Loraxichthys, Salcedo, Norma J., 2013

Salcedo, Norma J., 2013, Description of Loraxichthys lexa, new genus and species (Siluriformes: Loricariidae) from the Río Huallaga Basin, central Peru, with notes on the morphology of the enigmatic Lipopterichthys carrioni Norman, 1935, Zootaxa 3640 (4), pp. 557-571 : 559-565

Loraxichthys , new genus

Type species. Loraxichthys lexa , new species

Diagnosis. Loraxichthys is distinguished from all other loricariids by two uniquely derived characteristics: crenulated skin folds on dorsal border along first pelvic-fin ray in mature males ( Fig. 1 ); and, posterior longest evertible cheek odontodes robust with hooked tips, less than twice the length of the odontodes immediately anterior to them ( Fig. 2 ). Furthermore it is distinguished by the following combination of characters unique within the Loricariidae : naked snout with no tentacles; absence of nuchal plate; absence of first dorsal-fin spinelet; absence of adipose fin; three median unpaired plates in position of adipose fin; dentary wide with anguloarticular slightly projected dorsolaterally ( Fig. 4 B); lateral anterior process of the basipterygia narrow, almost in contact with the medial anterior process of the basipterygia at midline ( Fig. 5 B).

Loraxichthys lexa , new species Figure 1 ; Table 1

Holotype. ANSP 179128, 45 mm SL, male; Peru: Departamento de Huánuco: Provincia de Leoncio Prado: Mariano Dámaso Beraun: vicinity of Tingo María, Cueva de las Pavas, Quebrada Luconyupe (09°22’15.1”S 75°58’32.7”W); Catherwood Foundation Peruvian-Amazon Expedition, 2 Oct. 1955.

Paratypes. All from Peru: ANSP 179129, 3, 45.4–48.9 mm SL, 1 CS, 49 mm SL; same as holotype. – ANSP 179124, 12, 15.7–40.6 mm SL, 1 CS, 33.2 mm SL; Departamento de Huánuco: Provincia de Leoncio Prado: Tingo María, vicinity of Tingo María, Río Rondos (09°15’00”S 76°05’00”W), Catherwood Foundation Peruvian- Amazon Expedition, 29 Sept. 1955.

Diagnosis. Same as for genus.

Description. Morphometric data in Table 1 . Head and body robust, greatest body width at cleithrum. Cleithral width greater than head length. Head and body depressed, body depth greater than caudal peduncle depth. Head profile convex from posterior border of naked snout to posterior border of nares, straight from posterior border of nares to posterior border of supraoccipital. Trunk profile slightly convex from posterior border of supraoccipital to anterior border of dorsal fin, straight along base of dorsal fin to anterior border of caudal fin. Ventral profile straight. Caudal peduncle triangular in cross-section, with apex dorsally, caudal peduncle width 62–82 % of caudal peduncle length.

Body dorsally and laterally covered by plates with odontodes; odontodes on each plate of about the same size. Pectoral-fin spine with enlarged dorsally oriented odontodes on medial border. Body naked ventrally from tip of snout to third ventral plate posterior to origin of anal fin. Posterior half of caudal peduncle with four to five coalescent plates ventrally along midline. Dense fat pads underneath the snout skin.

Dorsal fin with 10* (16) to 11 (2) rays, first unbranched. Dorsal-fin base plates 8 (1), 9 (7) or 10* (2). Adipose fin absent, 2 (2) to 3* (16) unpaired plates on midline in place of adipose-fin region. Plates on adipose-fin region forming shallow ridge on specimens smaller than 30 mm SL, or indistinct to shallow ridge on specimens larger than 30 mm SL. These plates will be referred from now on to as adipose ridge. Dorsal fin reaching anterior edge of adipose ridge to first half of adipose ridge, when depressed. Plates between dorsal fin and adipose ridge 6 (8), 7* (2). Plates between adipose ridge and caudal fin 4* (1), 5 (6), 6 (3). Anal fin absent (5) to inconspicuous* (13). When present anal fin with 1 (1), 2* (7) or 3 (1) rays, all unbranched (specimens less than 24 mm SL not included). First anal-fin ray with no odontodes. Plates between anal fin and caudal fin 8 (1), 9* (6), 10 (3). Caudal fin truncated, all specimens with two unbranched and 14 branched rays, dorsalmost and ventralmost rays unbranched (one specimen with 13 branched rays, one branched ray apparently fused with ventralmost unbranched ray). Posterior process of cleithrum partially exposed laterally; exposed part of cleithrum more or less rectangular, oblique, posterior margin straight. Pectoral fin with one spine and six branched rays. Pectoral-fin spine strong. Pectoral-fin spine not reaching origin of pelvic fin when adpressed in most specimens (females and immatures), pectoral-fin spine reaching origin of pelvic fin to slightly beyond origin of pelvic fin when adpressed in males. Pelvic fin with one unbranched and five branched rays. First unbranched pelvic-fin ray thick.

