Unraveling a 146 Years Old Taxonomic Puzzle: Validation of Malabar Snakehead, Species-Status and Its Relevance for Channid Systematics and Evolution

Allen Benziger,Reynold Peter,Neelesh Dahanukar,Mithun Sukumaran,Fibin Baby,Siby Philip,Rajeev Raghavan,Agostinho Antunes,Mohamed Abdulkather Haniffa,Josin C Tharian,Palakkaparambil Hamsa Anvar Ali,Karunakaran Rema Devi,Kizhakke Veetil Radhakrishnan,Ralf Britz,Dirk Steinke

doi:10.1371/journal.pone.0021272

Abstract

BackgroundThe Malabar snakehead Channa diplogramma is one of the most enigmatic and least understood species within the family Channidae, which comprise one of the most important groups of freshwater food fish in tropical Asia. Since its description from peninsular India in 1865, it has remained a taxonomic puzzle with many researchers questioning its validity, based on its striking similarity with the South East Asian C. micropeltes. In this study, we assessed the identity of the Malabar snakehead, C. diplogramma, using morphological and molecular genetic analyses, and also evaluated its phylogenetic relationships and evolutionary biogeography.Methodology/Principal FindingsThe morphometric and meristic analysis provided conclusive evidence to separate C. diplogramma and C. micropeltes as two distinct species. Number of caudal fin rays, lateral line scales, scales below lateral line; total vertebrae, pre-anal length and body depth were the most prominent characters that can be used to differentiate both the species. Channa diplogramma also shows several ontogenic color phases during its life history, which is shared with C. micropeltes. Finally, the genetic distance between both species for the partial mitochondrial 16S rRNA and COI sequences is also well above the intra-specific genetic distances of any other channid species compared in this study.Conclusions/SignificanceThe current distribution of C. diplogramma and C. micropeltes is best explained by vicariance. The significant variation in the key taxonomic characters and the results of the molecular marker analysis points towards an allopatric speciation event or vicariant divergence from a common ancestor, which molecular data suggests to have occurred as early as 21.76 million years ago. The resurrection of C. diplogramma from the synonymy of C. micropeltes has hence been confirmed 146 years after its initial description and 134 years after it was synonymised, establishing it is an endemic species of peninsular India and prioritizing its conservation value.

Highlights

Freshwater fishes comprise one of the most diverse groups of vertebrates with an estimated 13,000 species worldwide, and many more waiting to be described in the tropics, especially in countries where exploratory surveys are still incomplete such as China and India [1]
Channa diplogramma: BMNH 1865.7.17.24, 81.6 mm standard length (SL), Malabar, India (Holotype: Unique); NMW 73835, 352 mm SL, Canara, India; NMW 73838, 230 mm SL, Mangalore, India; NMW 84220, 380 mm SL, Canara, India; Six specimens collected from Meenachil River, Kerala, India and four specimens collected from Pamba River, Kerala, India deposited at the Museum of the Conservation Research Group, St
It further differs from all other Channa species, except C. bankanensis, C. lucius, C. micropeltes and C. pleurophthalma by the presence of gular scales, a patch of scales between the anterior tips of the lower jaws, visible in ventral view

Summary

Introduction

Freshwater fishes comprise one of the most diverse groups of vertebrates with an estimated 13,000 species worldwide, and many more waiting to be described in the tropics, especially in countries where exploratory surveys are still incomplete such as China and India [1]. Snakeheads of the genus Channa comprise one of the most important groups of freshwater food fish in tropical Asia [4], with a wide natural distribution extending across the continent from Iran in the West, to China in the East, and parts of Siberia in the Far East [5]. They are one of the most common staple food fish in Thailand, Cambodia, Vietnam and other South East Asian countries where they are extensively cultured [4,6]. We assessed the identity of the Malabar snakehead, C. diplogramma, using morphological and molecular genetic analyses, and evaluated its phylogenetic relationships and evolutionary biogeography

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Discussion

Conclusion