus fin length averages 29% of 

 body length (range of 26 to 31%). 



The two species can be separated by a combination of 

 meristic characters. Sebastolobus altivelis usually has 

 one or two more pectoral fin rays and one or two less ver- 

 tebrae than S. alascanus (Table 28). 



The melanophore pattern of larvae of S. altivelis is in- 

 distinguishable from that of S. alascanus. At the begin- 

 ning of the larval stage (3.5 mm) there are large median 

 blotches opposite each other about midway back on the 

 tail. In some specimens, the blotches are expanded to 

 form a band. Also, melanophores cover the dorsolateral 

 surfaces of the posterior region of the gut. The melanis- 

 tic tail blotches are transitory; they are lost in some lar- 

 vae as small as 4.2 mm and one or both are absent in 

 most larvae between 5.0 and 6.0 mm in length. The dor- 

 sal blotch was absent in all larvae larger than 6.0 mm 

 and the ventral one was absent in all larger than 6.4 mm. 

 In contrast, the gut pigment is augmented throughout 

 the larval period, extending forward to the axillary region 

 and internally anterior to the cleithrum in larvae about 

 5.0 mm long. When the larvae reach 6.0 mm, the pig- 

 ment extends onto the ventral surface of the gut and dor- 



Table 26. Measurements Cmm) of Sebastolobus spp. larvae. (Specimens between dashed lines are undergoing notochord flexion) 



43 



