Taxonomy & naming
Ptychochromis inornatus was described by the American ichthyologist John S. Sparks in 2002, in a Copeia paper titled 'Ptychochromis inornatus: a new cichlid (Teleostei: Cichlidae) from northwestern Madagascar, with a discussion of intrageneric variation in Ptychochromis.' The holotype (UMMZ 237492) was collected in the Anjingo River, a tributary of the Ankofia drainage northeast of Antsohihy in Madagascar's Mahajanga (Majunga) Province, with a paratype series split between the University of Michigan Museum of Zoology and the American Museum of Natural History. The species sits in the genus Ptychochromis, erected by Franz Steindachner in 1880, within the subfamily Ptychochrominae — the clade of cichlids endemic to Madagascar (together with the brackish Etroplinae, these are the island's two native cichlid lineages, far removed from the great radiations of the African Rift lakes). When Sparks described inornatus the genus was poorly understood; he used the new species as a vehicle to discuss how variable its congeners were. Four years later, Melanie Stiassny and Sparks (2006) formally revised Ptychochromis, describing five further species and confirming inornatus as a valid, distinct member. The Catalog of Fishes lists no junior synonyms. The fish is sometimes attached to the catalogue name 'Grey Madagascar cichlid,' a descriptive label generated for databases rather than an established hobby name; in the aquarium literature it is known simply by its binomial.
Morphology
Ptychochromis inornatus is a moderately deep-bodied, laterally compressed cichlid reaching about 5 in in standard length — a small to mid-sized fish by cichlid standards. The dorsal fin carries 13 to 14 spines and 9 to 11 soft rays, the anal fin 3 spines and 8 to 9 soft rays, over 26 to 27 vertebrae. The defining feature is negative: unlike most of its congeners, inornatus shows no series of large dark blotches or bands along the lateral midline, and it is this overall plain, unmarked appearance — a grey to olive-brown ground — that gives the species its name. The understatement of the flanks is offset by the fins, which in life are a deep orangish-red. Sparks diagnosed the species on a suite of internal characters: the second pharyngobranchial tooth plate bears two rows of teeth, the uncinate process of the first epibranchial bone is robust (at least twice the diameter of the anterior arm) with a reduced angle between the arms, the supraoccipital crest has a truncate, rounded hind margin, and the anterior chest scales are embedded and reduced in size. There are modally ten gill rakers on the lower limb. As in the genus generally, the sexes are not strongly dimorphic in pattern; mature males tend to be the larger fish and ripe females noticeably rounder in the belly, but reliable separation outside breeding condition is difficult.
Habitat
The species is endemic to the Ankofia River basin and its tributaries in northwestern Madagascar, an area in the eastern part of the historical Mahajanga (Majunga) Province lying roughly between 14° and 16° south. Confirmed localities include the Anjingo River (the type locality), the wider Ankofia drainage, and Lac Andrapongy, a lake within the basin. These are tropical lowland-to-foothill waters. Sparks and later collectors found the fish in shallow, clear, moderate-to-swift-flowing river reaches, but also in deeper pools and tucked under overhanging banks and marginal vegetation — a flexible occupant of the available microhabitats rather than a specialist of any one. As with most Ptychochromis, the species tolerates a wide chemical envelope: FishBase classes it as both freshwater and brackish and benthopelagic, reflecting the genus's general hardiness and salt tolerance, though inornatus itself is a fish of inland rivers and lakes rather than estuaries. Documented depths are shallow — the stream and shoreline band of a few metres rather than open deep water. No detailed in-situ chemistry has been published for this species; by the standards of its lowland tropical range the water is warm, and aquarium practice for the genus settles on a near-neutral to mildly alkaline pH of roughly 7.0 to 8.0 and temperatures of about 72–82 °F.
Feeding
Ptychochromis inornatus is an omnivore. The original collections recorded a highly variable diet, and FishBase places the species at a trophic level near 3.3 — squarely that of a generalist forager that takes both animal and plant material rather than a dedicated piscivore or herbivore. In the moderate-to-swift river reaches and pools it inhabits, that translates to picking aquatic insects and their larvae, small crustaceans and other benthic invertebrates from the substrate and from among submerged roots and vegetation, supplemented by algae, detritus and whatever drifting matter the current delivers. Malagasy cichlids of this genus have robust pharyngeal jaws — the 'fold' that gives Ptychochromis its name refers to a lamellar structure on the gill arch — and are well equipped to crush hard-shelled prey such as snails when these are available. In its native rivers the species functions as one of the larger native predators of small invertebrates, a role increasingly contested by introduced fishes across Madagascar's fresh waters.
