Osteobrama bhimensis ( Cypriniformes : Cyprinidae ) : a junior synonym of O . vigorsii

Osteobrama bhimensis (Singh & Yazdani) was described from the Ujani wetland on Bhima River in Maharashtra, India, about 100 km downstream of the type locality of O. vigorsii (Sykes). Based on examination of the type material of O. bhimensis and comparison with O. vigorsii collected from different localities in the Krishna and Godavari River systems, we show that O. bhimensis is conspecific with O. vigorsii.


INTRODUCTION
Sykes (1839) described Rohtee vigorsii (now Osteobrama) from the Bhima River at Pairgaon (approx.18.506 0 N & 74.704 0 E).Although the types of this species are missing (Eschmeyer & Fricke 2011), Sykes (1841) provided a clear illustration of the species and gave an adequate description for purposes of identification.The species is widely distributed in the Krishna, Godavari and Mahanadi river systems of peninsular India and is common throughout its range (Dahanukar 2011).Singh & Yazdani (1992) described Osteobrama bhimensis from the Ujani Wetland on Bhima River, about 100km downstream of the type locality of O. vigorsii.Osteobrama bhimensis has since been considered a valid species by most authors (e.g., Menon 1999; Jayaram 2010).Even though Singh & Yazdani (1992) considered O. bhimensis to be closely related to O. cotio, owing to the lack of barbels, their figure of O. bhimensis resembles O. vigorsii more than it does O. cotio.Singh & Yazdani (1992) did, however, mention the similarity between O. bhimensis and O. vigorsii and sought to distinguish the two species through a number of characters (discussed below).
Recently we had an opportunity to study all the type material, comprising the holotype and five paratypes, of O. bhimensis currently in the collection of the Zoological Survey of India, Western Regional Centre, Pune.We compared the type material of O. bhimensis with specimens of O. vigorsii from the Krishna and Godavari river systems.Our study suggests that O. bhimensis and O. vigorsii are conspecific.
Zoological Survey of India, Western Regional Centre, Pune (ZSI Pune).Specimens of O. vigorsii and O. cotio peninsularis were available in the Wildlife Information Liaison Development, Coimbatore (WILD) and ZSI Pune.Morphometric and meristic data were recorded following Jayaram (2010).Measurements were taken point to point using dial calipers to the nearest hundredth of an inch and then converted to millimetres.Subunits of the body are presented as a percent of standard length (SL) and subunits of the head are presented as a percent of head length (HL).All pored scales were counted for reporting the lateral lines scales.We dissected three specimens of O. vigorsii (P/2671, 110mm SL; P/2672, 105mm SL and P/2673, 128mm SL) to resolve the structure of the urohyal bone.