Anterior margin of snout rounded (most specimens, particularly females) to irregularly rounded (particularly males, depending on preservation) in dorsal view. Snout naked, covered with blister-like, round-shaped papillae, particularly conspicuous in mature males.

Head with shallow medial ridge from posterior border of naked snout towards anterior border of nares, wide shallow ridges from nares to anterior border of eyes. Head flat from posterior border of nares to posterior border of supraoccipital, covered with thick layer of skin. Odontodes absent on frontals and supraoccipital. Oral disk densely covered by blister-shaped papillae, smaller than papillae on snout. Posterior lip margin with irregular lobes along its edge. Maxillary barbels short, conspicuous. Posterior soft border of each premaxilla smooth. Roof of mouth between premaxillae without buccal papilla. Anterior border of dentary with one to five blister-shaped papillae on middle third.

Teeth arranged in one row on premaxilla (31–41) and dentary (41–50), more numerous in dentary. Teeth slender, asymmetrically bifid, cusp tips sharp. Medial tooth cusp twice as long as lateral tooth cusp. Lateral tooth cusp not juxtaposed over medial cusp.

Hypertrophied odontodes on evertible cheek-plates embedded in soft connective tissue overlaying short, thin fleshy flap anterior to opercular flap. Fleshy flap inconspicuous in females and juvenile specimens. Evertible cheek-plates formed by three thick plates supporting seven to 21 hypertrophied odontodes. None to many slender odontodes with straight to slightly curved tips, five to nine longer odontodes with slightly curved tips and two to four (at least two) longest and robust odontodes with hooked tips. Exposed part of opercle triangular, its posterior free border with enlarged odontodes. Small opercular opening covered by fleshy opercular flap, bordered posteriorly by exposed cleithrum.

Infraorbital sensory canal extending beyond the anterior border of first infraorbital canal-bearing plate (IO1). First infraorbital plate (IO1) with lateral laminar projections, one third to half the length of infraorbital sensory canal section ( Fig. 2 ). Second infraorbital plate (IO2) approximately two times larger than first infraorbital. Third infraorbital plate (IO3) along lateral rim of nostril. Fourth infraorbital plate (IO4) through sixth infraorbital plate (IO6) along anterolateral margin of orbit. Nasal plate expanded medially, nasal-plate lamina as wide or slightly wider than canal. Frontal large and elongated, along posteromedial rim of nostrils and medial margin of orbit. Sphenotic rectangular, with wide lateral projection in contact with IO6, along posteromedial margin of orbit. Pterotic-supracleithrum not in contact with posterior margin of orbit. Suprapreopercle with wide lateral projections. Suprapreopercle in contact with IO6.

Lateral line extending from posterior border of suprapreopercle to base of caudal fin or to one plate before last plate on median lateral series. Lateral-line plates 24 (3) to 25* (7). First median plate of lateral series half length of second median plate, second median plate half length of third median plate, third median plate about same size as fourth median plate.

Vertebrae 28. Ten to 11 pairs of ribs (holotype with 11 ribs on left side and 10 on right side), first pair thick and articulating directly to sixth centrum, second pair articulating to eighth centrum. Epural bladelike, articulating dorsally to base of two posteriormost procurrent rays and ventrally to 27th and 28th centra, separated from fused hypurals (hypurals 3–5 + uroneural).

