FISHERY BULLETIN: VOL. 72, NO. 4 



Table 1. — Meristic characters of larval and juvenile Opisthonema oglinum. 



the number of myomeres between the end of the 

 dorsal fin to the origin of the anal fin. In O. 

 oglinum larvae less than 16 mm, we counted 8, 

 9, or 10 myomeres between the two fins. Trans- 

 forming larvae and small juveniles (17 to 25 mm) 

 had from 5 to 7 myomeres between the fins. We 

 were unable to count these numbers with accuracy 

 in specimens longer than 26 mm. 



In life the larvae are very transparent and 

 gradually become opaque during transformation 

 because of an increase in pigmentation and a 

 compacting of the visceral cavity. Other than the 

 gross features of the gut mentioned above, the 

 development of the visceral organs was not 

 considered in the present study, but we assume 

 that abrupt changes take place. The swim bladder 

 first appears during transformation. Before 



transformation, a cavity develops above the 

 anterior end of the hindgut (just posterior to the 

 pelvic fins) in larvae as small as 10 mm, but a 

 definite swim bladder is not apparent until the 

 larvae are 15 mm long. In living larvae the 

 swim bladder is well defined. 



OSTEOLOGICAL DEVELOPMENT 



Larvae of O. oglinum undergo no ossification 

 of any parts before they measure about 10.0 mm 

 SL (all body lengths will be given in standard 

 length unless otherwise indicated). In the young- 

 est cleared and stained larva examined (4.1 mm 

 TL, total length), the cranial bulb was outlined, 

 as were the lower jaw, hyoid apparatus, and 

 dorsal and caudal fin lobes (Figure 2). All these 



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