FISHERY BULLETIN: VOL. 84, NO. 3 



fused after ossification, but the small hypural 5 re- 

 mained separate. Preural centra 2 and 3 each had 

 an autogenous haemal spine. Two epurals and one 

 uroneural developed dorsad. The anterior epural 

 fused with the neural arch of Pu 2 and the uroneural 

 fused to the urostyle (Potthoff 1975). The neural and 

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

 ported the procurrent caudal rays. A procurrent 

 spur and basally foreshortened ray were absent in 

 the Thunnini (Johnson 1975) (Table 1). 



FAMILY ISTIOPHORIDAE 



Figure 14 



One hundred and sixteen istiophorids (3.0-227 mm 

 NL or SL) were available. Most specimens were 

 caught in the Gulf Stream off Miami, FL. In 67 of 

 the specimens we were able to count vertebrae; all 

 had a count of 12 + 12. This identified them as Istio- 

 phorus platypterus or Tetrapturus spp. (Merrett 

 1971; Richards 1974). The 67 specimens with the 

 12 + 12 vertebral count, and the remainder, which 

 were too small for vertebral counts, probably were 

 I. platypterus because most adult istiophorids cap- 

 tured in the Gulf Stream off Miami are that species. 

 In addition, 12 Makaira nigricans (3.3-5.9 mm NL, 

 13.3 and 220 mm SL) identified by W. J. Richards 4 

 were examined. The 13.3 and 220 mm SL specimens 

 had a count of 11 + 13 vertebrae. 



Development of the vertebral column initially 

 started in three places on the notochord: 1) antero- 

 dorsad (neural arches and spines on future centra 

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

 trad at the center (anterior haemal arches and pos- 

 terior parapophyses). The neural arches and spines 

 were added in a posterior direction. The haemal 

 arches and spines also were added in a posterior 

 direction at the time when neural arches and spines 

 appeared above on the notochord. Parapophyses 

 were added anteriorly. Hypural bones were added 

 in a posterior direction, but the parhypural and the 

 two autogenous haemal spines were added anterior- 

 ly. Ossification of the vertebral column in istiophor- 

 ids initially started in two places: ossification of the 

 anteriormost neural spines and arches proceeded in 

 a posterior direction. The hypural complex started 

 ossification before all neural and haemal spines were 

 ossifying. Saddle-shaped ossifications of the verte- 

 brae as observed in the Scombrolabracidae, Gem- 

 pylidae, and Scombridae were not observed in the 



4 W. J. Richards, Senior Scientist, Southeast Fisheries Center 

 Miami Laboratory, National Marine Fisheries Service, NOAA, 75 

 Virginia Beach Drive, Miami, FL 33149, pers. commun. 1983. 



Istiophoridae during ontogeny. First ossification of 

 vertebrae in Istiophoridae was evidenced by the for- 

 mation of rings of bone around the notochord (Table 



2). 



Cartilaginous dorsal pterygiophores appeared first 

 above interneural spaces 3-5. Dorsal pterygiophore 

 addition was mostly in a posterior direction, except 

 that those pterygiophores over interneural spaces 

 2 and 1 were added in an anterior direction. When 

 dorsal pterygiophore development extended to 

 above the anterior portion of the anal fin fold, car- 

 tilaginous anterior anal pterygiophores were seen 

 below interhaemal spaces 13 and 14, and their addi- 

 tion was posteriorly abreast of the dorsal pterygio- 

 phores. At larger sizes dorsal and anal finrays 

 developed in the same sequence as their supporting 

 pterygiophores (Table 2). 



Istiophorids did not have predorsal bones, instead 

 the first three interneural spaces were filled with 

 fin spine supporting pterygiophores. The first dor- 

 sal pterygiophore originated from one piece of car- 

 tilage and inserted in the first interneural space sup- 

 porting three spines (two supernumerary spines). 

 The anteriormost spine was either small, reduced, 

 or vestigial. The first anal pterygiophore developed 

 from two pieces of cartilage supporting two fin 

 spines (one supernumerary spine). Istiophorids had 

 one middle radial and one posteriorly bifur- 

 cated (sometimes nonbifurcated) stay with the 

 posteriormost dorsal and anal pterygiophore. The 

 posteriormost dorsal and anal ray were double 

 (Table 1). 



In istiophorids, the caudal complex started to 

 develop after the precaudal neural spines had devel- 

 oped. The parhypural and hypurals 1-4 developed 

 as separate cartilages. In most istiophorid specimens 

 the cartilages of hypurals 1 and 2 and hypurals 3 

 and 4 fused to a lower and upper hypural plate 

 before ossification; in some specimens fusion did not 

 take place until after ossification onset for the up- 

 per and lower hypurals. Also, there were specimens 

 in which none of the cartilaginous hypurals fused. 

 The 5th hypural did not develop in istiophorids. Dor- 

 sad 3 epurals and 1 uroneural developed. Preural 

 centra 2 and 3 each had one autogenous haemal 

 spine. In adult istiophorids, the fusion of the bones 

 in the caudal complex was extensive (Gregory and 

 Conrad 1937); we examined adult specimens of 

 Istiophorus, Tetrapturus, and Makaira and found 

 identical hypural fusions in the three genera. The 

 three epurals remained autogenous, but the uro- 

 neural, hypurals 1-4, and the parhypural were fused 

 with each other and with the urostyle to form a 

 notched hypural plate. The neural and haemal 



672 



