Taxonomy & naming
The Nautla cichlid is one of the oldest-named cichlids of Mexico: it was described by the Austrian ichthyologist Johann Jakob Heckel in 1840 as Heros deppii, on material collected by the German naturalist and collector Ferdinand Deppe during his travels in Mexico in the 1820s. The species passed through the usual succession of generic names for Middle American cichlids — Cichlasoma, Parapetenia, Nandopsis — before Sven Kullander's work fixed it in Herichthys, where FishBase and Eschmeyer's Catalog of Fishes retain it as a valid species. Unlike its molar-toothed northern relatives of the Pánuco springs, deppii was not transferred to the genus Nosferatu erected by De la Maza-Benignos and colleagues in 2015; it remains a true Herichthys, and indeed the southernmost member of the genus, occupying river basins in central Veracruz that lie south of the range of the rest of the group. Its type locality is the Nautla and Misantla river systems of the Atlantic slope of Veracruz.
Morphology
Herichthys deppii is a modest-sized cichlid, reaching about 4.5 in in total length, with the moderately deep, laterally compressed body typical of the genus and a fairly small, slightly subterminal mouth. It is a less heavily built fish than the snail-crushing Pánuco species, lacking their massive molariform pharyngeal pavement. Coloration is the genus pattern: an olive to brassy-grey ground, often overlaid with pearly or bluish flecking and a row of dark mid-lateral blotches, with a dark spot at the caudal base. In breeding condition the fish develops the contrasting pale-and-dark patterning of its relatives, the forward body lightening and dark fields strengthening on the rear flank. Sexual dimorphism is weak — males average slightly larger and may carry marginally longer fins — so venting is the most reliable way to sex the fish. Overall it is a comparatively plain, riverine cichlid rather than one of the spectacular breeding-coloured spring endemics of the genus's northern range.
Habitat
The Nautla cichlid is endemic to the Nautla and Misantla river basins of central Veracruz, on Mexico's Atlantic slope — short, independent coastal drainages that descend from the eastern Sierra Madre to the Gulf of Mexico. It occupies both fast-flowing river reaches over stony bottoms and slower, calmer stream stretches, a fish of clear to moderately turbid running water rather than of still springs or lakes. FishBase records a temperature around 79 °F and a pH up to about 7.4, indicating warmish, near-neutral to mildly alkaline conditions — softer and less strongly alkaline than the hard karstic springs of the Pánuco species. It is a benthopelagic inhabitant of the river channel, working the bottom and lower water column around rocks and cover. Its range, confined to these two small Veracruz basins, is geographically distinct from and well south of the Pánuco–Tamesí heartland of the rest of the genus.
Feeding
Herichthys deppii is a generalist omnivore of the riverbed, with a trophic level around 3.3. Lacking the heavy snail-crushing pharyngeal mill of its northern relatives, it forages over stony and sandy bottoms for a mixed diet of aquatic insect larvae and other invertebrates, algae, organic detritus and plant material, taking advantage of whatever the fast and slow reaches of its rivers offer. This dietary flexibility suits a fish of variable stream habitats, where food availability shifts between riffle and pool and with the seasons. In its river community it functions as a mid-level omnivorous forager rather than a specialised predator or molluscivore.
Mating
The Nautla cichlid is a monogamous, pair-bonding substrate spawner like the rest of Herichthys. Pairs form as fish come into condition and become territorial, claiming and defending a patch of streambed around a stone or other cover, with the strengthened breeding pattern serving as a courtship and threat display. In the seasonally variable rivers it inhabits, breeding is likely cued by the warmer, more stable part of the year rather than proceeding continuously as it does in the thermally constant springs of the genus's northern endemics. As in the tribe Herichthyini, both members of the pair hold the territory jointly, the female taking the larger role in direct egg and larval care and the male defending the perimeter.
Breeding
Herichthys deppii is a biparental substrate spawner. The pair cleans a firm surface — a flat stone or the wall of a small excavated pit on the riverbed — and the female lays an adhesive clutch of ovoid eggs onto it, after which both parents guard and fan the developing eggs and then shepherd the free-swimming fry in a tight school over the substrate. The female concentrates on the eggs and larvae while the male patrols and defends the wider territory; the parents continue to guard the mobile fry for some time after they leave the spawning site. As with most riverine Herichthys, clutches run to a few hundred eggs and the cycle follows the warm-season pattern of its variable stream environment. It is a hardy egg-layer that breeds along the lines of its better-known congeners.
In the aquarium
The Nautla cichlid is an uncommon fish in the hobby, kept mainly by Central American cichlid specialists rather than appearing in general trade, but it is among the more manageable members of its genus thanks to its modest size and riverine adaptability. A pair can be kept in an aquarium of around 65–80 US gal, longer rather than taller, furnished with a sand or fine-gravel bottom, smooth rockwork and wood arranged into caves and broken sightlines, and some current to echo its flowing-water origins.
Water chemistry should be hard-ish and neutral to mildly alkaline — this is not a soft, acidic blackwater fish — but deppii is less exacting about high pH and hardness than the karstic-spring endemics of its genus, its wild waters running near neutral (pH to about 7.4) and warm (around 79 °F). Good filtration, oxygenation and moderate flow reproduce its river habitat. It is an unfussy feeder that accepts standard aquarium foods, taking a varied omnivorous diet of prepared, frozen and occasional vegetable foods readily. Tankmates should be robust, similarly sized Central Americans able to handle a territorial pair; as with all Herichthys, a spawning pair becomes assertive and will not tolerate crowding, so it is best regarded as a robust-community to species-tank fish rather than a gentle community cichlid. Its smaller size and forgiving requirements make it one of the more accessible entry points into the genus.
Conservation
Herichthys deppii is assessed by the IUCN Red List as Least Concern (assessed 18 September 2018). The basis is that, although restricted to the Nautla and Misantla basins, it remains reasonably widespread and abundant within those drainages and is not subject to evidence of a steep decline. This relatively secure status sets it apart from the narrow-range spring endemics of its genus's northern range (such as minckleyi of Cuatro Ciénegas or the Endangered Río Verde snail-eaters), which are far more exposed. That security is not unconditional, however: the short Veracruz coastal rivers it occupies face the familiar pressures of habitat alteration, water extraction, agricultural and urban pollution, and introduced fishes, and a species confined to just two small basins has limited room to absorb sustained degradation. For now, though, the Nautla cichlid is one of the more comfortably placed members of Herichthys.