SUMIDA ET AL.: EARLY DEVELOPMENT OF SEVEN FLATFISHES 



diameter (Table 2). There was no evidence of other 

 small oil globules in the yolk, although a few eggs 

 had a damaged oil globule which had separated in 

 two. However, the original oil globule could easily 

 be determined because of surrounding pigment. 

 The oil globule is positioned near the center of the 

 developing embryo in middle-stage eggs. The body 

 of the late-stage embryo is heavily pigmented, 

 similar to the newly hatched larvae. 



Hippoglossina stomata 



Eggs of H. stomata have not been previously 

 described. Eggs are round with a slightly pinkish, 

 unornamented shell and a single oil globule. The 

 egg has a mean diameter of 1.29 mm (range 1.22- 

 1.38 mm) and the oil globule a mean diameter of 

 0.23 mm (range 0.20-0.26 mm) (Table 2). The oil 

 globule lacks pigment and lies near the tip of the 

 tail of developing embryos in middle-stage eggs. In 

 late-stage eggs the oil globule is in the posterior 

 part of the yolk sac; the embryo is heavily pig- 

 mented over the body except for the posteriormost 

 portion of the tail; pigment patches occur on the 

 finfolds in the same places as in early preflexion 

 stage larvae; pigment is widespread over the yolk 

 surface. 



DESCRIPTION OF 



DEVELOPMENTAL STAGES— LARVAL, 



TRANSFORMING, AND EARLY 



JUVENILE 



Pleuronichthys decurreiis Jordan and 



Gilbert (curlfin turbot) 



Figures 3, 4 



Literature. — A series of egg stages and two preflex- 

 ion larvae of P. decurrens were described and il- 

 lustrated by Budd ( 1940) but incorrectly identified 

 as P. coenosus. His larval illustrations,were based 

 on a recently hatched specimen, 5.54 mm, and an 

 emaciated specimen. 8 days old, of somewhat 

 smaller size. 



Distinguishing characters. — Larvae of this species 

 are unique in the genus Pleuronichthys in de- 

 veloping a pterotic spine on each side of the head, 

 in having a higher precaudal vertebral number of 

 14 or 15, and in having the largest larvae during 

 all stages of development. Larval pigmentation is 

 heaviest in this species with the body and finfold 

 entirely pigmented except for the posteriormost 



region. Because of their relatively large size and 

 dense pigment, P. decurrens larvae cannot be con- 

 fused with Hippoglossina stomata or Hypsopsetta 

 guttulata. 



Pigmentation. — Newly hatched, preflexion, and 

 early flexion larvae (4.9-9.8 mm NL) are heavily 

 pigmented over the head, trunk, tail, and finfolds 

 with only the pectoral fin and posteriormost tip of 

 the notochord and finfold unpigmented (Figure 

 3 A, B, C). As the first few caudal rays become 

 evident (ca. 9.7 mm NL), several small, discrete 

 melanophores appear on the pectoral fin base 

 (Figure 3Ci. In late flexion and early postflexion 

 stages during dorsal and anal fin development, the 

 continuous heavy pigment on the finfolds changes 

 to form three to four dorsal and three ventral 

 bands of pigment which extend out from the body 

 margin to part of the rayed fin membrane (Figure 

 3D). Larvae at this stage have a soft, saccular body 

 with semitransparent and sparsely pigmented 

 areas in the pterygiophore region between the 

 body proper and developing dorsal and anal fins. 

 Larvae >11.2 mm SL have dorsal and anal 

 pterygiophores fully developed; the pterygiophore 

 region is no longer transparent and the specimens 

 become robust (Figure 4). 



Morphology. — Larvae of P. decurrens are the 

 largest members of the genus at hatching and 

 attain the largest size before transformation. Our 

 smallest specimen is 4.9 mm NL and has yolk 

 remnants (Table 4). The left eye begins to migrate 

 at 10.5 mm SL and has not completed migration in 

 a larva 21.0 mm SL. The smallest available 

 juvenile is 29.4 mm SL. 



The gut begins as a tube which diminishes in 

 diameter posteriorly and ends with a free terminal 

 section that diverges from the body in a slight 

 posteriad direction. In 5- to 7-mm NL larvae, the 

 gut increases markedly in diameter and the free 

 terminal section becomes vertical to the body axis. 

 At about 8.0 mm NL, the gut begins to coil and its 

 terminal section begins to slant anteriad. Coiling 

 and the anterior displacement of the anus become 

 more marked as development proceeds. This is 

 reflected in the decreasing relative snout-anus 

 length in postflexion larvae and especially in 

 juveniles (Table 5). 



Relative head length increases during larval 

 development whereas relative snout length de- 

 creases (Table 5). Relative eye width decreases 

 slightly during the three phases of the larval 



111 



