Parotocinclus robustus, A, Pablo Lehmann & Reis, Roberto E., 2012

A, Pablo Lehmann & Reis, Roberto E., 2012, A new species of Parotocinclus (Siluriformes: Loricariidae) from the upper Rio São Francisco, Brazil, Zootaxa 3390, pp. 56-64 : 57-62

Parotocinclus robustus , new species

Fig. 1 , Table 1

Holotype: MCP 46689, 42.0 mm SL, male, Brazil, Minas Gerais, Bocaiúva, Rio São Francisco basin, creek 45 km S of Montes Claros on highway BR-135 towards Bocaiuva, Rio Jequitaí basin (17°05’31”S 043°49’48”W), 20 July 1993, R. Reis, J. Silva, E. Pereira & S. Schaefer.

Paratypes: Brazil, Minas Gerais, Rio São Francisco drainage: MCP 16746, 7, 26.5−30.7 mm SL + 1 c&s, 39.3 mm SL (5, 26.5−30.7 mm SL), and ANSP 192455, 3, 29.7−33.9 mm SL, collected with the holotype. MCP 36847, 8, 22.7−29.5 mm SL + 2 c&s, 24.2−29.2 mm SL (8, 22.7−29.5 mm SL), Francisco Dumont, Córrego Diamante on road from Buriti Grande and the highway BR-135, Rio Jequitaí basin (17°25’53”S 044°07’17”W), 11 October 2004, R. Reis, P. Lehmann & E. Pereira. MCP 23645, 2, 22.3−28.2 mm SL + 1 c&s, 26.2 mm SL (2, 22.3−28.2 mm SL), Santana do Riacho, Rio Cipó on road from Jabuticatubas to Santana do Riacho, Rio das Velhas basin (approx. 19°12’S 043°43’W), August 1994, F. Vieira, C. B. M. Alves & G. B. Santos. UFRGS 9881, 8, 21.2−30.2 mm SL (4, 26.7−30.2 mm SL), João Pinheiro, Rio Santo Antônio on highway BR-040 from Canoeiros to João Pinheiros, Rio Paracatu basin (17°57’37”S 045°42’17”W), 24 May 2008, T. Carvalho & F. Jerep.

Diagnosis. Parotocinclus robustus differs from all its congeners, except P. prata , by having the abdomen completely devoid of dermal plates between the pectoral girdle and the anus (vs. abdomen varying from fully covered with dermal plates to just a few plateles near the pectoral-fin axilla or anterior to the anus). From P. p r a t a it is readily distinguished by having the ventral surface of the head behind the lower lip smooth, without rugosities in adults (vs. ventral surface of the head behind the lower lip highly rugose in adult specimens; Fig. 2 ), and by having the postrostral plate 4 contacting the infraorbitals 3 and 4 (vs. postrostral plate 4 not contacting the infraorbital series). The new species is also distinguished from most congeners, except P. arandai , P. b a h i e n s i s, P. prata , and P. s p i l u r u s, by having the rostral plate not visible ventrally on the snout tip (vs. rostral plate visible ventrally on the snout tip). Parotocinclus robustus is further distinguished from most congeners, except P. s p i l u r u s, P. cearensis , P. p r a t a, P. ju m b o, P. spilosoma , and P. cesarpintoi , by having the pectoral girdle covered by skin medially and exposed and supporting odontodes only laterally (vs. pectoral girdle exposed and supporting odontodes both medially and laterally).

Description. Proportional measurements and counts in Table 1 . Adult size medium for members of this genus (maximum size 42.0 mm in SL). Body stocky, without conspicuous keels. Caudal peduncle vertically oval in cross section. Dorsal profile of body convex anteriorly, rising from snout to supraoccipital tip, approximately straight from that point to dorsal-fin origin, slightly concave from dorsal-fin origin to adipose-fin origin, and then descending to end of caudal peduncle. Greatest body depth at dorsal-fin origin. Least body depth at shallowest part of caudal peduncle. Ventral profile slightly concave from snout tip to gill opening, slightly elevating posteriorly along anal-fin base, almost straight along caudal peduncle. Lateral-line canal with pored tube visible from compound pterotic to penultimate or antepenultimate plate in middle lateral series. Lateral line complete or with small gap of 1−3 plates after the first 8 pored plates. Mid-dorsal and mid-ventral series of lateral plates incomplete, terminating 3−5 plates before caudal fin. Dorsal surface of body covered by plates except for small naked area at opening of swimbladder capsule posteroventrally to compound pterotic. Ventral surface of head and abdomen naked. Lateral abdominal plates absent between pectoral-fin axilla and pelvic-fin origin. Pectoral girdle covered by thick skin medially, exposed and supporting odontodes only laterally. Arrector fossa widely open medially, with ventral expansion of cleithum and coracoid present only laterally.

holotype.

