Ictalurus nazas, Avila-Treviño & Cardoza-Martínez & Alonzo-Rojo & Pérez-Rodríguez, 2025

Avila-Treviño, Edith, Cardoza-Martínez, Gabriel Fernando, Alonzo-Rojo, Fernando & Pérez-Rodríguez, Rodolfo, 2025, Ictalurus nazas sp. nov., a new species of North American catfish (Siluriformes, Ictaluridae) from Mexico, ZooKeys 1248, pp. 33-51 : 33-51

Ictalurus nazas sp. nov.

Fig. 5 , Tables 4 , 5

Type locality.

Ramos River, 1.12 km north of El Olote, Santiago Papasquiaro, Durango, Mexico.

Type materials.

Holotype. • UMSNH -2654 , adult, 302 mm SL, Ramos River 1.12 km north of El Olote , Santiago Papasquiaro, Durango, Mexico, endorheic drainage Ramos River; 25°14'13.2"N, - 105°27'0.4"W, collected on June 2, 2008 . Paratypes. • UMSNH -7266 (N = 1), El Olote , Santiago Papasquiaro, Durango, Mexico, endorheic drainage Ramos River; 25°13'17.04"N, - 105°26'37.79"W, collected on May 10, 2004.; • UMSNH -1642 (N = 3) river to the east of Santiago Papasquiaro , Durango, Mexico, endorheic drainage Ramos River; 25°2'26.12"N, - 105°24'54.67"W, collected on September 19, 2005; • CNPE-IBUNAM-17795 (N = 5) Nazas River, main body , Nazas, Durango, Mexico, endorheic drainage Nazas River; 25°12'57"N, - 104°10'25"W, collected on April 4, 2004; • CNPE-IBUNAM-17779 (N = 1) Dolores Hidalgo , Nazas, Durango, Mexico, endorheic drainage Nazas River; 25°15'59"N, - 104°05'24"W, collected on April 4, 2004; • CP-UJED-0018 (N = 1) Balneario “ Belem ” Peñón Blanco , Durango, Mexico, endorheic drainage Nazas River; 24°44'36"N, - 104°04'36"W, collected on September 18, 1989; • CPUJED-0001 (N = 4 El Ranchito , Peñón Blanco, Durango, Mexico, endorheic drainage Nazas River; 24°59'19"N, - 104°19'39"W, collected on August 5, 2015; • CPUJED-0002 (N = 2) Arroyo Covadonga , Nazas, Durango, Mexico, endorheic drainage Nazas River, 25°11'31"N, - 104°11'41"W, collected on December 13, 2022; • CPUJED-0003 (N = 1) Amoles , Nazas, Durango, Mexico, endorheic drainage Nazas River, 25°07'47"N, - 104°29'47"W, collected on December 1, 2022; • CPUJED-0004 (N = 4) Nuevo Covadonga , Peñón Blanco, Durango, Mexico, endorheic drainage Nazas River, 24°54'35"N, - 104°04'47"W; collected on May 22, 2023; • CPUJED-0005 (N = 1) El Ranchito , Peñón Blanco, Durango, Mexico, endorheic drainage Nazas River; 24°59'19"N, - 104°19'39"W, collected on May 21, 2023 .

Diagnosis.

Ictalurus nazas sp. nov. differs from I. pricei by the following combination of characters: 16–18, rarely 19, anal fin rays (vs. 19–24); shorter premaxillary barbel, reaching only to the opercle margin (vs. extending beyond the margin of the opercle); shorter base of anal fin, 5.0 times into the SL (vs. larger base, 4.4 times into the SL); shorter length of pectoral fin, 7.6 times into the SL (vs. larger pectoral fin, 6.4 times into the SL); shorter length of pelvic fin, 8.8 times into the SL (vs. larger pelvic fin, 7.9 times into the SL); lower number of posterior dentations, 5–8, rarely 9 and 10, (vs. higher number of dentations, 8–11, rarely 12–14 dentations) (Fig. 6 ); weaker development of dentations (vs. stronger development) (Fig. 6 ), and dentations concentrated in the apical part of the pectoral spine (vs. dentations extended from apical to median part of the pectoral spine) (Fig. 6 ).

