Matsui: Description of young platytroctids from northeastern Pacific Ocean 



21 I 



A 



YOLK 



c 



Figure 1 



Camera lucida drawings of the young of Holtbyrnia latifrons: (A)Ml-2-l, 15-mm larva; (B) SIO 65-439, 14-mm transitional specimen; 

 (C) 65-443, 14-mm juvenile. GO, = posterior gular organ; IVO = intraventral organ. 



juveniles is shorter than that of the larva, their head 

 length is two times greater (Table 1). Head length in- 

 creased from 15% of SL in the larva to the adult pro- 

 portion of 30% of SL at the end of the transitional 

 period. Head length of juveniles is proportionately 

 larger than that of adults even from the earliest stages, 



measuring 29-37% of SL in the 12-18 mm SL range, 

 with maximum of >40% SL at 36-45 mm SL (Table 2). 

 Head depth increased from 9% SL in the larva, to 

 10-17% SL in transitional specimens, to 16-23% SL 

 in juveniles as large as 50 mm. 



