Pseudohemiodon apithanos Isbrücker & Nijssen 1978

Provenzano-Rizzi, Francisco, Argüello, Pablo & Barriga-Salazar, Ramiro, 2022, The genus Pseudohemiodon (Siluriformes, Loricariidae) in Ecuador, with the description of a new species, Zootaxa 5129 (1), pp. 77-91 : 82-85

Pseudohemiodon apithanos Isbrücker & Nijssen 1978

Figures 3 , 4 , 5 , Table 2

Pseudohemiodon apithanos Isbrücker & Nijssen 1978:195–202 , fig. 6–8. Type locality: Ecuador, Prov. Napo, Rio Conejo, a tributary of Rio San Miguel, vicinity of Santa Cecilia , 00° 06”N, 76°51”W, upper Rio Amazonas system.

Pseudohemiodon apithanos Isbrücker 1980:121 , Burgess 1989:444, Isbrücker 2001:32, Isbrücker 2002:28, Ferraris in Reis, et al. 2003:340, Ferraris 2007:288, Rojas-Molina, et al. 2019:9.

Pseudohemiodon laticeps (not Regan 1904) Isbrücker & Nijssen 1978: 200–203, fig. 9, Pastaza River, Ecuador.

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Material examined: All from Ecuador, Orellana Province: MEPN 15125, 173.9 mm SL, Confluence Pañacocha and Napo Rivers, approx. 00°26’55”S 76°04’18”W, 07 Jan. 1998, R. Barriga & D. Stewart. Pastaza Province: MEPN 8980, 139.3 mm SL, Lliquino River near Villano oil well, Napo River system, 01°27’36”S 77°26’56”W, 27 May 1999, R. Barriga. MEPN 10508 , 3 , 189.0– 198.2 mm SL, Cotapaza River , tributary of Pastaza River, approx. 01°54’23”S 77°31’37”W, Oct. 1963, P. Mena. MEPN 10578 , 3 , 170.2 – 198.2 mm SL, Chicherota, Bobonaza River , tributary of Pastaza River, 02°25’06”S 76°38’38”W, Dec. 1949, R. Olalla. MEPN 13395, 158.9 mm SL, Cononaco River , near Bameno community, Napo River system, 01°17’50”S 76°09’13”W, 25 Jan. 2014, R. Barriga. MEPN 15112 , 24.3 mm SL, Tiguino River No. 2, 4 km from Pozo de Petrocanada , Cachiyacu No. 2, Napo River system, 01°10’12”S 76°55’49”W, 11 Feb. 1990, R. Barriga. MEPN 15176 , 49.2 mm SL, Tiguino River N ° 3, below the water intake, 01°11’28”S 76°55’49”W, 02 Feb.1990, R. Barriga. MEPN 18373 , 12 , 62.4–76.9 mm SL, Tiguino River No. 3, 150 m from Pozo de Petrocanada , Cachiyacu No. 1, Napo River system, 01°11’27”S 76°55’33”W, 08 Feb. 1990, R. Barriga. MEPN 18374 , 4 , 66.3–97.5 mm SL, Tiguino River No. 2, 4 km from Pozo de Petrocanada , Cachiyacu No. 2, Napo River system, 01°10’12”S 76°55’49”W, 11 Feb. 1990, R. Barriga. MEPN 19581 , 2 , 171.5 – 173.3 mm SL, Tigrillo River , tributary of Conambo River , near Pozo Tigrillo, Tigre River system, 01°56’29”S 76°40’06”W, 14 May 1989, R. Barriga. Sucumbíos Province: MEPN 18375, 175.9 mm SL, Aguarico River , near commune Duvuno, Napo River system, 00°01’20”S 77°06’23”W, 27 Apr. 1995, R. Barriga.

The identity of specimens of P. apithanos sized circa 115 mm SL have no doubt, because they have the striking and easily distinguishable color pattern diagnostic for the species as shown by Isbrücker & Nijssen (1978) ( Fig. 3 ). Additionally, they have a different head contour, in dorsal view, when compared with P. almendarizi , and P. lamina ( Fig. 3 ). The identification of specimens larger than 170 mm SL (large morphotype) could have some degree of difficulty. The largest specimens (> 180 mm SL) don’t have transverse dark bands on the caudal peduncle ( Fig. 4a ). The belly is covered completely with plates ( Fig. 5a ), and the head and body are wider with differently shape when are compared with the small specimens of P. apithanos ( Figs. 3b , 4a, b ). They don’t have small plates in front of gill openings, characteristic of P. lamina ( Fig. 5 ). The larger specimens match with the figure offered by Isbrücker & Nijssen (1978: fig 9) as P. laticeps from Ecuador. Some of the specimens analyzed here come from the same locality as those of Isbrücker & Nijssen (op. cit.). Also, the morphometric and meristic data for P. laticeps offered by Isbrücker & Nijssen (op cit) shows little or no differences when compared with our largest specimens.

