64 



1. The first loop is formed in the following way: the anterior portion of the intestine runs 

 caudally at the left of the body, then turns right, forward then caudally to form the se- 

 cond loop. 



2. The beginning of the intestine is located on the left side of the body, whereas the po- 

 sterior end of the intestine is on the right side of the body. 



Significant interspecific variation in Phoxinus occurs in the coiling pattern of the intesti- 

 ne. Based on the length, the number and the complexity of loops of the intestine, four ty- 

 pes, i.e.. phoxinus-, eos-, cumberlandensis-typt, and oreas-iype. can be defined in the 

 genus. 



P. phoxinus -type: The intestine is short: its length is shorter than, or equal to standard 

 length of the individual: only 1.5 loops are formed. This type is present in P. phoxinus, 

 brachyurus, issykkulensis. and neogaeus (Figs.31A-C). 



P. <?05-type: The intestine is longer than the phoxinus-typt: its length is about 200% of 

 standard length. Three loops are present. The third loop encloses most of the first one. 

 This type is present in P. eiythrogaster, eos. and tennesseensis (Figs. 3 IE. 32A. C). 

 P. cumb e viand en si 5- type: The intestine is longer than the eos-Xypt. Its length is 230% 

 of the standard length. The coiling pattern of the intestine is more complicated: six loops 

 are present. This type is present in P. cwnberlandensis only (Fig.31G). 

 P. oreas-type: This is the most complicated one in the four types. About 10 loops are 

 formed. Its length is about 180% of the standard length. This type is present in P. oreas 

 only (Fig.32D). 



Ontogenetically. the younger individuals have simpler coiling patterns than the adults in 

 the Phoxinus species with a coiled intestine. For instance, P. cwnberlandensis which bears 

 cumberlandensis-type in adults has two loops with a simple coiling in a 24 mm SL indi- 

 vidual: two loops with more complicated looping are present in a 33mm SL individual: 

 more complicated looping and more loops are present in a 51.3 mm SL specimen (Fig. 3 ID, 

 F. G). In the outgroups, the intestine is short and the coiling type is simple, similar to the 

 Phoxinus-Xypt. Therefore, I hypothesize the polarity of this transformation series is from 

 simple pattern to complicated ones. i.e.. P. phoxinus-iypt (TS 29[0]) — > P. eos-type (TS 

 29[1]) — » P. cumberlandensis-type (TS 29[2]) P. oreas-type (TS29[3](. 



Gas bladder (Figs.33A-B: 34A-H) 



The gas bladder (air-bladder, swim bladder) in cyprinids consists of two chambers (ante- 

 rior and posterior ones) and a constriction (or isthmus - Harder 1975) between the two 

 chambers 1 . A pneumatic duct (tractus pneumaticus) originates from the dorsal wall of the 

 esophagus and connects with the posterior chamber or with the constriction at its poster- 

 ior end. 



The anterior chamber in Phoxinus is shorter than the posterior one. The anterior end of 

 the anterior chamber is slightly broader than its posterior part. The posterior chamber is 



) However, three chambers of the gas bladder are also found in some genera of Cyprinidae (e.g.. 

 Megalobrama. Erythroculter, see Yi & Wu 1964). 



