Matsui: Description of young platytroctids from northeastern Pacific Ocean 



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specimens, sparse epidermal pigment is found around 

 the lower jaw, with a broken line at the midline be- 

 tween the anal and dorsal fins. This pigmentation 

 spreads and intensifies in the juveniles, resulting in the 

 blue-gray to black coloration. 



Morphometries A large yolk mass extends from the 

 cleithrum to about halfway to the anus in the single 

 larval specimen, which has a small head (headlength 

 = 17% of SL) and mouth and undeveloped fins. Head 

 length in transitional specimens nearly doubles to 

 26-33% of SL. Maxillary length increased from 7% SL 

 to 9-13% SL during transition. Body length shortened 

 or remained about the same (Table 3), as body length 

 behind the head shortened. Head length and depth in 

 transitional specimens are similar proportionately to 

 adults, but the mouth is smaller than in adults and ex- 

 tends only to mideye, instead of behind the eye. Max- 

 illary length is 9-13% SL during transition and 14-16% 

 SL in adults. Eye length in the larva is proportionate- 

 ly similar to eye diameter in adults; however, eye depth 

 is only half of the length in the former. 



Head, mouth, and eye are proportionately largest in 

 the 20-60 mm juveniles. Head length was mainly 

 35-38% of SL at this range (Table 4) but <30% of SL 

 in individuals larger than 150mm SL. 



Fins All specimens have a flexed notochord and 19 

 principal caudal rays. Dorsal and anal fin rays are ab- 

 sent in the larval specimen, but pterygiophores of 11 

 anal and 13 dorsal rays are present. Counts of 13-16 

 dorsal, and 12-15 anal rays of the transitional speci- 

 mens (Table 3) were nearly in the adult range of 16-18 

 dorsal and 14-16 anal finrays. Most juveniles over 

 20 mm SL had the adult counts. Pectoral fin rays are 

 absent in specimens <18mm. There were 0-7 pelvic 

 rays at that length. Adult counts on all fins are found 

 in juveniles >30mm SL. There are 9-10 (usually 9) 

 pelvic and 14-18 pectoral fin rays in the adult. 



Branchial region Branchiostegal rays and gill rakers 

 are absent in the larval specimen. Except for one indi- 

 vidual with 7 rays, transitional specimens have the 

 adult count of 8 branchiostegal rays. There are 8-11 



