Zuniga and Acuna' Development of Paralichthys spp larvae 



613 



During metamorphosis (Fig. 3C) pigmentation in- 

 creases, especially on the left side of the body. Dorsal- 

 fin pigmentation is concentrated in the posterior half 

 of the fin. Groups of melanophores are present on the 

 interradial membrane of the anal fin. The pelvic fin is 

 almost completely pigmented. 



Fin development Dorsal-fin pterygiophores and rays 

 begin to form simultaneously at ~6.5mmNL, reach- 

 ing their full complements at 8.8mmSL (Table 2). The 

 anal-fin pterygiophores appear in advance of their cor- 

 responding fin rays, at 8.1-8.6mmNL. In both fins, 

 development proceeds posteriad. The pelvic fin appears 

 at 8.5mmNL, and all six rays are present at 10.1mm 

 SL. The hypural complex develops between 8.1 and 

 8.6mmNL. There are 18 caudal-fin rays, plus 2 pro- 

 current rays. 



Morphology With absorption of the yolk, the yolksac 

 larva becomes slender; the gut, jaws, and pectoral fins 

 develop; and two sphenotic spines begin to develop on 

 each side of the head. At 3.5mmNL (4-5 days post- 

 hatching), the yolk is exhausted, the mouth is func- 

 tional, eyes are pigmented, and the pectoral fin is 

 formed. 



Two sphenotic spines appear at ~3.0mmNL on each 

 side of the head (Fig. 2); initially the upper one is the 

 larger. Both spines are reabsorbed before development 

 of elongated dorsal-fin rays, near the end of this stage. 

 On some specimens, a third, smaller sphenotic spine 

 can be found below the first two. 



At about 4.5mmNL, preopercular and opercular 

 spines appear; the former are located along the pos- 

 terior margin of the preoperculum and on the anterior 

 preopercular ridge. Opercular spines are located at the 

 upper portion of the bone and are more prominent than 

 preopercular spines. 



At ~6.5mmNL, the elongated rays of the dorsal-fin 

 crest begin to appear. Three rays (corresponding to the 

 second, third, and fourth dorsal-fin rays of the adult) 

 form the initial crest. At 6.2mmNL the gut begins to 

 coil. During preflexion, body depth is moderate (13.9% 

 NL) and preanal distance is ~41.4%NL. These propor- 

 tions remain relatively constant during later develop- 

 ment (Table 1). There are 33 myomeres (11 preanal and 

 22 postanal) at the end of the stage. 



The beginning of the flexion stage is characterized 

 by an increase in body depth (22.8% NL) and develop- 

 ment of the caudal fin. Preopercular spines are in two 

 series in the upper and lower margins of the bone. 

 Opercular spines are also in two groups: an upper group 

 on the body of the operculum and a lower one along 

 its margin. Elongated dorsal-fin rays remain, the mid- 

 dle one being the longest. At ~7.5mmNL, the pelvic 

 fins begin to form and, by the end of the stage, rays 



and pterygiophores of dorsal, anal and caudal fins are 

 more evident. 



Morphometric proportions are similar to those of the 

 previous stage, except body depth which increases. A 

 small increase in head length is also apparent (Table 

 1). There are 33 (9 preanal and 24 postanal) myomeres 

 at the end of the stage. 



During postflexion, body depth increases to 35.8% 

 SL; head length reaches 30.6% SL (Table 1). Dorsal- 

 crest fin rays increase in relative length; the second 

 reaches 50% SL. The short dorsal-fin ray anterior to 

 the crest begins to develop. 



Preopercular and opercular spination increases in 

 some specimens, but the spines begin to reabsorb at 

 the end of the stage. The interocular region begins to 

 change in preparation for eye migration. There are 33 

 (7-8 preanal and 25-26 postanal) myomeres at the end 

 of the stage. 



During metamorphosis, body depth continues to in- 

 crease (39.0% SL), and snout length decreases (18.3% 

 HL); however, other body proportions do not change 

 substantially (Table 1). The second elongated dorsal- 

 fin ray reaches its maximum length (~53.9% SL) before 

 being reabsorbed. Migration of the right eye to the left 

 side begins. Pectoral-fin rays form. Preopercular and 

 opercular spines are lost, as are the elongated dorsal- 

 fin rays. Eye migration is completed at ~13.0mm. The 

 smallest juvenile was 12.3 mm SL (Fig. 3C). There are 

 33 (4-6 preanal and 27-29 postanal) myomeres at the 

 end of the stage. 



Paralichthys microps 



Hatching occurs 57-68 hours postfertilization; yolksac 

 larvae are ~1.5mmNL; one oil globule is present. 

 Yolksac development is similar to P. adspersus yolk- 

 sac larvae, except that melanophores form on the dor- 

 sal and anal finfold and a simple sphenotic spine begins 

 to develop at yolk exhaustion (~3.2mmNL, 4-5 days 

 after hatching). 



Diagnosis Distinguishing features of preflexion P. 

 microps larvae are the presence of only one sphenotic 

 spine (Fig. 2) and the dorsal finfold with pigmentation. 

 After notochord flexion until metamorphosis, the most 

 distinguishing feature is the presence of more than 3, 

 and later 6, elongated dorsal-fin rays (Figs. 4E, 5). 

 After reabsorption of these elongated rays, diagnosis 

 is mostly based on morphometric relationships. 



Pigmentation During the preflexion stage, the pig- 

 mentation pattern is similar to that of P. adspersus, 

 but P. microps larvae have a different arrangement of 

 body and finfold melanophores and less head pigment. 

 Melanophores are relatively sparse over the trunk and 



