Glyptothorax poonaensis, Hora, 1938

Dahanukar, Neelesh, Diwekar, Manawa & Paingankar, Mandar, 2011, Rediscovery of the threatened Western Ghats endemic sisorid catfish Glyptothorax poonaensis (Teleostei: Siluriformes: Sisoridae), Journal of Threatened Taxa 3 (7), pp. 1885-1898 : 1891-1897

Redescription of Glyptothorax poonaensis

Detailed morphometry of G. poonaensis is given in Table 4 and details of the body structure, head structure and details of skin are presented in Images 1, 2 and 3 respectively. The redescription is based on the freshly collected specimens as indicated in Table 4. The specimens deposited in WILD match exactly in morphology the types (4 specimens bearing the registration number F12126/1) deposited at the Zoological Survey of India, Kolkata .

Head depressed, body subcylindrical. Dorsal profile rises evenly from tip of snout to origin of dorsal fin then slopes gently ventrally from origin of dorsal fin to end of caudal peduncle. Ventral profile flat from snout tip to anal fin base, then slopes gently dorsally from anal fin base to end of caudal peduncle. Anus and urogenital openings located at vertical through middle of adpressed pelvic fin. Skin smooth on body and head but could be wrinkled in some specimens occurring either as a preservation artifact or molting ( Image 3). Lateral line complete, mid-lateral in position.

Head depressed and broad. Snout prominent. Anterior and posterior nares large and separated only by base of nasal barbels. Gill opening broad, extending from immediately ventral to post-temporal to isthmus. Bony elements of dorsal surface of head covered with thick, smooth skin. Occipital process does not reach base of dorsal fin. On either side of supraoccipital process, supracleithrum forms two finger like projections separated by large interspace as shown by Hora (1938: fig. 1c). Eye ovoid, located entirely on dorsal half of head, its horizontal axis longest, its diameter 9.8-13.5% HL.

Barbels four pairs, maxillary barbel long and slender extending to middle of pectoral fin base. Nasal barbels slender, barely reaching eye. Inner mandibular barbel origin close to midline extending up to gill opening on ventral surface. Outer mandibular barbel originating posteriolateral of inner mandibular barbel extending to origin of pectoral fin. Mouth inferior, premaxillary tooth band partially exposed when mouth is closed. Oral teeth small and villiform in irregular rows, premaxillary teeth in single broad semilunate band. Dentary teeth in two narrow crescentic bands separated at midline.

Dorsal fin located above anterior third of body with I,5 (N=1) or I,6 (N=10) rays; fin margin convex; spine short and gently curved. Adipose fin with anterior margin concave. Caudal fin strongly forked with lower lobes slightly longer than upper lobes. Procurrent rays symmetrical, extending slightly anterior on fin base. Anal fin base ventral to adipose fin origin. Anal fin with concave anterior margin and straight posterior margin with ii,8 (N=8) or ii,9 (N=3) rays. Pelvic fin origin slightly behind the posterior end of dorsal fin base. Pelvic fin with slightly convex margin and i,5 rays. Tip of adpressed fin not reaching anal fin origin but covers anus and urogenital area. Pectoral fin with I,7 (N=1) or I,8 (N=7) or I,9 (N=3) fin rays posterior fin margin slightly convex. Anterior spine margin smooth, posterior margin with 17–21 serrations.

Thoracic adhesive apparatus present, weakly developed, forming a narrow band and somewhat V shaped appearance ( Image 2c), with median depression present on posterior half and extending from isthmus to level of middle of pectoral fin. Median ridges oriented longitudinally, ridges uninterrupted.

In 4% formaldehyde dorsal and lateral surfaces of head grayish with yellow tinge. A dark gray patch on the dorsal profile extending from occipital process to posterior base of adipose fin. Ventral surface yellow to pale yellow. Dorsal fin gray with white band in middle, pectoral, ventral and anal fins with yellow base and gray tips. Caudal fin with black or dark gray base followed by gray tips. Head and body studded with randomly-distributed minute black dots. On the lateral surfaces of the body gray with yellow tinge sometimes give rise to brownish coloration.

