FISHERY BULLETIN: VOL. 84, NO. 3 



Sarda did not develop predorsal bones. The first 

 dorsal pterygiophore originated from one piece of 

 cartilage and inserted in the second interneural 

 space supporting two spines (one supernumerary 

 spine). We do not know if the first anal pterygio- 

 phore originated from one or two pieces of cartilage, 

 but it is most likely that it originated from two pieces 

 because it supported three fin elements (two super- 

 numerary spines). The posteriormost seven to nine 

 dorsal and anal pterygiophores had middle radials. 

 The last dorsal and anal pterygiophore supported 

 a double finlet and had a posteriorly bifurcated stay 

 (Table 1). 



In Sarda first caudal development of the carti- 

 laginous parhypural and hypurals 1 and 2 was con- 

 current with the beginning development of the ante- 

 riormost neural arches and spines. Hypurals 1 and 

 2 fused in the cartilaginous state to form the ven- 

 tral hypural plate. In three specimens, hypurals 3 

 and 4 were separate after ossification onset. These 

 hypurals were fused to the dorsal hypural plate in 

 juveniles. Hypural 5, the uroneural and two epurals 

 were separate in our juveniles. Collette and Chao 

 (1975) found that in adults the dorsal and ventral 

 plates fused to one hypural plate without a notch 

 and that the uroneural fused with hypural 5, but the 

 two epurals remained autogenous. The neural and 

 haemal elements of preural centra 2, 3, 4, and 5 sup- 

 ported the procurrent caudal rays. A procurrent 

 spur and a basally foreshortened ray were absent 

 in Sarda (Johnson 1975) (Table 1). 



Tribe Thunnini 

 Figure 13 



More than 86 specimens were available: 86 Thun- 

 nus (mostly T. atlanticus and a few Thunnus spp., 

 3.7-9.7 mm NL or SL), and a small number of Auxis, 

 Euthynnus, and Katsuwonus. We were unable to 

 observe early cartilaginous development in all 

 genera except Thunnus. 



Development of the vertebral column in Thunnus 

 initially started in four places on the notochord: 1) 

 anterodorsad (neural arches and spines of future 

 vertebrae 1-3), 2) posteroventrad (hypurals 1 and 

 2), 3) ventrad at the center (anteriormost five 

 haemal arches and spines and posteriormost two 

 parapophyses), and 4) dorsad at the center (five 

 neural arches and spines above initial haemal arch 

 and spine development). The anterior neural arches 

 and spines were added in a posterior direction, the 

 central neural arches and spines were added ante- 

 riorly (coalescing around the future 14th centrum) 

 and posteriorly toward the epurals. The parapophy- 



ses were added in an anterior direction, whereas the 

 haemal arches and spines were developing in a pos- 

 terior direction. In the hypural complex hypurals 

 were added posteriorly, but the parhypural and the 

 two autogenous haemal spines were added in an 

 anterior direction, coalescing with the central 

 haemal arches and spines. Ossification of the verte- 

 bral column in Thunnini initially started in two 

 places similar to the ossification described for Scom- 

 beromorus. Saddle-shaped vertebral ossification 

 development was observed in all Thunnini examined, 

 similar to the development described for Scombro- 

 labra-x (Table 2). 



In Thunnini, cartilaginous first dorsal fin pteryg- 

 iophores developed anteriorly in interneural spaces 

 3-6 when only few cartilaginous neural spines were 

 present. Additional pterygiophores were added in 

 a posterior direction. Later, small cartilaginous sec- 

 ond dorsal fin pterygiophores appeared in the mid- 

 dle of the vertebral column above interneural spaces 

 15-22. As the first dorsal fin pterygiophores devel- 

 oped in a posterior direction, the second dorsal fin 

 pterygiophores developed in an anterior and poste- 

 rior direction until all the dorsal pterygiophores 

 were continuous. Anal pterygiophores appeared 

 below interhaemal spaces 20-25 and developed in an 

 anterior and posterior direction. Addition of the first 

 dorsal fin spines was in a posterior direction, except 

 for the anteriormost spine (supernumerary), which 

 developed when the second and third spine were 

 already present. The second dorsal and anal fin rays 

 developed in the same sequence as their correspond- 

 ing pterygiophores but a little later (Table 2). 



All Thunnini species examined lacked predorsal 

 bones. The first dorsal pterygiophore originated 

 from one piece of cartilage and inserted in the third 

 interneural space supporting two fin spines (one 

 supernumerary spine). The first anal pterygiophore 

 developed from two pieces of cartilage and sup- 

 ported three fin spines (two supernumerary spines) 

 (Potthoff 1975). Middle radials were present on the 

 posterior eight or nine finlet supporting dorsal and 

 anal pterygiophores. A one-part posteriorly bifur- 

 cated stay developed with the posteriormost dorsal 

 and anal fin pterygiophores (Table 1). 



In Thunnus, the caudal complex began to develop 

 very early concurrently with the first anteriormost 

 neural spines. Hypurals 1 and 2 and hypurals 3 and 

 4 developed separate cartilages and fused to a car- 

 tilaginous dorsal and ventral hypural plate. Potthoff 

 (1975) stated that hypurals 1 and 2 developed as one 

 piece of cartilage from the start, but he examined 

 only specimens larger than 5.0 mm NL not stained 

 for cartilage. The dorsal and ventral hypural plates 



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