MOSER and AHLSTROM: DEVELOPMENT OF SCOPELOPSIS MULTIPVNCTATUS 



Table 1. — Measurements (mm) of larvae of Scopelopsis multipunctatus. 



pleted notochord flexion.) 



(Specimens below dashed line have com- 



1 Transformation stage. 

 * Juvenile. 



FIN DEVELOPMENT 



Our smallest specimen (5.4 mm) is under- 

 going flexion of the tip of the notochord and al- 

 ready has the adult complement of 10 superior 

 and 9 inferior principal caudal rays (Table 2): 

 In the next smallest larva (6.2 mm) , also under- 

 going notochord flexion, a single procurrent ray 

 is forming in the superior and inferior series. 

 The adult complement of 10-11 superior and 10- 

 12 inferior procurrent rays is present in larvae 

 13.0 mm and larger. 



The pectoral fins are represented by their in- 

 conspicuous bases in the 5.4- and 6.2-mm speci- 

 mens; the fins themselves are membranous, with 

 no ossified rays. Description of the gradual ac- 

 quisition of ossified rays described for pectoral 

 fins of other species (Moser and Ahlstrom, 1970) 

 is precluded by the gap in our series of Scopelop- 

 sis. Larvae 10.8 mm and larger have the adult 

 complement of 10-11 rays in each fin. 



The bases of the dorsal and anal fins are be- 

 ginning to form on the 5.4- and 6.2-mm larvae, 

 but no rays are ossifying. Larvae 10.8 mm and 

 larger have the adult complement of 21-23 dor- 

 sal and 23-25 anal rays. 



The pelvic fin buds are present in the 6.2-mm 

 larva, and larvae 10.8 mm and larger have the 

 adult number of 8 rays in each fin. The adipose 

 fin is beginning to develop at 6.2 mm and is well 

 formed by 10.8 mm. 



Gill rakers and vertebrae develop later than 

 do the fins. Gill rakers are first apparent in the 

 10.8-mm larva and are added gradually. On 

 the first arch, the full complement of 7-9 epi- 

 branchial rakers is achieved at 13.5 m^n while, on 

 the lower limb of the arch, the full complement 

 of 15-17 rakers is present at 15.2 mm, A 10.8- 

 mm larva already has 34 vertebral centra form- 

 ing; the adult number of 37-40 vertebrae is 

 present in larvae 12.2 mm and larger. 



546 



