Panaqolus pantostiktos, 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 : 120-124

Panaqolus pantostiktos new species urn:lsid:zoobank.org:act:2940C8C0-B8ED-4027-99A3-6E71C4490EF9

( Figs. 6 , 2b and 3b ; Tab. 2 )

Holotype. MEPN-I 19495, 163.4 mm SL, Ecuadorian Amazon, Pastaza Province, Tigre River system, in Tigrillo River a tributary of Conambo River , near oil well of TENNECO oil company, approx. 02°06´25” S, 76°29´18” W, 218 masl, 14 May 1989, R. Barriga, A. Gavilanez & A. Cortazar.

Paratypes. Eight specimens came from same locality as holotype: MEPN-I 19496 , 7 , 27.3–129.5 mm SL, 13 May 1989 , RBS89-07. MEPN-I 19497, 157.6 mm SL, 12 May 1989 .

Diagnosis. Panaqolus pantostiktos can be distinguished from all congeners, except P. albomaculatus , P. nix , and P. orcesi by its color pattern: 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 pantostiktos is further distinguished from P. albomaculatus by 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 in reaching larger sizes (maximum standard length 163.4 mm vs. 90.5 mm). Panaqolus pantostiktos can be distinguished from P. nix by shorter inter-dorsal distance (10.3–12.0% SL vs. 13.7–19.4% SL), shorter abdominal length (22.1–24.3% SL vs. 29.5–34.9% SL), longer dorsal-fin base length (32.4–33.6% SL vs. 20.5–28.8% SL), longer dorsal and pectoral-fin spines (35.2–38.4% SL vs. 26.2–32.5% SL and 35.0–37.6 % SL vs. 29.5–34.9% SL, respectively), deeper caudal peduncle (11.9–12.9% SL vs. 9.3–11.4% SL), larger orbital diameter (17.0–19.9% HL vs. 12.5–16.8% HL), somewhat larger snout length (62.7–68.9% HL vs. 49.7–63.7% HL), and reaches larger sizes (maximum standard length 163.4 mm vs. 112.2 mm). Panaqolus pantostiktos is further distinguished from P. orcesi by having larger mid-lateral dots ( Fig. 5a ) with relatively lower density on head, body and fins ( Fig. 5b ; also compare Figs. 1–3 , and 6); narrower interorbital distance (40.2–43.7% HL vs. 44.5–45.8% HL); shorter snout length (62.7–68.9% HL vs. 68.5–70.3% HL); and shorter inter-dorsal length (10.3–12.0% SL vs. 12.1–12.7% SL) ( Fig. 4a–c ). As noted above, may also have longer dorsal-fin spine (35.2– 38.4% SL vs. 34.0–34.1% SL).

Description. Morphometric data in Tab. 2 . Medium-sized loricariid with maximum standard length up to 163.4 mm SL. Body robust, depressed anteriorly and compressed posteriorly ( Fig. 6 ). Dorsal profile of head from snout tip to anterior border of orbit straight and inclined, with a slope of approximately 60 degrees, then gently convex to dorsal-fin origin, from there 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. 6 ). Ventral profile of head and body flat ( Fig. 6 ).

In dorsal view, body widest near dorsal-fin origin, narrowing posteriorly. Eye dorsolaterally placed; orbit diameter 17.0–19.9% HL. Interorbital width 40.2–43.7% HL, almost flat or slightly concave near eyes. Nares small and ovoid, slightly longer than wide ( Fig. 6 ).

Oral disk rounded to transversely elliptical, maxillary barbels developed and evident; lips papillose with smooth borders; lower lip larger and more developed than upper lip ( Fig. 2b ). Teeth spoon-shaped, unicuspid or with very small lateral cusp. Premaxillary teeth 5–6 per ramus (mode 6); dentary teeth 5–7 per ramus (mode 7). Premaxillary and dentary tooth rows both meet distally at an angle of approximately 45° ( Fig. 2b ). 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 large specimens, lateral plates of body have enlarged odontodes, like spines ( Fig. 6 ). Behind anal-fin origin, the developed spines on lateral plates arranged in five longitudinal rows, which seem to form keels ( Fig. 6 ); 23–24 lateral plates. Supraoccipital bordered posteriorly by 2 plates on each side; 8–10 plates along dorsal-fin base; 5–6 plates between dorsal and adipose fins; 4–5 plates between adipose-fin and caudal-fin origin; 3–4 plates along anal-fin base; 10–11 plates between last anal-fin ray and caudal-fin origin. Cheek hypertrophied odontodes 15–25, increasing in size posteriorly; longest odontodes surpass pectoral-fin base; odontode tips curved.

Dorsal-fin I,7, 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. Adpressed dorsal-fin overlaps adipose-fin origin; anterior dorsal-fin spinelet triangular, dorsal-fin spine lock functional; last ray of dorsal-fin without posterior membrane. Pectoral-fin origin anterior to posterior margin of orbit, when adpressed, the spine almost covering first 1/3 of pelvic-fin spine; pectoral-fin spine robust, dorsal surface of spine with well-developed odontodes, larger near its distal tip; membrane between spine and first ray without fleshy extension. Pelvic-fin origin at vertical between bases of second and third dorsal-fin rays; distal tip of pelvic spine slightly curved; when adpressed reaching or surpassing middle of anal-fin. Anal-fin origin behind vertical below last dorsal-fin ray base. 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. Head, body and all fins with uniform base color, brown, black, or dark grey, with whitish or cream rounded dots; dots anterior to eyes relatively smaller than those farther posterior ( Fig. 6 ). Dorsal surface of pectoral fins show positive allometry in spot counts relative to body length ( Fig. 5b ). Spotting on pelvic fins show a similar pattern.

Color in life. Based on photo of one freshly captured specimen, the dots are yellow or golden on a dark gray background ( Fig. 3b ).

Sexual dimorphism. Some large specimens have well-developed odontodes on the pectoral spines and posteriorly on lateral and dorsal plates of the trunk ( Fig. 6 ); some odontodes have notable sizes like those reported for mature males in other hypostomine species, but our specimens were not sexed.

Distribution and Habitat. Known only from piedmont fluvial habitats of the Tigre River system, eastern Ecuador; this river joins the Amazonas River in northern Peru west of Iquitos ( Fig. 7 ). Capture sites were about 12 m wide and 0.5–1.30 m deep, without beaches, and the water was black. The substrate was muddy with submerged woody debris where specimens were captured using seines of 4 x 2 m.

Etymology. The species name “ pantostiktos ” from the Greek “ pantoú” meaning everywhere, and “ stiktós” meaning spotted, spotty, or punctuate. Everywhere, all over or ubiquitous spotting alludes to color pattern of the head, body, and fins covered with light dots on black or dark brown background; pantostiktos , adjective.

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).