Markle et al.: Metamorphosis of Microstomus paaftcus 



291 



Figure 6 



Right-side midlateral pigmentation patterns during 

 development in Dover sole Microstomus pacificus : 



(A) OS13115, Stage 2, developmental score 5, 

 larval pattern of no melanophores on myomeres; 



(B) OS13118, Stage 2, developmental score 8, tran- 

 sitional pattern of melanophores on myosepta; 

 and (C) OS13117, Stage 3, aggregated pattern of 

 melanophores in circular area on caudal peduncle 

 and anterior trunk. 



and transitional patterns equally and 

 consider the circular aggregations as 

 the first indication of asymmetrical 

 coloration. 



Coincident with changes in these six 

 features are changes in features that 

 are not easily coded: gradual loss of 

 otic spines, reduction in body depth 

 (Figs. 3 and 8), reduction in interor- 

 bital width (Fig. 7), increase in right 

 eye diameter (Fig. 7), and increase in 

 right upper jaw length (Fig. 3). Devel- 

 opment of body scales also begins in 

 Stage-2 specimens with metamorphic 

 scores of 7 or 8. Body scales first form 

 above and below the lateral line, 

 anteriorly near the pectoral fin base, 

 and on the caudal peduncle. 



Stage 3 (metamorphic competent 

 larvae), 40.7-74.9 mm SL Stage-3 

 specimens have a metamorphic score 

 of 9, indicating that all six initiation- 

 event features have either begun or 

 reached the adult state. These speci- 

 mens have a translucent appearance, 

 intermediate between the earlier 

 transparent stages and later opaque 

 stages. Stage-3 specimens have asym- 

 metrical coloration, retain the coiled, 

 larval gut configuration, and have 

 resorbed the posterior process of the 

 coracoid. Some morphometric features 

 initiated in Stage 2, such as increasing 

 right eye diameter and shrinkage in 

 body depth, continue in Stage 3 (Fig. 

 2). Ossification of pelvic-fin rays and 

 radials is initiated in Stage 3, appar- 

 ently after settlement (1 of 10 pelagic 

 specimens and 4 of 4 benthic Stage-3 

 specimens have ossified pelvic fin rays 

 and radials). 



