BERRIEN: EGGS AND LARVAE OF SCOMBER 



rays were forming at a length of 5 mm and in S. 

 scombrus at 7 mm. 



Pigmentation 



Differences in pigmentation were found be- 

 tween larvae of the two species. Pigmentation over 

 the gut and midbrain and on the caudal region is 

 not described in detail because it does not differ 

 between the two species. A series of 210 S. 

 japonicus specimens ranging from 2.8 to 49.0 mm 

 long and 187 S. scombrus, 2.6 to 21.6 mm long, 

 were used in the pigmentation comparison. Figure 

 3 illustrates the development of pigmentation and 

 various body features. 



Forebrain 



Scomber scombrus larvae usually acquire 

 melanophores on the forebrain at smaller sizes 

 than S. japonicus. They were present on S. scom- 

 brus as small as 3.7 mm and were present on all 

 larvae larger than 5.5 mm. The smallest S. 

 japonicus with such pigment was 5.2 mm, and not 

 until 8.7 mm was attained did all larvae have this 

 pigment. Forebrain pigment should not be con- 

 fused with that on the midbrain which larvae of 

 both species possess at all sizes. 



Hindbrain 



Pigmentation on the hindbrain begins as a 

 single melanophore then increases to three to five 

 melanophores on the posterior and middle portion 

 of the hindbrain. This pigmentation is increas- 

 ingly obscured by overlying tissue after about 5 

 mm. All S. scombrus larvae examined had this 

 pigment, but S. japonicus <3.5 mm did not. 



Snout 



Pigmentation on the snout refers to 

 melanophores on, or within, epidermal tissue, not 

 subsurface as on the forebrain. Melanophores ap- 

 pear first near the tip of the snout. Scomber scom- 

 brus generally develop snout pigmentation at 

 smaller sizes than S. japonicus. The smallest S. 

 scombrus with such pigmentation was 4.3 mm 

 long and it was present in all that were 6.3 mm and 

 greater. It was first observed in S. japonicus at 5.2 

 mm and was present in all specimens 10.5 mm and 

 longer. 



Cleithral Symphysis 



Pigmentation at the symphysis of the cleithra, 

 and on the isthmus immediately anterior to the 

 symphysis, was lacking in all specimens of S. 

 japonicus. However, in S. scombrus prominent 

 melanophores were noted at this location in larvae 

 as small as 3.7 mm and occurred in all larvae >8.0 

 mm (Figures 3, 4). Melanophores occurred on the 

 isthmus of S. scombrus in: 13% of those 4.0 to 4.9 

 mm long; 41% of those 5.0 to 5.9 mm; 67% of those 

 6.0 to 6.9 mm; 95% of those 7.0 to 7.9 mm; and in all 

 specimens 8.1 mm and longer. In larvae <8 mm 

 the presence of melanophores at the cleithral 

 symphysis indicates S. scombrus; however, the 

 absence of this pigment at this size does not indi- 

 cate either of the two species. At sizes >8 mm the 

 presence of this pigment indicates S. scombrus 

 and its absence indicates S. japonicus. 



Lower Jaw 



Melanophores on the lower jaw first appear at 

 the mandibular symphysis, then spread laterally 

 and posteriorly. Scomber scombrus acquire this 

 pigment at a smaller size than S. japonicus. The 

 smallest larval S. scombrus observed with lower 

 jaw pigmentation was 4.6 mm long and it occurred 

 in all specimens 6.2 mm and greater. The smallest 

 S. japonicus with such pigment was 8.3 mm long 

 and it occurred in all larvae of this species 11.7 mm 

 and greater. 



Ventrum of Gut 



In his paper on the development of S. japonicus, 

 Kramer (1960) referred to two or three charac- 

 teristic, minute melanophores on the ventral sur- 

 face of the gut, found after yolk absorption. During 

 my study pigment in this location was observed in 

 both S. japonicus and S. scombrus. The percent 

 occurrence of melanophores on the ventrum of the 

 gut in S. japonicus <12 mm long varied from 70% 

 to 92% for each 1-mm size group, with an average 

 of 88% occurrence. The occurrence for the same 

 sizes of iS. scombrus varied from 10% to 41%, with 

 an average of 28%. 



Dorsum of Trunk 



There are substantial differences between the 

 two species in pigmentation on the dorsum of the 



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