Zuhiga and Acuna: Development of Paralichthys spp larvae 



61 



the criteria of Ginsburg (1952), who observed that the 

 origin of the dorsal fin in P. microps was over the 

 center of the upper eye, while in P. adspersus it was 

 over the eye's anterior margin. Furthermore, the 

 number of gill rakers over the lower portion of the first 

 arch is larger in P. microps (18-23) than in P. adsper- 

 sus (15-19). An additional criterion found by Zuniga 

 (1988) referring to the size of the nostrils was also used. 



Description 



Paralichthys adspersus 



Hatching occurs ~60 hours after fertilization. Larvae 

 are ~1.7mmNL; yolksac is more than half the body 

 length; a small oil globule (0.13mm) is present posterior 

 to the yolksac (Fig. lA). 



Diagnosis The most important distinguishing fea- 

 tures of preflexion P. adsperstis larvae are the presence 

 of two sphenotic spines (Fig. 2) and the lack of pigmen- 

 tation in the dorsal finfold (Fig. 1). This last character 

 may be useful through postflexion. Starting at noto- 

 chord flexion, the presence of two groups of numerous 

 opercular and preopercular spines, as well as 2-3 

 elongated dorsal-fin rays, is diagnostic. This last fea- 

 ture is useful until metamorphosis. Beyond metamor- 

 phosis, diagnosis should be based mostly on mor- 

 phometric relationships. 



Pigmentation Eyes of yolksac larvae are not pig- 

 mented. Few, relatively-large melanophores are found 

 on the head, trunk, and yolksac except at the ventral 

 margin (Fig. lA). A series of small melanophores is 

 present near the tip of the notochord. Pigment forms 



Figure 2 



Heads of Paralichthys adspersus (left) and P. microps (right) >arvae, showing number, size, and location 

 of sphenotic, preopercular, and opercular head spines. Bars = 1.0 mm. 



