FISHERY BULLETIN: VOL. 80, NO. 2 



1mm 



Figure 25.— Left lateral view of the second anteriormost 

 vertebra from Xiphias gladius, showing the ontogeny. Start- 

 ing from left the specimens' lengths in millimeters are: top, 5.1 

 ENL, 7.8 ESL.12.6 ESL; center, 21.4 ESL, 52.4 ESL; bottom, 

 225 ESL. F, neural foramen; Nc, notochord; NPo, neural 

 postzygapophysis; NPr, neural prezygapophysis; Ns, neural 

 spine; Pa, parapophysis. Cartilage, white (except in 5.1 mm 

 ENL specimen in top row left where entire stippling signifies 

 cartilage); ossifying, stippled. 



26). Haemal postzygapophyses were present on 

 precaudal vertebrae numbers 3 to 15, sometimes 

 on 2 to 15 (Figs. 13, 26). 



All caudal vertebrae had nonautogenous 

 haemal spines, except preural centrum 2 and the 

 urostyle. Preural centrum 2 had an autogenous 

 haemal spine. The urostyle had an autogenous 



parhypural with a tunnellike foramen for the 

 haemal canal. The parhypural is homologous to 

 the autogenous haemal spine of preural centrum 

 2 (Figs. 20-24). The 16th centrum sometimes 

 lacked a haemal spine, sometimes had a vestigial 

 haemal spine, or it had a normal haemal spine. 

 Haemal pre- and postzygapophyses were present 

 on all caudal centra except on preural centrum 2 

 and the urostyle. Neural foramina were present 

 on most precaudal and caudal centra on larger 

 specimens (Figs. 13, 22, 23, 25-28). 



Five out of eight Xiphias with all ribs devel- 

 oped had six paired ventral ribs, which loosely 

 articulated with the parapophyses on centra 1-4, 

 14, and 15 (Figs. 25-27). Two specimens had 

 seven pairs of ribs on centra 1-5, 14, and 15 and 

 on centra 1-4 and 13-15. One Xiphias had nine 

 pairs on centra 1-6 and 14-16. 



The neural arches fuse distally during ossifica- 

 tion to form neural spines. The fusion and spine 

 formation is over a size range and proceeds from 

 posterior in an anterior direction (Fig. 27; Table 

 13). Our largest four specimens of Xiphias, 131- 

 668 mm ESL, had three to six anterior neural 

 arches and spines split. These arches and spines 

 remain split in adults (Bruce B. Collette 3 ). 



Development of the centra starts with the 

 appearance of distally opened cartilaginous 

 neural arches. One arch was seen behind the 

 head on top of the notochord in our smallest 3.7 

 mm ENL specimen (Fig. 29). As length in 

 Xiphias increased, more arches were added in a 

 posterior direction (Fig. 29; Table 14). All 

 specimens >6.5 mm ENL had the complete count 

 of 25 neural arches. 



Two cartilaginous split haemal arches were 

 first observed at 5.0 mm ENL when 16 neural 

 arches were present. The two haemal arches 

 were opposite the 16th and future 17th neural 

 arch. Additional haemal arches and spines were 

 added in a posterior direction (Fig. 29; Table 15). 



3 Bruce B. Collette, Systematic Zoologist, National Marine 

 Fisheries Service, NOAA, Systematics Laboratory, Washing- 

 ton, DC 20560, pers. commun. July 1981. 



Table 13.— Number of split neural arches and spines counted from anterior to posterior for various 

 size ranges in 159 Xiphias gladius 5.5 mm ENL-668 mm ESL. N = number of specimens, X= mean. 



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