Biogeography 14. 19-24. Sep. 20, 2012 A rare freshwater goby Odontobutis hikimius collected from the Nishiki River flowing down the southern slope of the drainage divide opposite to the Takatsu River, the type locality Harumi Sakae*, Toshihiro Hatama2 and Akihisa Iwata3 I Department of Aquabiology, National Fisheries University, 2-7-1 Nagata-Honmachi, Shimonoseki, Yamaguchi, 759-6595 Japan 2 Inland Sea Research Division, Yamaguchi Prefectural Fisheries Research Center, 437-77 Aio-Futashima, Yamaguchi, Yamaguchi, 754-0893 Japan 3 Graduate School of Asian and African Area Studies, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto, 606-8501 Japan Abstract. A rare freshwater goby Odontobutis hikimius Iwata & Sakai, 2002 was collected from the Nishiki River flowing into the Seta Inland Sea. The species was described based on specimens from three rivers flow- ing into the Sea of Japan, the Takatsu, Tama, and Masuda Rivers, as an endemically distributed new species. The Nishiki River flows the southern slope of the drainage divide opposite to the Takatsu River. It is thought that the Fukatani River that was a tributary of the Takatsu River has become a tributary of the Nishiki River due to a stream capture event. Following this event Odontobutis hikimius possibly immigrated to the Nishiki River system from the Takatsu River system. Key words: freshwater goby, Odontobutis hikimius, new locality, stream capture, immigration, morphology Introduction Specimens collected from the Nishiki River are identified with O. hikimius morphologically (Fig. 1). An endemic rare freshwater goby Odontobutis The Nishiki River flows on the opposite slope of the hikimius Iwata & Sakai, 2002 was described as a drainage divide to the Takatsu River and goes into the new species based on specimens collected from three Seto Inland Sea (Fig. 2). These two rivers are known rivers flowing into the Sea of Japan, the Takatsu, to have experienced a stream capture event with each Tama and Masuda Rivers. Due to its endemism, Shi- other (Shindo, 1938; Inami, 1951 ; Nishimura, 1962). mane Prefecture (2004) categorizes O. hikimius as a Distribution pattern of O. hikimius is discussed in rela- near threatened species (NT). This species is not only tion to the stream capture event. genetically different from O. obscura (Temminck & Schlegel, 1848), a common congener in Japan, due Materials and Methods to having its own allozyme-allelic composition (Sakai et ai., 1998), but also morphologically different due Ten specimens of O. hikimius were collected to having a distinct cephalic lateral line system (Iwata in 2011 from three tributaries of the Nishiki River & Sakai, 2002). system, namely the Usa, Fukatani, and Ohno Rivers (locality number 1, 2, and 3, respectively, in Table 1 *Corresponding author: [email protected] and Fig. 2) with an electric fishing gear (Electrofisher - 19 - Odol1tobutis hikimills from the Nishiki River Fig.1. Odontobutis hikimius from the Fukatani River, Nishiki River system, LBM 1210053516, male, 149.4 mm SL. 12B, Smith-Root Inc., USA). All the specimens in ethanol were deposited to the Lake Biwa Museum (LBM). Method for morphological observation followed Masuda et ai. (1984) and Iwata et al. (1985). The specimens were identified according to the key characteristics described by Iwata & Sakai (2002), namely the presence of canal C and the connection between pit lines 17 and 19 of the cephalic lateral line system (see Fig. 3). Counts and relative mea- ¢=' Stream Capture surements were compared with those presented by Iwata & Sakai (2002). For plotting distribution sites on the map (Fig. 2), data shown by Sakai et al. (1999) and personal collection data by one of the authors (TH), the speci- mens of which were not in suitable condition for measurement, were added as well. Results and Discussion All the present specimens were identified with O. hikimius based on the presence of the cephalic canal C and/or the connection between the cephalic pit lines 17 and 19 (Table 1). However, some had no ca- nal but had a groove on the left or right side instead 136" E (Table 1, Fig. 3A), and others had slightly separated Fig. 2. Map showing collection locations of Odontobutis hiki- mius (closed symbol) and O. obswra (open symbol). pit lines on the left and/or right sides (Table 1, Fig. Stars indicate those of the specimens in the present 3B). These character states look somewhat interme- study. Triangles and circles are for the data by Sakai diate between those of O. hikimius and O. obscura et al. (1999) and personal collections by one of the authors (TH) respectively. (Iwata & Sakai, 2002). Sakai et ai. (1999) reported the existence of occasional introgression from O. hikimius to O. obscura