Taxonomy & naming
The white snail cichlid was described in 2013 by Mauricio De la Maza-Benignos and María de Lourdes Lozano-Vilano, on material from the Río Gallinas drainage — including the Río Tamasopo and the Ojo Frío and Agua Buena springs — upriver of the Tamul waterfall in San Luis Potosí, Mexico. The authors originally placed it in Herichthys; two years later, in their 2015 Hydrobiologia phylogeography of the genus, De la Maza-Benignos and colleagues erected the genus Nosferatu for the molar-toothed snail-eaters of the southern Pánuco (the 'labridens species group') and moved pame into it. The new genus is named for the dark vertical bar these fish raise in breeding colour, likened to F. W. Murnau's 1922 silent-film vampire. The split is contested — FishBase and Eschmeyer's Catalog of Fishes retain the fish as Herichthys pame, and the Catalog explicitly notes the Nosferatu combination while keeping Herichthys as the valid genus — so Herichthys pame and Herichthys pame denote the same animal. The species is closely tied to, and was long confused with, the larger Tamasopo-system snail-eater Nosferatu steindachneri, from which it differs in size, dentition and colour; the two occur in the same upper-Gallinas waters.
Morphology
Herichthys pame is one of the smaller members of its genus, reaching only about 4.5 in in standard length. It is a moderately deep-bodied, laterally compressed cichlid with a small, slightly subterminal mouth and the steep forehead typical of the group. Its defining feature, like that of its relatives, is internal: a stout lower pharyngeal plate paved with rounded molariform teeth for crushing snails. The body in non-breeding fish is a pale, often whitish to silvery-tan ground — the source of the 'white snail-eater' name — usually marked with a row of dark mid-lateral blotches and a dark spot at the caudal base. In breeding condition the fish raises the dark vertical bar (or paired dark fields) that the genus Nosferatu is named for, contrasting with the pale flanks; unlike the canary-yellow Nosferatu labridens, pame does not develop a strongly yellow breeding ground colour, which is one of the features the describers used to separate the two. Sexual dimorphism is weak: males grow a little larger, and the sexes are most reliably distinguished by venting.
Habitat
The white snail cichlid is a narrow-range endemic of the upper Río Gallinas system in San Luis Potosí, on Mexico's Atlantic slope, within the Pánuco basin. It occurs above the spectacular Tamul cascade in the Ríos Gallinas and Tamasopo and their associated springs (Ojo Frío, Agua Buena), recorded across five municipalities of the state. These are clear, hard, strongly alkaline waters — FishBase gives a pH range of 7.8–8.3 — running over sand, gravel, rock and travertine in spring-fed streams and pools at moderate elevation. The fish is a benthic, shallow-water inhabitant that works the bottom around stones and aquatic vegetation. Its distribution lies just upstream of, and largely separate from, the Río Verde spring system that holds Nosferatu labridens and Nosferatu bartoni, the Tamul waterfall and the valley's geography keeping the snail-eater faunas of the two systems distinct.
Feeding
As its common name advertises, Herichthys pame is a snail-eater. Its molariform pharyngeal mill crushes the hard-shelled gastropods of the upper Gallinas, and dietary accounts describe it as a benthic feeder taking snails together with detritus and filamentous algae, with a trophic level around 3.3 — slightly lower than the more piscivorous Nosferatu steindachneri it shares the system with. It is therefore best understood as a benthic molluscivore-omnivore: a fish that grazes and grinds along the bottom, exploiting snails as a key resource but supplementing them with algae, organic matter and small invertebrates. The co-occurrence of pame and the larger, more predatory steindachneri in the same waters is another instance of the trophic partitioning that runs through the whole Nosferatu radiation of the Pánuco springs.
Mating
Herichthys pame is a monogamous, pair-bonding substrate spawner like the rest of its genus. Pairs form as fish come into condition, claim a patch of the streambed around a stone or other cover, and defend it against conspecifics and other fishes, the dark breeding bar doubling as a courtship and threat signal. Because the spring-fed Gallinas headwaters are thermally stable, pairs can come into breeding condition through much of the year rather than on a strict seasonal trigger. As in the tribe Herichthyini generally, both members of the pair hold the territory jointly, the female taking the larger role in direct egg and larval care and the male patrolling and defending the perimeter.
Breeding
Breeding in the white snail cichlid follows the biparental substrate-spawning pattern of its genus, though it has been less documented than that of its showier relatives. The pair cleans a firm surface — a flat stone or the wall of a small excavated pit — and the female deposits an adhesive clutch of ovoid eggs onto it, after which both parents guard and fan the eggs and then escort the free-swimming fry in a school over the substrate. As a smaller species, pame produces correspondingly smaller clutches than the larger members of the group, but the care pattern is the same: female-led tending of eggs and larvae with the male defending the wider territory. The stable spring environment allows reproduction to proceed across much of the year. It is an egg-layer, but with no large captive following its breeding has been recorded mainly in passing rather than studied in detail.
In the aquarium
Herichthys pame is rare in the aquarium hobby — a recently described, small-range Mexican endemic kept almost exclusively by Central American cichlid specialists rather than appearing in general trade. The husbandry that suits its larger relatives applies, scaled to a smaller fish: a pair can be kept in a tank of around 55–80 US gal, longer rather than taller, furnished with a fine sand bottom it can sift, plus rock and wood arranged into caves and broken sightlines to give a spawning pair structure and to temper aggression.
The critical requirement is water chemistry. This is a hard-water, strongly alkaline species from clear, mineral-rich spring streams, and it does best at pH well above neutral (its wild waters run pH 7.8–8.3) with high hardness; soft, acidic water is wrong for it. A keeping temperature in the mid-20s °C with strong filtration and good oxygenation reproduces its clear, flowing spring habitat. It accepts standard foods but its molluscivorous nature should be honoured — snails are an ideal and natural item, alongside a varied carnivore-leaning diet with some algal and vegetable content. Tankmates should be robust, similarly sized fish; as a small but territorial cichlid it is not a community fish and a spawning pair will hold its corner firmly. Because it is so seldom kept, anyone maintaining it is effectively helping conserve a tiny-range endemic, and care should reflect that.
Conservation
Herichthys pame has not yet been formally evaluated by the IUCN Red List — its FishBase record lists it as Not Evaluated — which reflects how recently it was described (2013) rather than any evidence of security. As a single-system endemic of the upper Río Gallinas and Tamasopo above the Tamul cascade, it is exposed to exactly the pressures that have driven its relatives in the same valley into threatened categories: water extraction and diversion for agriculture, tourism and recreational pressure on the spring systems, pollution from domestic and agricultural runoff, and the spread of introduced and translocated fishes through the Pánuco headwaters. Its larger congener Nosferatu steindachneri, which shares the same waters, is listed as Endangered, and the neighbouring Río Verde endemics Nosferatu bartoni and Nosferatu labridens are likewise Endangered — so the white snail cichlid's tiny range should be regarded as inherently vulnerable, and a formal assessment is overdue.