Taxonomy & naming
Thorichthys panchovillai was described in 2017 by Luis Fernando Del Moral-Flores, Eduardo López-Segovia and Tatiana Hernández-Arellano, in the Revista Peruana de Biología, from the Río Almoloya near the village of Guivisia in the upper Río Coatzacoalcos basin of Oaxaca, Mexico (holotype CIFI-501; type-locality coordinates 16°57′N, 94°57′W). It honours José Doroteo Arango Arámbula (1878–1923), better known as Francisco Villa, or "Pancho Villa," described by the authors as a "historical, chief and fundamental pillar of the Mexican Revolution." The species is diagnosed by a combination of fin-ray and gill-raker counts (dorsal XVI, 8–9; anal VII, 6–7; pectoral I, 11–12; 11–12 gill rakers on the first arch), a weakly developed subopercular mark, and its distinctive sexual dimorphism. It is recognised as valid in Eschmeyer's Catalog of Fishes and by López-Segovia et al. (2020) and Fricke et al. (2024). A 2025 study (Mejía-Mojica and colleagues, in Zootaxa) examined the evolutionary history of this polymorphic Coatzacoalcos endemic, underscoring its standing as a distinct species within the genus.
Morphology
Thorichthys panchovillai is a typical deep-bodied, laterally compressed firemouth; the male holotype measured about 3 in standard length, placing the species in the same modest size class as its congeners (broadly comparable to the ~5.5 in SL of the related Thorichthys callolepis). The body is golden to grey-olive, overlaid with the rows of iridescent blue-green spangling characteristic of the genus on the flanks, cheeks and fins, with the usual reddish wash on the lower head and throat and a dark, light-ringed gill-cover ocellus for frontal display. The species' most notable feature is its sexual dimorphism: females in reproductive condition develop a prominent black blotch on the upper dorsal fin, between the fifth and sixth dorsal spines, which males do not show — an unusually clear sex marker for a firemouth. The original description also notes that the species is polymorphic, with variation in pattern across the populations of the Coatzacoalcos tributaries.
Habitat
The species is endemic to the upper Río Coatzacoalcos basin on the Atlantic slope of Mexico, in Oaxaca and Veracruz, where it occupies the river's tributaries — the type series came from the Río Almoloya near Guivisia. As with the other Coatzacoalcos-headwater firemouth, Thorichthys callolepis, it is a fish of clearer, flowing upland streams rather than still lowland margins, implying warm, well-oxygenated, generally hard and alkaline water draining the limestone uplands of the isthmus region. Its restriction to a single river system, and within it to the headwater tributaries, gives it a narrow natural range. Detailed in-situ chemistry is not published in the popular literature, but its biotope is that of the clear, current-swept Coatzacoalcos uplands.
Feeding
Like the rest of the genus, Thorichthys panchovillai is expected to be a benthic omnivore, foraging over the substrate of its stream habitat for small invertebrates, insect larvae, crustaceans and organic detritus, with algae grazed from rocks and surfaces. The genus's sifting and grubbing technique is applied to the firmer, current-swept bottoms of its headwater tributaries. FishBase places the genus at a trophic level around 3.3. Diet-specific field study for this newly described species is limited, so its feeding is described from the well-established genus pattern.
Mating
As a firemouth, Thorichthys panchovillai is a monogamous pair-spawner that uses the genus's frontal threat display to settle disputes and to court. The species' pronounced female-specific dorsal blotch suggests sex recognition plays a clear role in pairing. Pairs are expected to form after mutual display, then to select and clean a spawning site and defend a surrounding territory. Detailed field observations of courtship in this recently described species are not yet published, and its social behaviour is understood by analogy with its better-studied congeners, particularly the neighbouring Thorichthys callolepis of the same basin.
Breeding
Thorichthys panchovillai is a biparental open-substrate spawner, following the universal pattern of the genus: a pair cleans a hard surface or sheltered site, deposits a clutch of a few hundred eggs, and both parents guard the eggs and then escort the hatched larvae and free-swimming fry, moving the wrigglers between sheltered pits. The female's reproductive-state dorsal blotch is itself evidence of a defined breeding condition. Specific wild clutch counts and developmental data for this newly described species are not yet documented, so its breeding is described from the genus-typical biparental pattern shared with its relatives.
In the aquarium
As a firemouth described only in 2017, Thorichthys panchovillai is rare in the aquarium hobby and seldom encountered outside specialist Central-American-cichlid circles; published keeping experience is limited. Where it is kept, husbandry should follow that of the other Coatzacoalcos-headwater firemouth, Thorichthys callolepis: a pair needs a tank of roughly 55 US gal or more with a footprint near 47 in, aquascaped to recreate a clear-stream biotope with rounded rocks and cobbles, open sand, and brisk, well-oxygenated water movement.
Water should be warm but well-aerated and on the harder, alkaline side, reflecting its upland Coatzacoalcos streams: temperature about 75–82 °F and pH roughly 7.5–8.2, with medium-hard to hard water. Strong filtration and good flow support the oxygenation a headwater fish expects, and large, frequent partial water changes maintain the clean conditions the genus needs to avoid head-and-lateral-line erosion. Feeding should be a varied omnivore diet — quality sinking foods, frozen and live invertebrates, and some algae- or vegetable-based food.
Temperament is expected to follow the genus: relatively peaceful outside breeding and reliant on display, but territorial when spawning. Suitable tankmates are sturdy, even-tempered fish that tolerate cooler, flowing, oxygen-rich water. Because the species is so new to science and to the hobby, any keeper working with it should treat husbandry guidance as provisional and observe the fish closely.
Conservation
Thorichthys panchovillai has not yet been assessed by the IUCN Red List; Eschmeyer's Catalog of Fishes records its IUCN status as Not Assessed. Because it is a single-basin endemic confined to the headwater tributaries of the upper Río Coatzacoalcos — and, like its neighbour Thorichthys callolepis, apparently dependent on clean, flowing upland water — it is inherently exposed to localised habitat degradation, and the lack of a formal assessment means its conservation status is genuinely unknown. The Coatzacoalcos basin faces well-documented pressures, including a long history of petrochemical pollution in its lower reaches and habitat alteration, sedimentation and water extraction upstream. Targeted survey and a formal Red List assessment of this narrow-range, recently described firemouth would be valuable.