In relation to other recognized species of Ictalurus (sensu Pérez-Rodríguez et al. 2023), Ictalurus nazas sp. nov. can be distinguished from its congeners, I. lupus (Miller et al. 2005) , I. dugesii ( Arce-H. et al. 2016), I. mexicanus ( Arce-H. et al. 2016), I. punctatus (Miller et al. 2005) , I. furcatus (Miller et al. 2005) , and I. balsanus (Mejía et al. 2013) , by presenting an anal fin base shorter than the head length, with 16 to 19 anal fin rays. Additionally, the premaxillary barbels do not extend beyond the posterior margin of the opercle (see Description for further details). Adult specimens of Ictalurus nazas sp. nov. also differ from most congeners, except I. dugesii , by exhibiting fewer and less developed posterior dentations on the pectoral spine, which are restricted to its apical portion.

Moreover, Ictalurus nazas sp. nov. can be diagnosed by the following characters: from I. punctatus by having a moderately forked caudal fin with a distal margin forming an “ U ” shape and fully rounded (vs. deeply forked caudal fin with a “ V ” shaped margin and pointed tips); from I. lupus , by having 7 to 9 (rarely 6 and 10) pectoral fin rays (vs. 9 to 10 rays); from I. mexicanus , by the presence of posterior dentations in the pectoral spine (vs. absence); from I. dugesii by presenting a blunt tip on the pectoral spine (vs. sharp tip); from I. furcatus by presenting fewer anal fin rays (16 to 19 vs. 28–38 rays), and from I. balsanus by presenting 17 to 19 caudal fin rays (vs. 22 rays).

Description.

Elongated body; large head, ventrally flattened, tapering anteriorly. Eyes small, diameter, 9.6 times into head the length, interorbital distance, 3.2. times into the head length. Terminal mouth position with eight barbels: four maxillary, two premaxillary, and two nasals. The premaxillary barbels do not reach the edge of the operculum.

Dorsal fin with 5 to 7, rarely 9 rays, its origin positioned at the midpoint of the pectoral fins. Pectoral fin length 8.4 times into the SL and contains 7 to 9 rays, though, on occasions, specimens may exhibit 6 or 10 rays. The pectoral spine features a series of 5 to 8 posterior dentations with weaker development; in rare cases, 9 or 10 dentations may be present. Pelvic fin is short, 9.5 times into the SL, with 7 to 8 rays, rarely 6 and 9; origin posterior to the base of the dorsal fin. Anal fin base shorter than head length, its length fitting 5.0 times into the SL; fin composed of 16 to 19 rays. Caudal peduncle short and moderately forked, with a rounded distal margin forming a “ U ” shape, with 17 to 19 rays.

Color. In life, the body is olive green, with a slightly darker pigmentation on the dorsal part of the head, fins, and premaxillary barbels. Ventral region, along with the maxillary and nasal barbels, appears noticeably lighter. The body features a few dark spots, while the caudal fin margin is distinctly black. In alcohol, the body takes on a gray hue, with the fins and ventral region significantly lighter. The fin margins remain black, and the premaxillary barbels appear darker than the maxillary and nasal barbels.

Habitat and ecology.

The species inhabits slow-moving waters with temperatures ranging from 17 to 22 ° C. It is generally found in areas with exposed bedrock slabs and crevices that provide refuge.

Distribution.

Ictalurus nazas sp. nov. is only known from the endorheic basin of the Nazas-Aguanaval System, including its main tributaries: the Rivers Peñón Blanco and Ramos (Fig. 7 ).

Etymology.

The specific epithet nazas is derived from the name of the basin in which the species is distributed and to which it is endemic.

Figures

Figure 5. Ictalurus nazas sp. nov. holotype, UMSNH - 2654, adult, SL 302 mm, Ramos River, 1.12 km north of El Olote, Santiago Papasquiaro, Durango, Mexico, endorheic drainage Ramos River.

Figure 6. View of the pectoral spine of Ictalurus species: A. I. nazas sp. nov., 33 mm. and B. I. pricei, 28 mm. Ictalurus nazas sp. nov. exhibits fewer posterior dentations, which are underdeveloped and can only be distinguished from the middle of the spine towards the apex.

Figure 7. Type locality of I. nazas sp. nov. Ramos River, 1.12 km north of El Olote, Santiago Papasquiaro, Durango, Mexico, endorheic drainage, Ramos River; 25 ° 14 ' 13.2 " N, - 105 ° 27 ' 0.4 " W.