Nuchal plate absent. First dorsal-fin spinelet absent. Dorsal fin supported by ten pterygiophores (1), with first pterygiophore articulating with neural spine of seventh vertebra. Anal fin supported by 1* (8) or 2 (1) pterygiophores, with first pterygiophore contacting hemal spine of sixteenth vertebra.

Color in alcohol. Head and body brown dorsally. Dark line between posterior margin of pteroticsupracleithrum and exposed cleithrum. Longitudinal dark stripe along median lateral series. Black spot present on base of membrane between first unbranched and first branched dorsal-fin rays. Four to five dark bars on each dorsal-fin ray, membrane not pigmented (SL> 30 mm). Dark brown first dorsal-fin ray, three to four dark bars on each ramified dorsal-fin ray, membrane not pigmented (SL<30 mm). Two dark bands dorsally on caudal peduncle, one anterior and one posterior to adipose ridge. Adipose ridge light brown on dark brown background. Dorsal procurrent rays light brown on dark brown background. Caudal fin with four to six dark bars on each ray. Body yellowish-brown ventrally. Anal fin not pigmented. Some melanophores around urogenital region and anal-fin base. Pectoral-fin spine and rays light brown dorsally, membrane not pigmented. Pectoral fin yellowish-brown ventrally. Pelvic-fin rays with three brown bars dorsally along their lengths when high concentration of melanophores present, membranes not pigmented. Pelvic fin yellowish-brown ventrally. Ventral plates of caudal peduncle yellowish-brown.

Sexual dimorphism. Mature males have well-developed naked snout, first four pelvic-fin rays with fleshy folds along their dorsomedial edges. Fleshy fold along dorsomedial border of first pelvic-fin ray thick, crenulated, with four to six bumps. Tuft of well-developed odontodes present on dorsal margin of the most-medial section of first, second, and third branched pelvic-fin rays. Pelvic fins reach anal-fin origin and extend past length of anal fin. Posterior margin of pelvic fin convex, with branched pelvic-fin rays gradually longer towards third branched pelvic-fin ray. Females and immatures have shorter naked snout, posterior margin of pelvic fins truncated, and pelvic fins barely reach origin of anal fin.

Etymology. Lorax is the name of a fictitious character, created by Theodor Seuss Geisel, that plights for the environment. Ichthys is based on a Greek noun meaning fish. Loraxichthys refers to the fish that speaks for other fishes. The species lexa is in recognition of Alexandra Keane, sustainability activist, currently a Political Sciences student at the College of Charleston. The specific epithet is used as a noun in apposition.

Distribution. Loraxichthys lexa is only known from clear water tributaries of the Río Huallaga near Tingo María (725–780 m), Departament of Huánuco, Peru ( Fig. 6 ).

Habitat. All habitat notes and comments are based on the Catherwood Foundation Peruvian-Amazon Expedition’s field notes and the limnological and systematic studies that report the results of the expedition in the Río Rondos (Patrick et al. 1966). The specimens were collected from Qda. Luconyupe, Cueva de las Pavas and Río Rondos by using rotenone in pools and fast water channels. There are no field data for the Cueva de las Pavas collection locality, taken during the Catherwood Foundation Peruvian-Amazon Expedition, so the habitat description corresponds only to the Río Rondos collection locality.

At the time of the Catherwood Foundation Peruvian-Amazon Expedition, the Río Rondos was a small tributary of the Río Huallaga in a relatively broad valley covered with forest. The area studied was owned by Sindicato Monzón, not many people lived along the banks of the river because it was private property, but some areas had been cleared for planting bananas. The substrate of the main channel of the Río Rondos was composed largely of sand, rubble, and rocks, with sandy mud here and there along its shallow banks and in the deep pools. The maximum width of the collection area was 46 m approximately (Patrick et al. 1966: 16, fig. 6). The depth of the collection area varied from around 10 cm in banks and riffles, to 1.2 m or more in pools. The speed of the water was variable through time as well, from slack (1.6 m /s on average, n=10) and slow riffles (1.7 m /s on average, n=10) to rapids (3.6 m /s on average, n=10). Methods for water chemistry measurements are described in Patrick et al. (1966). The Río Rondos was a clear acid water river ( pH 5.0), with total transparency (approximately 2 m in a pool). Dissolved oxygen was high (7.88 ppm) compared to the Río Bella (7.60 ppm), affluent of Río Rondos, but slightly lower than two other rivers in the vicinity (8.96–9.46 ppm). The total hardness, as CaCO3, (14 ppm) was lower than that of rivers in the vicinity (36.4 ppm in Río Bella, 241.2–247.2 ppm in two white water rivers), but higher than the Río Nanay (3 ppm), another clear water river studied by the Catherwood Foundation Peruvian- Amazon Expedition that year. The concentration of total dissolved solids was the lowest (23 mg /L) compared to other rivers in the vicinity (49.5mg /L in Río Bella; 242.6–309.8 mg /L in two white water rivers), even lower than the Río Nanay (36.4 mg /L).

