YOUNG JACK CREVALLES 



423 



lateral line by the length of the curved part of 

 the lateral line from each side, was used as the 

 mean lateral-line ratio. This is expressed by the 

 following formula: [(straight right -=- curved 

 right) + (straight left h- curved left)] -5- 2 = 

 mean lateral-line ratio. 



Use of three variates in determining the rela- 

 tionship of the lateral-line ratio to standard length 

 illustrates the interspecific differences of the 

 lateral line better than use of only two variates. 

 Previous taxonomic emphasis was placed on the 

 ratio by Nichols (1921b, 1937a, 193Sb, 1939), 

 Nichols and Breder (1927), Wakiya (1924), and 

 others. The mean of the ratios from both sides 

 was used because frequent and appreciable dif- 

 ferences were found between the two sides of a 

 fish. For example, on a 44-mm. specimen of 

 bartholomaei the point of junction of the curved 

 and straight parts of the lateral line on the left 

 side was under the fifth dorsal ray and on the 

 right side it was under the eleventh dorsal ray. 



PREOPERCULAR SPINES 



Description. — The five common species of 

 Caranx possess a spine, the preopercular-angle 

 spine, that protrudes from the posterior margin of 

 the preoperculum in the smallest sizes examined 

 and persists to 16 to 49 mm. standard length 

 (the maximum size of retention is variable among 

 the species). Fish within this range may also 

 possess from 1 to 8 smaller spines, the preopercular 

 upper- and lower-limb spines, arranged in grad- 

 uated series on the margins of the upper and lower 

 limbs of the preoperculum. 



Ontogeny. — The preopercular spines increase in 

 length only up to a certain size (possibly to 7 mm. 

 in crysos). Above this size, the lengths di- 

 minish, due to a cessation or diminution of spine 

 growth and ventral and posterior expansion of 

 the preopercular margin, until the spines are 

 completely absorbed by the preoperculum. 



Counts. — Spines were counted only if they pro- 

 truded from the margin of the preoperculum and 

 were not covered by a thickened layer of skin. 



Lengths. — The preopercular-angle spine (the 

 longest preopercular spine and the last to be 

 absorbed) was the only spine measured. The 

 measurement taken is represented by line a in 

 figure 24. The longer spine was measured for 

 each fish that showed bilateral variation in this 



length; if damage was obvious, a spine was not 

 measured. 



PIGMENTATION 



Descriptions of pigmentation represented in the 

 illustrations were made from microscopic obser- 

 vations of preserved specimens. Most of the 

 specimens were preserved in formalin — a few in 

 ethyl or isopropyl alcohol. Consequently, the 

 yellows, greens, and other shades present in living 

 or freshly caught specimens are absent. Melano- 

 phores have apparently faded from some of the 

 smaller specimens, and their pigment descriptions 

 may be incomplete. 



DEVELOPMENTAL STAGES 



Larval. — Defined as the stage of development 

 commencing with hatching and ending with the 

 completion of formation of the adult complement 

 of fin rays. A ray was considered to be completely 

 formed when it became partially ossified, as indi- 

 cated by its staining red when treated with aliz- 

 arin. The secondary caudal-fin rays are the last 

 rays to complete their formation, which progresses 

 anteriorly. The size at termination of the larval 

 stage was difficult to delimit because only a few 

 larval specimens were available, larvae of all 

 species were not identified, and intraspecific varia- 

 tion in the size at completion of fin-ray formation 

 could not be determined. Study of a series of aliz- 

 arin-stained specimens of crysos (the most com- 

 plete series available) showed that the fin rays had 

 not completed formation on fish 7.5 mm. standard 

 length and smaller, and that the next largest speci- 

 men, 8.5 mm., and all larger specimens had adult 

 complements of fin rays. The specimens identified 

 as "latus and/or hippos" (see p. 487) and the two 

 smallest specimens of bartholomaei apparently show 

 a similar size on formation of the adult complement 

 of fin rays. Of the "latus and/or hippos" series, the 

 8.3-mm. specimen had completed development of 

 the fin rays and the 6.9-mm. specimen had not. 

 The 6.0-mm. bartholomaei had only partially com- 

 pleted formation of the fin rays, the 8.1-mm. bar- 

 tholomaei had completed the formation with the 

 possible exception of one or two dorsal and ventral 

 secondary caudal rays, and the 10.5-mm. bar- 

 tholomaei had completed formation of all fin rays. 

 By analogy, the size at transformation from larva 

 to juvenile in Caranx is estimated to be about 8.0 

 mm. standard length. 



