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Guillermo Terán (1)

There is at present (2010) nine species in this genera and they used to all be in the Pimelodidae genus. Description: Dorsal soft rays (total): 7; Anal soft rays: 14 - 18; Vertebrae: 47. Heptapterus mandimbusu can be diagnosed from its congeners by having a unique colouration pattern consisting of aggregated melanophores scattered on dorsal and lateral surfaces of body, forming conspicuous blotches of variable size (vs. this colour pattern absent in other congeners). Heptapterus bleekeri, H. fissipinnis, H. multiradiatus, H. mustelinus, H. qenqo, H. stewarti, H. sympterigium and H. tapanahoniensis possess a uniform earth-brown coloration pattern (with some irregular markings on head and sometimes indistinct on back in H. bleekeri); while H. mbya has grayish and H. ornaticeps has blackish uniform coloration pattern. It differs from other congeners in Argentinean basins by having longer interdorsal distance (13.8-18.9 % SL vs. 3.1-5.0 % SL in H. mustelinus, 9.5-13.2 % SL in H. qenqo, and 5.8-8.3 % SL in H. mbya), 47 free vertebrae (vs. 51- 52 in H. qenqo; 51-53 in H. mbya), caudal peduncle depth is shallower than in H. qenqo (13.8-19.3 % SL vs. 19.8-25.4 % SL), and the adipose-fin base is shorter than in H. mbya (33.8-41.5 % SL vs. 47.4-58.55 % SL). It can be further distinguished from H. mustelinus by having shorter distance between the anal-fin origin and hypural plate (32.9-39.1 % SL vs. 39.6-45.7 % SL), a longer distance between the origins of pelvic and pectoral fins (24.5-28.1 % SL vs. 20.4-24.2 % SL), a shorter adipose-fin base (33.8-41.5 % SL vs. 51.5-59.6 % SL), a shorter anal-fin base (15.7-20.9 % SL vs. 20.9-28.0 % SL), a smaller orbital diameter (10.3-14.1 % HL vs. 15.0-19.9 % HL), and a lower number of anal-fin rays (14-18 vs 18-22). It differs from H. stewarti and H. sympterygium by its dorsal fin never reaching the adipose fin; from H. bleekeri, H. fissipinnis, H. multiradiatus, H. ornaticeps, H. stewarti, and H. sympterygium by having lower number of anal-fin rays (14-18 vs. 20-22 in H. bleekeri; 23 in H. fissipinnis; 38-46 in H. multiradiatus; 19; 30 in H. ornaticeps, and 22-29 in H. stewarti); from H. bleekeri, H. fissipinnis, H. multiradiatus, H. stewarti, H. sympterigium, and H. ornaticeps by the shorter maxillary barbel length that never reaches the pectoral fin, even in small juveniles; and from H. tapanahoniensis by the higher number of vertebrae (47 vs. 43) and branchiostegal rays (8-9 vs. 7) and the adipose fin confluent with the caudal fin (vs. separated). The monospecific genus Acentronichthys Eigenmann & Eigenmann, probably allied to Heptapterus due to the share of an elongated body and the adipose fin confluent to caudal fin, can be differentiated from Heptapterus mandimbusu by having caudal fin deeply forked (vs. distal profile of caudal fin slanted). Habitat: Occurs in stream at the type locality with clear water, current velocity, and structure consisting of sequences of pools of 1 to 1.5 meters and shallow riffles, surrounded by native vegetation. Aquarium Care: Not usually kept in aquaria but there is a report that H. leptos was kept on a soft substrate with subdued lighting as they are quite secretive. Diet: Most prepared foods but prefers live.

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Heptapteridae

South America: Uruguay River Basin in Misiones, Northeastern Argentina. Type locality: Melo stream, Uruguay River basin, Misiones, Argentina, 27°25'2.67"S, 54°42'7.93"W.

17.5cm. (7ins)

18-24°C (63-75°F)

6.5-7.2.

Aguilera, G., M. Benitez, G.E. Terán, F. Alonso & J.M. Mirande (2017): A new species of Heptapterus Bleeker 1858 (Siluriformes, Heptapteridae) from the Uruguay River Basin in Misiones, Northeastern Argentina. Zootaxa 4299 (4): 572-580.
Peces Criollos. Freshwater Fishes of Argentina.
Froese, R. and D. Pauly. Editors. 2019. FishBase. World Wide Web electronic publication. www.fishbase.org, ( 12/2019 ).