POTTHOFF: DEVELOPMENT AND STRUCTURE OF FINS IN CORYPHAENA 



pterygiophores had to be added from place of 

 origin anteriorly than posteriorly. Small C. hip- 

 purus (5 mm NL-11 mm SL) usually had fewer 

 fin rays compared to equal-sized C equiselis 

 (Figure 1). Between 12 and 14 mm SL both species 

 had about equal dorsal fin ray numbers. Spec- 

 imens of C. hippurus 15 mm SL and longer 

 usually had more dorsal fin rays than equal-sized 

 C. equiselis. 



The developmental sequence of dorsal fin rays 

 in Coryphaena spp. is similar to that observed in 

 Trachurus symmetricus ( Ahlstrom and Ball 1954), 

 Haemulon plumieri (Saksena and Richards 1975), 

 and Archosargus rhomboidalis (Houde and Pott- 

 hoff 1976). It is as though Coryphaena spp. is 

 developing two dorsal fins in the same pattern of 

 the above examples, e.g., first the second dorsal fin 

 followed by the first dorsal. It is of interest to note 

 that most scombroids do not follow this pattern 

 and develop the first dorsal fin first (Voss 1954; 

 Potthoffl975). 



Dorsal Fin Pterygiophores 



Counts 



There was a supporting pterygiophore in both 

 species of Coryphaena in a jointed series for each 

 dorsal fin ray, except for the first two or three 

 anteriormost rays. Each pterygiophore had a 

 proximal and a distal radial. The distal radial 

 was located between the bifurcate base of the fin 

 ray. Proximal and distal radial and fin ray formed 

 a series, hence, a serial association. Each fin ray 

 also closely approximated the following posterior 

 pterygiophore in a secondary association. Thus, 

 each pterygiophore supported a ray in a serial 

 association and an immediately anterior ray in a 

 secondary association. The exceptions were found 

 at the beginning and the end of the fin. The 

 anteriormost pterygiophore supported from one to 

 three rays, but most often two rays (Table 2). Also, 

 in 2 out of 70 specimens of both species, no rays 

 were associated with the anteriormost pterygio- 

 phore, and the pterygiophore was very small and 

 almost a vestige. The posteriormost ray in the 

 dorsal fin was a double ray which was serially 



Figure 2. — Schematic representation of dorsal and anal.fin and 

 pterygiophore development in Coryphaena hippurus in relation 

 to the vertebral column and head. Oval -shaped representation 

 of pterygiophores are cartilaginous when white and ossifying 

 when black. Scale represents interneural and interhaemal 

 spaces and points align with midpoint of vertebral centra. 



Table 2. — Number (adult count) of anteriormost dorsal fin rays 

 without distal radials and number of dorsal fin rays associated 

 with the anteriormost dorsal fin pterygiophore for 28 Cory- 

 phaena hippurus (78.8-176 mm SL) and 35 C. equiselis (74.1-172, 

 314mmSL). 



associated with the posteriormost pterygiophore. 

 This was the only ray in the dorsal fin which 

 lacked a secondary association. Total dorsal fin 

 ray count in both species was either one less than 

 the pterygiophore count, equal to the pterygio- 

 phore count, or one or two greater than the 

 pterygiophore count. Thus, the two species dif- 

 fered in their pterygiophore number as they 

 differed in their fin ray counts. 



In larvae, juveniles and small-sized adults of 

 Coryphaena spp. the proximal radials of the 

 dorsal fin were inserted in interneural spaces. The 

 first interneural space was bounded anteriorly by 

 the head and posteriorly by the first neural spine, 

 followed posteriorly by the remaining interneural 

 spaces which were bounded by all other neural 

 spines (Figure 3). 



Fully developed specimens of the two species of 

 Coryphaena differed by the number of pterygio- 

 phores that occupied the interneural spaces. The 

 number of pterygiophores found in the first inter- 

 neural space separated the species most of the 

 time, with 10-14 (x = 11.0) for C hippurus and 

 7-11 ix = 8.0) for C. equiselis (Figures 3, 4). The 

 species also differed in the number of pterygio- 

 phores associated with the remainder of the inter- 

 neural spaces. Although individual variability 

 within each interneural space was too great to 

 allow this character to be used to separate the 

 species, the mean number of pterygiophores in 

 each interneural space was always greater for 

 C hippurus. 



The species also differed in the number of 

 interneural spaces that were occupied by the 

 dorsal fin pterygiophores (Figure 3; Tables 3, 4). 

 In C. hippurus the dorsal fin pterygiophores 

 extended to the 26th interneural space and seldom 

 to the 27th, whereas in C. equiselis they extended 

 to the 28th and seldom to the 27th or 29th space. 

 There was some overlap for the two species in this 

 character, but if the termination of the anal fin 

 pterygiophores was taken into account, together 



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