Research shows exceptional diversity among popular ornamental fish known as ‘puntius’ – Malaka Rodrigo
Popular freshwater fish that belonged to the genus Puntiushave been re-classified into 5 new genera by Sri Lankan scientists. The results were published last week in a paper in the journal ‘Ichthyological Exploration of Freshwaters’, authored by Rohan Pethiyagoda, now attached to the Australian Museum in Sydney, together with Dr Madhava Meegaskumbura and Dr Kalana Maduwage, both of the University of Peradeniya.
A genus (genera in plural) is a grouping of one or several species that possess common characteristics which also denotes by the first part of binomial scientific names. Based on this new analysis, the South Asian fishes formerly in Puntius have been divided into five genera, namely Puntius, Systomus, Dawkinsia, Pethia and Dravidia. While the first four genera have representatives in Sri Lanka, Dravidia (named for the Dravidian people of South India) is restricted to Kerala, Tamil Nadu and Karnataka.
The filamented-fin barbs have been allocated to a new genus, Dawkinsia, named after the British evolutionary biologist and anti-religion advocate Richard Dawkins, author of the best-seller ‘The selfish gene’. These now include Dawkinsia singhala and Dawkinsia srilankensis. The following four species, meanwhile, have been transferred to the genus Systomus: asoka, martenstyni, pleurotaenia, spilurus (the wet-zone species formerly known as ‘sarana’) and sarana. The bulk of the remaining species have been allocated to a new genus, Pethia, which is also the local Sinhala name for these small fishes. These are Pethia bandula, cumingii, melanomaculata, nigrofasciata and reval. The only Sri Lankan fish that still remain in the genus Puntius are kamalika, vittatus, bimaculatus, thermalis and titteya.
These small freshwater fishes commonly called ‘pethia’ in Sinhala, are also among the most popular inhabitants of tropical aquariums. Many of the 18 species of Sri Lankan Puntius, have for decades been bred by aquarists worldwide and are very popular ornamental fish. These include the ‘bulathhapaya’ (Puntius nigrofasciatus), ‘le titteya’ (Puntius titteya) and Cuming’s Barb (Puntius cumingii). The relationships of such species to Southeast Asian ones such as the Tiger Barb (Puntius tetrazona) have for long been questioned. Could fishes that show such a variety of shapes, sizes and other anatomical characters all belong to a single genus, or have scientists over the years simply been ‘dumping’ new species into Puntius simply for reasons of convenience?
While many have asked the question, few have elected to do a comprehensive study to find answers. The scientists anlysed 31 species of fishes belonging to Puntius from across South Asia using three methods: analysis of DNA, their osteology (a study of their bone structures) and external morphometrics (the proportions of their bodies, the number of scales, etc). The study was by no means easy, they say, and took eight years to complete.
Pethiyagoda explains that there has been a long-felt need to bring the taxonomy of these fishes into line with their evolutionary context. “Attempts to do these using external characters alone over the past several decades have failed. It was time for a multi-pronged approach.” As a result of the species-groups they identified among the Southeast Asian fish formerly in Puntius, it is expected that a cascade of new genera will follow from that region, too.
Being among the most popular ornamental fishes, Sri Lanka Customs’ data show that many of these species are being heavily exported. It is believed that many of them are caught from the wild, which will deplete their wil populations. Loss of quality of riverine habitats suited to them and invasive fish introduced to waterways too, make an impact on their decline. One of the endemic fish that got a new name, Pethia bandula, is confined only to single stream and if this gets contaminated, the entire species could go extinct. So the scientists call for more attention to be paid to the conservation of these fishes.
Published in July.2012
Tags: Freshwater fish