Taxonomy & naming
Pethia melanomaculata was described by Deraniyagala in 1956 from Sri Lanka, originally placed within the broad genus Puntius. For many years it was treated as a synonym or local variant of Pethia ticto, the widespread "ticto barb" of the Indian subcontinent, and Sri Lankan populations of the two were not reliably distinguished in the aquarium literature. A redescription published in 2015 (noted in FishBase reference data) clarified the characters separating P. melanomaculata from P. ticto, confirming that Indian records of P. ticto do not extend to Sri Lanka as the same taxon.
The genus Pethia was erected by Pethiyagoda, Meegaskumbura and Maduwage in 2012 to accommodate a cluster of South Asian barbs removed from the old, polyphyletic Puntius (Ichthyologia Exploratoria Freshwateriorum 23(1):69–95, 2012). That paper separated the Indian subcontinent's small, often spotted or banded barbs into several new genera; Pethia takes species with a black spot at the base of the last dorsal ray and typically a spot or blotch on the caudal peduncle. The Catalog of Fishes follows this arrangement and records the valid name as Pethia melanomaculata (Deraniyagala, 1956).
Molecular phylogenetic and phylogeographic work on Sri Lankan Pethia (published in ZooKeys / ResearchGate, 2021) has placed P. melanomaculata within a Sri Lankan radiation and confirmed its distribution in the dry and intermediate zones of the island, distinct from the wet-zone species assemblage.
Morphology
Pethia melanomaculata is a small, moderately deep-bodied barb reaching approximately 1.5 in in standard length. The body is laterally compressed and the profile relatively high-backed, as is typical for the genus. The common name "fire fin barb" refers to prominent reddish to orange coloration in the fins — most conspicuous on the dorsal fin, which also bears a characteristic black spot at the base of its last branched ray, a diagnostic character shared across the genus Pethia.
The species carries the name melanomaculata (black-spotted) for the dark markings that punctuate the body or fins; a dark blotch on the caudal peduncle is typical for the group. Coloration is brightest in fully conditioned males. Females tend to be deeper-bodied and less intensely coloured, particularly outside the breeding season.
Habitat
Pethia melanomaculata is endemic to Sri Lanka, where it occurs in the lowland freshwaters of the dry and intermediate climatic zones. Molecular phylogeographic studies confirm a distribution that is distinct from the wet-zone species of Sri Lanka and from Indian mainland representatives of similar-looking barbs. It inhabits streams and rivers with gravel and pebble substrates, in the calm-to-moderate reaches that characterise lowland drainage systems in these zones.
Sri Lanka's dry-zone rivers are subject to strong seasonal fluctuation — high discharge during the northeast monsoon and greatly reduced, sometimes intermittent, flow in the dry season. Fish communities in these systems must tolerate considerable variation in water level, temperature and chemistry across the year. Broadly neutral, moderately warm conditions are typical, though the specific physicochemical parameters of P. melanomaculata's preferred microhabitats have not been thoroughly characterised in the published record.
Feeding
Like the majority of small Pethia species, P. melanomaculata is an opportunistic omnivore in the wild. It grazes on small invertebrates — insect larvae, microcrustaceans and worms — along with aufwuchs, algae and organic detritus picked from gravel beds and the water column. Its small size and active, shoaling disposition suit continuous foraging over open substrate rather than ambush feeding.
In aquaria it accepts a wide range of prepared and live foods without difficulty. Good-quality micro-pellets and fine flakes supplemented with small live and frozen invertebrates (daphnia, brine shrimp nauplii, bloodworm) suit it well. Varied feeding supports healthy fin colour and general condition.
Mating
Pethia melanomaculata is an egg-scattering, non-guarding spawner — the reproductive mode universal among barbs. There is no nest construction, no pair bond beyond the act of spawning, and no parental care of any kind. As condition improves and the fish approach readiness, males intensify in colour and begin to drive gravid females persistently through the shoal and through any available vegetation or over the gravel substrate.
Courtship consists of the male pressing alongside or beneath the female, the two fish releasing eggs and milt in brief, tight embraces as they move through the water. The eggs are adhesive and fall among substrate particles or catch in fine vegetation. Adults typically scatter their eggs widely and show no further interest in them.
Breeding
Like other small Pethia, P. melanomaculata can be bred in a dedicated spawning aquarium. A shallow tank with a fine gravel or pebble bottom, a few stems of fine-leaved plants or a spawning mop, and clean, slightly warm neutral-to-soft water is suitable. A mesh or loosely packed pebble layer helps protect eggs from the adults, which will eat them readily.
Well-conditioned fish placed into the spawning tank in the evening typically spawn in the morning, with the female releasing a clutch of adhesive eggs that settle to the bottom. The adults should be removed after spawning. Eggs hatch within one to two days at tropical temperatures; the larvae become free-swimming after a further few days and can be started on infusoria and then newly hatched brine shrimp. The species is not widely bred in the hobby due to limited availability, but no unusual difficulty is reported.
In the aquarium
Pethia melanomaculata is rarely encountered in mainstream aquarium trade and appears sporadically in specialist collections. As a small, active shoaling barb it benefits from being kept in groups of six or more, which allows the natural social hierarchy to develop within the group rather than being redirected as harassment toward tankmates. A well-planted aquarium with open swimming space and moderate water movement suits it well.
Water conditions reflecting its Sri Lankan lowland origins — broadly neutral pH, moderate hardness, and temperatures in the low-to-mid twenties Celsius — are appropriate. It is undemanding in feeding and compatible with other peaceful, similarly sized fish. Peaceful nano-community aquaria with other South and Southeast Asian species make appropriate settings. Its relative scarcity in the hobby is a function of limited export, not husbandry difficulty.
Conservation
Pethia melanomaculata is assessed as Least Concern (LC) on the IUCN Red List, with an assessment completed on 7 August 2019 by Malka Fernando, Sampath de Alwis Goonatilake and Odatha Kotagama. The assessors note its continued presence across suitable habitats in Sri Lanka's dry and intermediate zones and do not identify a decline meeting the threshold for a threatened category.
Nonetheless, Sri Lanka's endemic freshwater fish fauna faces ongoing pressures from agricultural water extraction, modification of river channels, gravel mining, and expanding human land use in the lowland river catchments that this species occupies. Its status as a Sri Lankan endemic with a range limited to particular climatic zones means it has less geographic buffering than widespread continental species. Continued monitoring of dry-zone river systems and protection of intact stream habitats are important for the security of the species and the broader endemic freshwater community it is part of.