Oda: Egg and larval development of Paralichthys califomicus and Xystreurys liolepis 



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Fin and spine formation Anlagen of the anterior- 

 most dorsal fin rays form at about 3mm NL. The 

 elongate second through sixth dorsal rays develop first, 

 followed by the first ray and anlagen for the remainder 

 of the dorsal fin and for the anal fin. The remaining 

 rays begin to form at approximately 5-6 mm FL; 

 development is anterior to posterior. The full comple- 

 ment of dorsal fin rays is complete by ~8mm SL 

 (Table 3). 



Larvae develop a series of three sphenotic spines. 

 The dorsal-most spine appears in yolksac larvae just 

 prior to or at the time the lower jaw forms (Fig. 5 A). 

 The middle and ventral-most spines develop on first 

 feeding preflexion larvae, and during this stage the 

 spines are relatively easily seen (Figs. 5C,D). The 

 relative size of the spines decreases and they become 

 difficult to locate by about the time the anlagen of the 

 first dorsal fin rays form (Fig. 5E). The spines usually 

 are not visible in late postflexion larvae when eye 

 migration begins (~7-8mm SL); the developing head 

 melanophores obscure the minute spines (Fig. 6C). 



Spines on the posterior margin of the preopercle are 

 visible by ~2.5mm NL (Fig. 5C). Five to seven spines 

 are present on the lower margin of the bone, and addi- 

 tional spines form on the upper margin at about 5 mm 

 FL (Fig. 6A). Opercular spines, present on postflex- 

 ion larvae at approximately 6-7 mm SL, usually form 

 along the posterior opercle margin. Another cluster of 

 spines develops at the dorsal margin of the opercle. 

 Opercular spines are not easily visible unless the speci- 

 men is stained. 



The full complement of 10 + 8 principal caudal rays 

 is present by about 8mm SL. A splinter ray, attached 

 to the ventralmost ray, is not included in this count. 

 Pigmentation Larvae are characterized by a row 

 of internal melanophores on the dorsal surface of the 

 notochord. This pigment first appears in late yolksac 

 larvae (Fig. 5B), forms a complete row in the early 

 preflexion stage (Fig. 5C), and remains visible through 

 the body musculature for the entire larval period. 



Pigment in the dorsal finf old of yolksac larvae varies 

 from a continuum of melanophores from the nape to 

 mid-tail, to two distinct patches, one at the nape and 

 the other even with the ventral finfold patch, located 

 about mid-tail (Figs. 5A,B). Finfold pigment increases 

 during preflexion and by the end of the stage is pres- 

 ent throughout the medial finfolds (Fig. 5E). During 

 flexion, melanophores form on the elongate dorsal fin 

 rays and anal fin anlage (Fig. 6A). 



Some melanophores present on the dorsal midline 

 of newly hatched larvae migrate ventrally to form a 

 double row of postanal ventral pigment extending from 

 the vent to a point about mid-tail. Lateral melano- 

 phores are located opposite the posteriormost ventral 

 pigment (Fig. 5B). Early in the preflexion stage, the 



rows of ventral melanophores increase in length, merg- 

 ing with pigment at the tail tip (Fig. 5C). Rows of dorsal 

 and ventrolateral pigment develop and extend from the 

 nape and anus, respectively, to the last myomere (Fig. 

 5E). Dorsolateral melanophores form during the 

 postflexion stage (Fig. 6C). 



Melanophores are present on the yolk and perito- 

 neum of early yolksac larvae and form on the gut and 

 ventral midline, from isthmus to anus, in preflexion 

 larvae (Fig. 5C). Except for the melanophores that 

 form on the lower jaw of yolksac larvae (Fig. 5B), pig- 

 ment on the head and snout is sparse. 



Xystreurys liolepis 



Morphology Preflexion larvae are slender (BD 

 ~20% BL), then transform into robust, deep-bodied 

 flexion and postflexion larvae (BD ~45-48% BL, Table 

 4). Head width varies from about 15% to 20% BL. Gut 

 shape matures from straight tubular to coiled in 

 preflexion larvae; preanal length remains relatively 

 constant, ~45% BL, and head length increases from 

 ~20 to 32% BL. 



Myomere counts range from 37 to 39; double-stained 

 specimens (Table 5) have 11 precaudal vertebrae and 

 26-27 caudal vertebrae. 



Fin and spine formation Anlagen for the first 

 dorsal fin rays are formed by ~4mm NL. The second 

 through the sixth or seventh rays are elongate and 

 develop first, followed by the first dorsal fin ray, and 

 the anlagen for the remainder of the dorsal fin and anal 

 fin. Fin ray formation proceeds posteriorly, and the en- 

 tire complement of dorsal and anal fin elements are 

 complete by approximately 8 mm SL (Table 5). 



Primordia for the developing hypural bones are first 

 visible as a thickening in the ventral finfold, and the 

 incipient caudal rays typically form at 5-5.5mm FL. 

 The full complement of 10 + 8 principal caudal rays 

 usually is complete around 7mm SL; a splinter ray on 

 the ventralmost ray is present but not included in this 

 count. 



The pectoral bud differentiates into a base and blade 

 between 2 and 2.5mm NL. The largest larva in the 

 LACM ichthyoplankton collection, 8.9mm SL, has no 

 pectoral fin rays. 



Spines are visible on the posterior margin of the 

 preopercle in preflexion larvae by 2-2.5 mm NL (Fig. 

 7C). The spines are minute in specimens larger than 

 7mm SL. 



Pigmentation Three patches of finfold pigment, in 

 the dorsal finfold near the nape, and in both the medial 

 finfolds at about mid-tail, are dense in yolksac larvae 

 (Figs. 7A,B) but less concentrated in preflexion in- 

 dividuals (Fig. 7C). Additional melanophores develop 

 in the dorsal finfold during the preflexion period and 



