Sunday, May 21, 2017

[Ichthyology • 2017] Cryptic Diversity in the Indian Clade of the Catfish Family Pangasiidae Resolved by the Description of A New Species, Pangasius silasi


Pangasius silasi 
Dwivedi, Gupta, Singh, Mohindra, Chandra, Easawarn, Jena & Lal, 2017 


Abstract
Among 22 species of the genus Pangasius, distributed in Southeast and South Asia, only one species, Pangasius pangasius, is known to exist in South Asia. Phylogenetic analysis based upon COI and Cytb sequences suggested that the P. pangasius species clade consists of two subclades. Based upon the genetic and the following morphological evidence, we conclude that these DNA sequence based sister subclades represent two distinct species, P. pangasius and an undescribed species from river Krishna, named as Pangasius silasi. Morphologically, P. silasi is differentiated from its congener P. pangasius by a combination of characters, such as vomero-palatal teeth confluent as an uninterrupted curved band (vs two lunate vomero-palatal teeth patches on each side with a wide gap in the center) and vertebral count of 48 (vs 44). For several morphological characters, P. silasi is also distinct from P. myanmar, which is reported from Myanmar and has overlapping distribution with P. pangasius. Finally, the vomero-palatine dentition in P. silasi is distinct from the dentition structures reported for all the other Pangasius species. The biogeographical significance of finding this new species, P. silasi, in a river of the Indian peninsula is also discussed in this report.

Keywords: Pangasius, River Krishna, DNA sequences, Molecular phylogeny, Morphology, Biogeography

Fig. 4: Lateral view of the Pangasius silasi (a) holotype (NBFGR/PP 76, 321.2 mm SL) Fresh condition and (b) Formalin Preserved. c Paratype, fresh condition (NBFGR/PP 78, 379.5 mm SL) 

 Pangasius silasi sp. nov
The specimens of Pangasius sp. nov., (named as Pangasius silasi) PP 72–78 and PSH 01 (eight specimens.), 247.8–407.4 mm SL, were collected through the fish landings from Krishna River at Nagarjuna Sagar Dam, 16°53′N 79°26′E; Guntur District, Andhra Pradesh, India; Lal et al., 3 May 2013 (Fig. 4). This water body is shared between the Two Indian states, Andhra Pradesh (district Guntur) and Telangana (district Nalgonda). These specimens were studied for morphomeristic measurements and DNA sequence analysis. For future reference, the designated holotype PP 76 (321.2 mm SL) and paratype PP 78 (SL 379.5 mm SL) are preserved in NBFGR repository. Paratype (NBFGR Acc. No. NBFGR/PP 71) has been deposited with Museum of Zoological Survey of India, Kolkatta (ZSI FF 5621).

Distribution: At present P. silasi is known only from the type locality, the Krishna River at Nagarjuna Sagar Dam in Telangana, India.

Etymology of Nomenclature: The species name of P. silasi is derived from the name of Dr. E.G. Silas, who has made important contributions to taxonomy of Indian fish species, their biogeography and evolutionary divergence with the eminent scientist Prof. S. L. Hora.


Arvind K. Dwivedi, Braj Kishor Gupta, Rajeev K. Singh, Vindhya Mohindra, Suresh Chandra, Suresh Easawarn, Joykrushna Jena and Kuldeep K. Lal. 2017. Cryptic Diversity in the Indian Clade of the Catfish Family Pangasiidae Resolved by the Description of A New Species. Hydrobiologia. DOI: 10.1007/s10750-017-3198-z

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