53 



four different orders that have breeding tubercles. Eight of the 15 families are in the or- 

 der Cypriniformes. Using Scanning Electron Microscope (SEM), Roberts (1982) studied 

 the unculi of ostariophysan fishes and showed the fine surface structure of some breeding 

 tubercles in these fishes. Wiley & Collette (1970) proposed that the breeding tubercles 

 have four primary functions: maintaining the body contact during spawning, defending 

 the nest and/or territories, stimulating females in breeding or spawning periods, and re- 

 cognizing a mate. 



Similar to other cyprinids, both mature males and females of Phoxinus species bear bree- 

 ding tubercles during breeding season. The breeding tubercles are much less developed in 

 females than in males. SEM study demonstrated that the morphology of tubercles is highly 

 diversified among the different regions of the same individual, and in the same region of 

 different species (Chen & Arratia 1996). Based on the observations used SEM, they stu- 

 died the distribution and fine surface morphology of the tubercles in Phoxinus, and reco- 

 gnized nine morphotypes, coded from A to I in Phoxinus. The following discussion is 

 based mainly on Chen & Arratia (1996) and only for the transformation series analyzed 

 herein. The readers are suggested to see this paper for details. Because no data on tuber- 

 culation are available in the outgroups, the exoglossin clade (Coburn & Cavender 1992) 

 is used as the outgroups to determine the polarity of the transformation series. 

 Tubercles are present on the dorsal side of the head in all species of Phoxinus. P. phoxi- 

 nus has type E tubercles which are large and few (TS 1 1 [ 1 ] ; Fig.24B). The dorsal side of 

 head in P. phoxinus has four or five large tubercles surrounding the dorsal margin of the 

 orbit, and two or three tubercles surrounding the nasal openings (TS 12[ 1 ] ; Fig.24B). Tu- 

 berculation similar to that in P. phoxinus is also present in Campostoma but not in other 

 minnows studied here. In all other Phoxinus species, tubercle type E is not found, but type 

 A and B tubercles are present (TS 1 1 [0]); the tubercles are small and numerous, and 

 randomly present from the posterior margin of the occipital to the anterior end of the snout 

 (Chen & Arratia 1996) (TS 12[0]; Fig.24A). 



Type I is present on the pectoral fin in Phoxinus erythro gaste r only (TS 13[1]), not found 

 in other species (TS 13[0]). In P. phoxinus, the whole opercle bears a very high density 

 of tubercles (TS 14[1]); whereas in other species of Phoxinus only part of the opercle 



EYE 



ANA 

 PNA 



Fig. 24: Dorsal view of heads 

 of (A) Phoxinus oreas (KU 

 3259, SL52.0 mm) and (B) P. 

 phoxinus (ZFMK 657-659. 

 79.6 mm SL). showing distri- 

 bution of tubercles on the 

 dorsum of head. Scale bars = 

 1 mm. 



