Aceves-Medina et al.: Larval development of Symphurus williamst from tfie Gulf of California 



741 



spots along the midventral line at the bases of the 

 anal-fin pterygiophores, and 1 to 2 similar spots lo- 

 cated on the anal-fin ray bases. At time of formation of 

 the anal-fin rays, a melanophore appears at the base 

 of each fin ray. A similar pigment is also found at the 

 base of each dorsal- fin ray in the posterior third of the 

 body in larvae less than 11.2 mm BL. The first 3 dorsal 

 rays are elongated in larvae less than 11.2 mm BL, 

 with the second and third of these longer than the first. 



Morphological features The body is compressed and 

 ribbonlike and has a deep head. The gut extends be- 

 yond the ventral profile. The intestine is noticeably 

 coiled and its terminal end is directed towards the 

 right side of the body. Larvae attain the appearance 

 of juveniles when the protruding gut is incorporated 

 within the ventral body profile at approximately 12 

 mm BL. At metamorphosis, a fleshy rostral beak is 

 formed anterior to the dorsal-fin origin. 



Migration of the right eye starts at 6.1 mm BL and 

 eye migration is completed in larvae of 11.1 mm BL. 

 The migrating eye crosses anterior to the dorsal-fin 

 origin, between the rostral beak and the interorbital 

 region. Notochord flexion begins at 5.0 mm BL and 

 is completed near 8.0 mm BL. The juvenile stage 

 begms at about 11.9 mm BL (Table 2). 



Growth is not isometric throughout larval devel- 

 opment (Table 3). Head length, snout-anus length, 

 and body depth decrease with respect to body length 

 from preflexion to juvenile stages. Body depth at the 

 anal-fin origin remains constant throughout devel- 

 "opment. Eye diameter in relation to head length de- 

 creases from preflexion to juvenile stages. 



