Cephalic Sensory Canals

　As shown in Figure 1, the cephalic sensory canals of bitterlings were comprised of the supraorbital canal (SOC), infraorbital canal (IOC), temporal canal (TC), mandibular canal (MC), preopercular canal (PC), and supratemporal canal (STC). SOC was disjunct from both IOC and TC, PC disjunct from TC, and right and left STCs did not meet. SOC extended posteriorly to the pterotic or parietal bone as a free canal in all species of Acheilognathus and Tanakia except T. signifer and T. himantegus chii: on the parietal in T. limbata, T. tanago, and all species/subspecies of Acheilognathus except A. melanogaster (Figs. 2B, 4 A-B, 5, 6 B-D, and 7A); on the pterotic in T. lanceolate and A. melanogaster (Figs. 2A and 6A); but extended posteriorly to neither the parietal nor the pterotic in T. himantegus chii, T. signifer, and all species of Rhodeus (Figs. 3, 4 C-D, 7 B-D, and 8).

　Bitterling cephalic sensory canals could be grouped into 3 types (Fig. 1) by completeness or incompleteness of IOC and presence/absence of TC and STC as follows:

　Type I (Figs. 2, 4-7, and 8A-C): Complete IOC combined with presence of TC and STC. All species in Tanakia, Acheilognathus, and Rhodeus except R. sericeus sericeus, R. s. amarus, and R. sinensis, belonged to this type.

　Type II (Figs. 3A and 8D): Incomplete IOC combined with presence of TC and STC. IOC in infraorbitals 3 and 4 was reduced. Only two subspecies, R. s. sericeus and R. s. amarus, belonged to this type.

Fig.1
Fig.1.
Three types (Types I-III) of the cephalic sensory canal system in the Acheilognathinae. (See p. 6 for explanation.) IOC, infraorbital canal; MC, mandibular canal; PC, preopercular canal; SOC, supraorbital canal; STC, supratemporal canal; TC, temporal canal; TRC, trunk canal.

　Type III (Fig. 3B): Complete or incomplete IOC, incomplete SOC, along with absence of TC and STC. SOC was absent in the nasal bone. A complete IOC was examined in two specimens (ZUMT k-190 and k-222) and an incomplete IOC in one specimen (ZUMT k-189). For the incomplete IOC, an interrupted distance was shorter than that in R. s. sericeus and R. s. amarus. Only R. sinensis belonged to this type.