LAROCHE: DESCRIPTION OF VERMILION SNAPPER 



Fin Formation 



Dorsal and pelvic fin formation begins by 4.0 

 mm (Figure 1A). Other fin development initiates 

 in the following sequence: caudal, anal, and pec- 

 toral. The pelvic fins are first to complete de- 

 velopment, while the dorsal fin is last. 



Dorsal Fin 



The anterior five dorsal spines are present on 

 the smallest larva (4.0 mm) with an undifferen- 

 tiated fin fold continuing to the caudal region 

 (Figure 1A). The fin develops from anterior to pos- 

 terior. At 4.8 mm, the adult number of dorsal fin 

 elements appears with the posterior 1-3 spinous 

 dorsal elements represented by soft rays. 



Development of the dorsal fin occurs rapidly be- 

 tween 4.0 and 4.8 mm. After the adult number of 

 fin-ray elements (23) appears, development to- 

 wards the final adult dorsal fin complement (XII, 

 11) proceeds slowly as spines form from soft rays 

 immediately posterior to the posteriormost spine. 

 Dorsal spine development is similar to that de- 

 scribed by Mansueti (1958) for anal spine de- 

 velopment in Roccus saxatilis. 



The dorsal fin is the last fin to attain the adult 

 complement of spines and rays. Attainment of full 

 dorsal fin complement between 8.3 and 10.9 mm 

 marks the division between larval and juvenile 

 stages. 



The fourth dorsal spine is longest in adult 

 Rhomboplites aurorubens (Jordan and Evermann 

 1898). The second dorsal spine is longest in all 

 specimens of my series except the largest juvenile 

 (14.2 mm) in which the third spine is longest (Fig- 

 ure 2C). The longest dorsal spine is longer than the 

 longest dorsal soft ray throughout the series. 



Dorsal spines are V-shaped in cross section, 

 with the V open posteriorly. The two posterior 

 edges are serrated nearly to the tip, which is sharp 

 and oval in cross section. On larger spines the 

 anterior edge is sometimes serrate for a short dis- 

 tance above the base (Figures IB, 2B, C). Speci- 

 mens between 4.8 and 9.0 mm have 29-40 serra- 

 tions along each posterior edge of the second dorsal 

 spine; larger specimens have 42-45 serrations. 



Pelvic Fins 



Pelvic fin spines and fin folds compose the pelvic 

 fins of the4.0-mm larva (Figure 1A). The pelvic fin 

 attains the adult complement of I spine and 5 rays 



between 4.7 and 4.8 mm. The pelvic spine is long 

 and serrate, extending slightly beyond the anus 

 (24% SL) at its longest (about time of dorsal fin 

 completion). Small specimens have spines which 

 are V-shaped in cross section with serrations 

 along all three edges. Specimens >4.5 mm have a 

 double row of serrations along the leading edge of 

 the spines creating an almost trapezoidal appear- 

 ance in cross section (Figure 2). 



Caudal Fin 



The adult caudal fin has 17 principal and 19-21 

 procurrent rays (Miller and Jorgenson 1973). 

 Principal rays are divided into two groups with 9 

 rays above and 8 rays below the midline of the 

 body. 



Notochord flexure occurs between 4.8 and 4.9 

 mm (Table 1). Flexure probably results in a slight 

 decrease in standard length because the angle of 

 the flexed notochord shortens the horizontal dis- 

 tance from snout tip to end of notochord. As a 

 result of flexure and individual variation in rate of 

 development, larvae of equal length may be at 

 various stages of development (Table 1). 



The caudal fin starts to form at the beginning of 

 notochord flexure, about 4.7 mm. Fifteen or six- 

 teen principal rays form simultaneously, slightly 

 below and ventral to the posteroventral margin of 

 the notochord. As the notochord flexes, these rays 

 become elevated into the terminal position. The 

 remaining rays are added dorsally and ventrally 

 until the adult principal ray number is attained at 

 about 4.8 mm (Figures IB, 2A). 



Anal Fin 



The adult fin ray complement for vermilion 

 snappers is III spines and 8 soft rays. Initial anal 

 fin formation occurs at 4.7 mm. Embryonic fin rays 

 (actinotrichia) are visible on 4.8-mm larvae. True 

 soft rays (lepidotrichia) begin to form by 4.9 mm. 

 The fin ray count remains II, 8 until about 5.4 mm 

 and then becomes II, 9 (Table 1). The posterior- 

 most ray forms last. The adult complement (III, 8) 

 appears at about 8.3 mm as the anteriormost soft 

 ray transforms into a spine. Each spine becomes 

 serrate along its posterior edge, larger spines hav- 

 ing a few serrations along the base of the anterior 

 edge. The second anal spine is longest throughout 

 the series studied, but in adults the third spine is 

 longer. 



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