Plecos · waters

The rivers behind the fish

Plecos are creatures of specific water: the tannin-black drainage of the Rio Negro, the oxygen-rich torrents of the Guiana Shield where rheophilic species cling to bedrock, the cold clarity of an Andean foothill stream, the warm turbidity of the Amazon floodplain. Knowing where a species comes from — which river system, which flow regime, which water chemistry — is the foundation of keeping it well. Here are the 11 South & Central American freshwater systems that shaped 699 of the 989 species in this atlas.

Amazon lowlands

8 species

The great central floodplain — the várzea, igapós and main-stem shallows — where seasonally inundated forests and turbid white-water channels host an astonishing diversity of corys, from the ubiquitous bronze cory to pygmy midwater swimmers like Corydoras hastatus.

Rio Negro & blackwater tributaries

34 species

Tannin-stained, acidic and mineral-poor: the Rio Negro drains the ancient Guiana Shield and northern Amazon, producing some of the world's most colourless, tea-dark water. This is the homeland of Corydoras adolfoi, C. robineae, C. nijsseni and a parade of look-alike long-snouted species found nowhere else.

Orinoco basin

125 species

The Llanos floodplain and Andean piedmont rivers of Venezuela and Colombia give rise to a distinct cory fauna that includes the salt-and-pepper Corydoras habrosus, the peppered-effect C. metae, and — in coastal drainages — C. melanotaenia and C. venezuelanus.

Guiana Shield rivers

88 species

The coastal drainages and Essequibo-system rivers of Suriname, Guyana and French Guiana, fed by the ancient Shield's granitic highlands. Corydoras guianensis, C. filamentosus, C. melanistius and the endemic Brochis approuaguensis typify this corner of the continent — still comparatively under-collected by science.

Andean foothills clearwater (Napo · Ucayali · Madre de Dios)

94 species

Clear, fast-running foothill rivers spilling east off the Andes — the Napo, Ucayali, Pastaza and Madre de Dios — where cool, oxygen-rich water and gravel-bottomed shallows shelter Corydoras panda, C. trilineatus, C. arcuatus, C. loretoensis and the spotted elegans group.

Guaporé–Mamoré · upper Madeira

11 species

The Guaporé (Iténez) marks the Brazil–Bolivia border and drains into the Mamoré, forming the upper Madeira — a mosaic of warm, seasonally flooded lowland forest, sandy channels and shield streams. Sterba's cory (Corydoras sterbai) is the calling-card species; the basin also holds C. caudimaculatus, C. guapore, C. mamore and the enigmatic C. negro.

Tapajós · Tocantins–Araguaia clearwater

122 species

Vast clearwater rivers of the Brazilian Shield, their transparency a world apart from the turbid Amazon mainstream. The Tapajós–Juruena and Tocantins–Araguaia basins share a distinctive cory fauna: Corydoras haraldschultzi, the spotted Aspidoras tribe (albater, brunneus, poecilus), and the Xingu-centred C. caramater and Aspidoras azaghal.

Upper Paraná & Iguaçu

82 species

The highland headwaters of the Paraná system, above the great Itaipu dam on the Brazil–Paraguay–Argentina border, and the Iguaçu tributary that plunges over its namesake falls. Home to the aspidoras group (Aspidoras lakoi, A. fuscoguttatus), Corydoras flaveolus, C. diphyes, C. lacrimostigmata and C. ehrhardti.

Paraguay–Paraná · La Plata

65 species

The subtropical plains of the lower Paraguay and Paraná, converging in the wide, shallow estuary of the Río de la Plata. Brochis britskii dominates the upper Paraguay marshes; C. paleatus — the peppered cory, the species that introduced armoured catfishes to European aquaria in the 1870s — ranges through the whole temperate lower basin.

Rio São Francisco

41 species

An ancient, geographically isolated basin draining the Brazilian highland plateau north-east into the Atlantic. Its endemism runs deep: Corydoras costai, C. lymnades, C. multimaculatus and C. garbei live only here, alongside several narrow-range Aspidoras of the caatinga and cerrado.

Coastal south-east Brazil · Mata Atlântica

54 species

The short, rain-fed drainages of the Atlantic Forest coast — Paraíba do Sul, Ribeira de Iguape, and the Mata Atlântica river systems of Rio Grande do Sul. Scleromystax, the barbed armoured catfishes, is largely a Mata Atlântica endemic; S. barbatus and S. prionotos anchor this fauna, joined by Corydoras nattereri and the cave-associated S. kronei.

Widespread · multiple basins

290 species

Species whose documented ranges cross several major basins, or whose ecoregion data places them in habitats spanning more than one region. Includes wide-ranging forms like the bronze cory complex and species for which distributional data remains incomplete.

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