Paratypes

Head deep; broadly round in dorsal view. Interorbital space flat to slightly convex; superior margin of orbit slightly elevated. Parieto-supraoccipital slightly elevated posterior to orbit. Smaller individuals with two slightly elevated crests on posterior portion of parieto-supraoccipital and few enlarged, slightly raised odontodes at its posterior tip; crests and raised odontodes absent in larger specimens. Snout tip with small area of naked skin, usually connected ventrally to the upper lip. Rostral and anterior postrostral plates without enlarged odontodes; all odontodes similar in size and shape to those on remaining of head. Preopercle exposed and supporting odontodes laterally, in front of opercle; canal-bearing lateral cheek plate moderately expanded mesially in triangular tip and with unbranched canal. Eye small, dorsolaterally placed. Iris with dorsal operculum. Nostrils at posterior terminus of pair of shallow depressions beginning close to snout tip, ovoid, slightly longer than wide, positioned closer to anterior margin of orbit than to snout tip. Internareal area slightly elevated. Oral disk roughly circular; lips well developed, occupying most of ventral surface of head. Lower lip short, not reaching to almost reaching line between mesial tips of contralateral canal-bearing cheek plates. Both lips densely covered by papillae; lower lip with larger papillae immediately posterior to dentaries and decreasing in size towards edge. Posterior edge of lower lip deeply fringed. Maxillary barbel short, mostly adnate to lower lip and with free distal portion smaller than pupil diameter. Teeth small and delicate; asymmetrically bifid. Medial cusp large and wide, rounded, lateral cusp small and pointed, reaching approximately one-third to half-length of medial cusp. Accessory patch of unicuspid teeth on both premaxilla and dentary bones absent.

Dorsal fin originating at or slightly anterior to vertical line passing through end of pelvic-fin base. Dorsal fin short, reaching 5−6 plates behind its base when adpressed. Nuchal plate exposed, not covered by skin. Dorsal-fin spinelet platelike, trapezoidal in shape, wider than base of dorsal spine. Dorsal-fin locking mechanism nonfunctional. Dorsal-fin spine moderately flexible, followed by seven branched rays. Adipose fin present and preceeded by 1−2 middorsal, azigous plates. Pectoral fin moderate in size, with slightly curved and flattened spine and six branched rays, first longest; subsequent branched rays decrease gradually in size. Posterior margin of pectoral fin straight to slightly round, overlapping one third to half-lenght of pelvic-fin when adpressed. Pectoralfin axillary slit absent. Pelvic fin with one unbranched and five branched rays, almost reaching to just passing analfin origin when adpressed. Pelvic-fin unbranched ray slightly depressed and curved, covered with minute odontodes ventrally and laterally; odontodes on ventral margin strongly turned mesially. Males with low dermal flap along posterodorsal margin of thickened first pelvic-fin unbranched ray, more conspicuous near base of ray; absent in females. Anal fin with one unbranched and five branched rays, reaching five plates behind its base when adpressed. Caudal fin forked to slightly concave; lower lobe slightly longer than upper; one upper unbranched, 14 branched, and one lower unbranched rays. Vertebral centra 28−30 (3 c&s).

Color in alcohol. Ground color of dorsal and lateral surfaces yellowish tan to light brown. Dorsolateral region of head, snout, predorsal area and most of dorsal and lateral surface of trunk with many dark brown dots, conspicuous in larger specimen ( Fig. 1 ); absent in smaller ( Fig. 3 ). Four irregular and variably conspicuous saddles; first crossing anterior dorsal-fin base; second immediately posterior to dorsal-fin base; third immediately anterior to adipose fin, and and fourth between adipose and caudal fins. Saddles broadly conneted laterally to dark brown stripe that spans from above pectoral-fin base to before end of caudal peduncle. Light stripe from snout tip to each nostril. Ventral surfaces whitish tan, with scattered patches of dark chromatophores, most concentrated on cheek and caudal peduncle. Fins mostly unpigmented, except for dark transverse bands; 3−4 in dorsal, 2−3 in pectoral and 1−2 in pelvic; 1−2 in anal fins. Caudal fin with vertically elongate, squarish dark blotch at base of rays, preceeded by conspicuous light transverse band at end of caudal peduncle. One of two irregular, sometimes oblicuous, dark bands on caudal fin, connected to each other by dark pigmentation in central caudal-fin rays.