Molecular phylogeny

ModelTest in MEGA 5 (Tamura et al. 2011) suggested that General Time Reversible + Gamma + Proportion Invariant (GTR+G+I) model was the best fit model for nucleotide substitution for our data and thus it was applied to generate phylogenetic hypothesis. The results for phylogenetic analysis based on maximum likelihood, maximum parsimony, minimum evolution and neighbor joining are shown in Fig. 2. The phylogeny based on a combined analysis of all three data partitions (16S rDNA, cyt-b and cox1) suggests that G. poonaensis is nested within a clade consisting of species from the northern part of the Indian subcontinent and China ( Fig. 2). Interestingly, G. poonaensis and G. davissinghi , both Western Ghats species, were separated by a larger distance suggesting that southern Indian Glyptothorax do not form a monophyletic group.

Molecular dating of divergence times between G. poonaensis and other northern Indian species suggests that G. poonaensis diverged from other northern Indian species between 1.9 to 2.5 million years ago ( Fig. 3). We used only cyt-b gene for molecular dating because (Peng et al. 2006) have considered cyt-b gene for their analysis and we are using same reference for the calibaration. Further, our total data matrix consisting of 16S rDNA, cyt-b and cox1 had non uniform substitution rates. Also, we could not use 16S rDNA and cox1 genes individually as their sequence length was small for statistical analysis. However, for cyt-b the sequence length was adequate for analysis and the null hypothesis of equal evolutionary rate throughout the tree was not rejected (p=0.2065) making the molecular dating more reliable.

Distribution and population status

The collection locality of one paratype of G. poonaensis is Kharadigaon (18.5450 N & 73.9490 E), Pune ( Hora 1938 ; Fraser 1942), while the type locality (where three paratypes were also collected) is more vague, being merely given as “near Poona [=Pune]”.We collected the species from the Village Markal (18.6710 N & 73.9810 E) situated on the right bank of Indrayani River , Pune. The two collection sites are numbered 1 and 2 respectively in Fig. 4 and the associated river basins are highlighted in blue. The total area drained by the two river basins is 6105.4km 2. However , it is suspected that the species could be locally extinct from the Mula-Mutha River ( Kharat et al. 2003), indicating that the current extent of occurrence ( IUCN 2001 ) of this fish could be reduced by at least half. We lack estimates of the population size of this species, but it is possible that it is relatively rare. This is based on the fact that in the extensive survey of Mula-Mutha River by Fraser (1942) only one specimen was collected. Further, previous study on Indrayani River (Yazdani & Mahabal 1976) failed to collect this species. Our discussions with the fishermen revealed that this species, locally called as Patthar-chatu, is found only during summer and early rainy season when the water level is low and even during this period the fish is very rare. However, since directed fishing efforts for this particular species are not done, we do not have exact estimates for the species abundance .

Biology

The length weight relation of unsexed G.poonaensis can be described by the equation W=0.0087 L 3.2436 ( Fig. 5, R 2 = 0.933, p <0.001). Since, the 95% confidence interval of scaling exponent was in the range 2.5882 - 3.8989, the null hypothesis, stated as the found value of the exponent is not significantly different from the predicted value of 3 by isometry, could not be rejected. Thus the fish grows isometrically. Gut content of three specimens of G. poonaensis suggested that the fish feeds on benthic macroinvertebrates such as freshwater prawns ( Image 4A), maxillopod crustacean (Branchiura) ( Image 4B) and Odonata nymph ( Image 4C). Our collection of gravid females suggests that this species probably breeds during June to August (the monsoon season). Similar observations are also made on other species of Glyptothorax (Dobriyal & Singh 1993; Nath 1994; Kaul 1994). Based on the fact that Glyptothorax are known to migrate downstream for breeding (Kaul 1994), we suspect that Markal could

of Glyptothorax poonaensis based on maximum likelyhood analysis of cyt-b gene and the molecular calibrations available for divergence time between Gagata cenia and Bagarius yarrelli and between Bagarius yarrelli and Glyptothorax fokiensis (Peng et al. 2006) . White bars on each node represent the 95% confidence interval of divergence time. Color code for species

names as per Figure 2.