RESULTS AND DISCUSSION
One of the most important characters that Singh & Yazdani (1992) used for diagnosing Osteobrama bhimensis was the absence of barbels.Our study of the type material of O. bhimensis revealed that the holotype and all the paratypes of O. bhimensis do in fact possess a pair of rudimentary maxillary barbels (Image 1), a character state also present in O. vigorsii.Indeed, if the character state 'barbels present' were applied to specimens of O. bhimensis using Singh & Yazdani's (1992) own key, the species keys out as O. vigorsii.Singh & Yazdani (1992) suggested that O. bhimensis is related to O. cotio and compared it with two subspecies of O. cotio, namely O. cotio cotio and O. cotio cunma.Even though these authors did not explicitly mention why they consider O. bhimensis to be affined to O. cotio, it appears they considered the absence of barbels in O. bhimensis to be synapomorphic in the O. bhimensis-O.cotio group.Our data, however, does not suggest a closer relationship between O. bhimensis and O. cotio than that between the former species and O. vigorsii, for two reasons.First, the holotype and all the paratypes of O. bhimensis do possess rudimentary barbels (Image 1).Second, the morphometric and meristic data of O. bhimensis do not coincide substantially with O. cotio, an observation that was also made by Singh & Yazdani (1992).Interestingly, Singh & Yazdani (1992)     Although Singh & Yazdani (1992) were aware of the resemblance between O. bhimensis and O. vigorsii, they separated the former from the latter based on the absence of barbels (vs.presence), 13-17 transverse scale rows between lateral line and pelvic fin base (vs.11-11½ ), the possession of 24-32 predorsal scales (vs.33-37), and the structure of urohyal.As already mentioned, the entire type series of O. bhimensis possesses rudimentary maxillary barbels, a character state shared with O. vigorsii.Although Singh & Pectoral fin rays i,13-i,14 i,13-i,14 Ventral fin rays i,8-i,9 i,8-i,9 Anal fin rays ii,22-ii,24 ii,22-ii,23 Yazdani (1992, Table 2) mention the number of transverse scale rows between lateral line and pelvic fin base as 13-15, we count 11 or 11½ (Table 1), which is the same range also for O. vigorsii (Hora & Misra 1940;Singh & Yazdani 1992; see also Table 1).The predorsal scales of O. bhimensis and O. vigorsii also have overlapping ranges (Table 1).An additional difference that Singh & Yazdani (1992) used to differentiate O. bhimensis from O. vigorsii was the shape of the urohyal.This is a single median triradiate bone with the anterior tip connected to the ventral hypohyals, the antero-dorsal part of which is connected to the first basibranchial and the posterior part of which is connected to the pectoral girdle by means of muscles (Johal et al. 2000).The shape of the urohyal of O. vigorsii (Image 3) matches that of O. bhimensis as illustrated in fig. 2 of Singh & Yazdani (1992).Singh & Yazdani (1992) suggested that the urohyal of O. vigorsii exhibits a radial process on the vertical plate, which is absent in O. bhimensis.However, in the three specimens of O. vigorsii we dissected, there is no such radial process (note that in Image 3a the thickened area on the lower surface is merely an undulation, not a process).Further, Singh & Yazdani (1992) mention that the dorsal spread ends in equal wings in O. bhimensis, while it ends in unequal wings in O. vigorsii.Our specimens of O. vigorsii show the dorsal spread to end in two equal wings (Image 3b).Therefore, the difference between the urohyals of O. bhimensis and O. vigorsii mentioned by Singh & Yazdani (1992) do not, in fact, exist.We did not dissect any of the type specimens of O. bhimensis.However, it is important to note that even though Singh & Yazdani (1992) mentioned that they studied the urohyal bone of O. bhimensis and O. vigorsii, they omitted to mention which specimens were used for their study.It is clear that none of the types of O. bhimensis have been dissected or cleared and stained.
The present study shows, therefore, that all the differences stated by Singh & Yazdani (1992) as distinguishing O. bhimensis from O. vigorsii do not in fact exist: the two nominal species are in fact conspecific and, O. vigorsii being the senior one, is valid, while O. bhimensis must now be placed in its synonymy.Dahanukar (2010) assessed the IUCN conservation status of Osteobrama bhimensis as Endangered under criteria B1ab(iii)+2ab(iii) (IUCN 2001) owing to the fact that the species is known only from its type locality in the Ujani wetland, with an Extent of Occurrence of 260km 2 and threats to the habitat and the species due to increasing urbanization, agricultural pollution and invasive exotic fishes.Dahanukar (2010)
did not compare O. bhimensis with O. cotio peninsularis described by Silas (1952) from Poona [= Pune], which is close to the type locality of O. bhimensis.Our comparison suggests that O. bhimensis differs from O. cotio peninsularis in a number of characters including ii22-ii24 (vs.ii27-ii32 in O. c. peninsularis) anal fin rays, 26-30 (vs.17-18) predorsal scales, 72-79 (vs.55-56) lateral-line scales and head length 26.0-28.3% SL (vs.22.3-24.0% SL).The type material of O. bhimensis and the figure given in Singh & Yazdani (1992, fig.1), however, is consistent with Sykes' (1842) description and figure of O. vigorsii, a species very widely distributed across the Krishna and Godavari river systems of the northcentral part of the peninsular India.A comparison of the morphometric data of the type series of O. bhimensis with the material of O. vigorsii referred to herein, from a number of locations across the Krishna River and Godavari basins (Fig. 1), suggests that

Figure 1 .
Figure 1.Study area showing sampling sites and type localities of Osteobrama vigorsii and O. bhimensis.

Morphometric and meristic data of type material of Osteobrama bhimensis.
also noted the need to validate the taxonomy of this nominal species because of its remarkable similarity to O. vigorsii.In the current study we have established that O. bhimensis is not a valid species but a junior subjective synonym of O. vigorsii.Osteobrama bhimensis.In: IUCN 2011.IUCN Red List of Threatened Species.Version 2011.1.