SCOTCAT.COM  

Shibatta et al. 2026 (3)

Description: Megalonema tinga is distinguished from M. xanthum, M. amaxanthum, and M. orixanthum by having a non-elongated pelvic fin and basipterygium (vs. elongated). It can be separated from M. pauciradiatum by the presence of 11 or 12 anal-fin rays (vs. 9). Megalonema tinga presents 6 to 8 gill rakers on the first ceratobranchial, a lower number than M. platanum (9 to 11) and M. psammium (10 or 11). In comparison with M. platycephalum, M. tinga shows a larger eye diameter (14.7–25.0% vs. 11.3–13.1% of SL), a shorter dorsal-fin base length (11.7–13.1% vs. 13.7–15.4% of SL), and a shorter adipose-fin base length (20.3–26.4% vs. 26.0–28.5% of SL). On average, it is further distinguished from M. platanum by a larger eye diameter (mean 20.0 ± 2.8% vs. 16.5 ± 2.8% of HL) and a smaller body depth (17.3 ± 1.1% vs. 19.8 ± 1.7% of SL), (Shibatta et al. 2026). Habitat: Widely distributed in the upper Paraná River basin. The presence in Argentina, in the lower Paraná River basin, revealed by molecular analysis, may be a consequence of the absence of a current geographic barrier. This species occurs in the middle Tibagi River, a region characterised by high topography and steep slopes (locally known as Serra do Cadeado; Maack, 2002). In this area, the river flows through deep canyons with rocky substrates and high-energy rapids. However, the new species was primarily associated with sandy substrates in backwaters and depositional zones. This psammophilous behavior suggests a specialized niche within the main river channel (Shibatta et al. 2026). Colouration in alcohol: Head and trunk dorsal region light yellow ochre; trunk becoming paler ventrally. Dorsal snout with dark brown longitudinal stripes, slightly concave, one laterally and one medially to the anterior and posterior nares. Short dark brown stripe posterior to maxillary barbel origin. Pectoral and pelvic fins translucent light ochre; dorsal fin translucent light ochre with melanocytes dispersed posteriorly; caudal fin dorsal lobe base with a faint dark brown spot; ventral lobe membranes with melanocytes (Shibatta et al. 2026). Aquarium Care: Provide a tank of at least 4ft x 2ft x 2ft with a medium water flow and weekly water changes. Diet: In the aquaria it will accept sinking pellets and most types of worms and shelfish. Etymology: The specific epithet tinga comes from the old Tupi, the classical Brazilian indigenous language, and means “white” (Navarro, 2013), alluding to the species’ whitish colouration. It is treated here as a noun in apposition. Remarks: The addition of this new species takes us up to six Megalonema genera described now (2026).

None

None

Pimelodidae

South America: Widely distributed in the upper Paraná River basin. Type locality: Middle Tibagi River.

25.0cm. (10ins)

22-27°C (71-81°F)

6.0-7.2.

Fish in the News 2026.
Shibatta OA, Souza-Filho HS de, Souza-Shibatta L. Cryptic lineages in Neotropical freshwaters: an integrative approach reveals a new species of Megalonema (Siluriformes: Pimelodidae) from the upper Paraná River basin. Neotropical Ichthyology, 2026;24(3):e260052