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Vertebral Column 



Weberian Apparatus. In cyprinids, the Weberian apparatus is located at the anterior 

 vertebral column, and function as an otophysic connection between the anterior chamber 

 of gas bladder and inner ear; thus, it can transmit movements of the gas bladder wall to 

 the ear, and aid in hearing and depth perception (Alexander 1962). Two divisions. can be 

 recognized from the Weberian apparatus, the pars sustentaculum and the auditum. The 

 pars sustentaculum is composed of the modified first four vertebrae, their arches and gas 

 bladder, and partially function as a supporter for the pars auditum. The pars auditum con- 

 sists of four paired Weberian ossicles, i.e., claustrum, scaphium, intercalarium, and tripus 

 (from anterior to posterior). The ossicles form a bony chain, connected by ligaments be- 

 tween the ossicles, to connect the gas bladder and inner ear, and to function (with the re- 

 lated ligaments) as a medium to pass the information from the gas bladder to the ear. 

 Numerous papers on the Weberian apparatus in cyprinids have been published. Watson 

 (1939), Alexander (1962), Rosen & Greenwood (1970), and Fink & Fink (1981) are only 

 a few important examples. 



The Weberian apparatus in Phoxinus is similar to that in other cyprinids. In Phoxinus, the 

 vertebral centrum (Figs 75A-E, 76A-D) is short with a short transverse process laterally 

 (transverse process 1). Anteriorly, it articulates with the proatlas of the basioccipital bone. 

 The scaphium and claustrum are placed at the dorsolateral side of the centrum. Variations 

 in Phoxinus include the length and relative position of the transverse process. The trans- 

 verse process is at the anterior margin of the vertebral centrum in P. cumberlandensis, 

 erythrogaster, tennesseensis, and phoxinus (TS 165[1]). The transverse process is located 

 at the middle of the lateral side of the vertebral centrum in other species and in the out- 

 groups (TS 165[0]). The transverse process is very short, and extends only to the base of 

 the transverse process of vertebra 2 (transverse process 2) in P. cumberlandensis (TS 

 166[1]). The transverse process is much longer, and almost equals about half of transverse 

 process 2 in length in all other species of Phoxinus and in the outgroups (TS 166[0]). 

 The second vertebral centrum ( Figs 75A-E, 76A-D, 77A-C) is more developed than the 

 first one. Its transverse process is elongated. The intercalarium is located at the lateral side 

 of the centrum. A developed neural arch (neural arch 2) is located at the dorsal side of 

 the centrum, and is more or less semi-round. In P. erythrogaster, neural arch 2 bears an 

 ascending process at its dorsal portion (TS 167[1]) that is absent in other species of 

 Phoxinus and in the outgroups (TS 167[0]). 



The third vertebral centrum is more developed than the previous two. No transverse pro- 

 cess is present on vertebra 3. Ventrally, a notch is present at the lateral side of the cen- 

 trum holding the medial ramus of the tripus. A developed neural arch is present at the 

 centrum's dorsal side. Articulating with the ventral portion of neural arch 2 and the neu- 

 ral complex dorsally, neural arch 3 is irregularly shaped and bears an anterior process and 

 a posterior notch. The process is narrow and relatively long in P. phoxinus (TS 1 68[ 1 ] ; 

 Fig.77A); the process is broad and relatively short in all other species of Phoxinus and in 

 the outgroups (TS 168[0]). 



The fourth vertebral centrum (Figs 76A-D, 77A-C, 78A-C) is of similar size to that of the 

 third centrum. A well-developed rib (rib 4) is located at the centrum's lateral side. The 



