Panaqolus orcesi, Provenzano-Rizzi & Barriga-Salazar & Stewart, 2024

Provenzano-Rizzi, Francisco, Barriga-Salazar, Ramiro & Stewart, Donald J., 2024, Two new species of the armored catfish genus Panaqolus (Siluriformes, Loricariidae) from the Ecuadorian Amazon, Zootaxa 5463 (1), pp. 112-126 : 114-120

Panaqolus orcesi , new species urn:lsid:zoobank.org:act:C6918B6A-5879-45B7-8DC1-AB0AA772A4FB

( Figs. 1 , 2a and 3a ; Tab. 1 )

Holotype. MEPN-I 19492, 180.6 mm SL, Ecuadorian Amazon, Orellana Province, Napo River basin , Quebrada La Cascada , Tiputini River tributary, approx. 00°50’03” S, 75°33’58” W, 190 meters above sea level (masl), 26 June 2006, R. Barriga, RBS06-12.

Paratypes. Two specimens from Ecuadorian Amazon, Orellana Province, Napo River basin: MEPN-I 19493, 170.9 mm SL, Rio Mengo Garita , 100 m upstream from bridge on Yasuni River , approx. 00°50’03” S, 76°20’42” W, 250 masl, 20–22 April 2005, R. Barriga, T. Caiza & J. Nenhimo, RBS05-08. MEPN-I 19494, 136.5 mm SL; Tiputini River , 1 km upstream from Campamento Politécnica, approx. 00°37´20” S, 76°30´25” W, 236 masl, 17 June 2007, R. Barriga & J. Silva, RBS07-15 .

Diagnosis. Panaqolus orcesi can be distinguished from all congeners, except P. albomaculatus , P. nix , and P. pantostiktos by base color of head, body, and fins uniformly grey, brown, or black, with light (cream, yellow or gold) dots vs. head, body, and fins with light or dark bars, bands, stripes, or saddles contrasting with the base color, never with light dots or rounded blotches. Panaqolus orcesi can be distinguished from P. albomaculatus by having more dentary teeth (5–7 vs. 3–5), having distal tips of the dentaries converging to form an acute angle vs. dentaries nearly parallel, and by reaching larger sizes (maximum standard length 180.6 mm vs. 90.5 mm). Panaqolus orcesi is further distinguished from P. nix by shorter inter-dorsal distance (12.1–12.7% SL vs. 13.7–19.4% SL), shorter abdominal length (23.0–25.3% SL vs. 29.5–34.9% SL), longer dorsal-fin base length (33.1–35.0% SL vs. 20.5–28.8% SL), longer dorsal- and pectoral-fin spines (34.0–34.1% SL vs. 26.2–32.5% SL and 35.8–37.4% SL vs. 29.5–34.9% SL, respectively), a deeper caudal peduncle (11.8–12.7% SL vs. 9.3–11.4% SL), longer snout length (68.5–70.3% HL vs. 49.7–63.7% HL), larger orbital diameter (17.1–18.3% HL vs. 12.5–16.8% HL), and apparently reaching greater sizes (maximum standard length 180.6 mm vs. 112.2 mm). Panaqolus orcesi is distinguished from P. pantostiktos by its wider interorbital distance (44.5–45.8% HL vs. 40.2–43.7% HL), longer snout length (68.5–70.3% HL vs. 62.7–68.9% HL), and longer inter-dorsal distance (12.1–12.7% SL vs. 10.3–12.0% SL) ( Fig. 4a–c ); P. orcesi also appears to have a shorter dorsal-fin spine (34.0–34.1% SL vs. 35.2–38.4% SL), but due to some broken spines, data were insufficient for a statistical test. Further distinguished from P. pantostiktos by having smaller average mid-lateral dot sizes for a given size individual ( Fig. 5a ), and by having higher average number of dots on dorsal surface of pectoral fin ( Fig. 5b ). Relatively smaller dot sizes and higher dot densities in P. orcesi are also evident in Figs. 1–3 and 6 .

Description. Morphometric data in Tab. 1 . Medium-sized loricariid with standard length of measured specimens up to 180.6 mm SL. Body robust, quite depressed anteriorly and compressed posteriorly ( Fig. 1 ). Dorsal profile of head from snout tip to anterior border of orbit straight and inclined with slope of approximately 45 degrees, then gently convex or straight to dorsal-fin origin and descending straight or gently convex to origin of first procurrent caudal-fin ray. Orbit dorsal margin and posterior tip of supraoccipital slightly elevated. Greatest body depth near dorsal-fin origin. Caudal peduncle compressed, ovoid in cross-section, deep and robust ( Fig. 1 ). Ventral profile of head and body flat ( Fig. 1 ).

In dorsal view, body widest near dorsal-fin origin, narrowing posteriorly. Eye dorsolaterally placed; orbit diameter 17.1–18.3% HL. Interorbital width 44.5–45.8% HL, almost flat or slightly concave near eyes. Nares small and ovoid, slightly longer than wide ( Fig. 1 ).