Figures

FIGURE 1. Loraxichthys lexa, holotype, ANSP 179128, 45 mm SL, male. A. Lateral view. B. Dorsal view. C. Ventral view.

FIGURE 2. Dorsal view of left infraorbital series and associated dermal bones of Loraxichthys lexa, paratype, ANSP 179129, 49 mm SL. Abbreviations: F = frontal, IO 1 - 6 = infraorbital plates, N = nasal, SP = sphenotic, SPO = suprapreopercle, nr = nostril, or = orbit. Anterior toward top. Scale bar = 1 mm.

FIGURE 4. Posterior view of right mandible of: A) Lasiancistrus heteracanthus, MUSM 14313, 61 mm SL; B) Loraxichthys lexa, same specimen as in Fig. 2; C) Lipopterichthys carrioni, MCZ 51702, 40 mm SL, left mandible reversed; D) Chaetostoma taczanowskii, MUSM 5186, 65 mm SL. Cartilages indicated by crossed hatching. Abbreviations: D = dentary; AA = anguloarticular. Arrow in B points to projected anguloarticular. Dorsal toward top. Scale bars = 1 mm.

FIGURE 5. Dorsal view of pelvic girdle of: A) Lasiancistrus heteracanthus, same specimen as in Fig. 4; B) Loraxichthys lexa, same specimen as in Fig. 2; C) Lipopterichthys carrioni, same specimen as in Fig. 4; D) Chaetostoma marmorescens, MUSM 13251, 86 mm SL. Anterior toward top. Scale bars = 1 mm.

FIGURE 6. Map of West Central South America, showing Peruvian Andes and main tributaries of the Amazon River, with collection localities of Loraxichthys lexa. Star indicates type locality.

Tables

TABLE 1. Morphometric data of Loraxichthys lexa. Mean and Range based on the holotype and eight paratypes. Asterisk denotes measurements of six specimens with anal fins, including the holotype.

	Holotype Range	Mean	Standard deviation
Standard length (mm)	45.0 31.2–48.9	41.2
Percents of standard length
Head length	32.2 29.1–32.4	31.0	1.2
Head depth	15.3 15.2–17.0	16.2	0.7
Body depth	16.0 16.0–18.3	17.1	0.8
Cleithral width	36.1 33.2–36.1	34.4	1.0
Interbranchial width	27.0 24.9–27.0	26.1	0.7
Pre-dorsal length	45.2 42.3–46.1	44.4	1.2
Base of dorsal-fin length	26.2 26.2–29.7	28.7	1.1
Pectoral-pelvic length	25.6 22.4–27.2	25.4	1.4
Pectoral spine length	27.0 22.1–28.0	24.4	1.9
First pelvic-fin ray length	26.1 20.8–26.1	23.0	1.6
Second pelvic-fin ray length	25.0 21.2–25.0	22.3	1.1
Caudal peduncle length*	24.8 23.0–24.8	24.1	0.7
Caudal peduncle depth	12.3 11.6–12.8	12.2	0.4
Percents of head length
Snout length	62.0 57.7–62.9	60.2	1.6
Internaris width	10.1 8.8–12.6	10.5	1.1
Interorbit width	32.1 32.1–37.7	35.5	1.9
Orbit diameter	17.7 16.3–19.6	18.1	1.0
Premaxilla length	28.0 25.4–29.1	27.2	1.2
Dentary length	29.5 26.9–33.6	31.2	2.4