through hybridization events - 20- Harumi Sakai, Toshihiro Hatama and Akihisa Iwata grooved cana l C in the Takatsu River though no morphological ob- JJt' servation has been done yet. Similar introgression events may have occuned in the Nishiki River with the result that the cephalic lateral line characteristics may have changed slightly. Such data will folIow a genetic comparison of both species from the Nishiki River. Counts and relative measurements of O. hikimius can,, 1C from the Nishiki River are shown in Tables 2 and JJt' 3, respectively, in comparison with those presented by Iwata & Sakai (2002). AIl characteristics of the present specimens agreed with those of O. hikimius from the other regions. Among which, however, the pre dorsal scales number of the present specimens is relatively large especiaIly in mean as compared with those of the specimens from the other region (Table Fig.3. Cephalic lateral line system of Odolllobutis hikimills from the Nishiki River. A, LBM 1210053516, male, 2). This brings a unique characteristic to O. hikimius 149.4 mm SL, pit lines 17 and 19 are connected but the from the Nishiki River, which may indicate that the place of canal C is only grooved; B, LBM 1210053511, male, 162.0 mm SL, canal C is present but pit lines 17 immigration of this species to the Nishiki River did and 19 are separated slightly. not originate from recent manual transplantation, but it occun'ed relatively a long time ago. Table 1. Specimens of Odontobutis hikimus from the Nishiki River and their character state of cephalic lateral line system Connection of cephalic Cephalic Standard length pit lines 17 and 19 sensory canal C Catalogue number (mm) Sex left right left right 1. Goukami, Usa River, Nishiki River system, Yamaguchi Prefecture, 29 September 2010 LBM 1210053511 163.0 M SS SS P P LBM 1210053512 162.0 M SS SS P P LBM 1210053513 136.0 F C C G P LBM 1210053513 109.3 F C C P P LBM 1210053515 102.3 F SS SS P P 2. Goukami, Fukatani River, Nishiki River system, Yamaguchi Prefecture, 14 October 2010 LBM 1210053516 149.4 M C C P P LBM 1210053517 146.2 M SS C P P LBM 1210053518 91.4 F C SS P G 3. Shimo-ohno, Ohno River, Nishiki River system, Yamaguchi Prefecture, 14 October 2010 LBM 1210053519 122.1 F SS SS P G LBM 1210053520 101.2 F SS C G P LBM, Lake Biwa Museum; M, male; P, female; SS, slightly separated; C, connected; P, present; G, grooved. - 21 - Odontoblltis hikimius from the Nishiki River Distribution localities are plotted in Fig. 2. Odon- since a geographical event occurred when the Ni- tobutis hikimius is distributed in the upper reaches shiki River captured a tributary of the Takatsu River. of the both slopes of the drainage divide. The Fuka- Because the population is very limited as compared tani River, a tributary of the Nishiki River, is thought with that of O. obscura of the same river (personal to have been an uppermost tributary of the Takatsu observation), O. hikimius popUlation of the Nishiki River, following which it was captured by the Ni- River should be conserved as well as those from the shiki River (Shindo, 1938; Inami, 1951; Nishimura, Takatsu, Tama, and Masuda Rivers. 1962). Odontobutis hikimius possibly immigrated Furthermore, future surveys would be interest- to the Nishiki River system from the Takatsu River ing if they could reveal whether other animals also system through this stream capture event, though it immigrate from the Takatsu to Nishiki Rivers, and is still unknown when the event occurred. whether O. hikimius has immigrated or not from the In conclusion, the Nishiki River popUlation of Takatsu River to other neighboring rivers such as the O. hikimius has its own unique morphological char- upper reaches of the Oze and Ohta Rivers which are acteristic, and they have possibly been inhabitants flowing into the Seto Inland Sea. Table 2. Frequency distributions of meristic counts of Odontobutis hikimius from the Nishiki River as compared with the data by Iwata & Sakai (2002) Dorsal spines Dorsal rays Anal rays Pectoral rays VI W Vill IX 7 8 9 10 6 7 8 9 14 15 16 17 Present specimens 6 3 1 4 5 7 3 2 7 1 Iwata & Sakai (2002) O. hikimius 23 13 5 22 9 21 14 9 26 O.obscura 11 80 13 17 6 25 2 29 56 14 3 3 28 64 9 Lateral scale rows 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 Present specimens 2 3 2 I Iwata & Sakai (2002) O. hikimius I 5 7 7 9 2 2 O. obscura 3 10 5 17 32 20 9 3 Lateral scales with sensory papillae Transverse scales 26 27 28 29 30 31 32 12 13 14 15 16 17 18 Present specimens 2 3 4 6 3 Iwata & Sakai (2002) O. hikimius 7 13 14 8 17 9 2 O.obscura 13 41 31 9 2 18 37 34 12 2 Predorsal scales 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Present specimens 2 3 2 Iwata & Sakai (2002) O.