Taxonomy & naming
Macrognathus lineatomaculatus was described by the ichthyologist Ralf Britz in 2010, making it one of the more recently formalised members of its genus. The Catalog of Fishes (Eschmeyer, the authority for valid names) places it in the genus Macrognathus, one of the two principal Asian genera of the spiny-eel family Mastacembelidae. Mastacembelidae sits within the order Synbranchiformes — the same order that contains the swamp eels (Synbranchidae) — and has no close relationship to the true eels of the order Anguilliformes. The eel-like body plan is convergent, shaped by a shared burrowing life rather than by shared ancestry.
Macrognathus is the sister genus to Mastacembelus within Asian Mastacembelidae and is distinguished primarily by features of the snout and dorsal-spine count. The species name compounds the Latin lineato- (lined, streaked) and maculatus (spotted), referencing the pattern of spots arranged in linear series along the flank — a description that sets it apart from plain-banded congeners. No junior synonyms are currently recognised for this species, which has been in the literature less than two decades.
Morphology
Macrognathus lineatomaculatus reaches a recorded maximum of 7 in standard length (SL), making it a small to mid-sized spiny eel comparable in scale to many of the peacock and dwarf spiny eels of the genus. The body is greatly elongate, laterally compressed posteriorly, and lacks visible scales — the skin is covered in tiny embedded scales beneath a coating of mucus, giving the fish its characteristic slippery feel. The snout is drawn into a short fleshy proboscis bearing tubular nostrils, a structure used to probe soft substrate in search of prey.
The dorsal profile carries 19–22 isolated, short spines ahead of the soft dorsal fin, which is continuous with the anal fin around the tapering tail. Meristic counts recorded from FishBase are 50–57 dorsal soft rays, 3 anal spines, 47–54 anal soft rays, and 74–76 vertebrae. The name-giving pattern consists of spots or blotches arranged in roughly linear rows along the flanks against a background of pale longitudinal streaking, though the precise ground colour and contrast may vary with condition. Sexual dimorphism is not well documented; ripe females of related species are typically fuller-bodied than males.
Habitat
The species is native to freshwaters of the Indian subcontinent, with records from India and the Nepal–India border region. It is a benthic fish associated with slow-moving or standing waters: floodplain pools, gentle river margins, and channels with dense submerged vegetation, soft muddy substrates, and accumulations of roots and detritus. These are characteristic lowland tropical freshwater habitats subject to seasonal flooding and draw-down.
Water chemistry data assembled from aquarium sources suggests a preference for warm, soft-to-neutral conditions — temperatures roughly 72–82 °F, pH 6.0–7.5, and a total hardness of approximately 5–15 °dGH. These figures are consistent with the soft, weakly mineralised lowland waters of the Gangetic plains and their tributaries. Like all scaleless mastacembelids, M. lineatomaculatus is sensitive to deteriorating water quality and to copper in any form. The species is classified as benthic by FishBase, and its trophic level of 3.3 places it among generalised invertebrate predators.
Feeding
Macrognathus lineatomaculatus is a predator that forages along and within the substrate. The fleshy, probing snout is adapted for rooting through mud and leaf litter in search of small invertebrates — insect larvae, worms, and similar soft-bodied organisms that form the diet of small Macrognathus species generally. FishBase assigns it a trophic level of 3.3, consistent with a diet centred on benthic invertebrates rather than fish.
In the aquarium, related small spiny eels of similar habits accept frozen bloodworm, small earthworm sections, and other meaty foods. Because this species is rarely kept, direct feeding observations in captivity are limited; aquarium references recommend offering live or frozen invertebrate foods in the evening, when the fish is naturally most active, and note that specimens often refuse dry foods entirely.
Mating
Macrognathus lineatomaculatus is a spiny eel and therefore a substrate egg-scatterer: it gives no parental care and does not undertake any marine spawning migration. It is not a true eel and the catadromous life history of Anguilla — the remarkable sea-going spawning journey of the true eels — does not apply here. In wild mastacembelids generally, including Macrognathus species studied in captivity, spawning is associated with the onset of the rainy season when rising water levels and warm, rain-diluted water trigger courtship.
A courting pair typically entwine and circle among vegetation or root masses near the substrate, and the female scatters adhesive eggs that adhere to fine plant material or leaf litter. No nest is constructed and no bond persists beyond spawning. Observations directly attributable to M. lineatomaculatus specifically are absent from the literature, and the mating behaviour described here is inferred from congeners and from the general mastacembelid template.
Breeding
No successful aquarium breeding of Macrognathus lineatomaculatus has been reported in accessible records. As with the majority of spiny eels, captive breeding is rare and most trade fish, if the species appears at all, would be wild-caught. The egg-scattering, no-care breeding mode of mastacembelids — adhesive eggs scattered among vegetation in fresh water, hatching in a few days, with larvae that require very fine live foods initially — is the framework that would apply here, but none of the sources consulted document a confirmed spawning of this species.
Breeding might in principle be attempted by mimicking seasonal transition: a period at the cooler end of the temperature range followed by large water changes with slightly softer, cooler water to simulate the onset of monsoon. Conditioning the pair on live and frozen invertebrate foods over several weeks prior to such a trigger is standard practice for small mastacembelids. Given how recently the species was described and how infrequently it enters the trade, the prospects of reliable captive breeding remain remote at present.
In the aquarium
Macrognathus lineatomaculatus is a rarely-kept species and is not a common aquarium fish. When it does appear, its requirements follow the pattern of small Asian Macrognathus: a well-filtered aquarium with a soft sand substrate it can burrow into, plenty of cave-like hiding places and shaded retreats, subdued lighting, and a diet of meaty live and frozen foods offered after dark. Aquarium sources suggest a minimum tank length of 47 in (approximately 65 US gal) for a small group, and recommend keeping 3–5 individuals where space allows, as the species may be more comfortable in loose groups than in complete isolation.
All spiny eels are notorious escape artists. They climb, squeeze through tiny gaps, breathe air at the surface, and will leave an uncovered aquarium and perish on the floor. A tight, fully sealed lid with no gaps is essential. As a scaleless fish, M. lineatomaculatus is sensitive to copper-based medications — any treatment for parasites or bacterial infection must be copper-free — and to poor water quality generally. It should not be housed with fish small enough to be swallowed, but it is not notably aggressive toward tankmates of appropriate size.
Conservation
Macrognathus lineatomaculatus is assessed as Data Deficient on the IUCN Red List (assessment published in the 2020.2 update). The Data Deficient listing reflects the species' recent description in 2010 and the limited information available on its population size, range extent, and habitat requirements rather than any specific evidence of threat or safety. The assessors could not determine whether it qualified as threatened without more survey data.
The freshwaters of the Indian subcontinent face well-documented pressures — agricultural run-off, wetland drainage, sand extraction, water abstraction, and pollution across the Gangetic plains and associated lowland river systems where this species likely occurs. A small, recently-described species with a restricted or poorly-defined range in such a landscape is inherently vulnerable to localised habitat loss even in the absence of targeted collection pressure. Until proper surveys establish the species' actual distribution and population status, no meaningful conservation prognosis can be offered beyond the precautionary note that the Data Deficient category does not mean the species is safe — it means it is unstudied.