Pethia shalynius

Pethia: the generic vernacular name for small cyprinids in the Sinhala language.

Type locality is 'Barapani Lake, about 20 kilometers north of Shillong, Khasi Hills, Meghalaya, India, elevation 1100 meters', and appears to be endemic to Meghalaya state where it's known from only a handful of localities in the Khasi and Jaintia hills.

It's apparently under threat from industrial activity in the region. Historical records from Assam appear to represent cases of misidentification.

A benthopelagic fish mostly recorded from streams and minor tributaries at relatively high altitudes of more than 1200 metres AMSL with cool, clear, well-oxygenated water and substrates of bedrock, boulders, cobbles, and gravel.

Aquatic plants aren't usually present though riparian vegetation may be well-developed.

It's also present in some ponds and small lakes, including some stagnant water bodies with muddy substrates.

One stream known as 'Seinpoh' in Meghalaya flows gently over a rocky substrate and P. shalynius was recorded both in the stream itself and spawning in nearby rice paddies (Engeszer et al. 2007).

Sympatric species at this locality include Danio rerio, D. meghalayensis, and Olyra longicaudata, plus unidentified members of Dario and Lepidocephalichthys.

Much of Meghalaya consists of forested hills which receive a great deal of rainfall meaning depth, flow rate, turbidity, and water chemistry are likely to fluctuate considerably at certain times of year.

Base dimensions of at least 75 ∗ 30 cm30 ∗ 12 in or equivalent are required.

Displays its best colouration under dim lighting and should look particularly effective in a heavily-planted arrangement with a darkish substrate, or a set-up designed to resemble a flowing river or stream with a substrate of variably-sized rocks and gravel and some large water-worn boulders.

This could be further furnished with driftwood branches and plants such as Microsorum, Bolbitis, or Anubias spp. which can be grown attached to the décor.

Since it naturally inhabits running water this species should never be added to a biologically immature set-up as it requires stable water conditions, and weekly water changes of 30-50 % aquarium volume should be considered mandatory.

Wild fish are probably foragers feeding on diatoms, algae, organic detritus, small insects, worms, crustaceans, and other zooplankton.

In the aquarium it's easily-fed but the best condition and colours offer regular meals of small live and frozen foods such as bloodworm, Daphnia, and Artemia, alongside good quality dried flakes and granules, at least some of which should include additional plant or algal content.

Very peaceful but unlikely to make an good choice for the general community aquarium due to its preference for cooler temperatures.

Fishes inhabiting similar biotopes in nature, especially comparably-sized, open water-dwelling cyprinids perhaps constitute the best choices but other potential options include balitorid, cobitid, and nemacheilid loaches as well as benthic cyprinids such as Crossocheilus and Garra species.

It's a schooling species by nature, and at least 6-10 specimens should be purchased.

Maintaining it in such numbers will not only make the fish less skittish but result in a more effective, natural looking display, plus males will develop better colours in the presence of conspecific rivals.

Adult males are noticeably smaller, slimmer, and more colourful than females, especially during the spawning season.

Unreported.

This species is not well known in the aquarium hobby and only available outside India on occasion although efforts are being made to produce it on a commercial basis for ornamental purposes.

P. shalynius can be distinguished from similar-looking species by the following combination of characters: barbels absent; 6-7 scales in the transverse row; 20-23 scales in the longitudinal row; lateral line incomplete ending on or before the 11th scale; no dark spot in the anterior portion of the body; two dark markings on the caudal peduncle, the anterior of which is most distinct; a longitudinal blue stripe on the body.

It was formerly included in the Puntius conchonius 'group' of closely-related species alongside P. ater, P. bandula, P. conchonius, P. cumingii, P. didi, P. erythromycter, P. gelius, P. khugae, P. macrogramma, P. manipurensis, P. meingangbii, P. nankyweensis, P. nigripinnis, P. nigrofasciatus, P. padamya, P. phutunio, P. punctatus, P. reval, P. shalynius, P. stoliczkanus, P. thelys, P. tiantian, and P. ticto, but all of these were moved to the new genus Pethia by Pethiyagoda et al. (2012), as were P. melanomaculata, P. pookodensis, P. muvattupuzhaensis, P. ornatus, and P. yuensis.

‘Puntius‘ narayani was not moved to the new genus and is currently of uncertain generic placement since it uniquely possesses 9 branched dorsal-fin rays and 6 branched anal-fin rays.

Pethia species are defined by the following combination of characters: rostral barbels absent; maxillary barbels minute or absent; possession of a stiff, serrated last unbranched dorsal-fin ray; presence of a black blotch on the caudal peduncle, and frequently, black blotches, spots or bars on the side of the body; infraorbital 3 deep and partially overlapping the preoperculum.

The genus Puntius was viewed as a polyphyletic catch-all containing over 100 species of small to mid-sized cyprinid for a number of years until Pethiyagoda et al. (2012) published a partial review covering South Asian members.

The majority of sub-Himalayan Puntius species were reclassified and new genera Dawkinsia, Dravidia, and Pethia erected to accomodate some of them, with the remainder either retained in Puntius or moved to the existing Systomus assemblage, though the definition of the latter was altered meaning some Southeast Asian species formerly placed there are no longer members.

It subsequently became clear that the name Dravidia was preoccupied by a genus of flesh fly, therefore the replacement name Haludaria was made available by Pethiyagoda (2013).

No species from Indochina, China, or Indonesia were included in the study meaning a significant number of former Puntius are currently classed as incertae sedis, i.e., of uncertain taxonomic placement, and this also applies to a number of South Asian species of unresolved status.

They’re perhaps best referred to as ‘Puntius‘ for the time being whereby the genus name is surrounded by quotation marks to denote its questionable usage, and that is the convention used here on SF at the moment.