FISHEKY BULLETIN: VOL. 81, NO. 4 



Morphology 



Measurements of the 23 larvae examined are sum- 

 marized in Table 1 . All body parts measured increase 

 relative to standard length with increasing larval 

 length. However, these changes are small. The 

 greatest changes are in body depth and preanal 

 length relative to standard length, from means of 0. 1 5 

 and 0.47, respectively, for preflexion-stage larvae to 

 means of 0.21 and 0.52, respectively, forpostflexion- 

 stage larvae. Despite these small changes in propor- 

 tions, the relationships of body parts with standard 

 length are adequately described by straight lines 

 (Table 2). These pigfish larvae are slightly more 

 robust than those described by Hildebrand and Ca- 

 ble (1930). 



The sequence of fin ray differentiation is as follows: 

 Principal caudal, second dorsal and anal, pectoral, 

 first dorsal, pelvic, and secondary caudal. Differen- 

 tiation of the first anal fin ray into the third anal fin 

 spine is delayed until after the larval stage. The 

 following description of fin development refers to 

 discernible, but not necessarily ossified, struc- 

 tures. 



Fin development generally is as described by 

 Hildebrand and Cable (1930). The caudal anlage is 

 developing in the smallest specimen examined (3.8 

 mm). Notochord flexion begins between 4.8 and 5.5 

 mm and is complete by ca. 7 mm. Principal caudal fin 

 rays begin developing during notochord flexion, with 



TABLE I.— Summary of measurements (in mm) of larval Orthopristis 

 chrysoptera. Specimens between dashed lines are undergoing noto- 

 chord flexion. 



the full complement of 9 + 8 attained just after flex- 

 ion (Table 3). Secondary caudal rays begin to 

 develop after ca. 9.2 mm but before 10.9 mm, with the 

 full complement of 1 3 + 12 present at the end of the 

 larval period (ca. 16 mm). 



Anal and dorsal fin anlagen develop simultaneously 

 during late flexion (between ca. 5.8 and 6.2 mm). The 

 dorsal fin base initially extends between myomeres 

 14 and 19 but elongates to between myomeres 4-5 

 and 20-21. Differentiation of second dorsal fin ray 

 supports begins at 6.4 to 7.0 mm followed by the rays 

 at 7.2 to 9.0 mm. Dorsal spines develop between 9.0 

 and 10.9 mm. The full dorsal fin complement of 12 

 spines and 15 to 17 soft rays is acquired by 10.9 mm. 

 The anal fin base initially lies between myomeres 11- 

 12 and 19, and ultimately extends caudad to myo- 

 mere 20-21. Anal fin ray support differentiation 

 begins almost simultaneously with the second dorsal 

 fin ray supports. Anal fin rays are first discernible 

 between 7.2 and 9.0 mm. All anal fin elements are 

 present by ca. 10.9 mm but the third anal spine does 

 not ossify from the first ray until well into the juvenile 

 stage (at ca. 31 mm). 



Pelvic fin buds appear near the end of notochord 

 flexion, and pelvic fin rays begin differentiating at ca. 

 10.9 mm. The full complement of elements (1,5) is 

 present by ca. 11.1 mm (Table 3). 



Upper pectoral fin rays first differentiate in 

 postflexion larvae at ca. 9.0 mm. The full comple- 

 ment of 19 rays is present at the end of the larval 

 period. 



The first preopercular spine appears at the angle in 

 preflexion larvae (ca. 4.8 mm). A second spine is add- 

 ed on the lower preopercular margin during flexion 

 (ca. 6.2 mm) and a third on the upper margin just 

 after flexion (ca. 7.3 mm). Fourth and fifth spines 

 subsequently appear along the lower and upper 

 margins, respectively. A second, more anterior, row 

 of one to three very small preopercular spines may 

 develop during notochord flexion. All of these spines 

 are short: The longest is no more than 109? of the 

 eye diameter. 



All gill rakers are present by ca. 13.2 mm (5 upper + 

 1 + 11 lower). 



TABLE 2. — Summary of regressions of measurements of 

 body parts (v) on standard length (.v) of larval Ortho- 

 pristis chrysoptera. 



'Specimens from Texas. 



852 