The comparative analysis indicates these largest specimens are P. apithanos . This conclusion is supported by the following. 1) Changes in the color pattern of P. apithanos were indicated by Isbrücker & Nijssen (1978) in the original description of P. apithanos , where the color of the anterior body region differs among the holotype and paratypes, and apparently, the holotype has a wider body than the small sized paratypes ( Isbrücker & Nijssen 1978: figs 6, 7). In the MEPN Fish Collection, some specimens larger than 150.0 mm SL have four or five transverse, dark bands on the caudal peduncle, and the head and body are wider in the largest ones ( Fig. 4b ). These larger specimens were compared with the image of P. laticeps, BMNH 1895.5.17.113, lectotype, from the ACSI images database ( Morris et al. 2006). The difference in head contours in dorsal and ventral views is obvious. The lateral margins of the head in the lectotype are slightly concave near the snout tip; but in our specimens the lateral margins of head are straight ( Figs. 4 , 5 ). This difference in head contour is weakly or not evident in the original description figure of P laticeps Regan (1904 : pl. XX, figs 1, 1a). Finally, we obtained photos of P. laticeps , of recently preserved specimens ( MCP 9308), which shows a narrower head and body in dorsal view compared with our specimens ( Figs. 4 , 5 ).

Thus, despite the overlap of morphometric and meristic data, differences in head and body shape between large sized P apithanos and P. laticeps are detectable ( Figs 4–6 ), and there are differences in the presence of transverse dark bands on caudal peduncle. This indicates that large specimens (> 150.0 mm SL) captured in eastern Ecuador, with two to five transverse dark bands on the caudal peduncle (or without bands), wider bodies (> 24% SL), and without bony plates in front of branchial opening correspond to large specimens of P. apithanos . There’s a chance, that transverse bands could have faded or been lost by preservation. The morphometric data of analyzed specimens is offered in Table 2 . In specimens between 62.4–97.5 mm SL counts are: plates in mid-lateral series 31–32, mode 31; coalescent plates (double keel) 15–16, mode 15; posterior plates (single keel) 15–17, mode 16; thoracic plates (between posterior end of pectoral-fin base and origin of pelvic-fin base) seven to nine, mode eight. Premaxillary teeth 2/3–3/5, mode 3/3; dentary teeth 2/6–7/7, mode 5/6. Dorsal-fin rays i,6; pectoral-fin rays i,6; pelvic-fin rays i,5; anal-fin rays i,5; and caudal-fin rays i,10,i. In specimens between 158.9–198.2 mm SL counts are: plates in mid- lateral series 30–32, mode 31; coalescent plates (double keel) 15–16, mode 15; posterior plates (single keel) 14–17, mode 16; thoracic plates (between posterior end of pectoral-fin base and origin of pelvic-fin base) six to eight, mode eight. Premaxillary teeth 3/5–6/7, mode 5/6; dentary teeth 6/8–8/9, mode 8/8. Dorsal-fin rays i,6; pectoral-fin rays i,6; pelvic-fin rays i,5; anal-fin rays i,5; and caudal-fin rays i,10,i.

Geographical distribution: The specimens come from tributaries of the Amazon River basin, in the Napo , Pastaza and Tigre rivers systems ( Fig. 6 ).

Figures

FIGURE 3. a) P. almendarizi, MEPN 17903, 87.9 mm SL, holotype. b) P. apithanos, MEPN 18374, 97.5 mm SL. c) P. lamina, MEPN 15095, 101.9 mm SL. d) P. laticeps, MCP 9308, 126.1 mm SL. Dorsal views, scale bar 1 cm. Photos a), b) and c) by P. Argüello; d) by B. Calegari.

FIGURE 4. a) P. apithanos, MEPN 10578, 198.2 mm SL. b) P. apithanos, MEPN 19581, 171.6 mm SL. c) P. lamina MEPN 16771, 168.9 mm SL. d) P. laticeps MCP 9308, 126.1 mm SL. Dorsal views, scale bar 1 cm. Photos a), b) and c) by P. Argüello; d) by B. Calegari.

FIGURE 5. a) P. apithanos, MEPN 19581, 171.6 mm SL. b) P. lamina, MEPN 16771, 168.9 mm SL. c) P. laticeps, MCP 9308, 126.1 mm SL. Ventral views, head, mouth and abdomen cover, detail. Scale bar 1 cm. Photos a) and b) by P. Argüello; c) by B. Calegari.

FIGURE 6. Map of Ecuador showing the geographic distribution of Pseudohemiodon species. P. almendarizi, red star, type locality, P. apithanos, yellow triangles, P. lamina, black circles. Some symbols may represent more than one lot.