Pareuchiloglanis

Heok Hee Ng, 2004, Two new glyptosternine catfishes (Teleostei: Sisoridae) from Vietnam and China., Zootaxa 428, pp. 1-12 : 10-11

[[ Pareuchiloglanis ]]

Discussion

The types of many nominal glyptosternine species are deposited in Indian and Chinese institutions, and are usually fairly inaccessible to researchers. This produces obstacles to easy comparison when new species of glyptosternines are described. The problem is also exacerbated by the limited availability of non-type material for comparison in institutions outside of China and India. Glyptosternine catfishes live in habitats that are difficult for researchers to gain access to and are difficult to capture using conventional sampling methods; these are the primary reasons for the paucity of (non-type) comparative material. Furthermore, much of this comparative material actually consists of material exchanged from Indian or Chinese institutions (for example, all the paratypes of P. macropterus had been exchanged from the Kunming Institute of Zoology in Yunnan, China). However, these obstacles can be overcome and adequate comparisons are possible, at least for the species described within the last 50 years, by using the data from the original descriptions. It is with this limitation in mind that the two species described herein are compared with other congeners.

Pareuchiloglanis macropterus has often been misidentified as P. kamengensis in the literature, but can be distinguished from it by the characters stated in the diagnosis. Furthermore, the two species are found in different drainages ( P. macropterus from the Salween River and Irrawaddy River drainages and P. kamengensis from the Brahmaputra River drainage) and are not likely to be conspecific, as glyptosternine catfishes, like many other highly specialized rheophilic fish species, have very restricted distributions.

Additional characters may exist to distinguish P. macropterus from P. kamengensis . The specimen of P. kamengensis collected from the Yarlong Tsangpo River (a tributary of the Brahmaputra River upstream of the type locality of P. kamengensis ) illustrated in Wu & Wu (1992: Fig. 155) shows a distinct postlabial and thoracic groove not present in P. macropterus , as well as the disposition of the premaxillary teeth in two distinct patches (although the accompanying text mentions the teeth as being arranged in a single band). The validities of these characters await confirmation by direct comparison of specimens and are therefore not used as diagnostic for the species. The figure does illustrate, however, some of the characters that distinguish P. kamengensis from P. macropterus (such as the shorter adipose fin).

Although the pale-colored patches on the body of P. macropterus are not particularly evident in Fig. 1, they can still be made out with some difficulty in pale specimens (as in Fig. 1), and are clearly visible in darker specimens (the BMNH paratypes). The presence of these patches is also mentioned in the literature and amply illustrated (e.g. Chu et al., 1990).

There are only two species of Pareuchiloglanis reported from the Red River (Song Hong) drainage: P. macrotrema (known from the Red River (Song Hong) drainage in Lao Cai province) and P. rhabdurus (found further to the west in the Song Lo drainage). The only other species reported from the region is P. nebulifer , which is known only from the Song Ma drainage, which lies immediately adjacent southwards to the Red River (Song Hong) drainage. Given how poorly the freshwater ichthyofauna of northern Vietnam is currently understood (Kottelat, 2001), it would not be surprising that more Pareuchiloglanis species await discovery there.

The material identified as P. macrotrema by Chu et al. (1990) from the upper Red River (Yuanjiang) drainage in China probably represents an undescribed species. As noted in Kottelat (2001), differences exist between the Vietnamese and Chinese material, with the former having a shorter caudal peduncle (13.7-18.2% SL vs. 20.8-24.4). However, the Chinese material was unavailable to me for further verification of its status. Another undescribed Pareuchiloglanis species from the Salween River (Nujiang) drainage possibly exists. The material identified as P. feae by Chu et al. (1990) is characterized by distinctly separate (vs. confluent) adipose and caudal fins and therefore does not appear to be conspecific with P. feae s. str.. Again, I was unable to obtain material to verify its identity.