Markle et al.: Metamorphosis of Miaostomus pactficus 



289 



Figure 3 



Jaw dentition during metamorphosis in Dover sole 

 Microstomus pacificus, left lateral views: (A) OS12578, 

 Stage 1 with canine teeth; (B) OS11377, Stage 2 with 

 canine and developing incisor teeth; and (C) OS11288, 

 Stage 5 with developed incisor teeth. 



outline at the base of the dorsal and anal fins around 35-40 

 mmSL (Pearcy et al. 1977a). 



Stage 2 (metamorphlc precompetent larvae), 42.3-60.4 



mm SL Six morphological characters that define the ini- 

 tiation event of metamorphosis are, in their approximate 

 order of development: jaw dentition, completion of eye 

 migration, position of anterior margin of dorsal fm, posi- 

 tion or presence of posterior process of the coracoid, 

 pectoral fin morphology, and beginning of asymmetrical 

 coloration. Numerical scores given to the two or three 

 states of each character are shown in Table 3. A metamor- 

 phosing presettlement individual can have a metamorphic 

 score of 1 to 8. A score of 9 defines Stage 3, metamorphic 

 competent larvae. 



Dover sole larvae have canine-like teeth on left and right 

 jaws (Fig. 3A). During Stage 2, incisor-like teeth develop 

 on the left premaxilla and dentary (Fig. 3B). The canine- 

 like teeth are lost from both jaws coincident with eruption 

 of incisors in the left jaw (Fig. 3C). 



In Stage 1 larvae, anterior dorsal-fin pterygiophores and 

 fin rays are posterior to the orbit of the left eye which is 

 located on the dorsal ridge of the cranium (Fig. 4A). Dur- 

 ing Stage 2, these pterygiophores move anterior to the orbit 

 of the left eye (Fig. 4B). 



The posterior process of the coracoid in larvae is a long, 

 slender element that projects posteriorly above the visceral 

 cavity, underneath the skin (Fig. 5A). During metamor- 

 phosis the process is resorbed. At the beginning of resorp- 

 tion, during Stage 2, the distal end of the process curls 

 anteriorly into a hook (Fig. 5B). In our samples there is 

 some indication that the process deteriorates (poor stain- 

 ing with alcian blue), but there is no gradual reduction in 

 length or thickness of the process. Specimens either have 

 the process or have lost it (Fig. 5C). 



The pectoral fin in Stage-1 larvae is a paddle-shaped 

 membrane with a thin, fleshy base and without radials. Dur- 

 ing Stage 2, a fleshy rectangular base, cartilaginous radials, 

 and the adult complement of fin rays form (Fig. 5). 



The Stage-1 larval color pattern consists of little or no 

 pigment on the midlateral areas. A transitional pattern, 

 in which melanophores aggregate along myosepta, is 

 followed by the first indication of melanophores aggre- 

 gating in two approximately circular groups anteriorly and 

 posteriorly along the lateral line (Fig. 6). We score larval 



Premaxilla 



Maxilla 



Dentary - 



1 mm 



Articular 



Angular 



B 



Premaxilla 



Dentary 



1 mm 



Maxilla 



Articular 



Angular 



Premaxilla 



Dentary 



1 mm 



Maxilla 



Articular 



Angular 