Mating
Reproductive behaviour in Ptychochromis inornatus has not been documented in the wild and is little reported in captivity, but the genus is consistent and the pattern is well established in its relatives. Ptychochromis are biparental substrate spawners that form pair bonds and defend a territory around a chosen spawning site. As pairing approaches, a male and female select and clean a hard surface — a flat rock, a slab, or the floor of a sheltered crevice — and the pair becomes increasingly intolerant of other fish near the nest. Courtship involves the usual cichlid repertoire of lateral displays, quivering and substrate-cleaning runs, with the fish often intensifying in colour as they come into condition; the orange-red fins of inornatus are presumably part of this signalling. Pairs are territorial and can be aggressive toward conspecifics and tankmates during spawning, so in confinement a compatible, well-matched pair with space to establish a defendable site is the key to a successful bond.
Breeding
No wild spawning of Ptychochromis inornatus has been described, and captive breeding records for this particular species are sparse; the account here is drawn from the consistent biology of the genus. Ptychochromis are open or sheltered substrate spawners: the female lays a sheet of adhesive eggs on a cleaned hard surface and both parents share guarding duties, the female tending and fanning the clutch while the male patrols the territory. Clutch sizes in congeneric Ptychochromis run to a few hundred eggs (genus-typical), and in the related Ptychochromis oligacanthus the larvae hatch after roughly eight to ten days, after which the free-swimming fry are led and guarded by both parents in a tight school. This biparental care — rather than the mouthbrooding seen in many African cichlids — is the rule throughout the Malagasy ptychochromines. Warmth, clean well-oxygenated water and conditioning on rich live and frozen foods are the usual triggers in captivity. Because the species is Endangered and genuinely rare in the trade, any aquarium breeding contributes directly to keeping a threatened lineage in cultivation.
In the aquarium
Ptychochromis inornatus is a rarely kept fish, encountered mostly through conservation-minded specialist channels rather than the general trade, but the genus has a reputation as forgiving and adaptable, and the husbandry mirrors that of its better-known relatives such as Ptychochromis oligacanthus and Ptychochromis grandidieri. A pair or small group needs a robust tank — on the order of 55 US gal or more for adults, with a longer footprint preferred so that fish can hold separate territories. The decor should echo the species' river home: a sand or fine-gravel substrate, a scatter of rounded rocks and flat stones to serve as spawning sites and territory markers, driftwood and roots, and open swimming lanes between cover. Because the fish handles a broad chemical range, water chemistry is undemanding — a near-neutral to mildly alkaline pH around 7.0 to 8.0, moderate hardness, and a temperature of roughly 72–82 °F suit it well; the genus's brackish tolerance means a little salt is harmless but not required for a freshwater population. Good filtration and current are appreciated given its preference for flowing, well-oxygenated water, along with regular water changes. Diet is easy: a varied menu of quality pellets, frozen and live foods (bloodworm, mysis, brine shrimp, the occasional snail) keeps the fish in colour and condition. The main caveat is temperament. Like most substrate-spawning cichlids, Ptychochromis become territorial and pugnacious when breeding, so tankmates should be robust, similarly sized fish that can stand their ground, and a spawning pair may need a tank to themselves. Sexing outside breeding condition is unreliable, which makes grow-out groups the usual route to forming a pair.
Conservation
The IUCN Red List assesses Ptychochromis inornatus as Endangered, under criterion B1ab(iii), assessed on 27 June 2016 by J.S. Sparks. The listing reflects a small, fragmented range confined to a single degraded river system. Nowhere is the species abundant within that restricted range, and the Ankofia and Anjingo basins are moderately to heavily disturbed throughout much of their course, with little original forest remaining. The small Bora Special Reserve preserves the last forested patch in the immediate region; tellingly, the species was found to be relatively more common in the small, forest-shaded Bemahavony River within the reserve than in the larger, more exposed river channels around it — a sign of how much it depends on intact riparian habitat. Lake Andrapongy, another population centre, is under high fishing pressure, with much of its basin converted to rice cultivation and several villages adding to the load. These pressures — deforestation, siltation, agricultural conversion, fishing, and the spread of introduced fishes — are the same forces that have pushed much of Madagascar's freshwater fish fauna toward extinction. The species is not evaluated under CITES. As a narrow-range endemic of a deteriorating watershed, Ptychochromis inornatus is a conservation priority among Malagasy cichlids, and ex-situ programmes aimed at the genus are part of the effort to keep these fish from disappearing entirely.