Sexual dimorphism. Males possess the characteristic conical urogenital papilla, positioned just behind the anal opening. Adult males also possess a low fleshy flap along the dorsal margin of the first thickened pelvic-fin ray, that is absent in females. The flap is slightly deeper basally and progressively narrows distally. Flap is absent in juvenile males and females.

Distribution and habitat. Parotocinclus robustus is known from three rivers belonging to the upper and middle Rio São Francico basin, the Rio das Velhas and Rio Jequitaí on the right margin and the Rio Paracatu on the left margin, suggesting that the species is widely distributed across the basin ( Fig. 4 ). The type-locality and other streams where the species was found are small to median-sized rivers with shallow water (0.4−1.5 m depth) and slow to median-speed waterflow. The streams had clear to slightly turbid water running over a mixed bottom composed of stones, gravel, sand and sometimes mud. Specimens were mostly collected on the marginal vegetation.

Etymology. The species epithet robustus is from the Latin, meaning robust, referring to the strong and robust appearance of the fish. An adjective.

Figures

FIGURE 1. Holotype of Parotocinclus robustus, MCP 46689, 42.0 mm SL, male. Brazil, Minas Gerais, Bocaiúva, Rio São Francisco basin, creek 45 km S of Montes Claros on highway BR- 135 towards Bocaiuva, Rio Jequitaí basin.

FIGURE 2. Ventral surface of head of Parotocinclus prata, MCP 28303, 47.7 mm SL, male.

FIGURE 3. Color variation in Parotocinclus robustus, MCP 16746. A— 27.0 mm SL, female; and B— 28.6 mm SL, female.

FIGURE 4. Drainage map of eastern Brazil showing the distribution of Parotocinclus robustus (dots) and P. p r a t a (squares) in the upper Rio São Francisco basin. Some symbols represent more than one collecting locality. Open symbol represent the type locality.

Tables

TABLE 1. Morphometrics and meristics of Parotocinclus robustus. SD = Standard deviation, n = number of specimens, H =

Standard length (mm) Percent of Standard Length Head length Predorsal Length	H 42.0 27.6 44.8	n 23 23 23	Low 22.3 26.4 43.8	High 42.0 29.8 48.5	Mean 28.4 28.4 45.9	SD - 0.97 1.20
Dorsal-fin spine length Anal-fin unbranched ray length Pectoral-fin spine length Pelvic-fin unbranched ray length Cleithral width Thoracic length	22.6 18.6 22.6 18.6 30.5 16.7	23 23 23 23 23 23	19.8 14.3 18.8 15.5 25.9 14.5	26.2 22.0 26.9 20.6 31.6 18.0	22.4 18.1 22.4 18.3 29.1 16.9	1.93 1.91 1.76 1.39 1.91 0.91
Abdominal length Body depth at dorsal-fin origin Caudal-peduncle length Caudal-peduncle depth	21.7 18.8 32.4 10.7	23 23 23 23	17.0 15.2 29.0 9.1	24.6 20.0 33.5 10.8	21.7 18.0 31.3 9.9	1.45 1.29 1.09 0.56
Percent of Head Length Snout Length	68.1	23	61.5	68.1	65.3	1.72
Orbital diameter Interorbital width Head depth Suborbital depth	17.2 49.1 67.2 32.8	23 23 23 23	17.2 43.3 54.3 25.4	24.3 51.4 67.2 32.8	20.6 47.2 59.5 28.7	1.59 2.31 4.16 2.41
Mandibular ramus	13.8	23	13.4	18.6	14.5	1.18
Counts
Left premaxillary teeth Right premaxillary teeth Left dentary teeth Right dentary teeth Left lateral scutes Right lateral scutes	22 23 24 23 27 27	23 23 23 23 23 23	18 18 19 19 24 24	26 28 26 25 27 27	22.1 22.3 22.2 21.6 25.0 25.2	2.04 2.16 2.0 3 1.90 0.67 0.71