dorsal surface of the gas bladder. This character is par- 

 ticularly useful in separating small larvae of Scorpaena, 

 Pontinus, and Scorpaenodes that have not yet formed 

 head spines. Another melanistic character useful in 

 separating Scorpaena larvae from those of Scorpaenodes 

 and Pontinus is the presence of a ventral midline blotch 

 just anterior to the juncture of the cleithra in Scorpaena. 

 This is absent in the other five genera. 



Scorpaena larvae have highly characteristic pectoral 

 fins. They are moderate in length, as opposed to the ex- 

 tremely elongate fins of Scorpaenodes, and are fan- 

 shaped in contrast to the aliform pectorals of Pontinus. 

 Pigmentation varies among the species of Scorpaena, but 

 the pectorals are usually heavily pigmented. 



According to a recent revision, there are nine species of 

 Scorpaena in the eastern Pacific (Greenfield 1974). Scor- 

 paena larvae usually occur nearshore, thus are not com- 

 mon constituents of our plankton hauls. Our collections 

 contain sufficient numbers of larvae for the following 

 descriptions of S. guttata and another form which we 

 designate as Type A. 



Scorpaena guttata Girard, Figure 31 



Literature. — The three publications on the early 

 developmental stages of S. guttata listed in the 

 preceding section describe stages up to 3.0 mm. Later 

 larval stages of S. guttata have not been previously de- 

 scribed. 



Distinguishing features. — The early stages of Scor- 

 paena guttata have been studied in detail (Barnhart 

 1932; David 1939; Orton 1955) and the following account 

 is a summary of these studies. The egg masses are spawn- 

 ed at about midnight and float to the surface. They are 

 bilobed gelatinous structures, each lobe measuring 16 to 

 26 cm in length. The matrix is about 2-mm thick and 

 within it the eggs are evenly spaced in a single layer. The 

 slightly elliptical eggs measure about 1.2 mm at the long 

 axis. The yolk mass is colorless and contains no oil 

 globule. The chorion is colorless, transparent, and un- 

 sculptured. There is no apparent perivitelline space. The 

 eggs hatch when freed from the matrix at an average 

 time of 3 days after fertilization in southern California 

 waters. The newly hatched young are 1.9 to 2.0 mm long, 

 have a large elliptical yolk sac, and have a voluminous 

 dorsal finfold that is inflated in appearance. The pec- 

 toral fin buds are small and inconspicuous. A patch of 

 dendritic melanophores covers the dorsal aspect of the 

 gut and similar melanophores are also below the gut. 



At about 4 days after fertilization, the larvae are 2.5 to 

 2.7 mm long, have 22 to 24 myomeres, and have a row of 

 melanophores along the ventral midline of the tail. At 

 about 5 days after fertilization, the yolk is half utilized, 

 and at about 6 days the mouth is formed. At 7 to 8 days 

 the yolk is depleted, the jaws are functional, and the pec- 

 torals are fan-shaped and have one to several rows of 

 melanophores along their distal margins. The previously 

 undescribed later larval stages of S. guttata are 

 delineated below. 



Early-stage larvae of S. guttata are deep-bodied, 

 become comparatively more slender during notochord 

 flexion, and thereafter become increasingly deep-bodied. 

 Body depth averages 369c of body length prior to 

 notochord flexion, 30% during flexion, and 40% fol- 

 lowing flexion (Table 33). 



The compact gut increases gradually in relative length 

 during the larval period. Snout-anus length averages 49% 

 of body length prior to notochord flexion, 51% during 

 flexion, and 60% following flexion. 



At the completion of yolk utilization the head of S. 

 guttata larvae is moderately large and increases in 

 relative size during later larval development. Head 

 length averages 30% of body length in preflexion larvae, 

 34% during flexion, and 38% following flexion. The eyes 

 are moderately small; eye diameter averages 32% of the 

 head length throughout the larval period with no ob- 

 vious trend of relative increase or decrease. Snout length 

 increases from an average of 31% of the head length in 

 preflexion larvae to 33% in larvae undergoing flexion, 

 then decreases gradually to 28% in our largest larva. 



The pectoral fins are small and poorly differentiated in 

 2.0-mm larvae but growth and differentiation is rapid 

 and, when the larvae have reached 3.0 mm, the fins have 

 a well-differentiated base, a deep fan-shaped blade, and 

 have doubled in length to 15% of the body length. Fin 

 length increases to an average of 21% of the body length 

 at notochord flexion. Following notochord flexion, fin 

 length averages 22% of body length up to about 10 mm, 

 and then there is a considerable jump in relative fin 

 length to 29% in our largest larva (12.8 mm). The depth 

 of the fin base is slightly smaller than in other scorpae- 

 nine genera. It averages 15% of the body length over the 

 entire larval period. Fin rays begin to ossify in larvae 

 about 4.0 mm long and the full complement of 17 to 19 

 rays is present in 5-mm larvae. 



The hypural anlagen of the caudal fin are apparent in 

 larvae as small as 2.5 mm. They begin to ossify in 5-mm 

 larvae and in the largest stained specimen (6.5 mm) the 

 large superior and inferior elements are well ossified. The 



Measurements (itm) of larvae of Scorpaena guttata - (Specir 

 are undergoing notochord flexion.) 



. between dashed lines 



55 