Oral disk longitudinally elliptical, maxillary barbels developed and evident; lips papillose with smooth borders; lower lip larger and more developed than upper ( Fig. 2a ). Teeth spoon-shaped and unicuspid or with very small lateral cusp. Premaxillary teeth 4–6 per ramus (mode 5); dentary teeth 5–7 per ramus (mode 6). Premaxillary and dentary tooth rows both meet distally at an angle of approximately 45° ( Fig. 2a ).

Head and body covered with plates. Ventral surface of head and belly covered with small and irregularly shaped plates, with small or very small odontodes. In the relatively large specimens available, lateral plates of body have enlarged odontodes, like spines ( Fig 1 ). Posterior to anal-fin origin, the developed spines on lateral plates are arranged in five longitudinal rows, which seem to form keels ( Fig 1 ); 24–25 lateral plates. Supraoccipital bordered posteriorly by 2 plates on each side; 9–11 plates along dorsal-fin base; 5–7 plates between dorsal and adipose fins; 3–5 plates between adipose-fin and caudal-fin origin; 3 plates along anal-fin base; 9–12 plates between last anal-fin ray and caudal-fin origin. Hypertrophied cheek odontodes 15–22, increasing in size posteriorly; longest odontodes surpass pectoral-fin origin; odontode tips curved.

Dorsal-fin I,7 with small anterior triangular spinelet; pectoral-fin I,6; pelvic-fin I,5; anal-fin i,4; caudal-fin i,14,i. Dorsal-fin origin anterior to pelvic-fin origin; when adpressed overlaps adipose-fin origin; dorsal-fin spine lock functional; last ray of dorsal-fin without posterior membrane. Pectoral-fin origin anterior to posterior margin of orbit; when adpressed, pectoral spine almost surpasses half of pelvic-fin spine; pectoral-fin spine robust, dorsal surface of spine with developed odontodes, larger at distal tip; membrane between spine and first ray without fleshy extension. Pelvic-fin origin at vertical through base of third dorsal-fin ray; distal tip of pelvic spine slightly curved, when adpressed reaching mid-length of anal-fin base. Anal-fin origin behind the vertical below last dorsal-fin ray. Triangular adipose-fin developed, with well-ossified spine bearing odontodes; adipose-fin membrane with posterior margin concave to nearly vertical. Caudal-fin obliquely truncate; unbranched caudal-fin rays with filaments.

Color in alcohol. Whole body and all fins have base color uniform brown, black or dark grey, with cream or beige rounded small dots, mostly uniform sized on head and body, but some between pectoral and pelvic fins may be more variable in size and irregularly shaped ( Fig. 1 ).

Color in life. In a photo of freshly captured specimen, cream-colored dots on a dark gray background cover the entire fish, including fins ( Fig. 3a ).

Sexual dimorphism. The three specimens analyzed have well-developed odontodes on the pectoral spines and on the lateral and dorsal plates of the trunk, mostly posteriorly; some odontodes on this area have notable size ( Fig. 1 ). These features have been indicated in various other species of hypostomines as secondary sexual dimorphism for males, but our specimens were not sexed.

Distribution and Habitat. The known distribution of this species is restricted to the Tiputini and Yasuni rivers, southern tributaries of the Napo River ( Fig. 7 ). Capture sites were in relatively small lowland to piedmont streams. Specimens were collected on submerged woody debris at about 0.8 m depth. The stream at the type locality was about 8 m wide with black water (pH 6.1), 23°C, and with sand and mud along the shores.

Etymology. The specific epithet honors Gustavo Orces, in recognition of his extensive contributions to the knowledge vertebrate biodiversity in Ecuador.

Figures

FIGURE 1. Panaqolus orcesi, MEPN 19492, 180.6 mm SL, holotype. Scale bar = 1 cm. Photos by F.P-R.

FIGURE 2. Close up of mouth and buccal disk for: a) Panaqolus orcesi, MEPN 19492, 180.6 mm SL, holotype; and b) P. pantostiktos, MEPN 19495, 163.4 mm SL, holotype. Photos by F.P-R.

FIGURE 3. Dorsal view of color patterns in specimens soon after capture for: a) Panaqolus orcesi, with cream-colored dots, and b) Panaqolus pantostiktos, with yellow- or gold-colored dots. Photos by R.B-S.

FIGURE 4. Comparisons of diagnostic relationships between the two new Panaqolus spp. for selected morphometric variables. Probability that allometric relationships for the two species are the same is indicated in each panel based on analysis of covariance.

FIGURE 5. Comparisons of diagnostic differences versus SL in: a) mid-lateral dot sizes (based on averages for 10 of the largest dots below dorsal fin), and b) pectoral-fin dot counts (based on average of counts for both pectoral fins of each specimen). Probability that allometric relationships for the two species are the same is indicated in each panel based on analysis of covariance.

FIGURE 6. Panaqolus pantostiktos, MEPN 19495, 163.4 mm SL, holotype. Scale bars = 1 cm. Photos by F.P-R.

FIGURE 7. Map of Ecuador and adjacent areas showing capture localities for Panaqolus orcesi red circles and red star (type locality), and for Panaqolus pantostiktos red rhombus (type locality).