(1) Kharadigaon (18.5450 N & 73.9490 E)

(2) Markal (18.6710 N &

73.9810 E).

be the breeding ground for G. poonaensis . This is because Markal is located on the main river and there are no hill streams in its immediate vicinity. Further, according to the local fishermen, the species is found in Markal area only during June to August, which is thought to be the breeding period of the fish.

Threats and conservation measures

There are several threats to G. poonaensis in its known range. Important threats to hill stream species like G. poonaensis include alteration of hydrological regimes because of damming, increasing pollution, deforestation leading to siltation, and introduced fish species. Dams cut the flow of water and lessen the speed of water creating semi-lacustrine conditions. These conditions may be highly disliked by hill stream fishes like Glyptothorax , which are specialized fro living in torrent streams ( Hora 1930 ). Also, Glyptothorax utilize gravel bed areas for spawning which are lost in rivers immediately below the dams (Kaul 1994; Nath 1994). Further, impeded water flow (both upstream and downstream of the dam) can lead to eutrophication and the creation of oxygen-poor habitats. As species of genus Glyptothorax require large amounts of oxygen in water ( Hora 1930 ) such habitat alterations are unsuitable for the species.Similar habitat alterations can also result from urbanization leading to organic pollution in rivers. Such changes in the rivers near the study area and their possible effects on the fish fauna are already documented (Kharat et al. 2003; Wagh & Ghate 2003). As stated before, we suspect that Indrayani River at Markal could be the breeding ground for G. poonaensis as Glyptothorax species are known to migrate downstream for breeding (Kaul 1994). If this is true then pollution in this area, which is an ongoing threat, is of major concern. An ongoing threat in terms of deforestation, leading to siltation, can also affect the breeding grounds of the fish. Recently we also observed sandmining on large scale at Markal ( Image 5), which is likely to affect the habitat of G. poonaensis .

Another major threat to the species could be the presence of introduced exotic fish. Introduced exotic fishes have been documented as major threats to fishes in the peninsular India (Kharat et al. 2003; Daniels 2006; Raghavan et al. 2008; Knight 2010). Kharat et al. (2003) have argued that introduced fish like Oreochromis mossambica , Poecilia reticulata, Gambusia affinis, Heteropneustes fossilis, etc. in Mula-Mutha River, are threatening the existence of many native fishes and might have caused even local extinction of some species including G. poonaensis .

and (b) downstream of Markal is a potential threat to G. poonaensis habitat.

Even in Indrayani River at Markal we recorded alien species such as Oreochromis mossambica and Clarias gariepinus . Although direct evidence is lacking we suspect that at least Clarias gariepinus is a potential threat to the current population of G. poonaensis as it is a voracious predator (Krishnakumar et al. 2011). Restricted distribution of the speceis, decline in the extent of occurance, ongoing threats to the habitats and possible threats to the speceis justifies the IUCN Red list threat catagory of this species as Endangered under the criteria B2ab(i,ii,iii,iv) as assessed by Dahanukar (2010).

The potential breeding grounds of the fish at Markal and the upstreams of Indrayani River, especially hill streams in the adjoining hilly areas need protection. Halting of siltation by re-plantations and avoidance of pollution could be helpful in saving the breeding grounds. Management of the introduced fishes, especially Clarias gariepinus , by controlled eradication of escaped stock and increasing public awareness for avoiding further introductions (Sato et al. 2010), could also be helpful.