Pseudancistrus zawadzkii, Silva, Gabriel de Souza da Costa e, Roxo, Fabio Fernandes, Britzke, Ricardo & Oliveira, Claudio, 2014

Silva, Gabriel de Souza da Costa e, Roxo, Fabio Fernandes, Britzke, Ricardo & Oliveira, Claudio, 2014, New species of the Pseudancistrus barbatus group (Siluriformes, Loricariidae) with comments on its biogeography and dispersal routes, ZooKeys 406, pp. 1-23 : 3-8

Pseudancistrus zawadzkii sp. n. Figure 1, Table 1

Holotype.

MZUSP 115056, male, 116.4 mm SL. Brazil: Pará State: municipality of Itaituba: rio Tapajós (Amazon basin), 04°33'09.7"S, 56°17'59.6"W, 11 June 2012, R. Britzke and CEPTA’s team.

Paratypes.

Brazil: Pará State: municipality of Itaituba: LBP 15045 (2 females, 97.9−128.7 mm SL), LBP 17724 (1 female, 87.5 mm SL), collected with holotype; LBP 16195 (1 male, 116.4 mm SL), rio Tracuá (trib. rio Tapajós), 04°28'11.2"S, 56°17'01.1"W.

Diagnosis.

Pseudancistrus zawadzkii is distinguished from all congeners, except species of the Pseudancistrus barbatus group, by presence of hypertrophied odontodes along the snout margin and the lack of evertible cheek plates. It further differs from two members of that group, Pseudancistrus barbatus and Pseudancistrus depressus , by having whitish spots that abruptly increase in size between the head (diameter 1.1−1.3 mm) and body (diameter 2.6−3.0 mm) (vs. whitish spots very small on whole body less than 1 mm), and snout odontodes yellowish (vs. snout odontodes reddish-brown). The new species differs from the other two members of the Pseudancistrus barbatus group, Pseudancistrus corantijniensis and Pseudancistrus nigrescens , by having odontodes along margin of snout increasing gradually in length from posterior of snout tip to cheek (vs. length of snout odontodes more uniform, smaller on tip of snout) and by having odontodes relatively longer on the most posterior portion of the nonevertible check plates (Fig. 1) (vs. odontodes shorter) (see fig. 3 in Chambrier and Montoya-Burgos 2008 for comparison of both characters). Additionally, Pseudancistrus zawadzkii differs from Pseudancistrus nigrescens by having rounded spots that do not cover more than one plate along the body (vs. whitish spots that become hazier along the body and can cover more than one plate, see Pseudancistrus nigrescens in fig. 3 in Chambrier and Montoya-Burgos (2008). Moreover, Pseudancistrus zawadzkii is distinguished by having a greater head depth, 67.0−72.7% of HL (vs. 38.3−44.9% of HL in Pseudancistrus barbatus ; 40.6−53.0% of HL in Pseudancistrus corantijniensis , data based on original description; and 52.5−56.6% of HL in Pseudancistrus nigrescens ); greater cleithral width, 35.2−38.0% of SL (vs. 31.1−32.7% of SL in Pseudancistrus nigrescens and 29.7−33.4% of SL in Pseudancistrus barbatus ); shorter distance between posteromedial margin of supraoccipital and origin of dorsal-fin, 6.7−9.2% of SL (vs. 10.4−11.6% of SL in Pseudancistrus nigrescens ); greater anal-fin spine length, 11.9−13.8% of SL (vs. 7.3−10.4 of SL in Pseudancistrus barbatus ); greater peduncle depth, 12.5−14.2% of SL (vs. 9.3−10.4 of SL in Pseudancistrus barbatus ); and wider internares distance, 12.7−16.6% of HL (vs. 9.9−11.8% of HL in Pseudancistrus barbatus ). Pseudancistrus zawadzkii differs from Pseudancistrus kwinti and Pseudancistrus guentheri , two probable members of Pseudancistrus barbatus group by having whitish spots of the body (vs. body mottled or with bars, in Pseudancistrus kwinti and body plates dark at the base and pale along the edges, in Pseudancistrus guentheri ).

Description.

Morphometric data presented in Table 1. In lateral view, dorsal profile convex from snout tip to dorsal-fin origin; straight, gradually descending from dorsal-fin origin to posterior insertion of adipose fin; straight, steeply ascending to insertion of caudal fin; ventral profile flat from snout tip to anal-fin origin; shallowly concave from anal-fin insertion to lower caudal-fin spine; greatest body depth at dorsal-fin origin. In dorsal view, greatest body width across cleithral region; snout broadly elliptical; body progressively narrowed from opercular region to caudal fin. Cross-section of body between pectoral and pelvic fins rounded dorsally and flattened ventrally; cross-section of caudal peduncle ellipsoid.

Body almost entirely covered by plates; ventral portions of head and abdomen and dorsal-fin base naked. Five lateral rows of dermal plates, dorsal plates 21−24, lateral mid-dorsal plates 19−21, lateral median plates 22−24, lateral mid-ventral plates 21−24, lateral ventral plates 18−20. Three predorsal plates; eight plates below dorsal-fin base; four plates between dorsal fin and adipose fin; five rows of plates on caudal peduncle. Dorsal spinelet present.

Body plates and cleithrum have minute odontodes. Odontodes slightly hypertrophied on pectoral-fin spines, becoming gradually larger towards tips. Numerous yellowish hypertrophied odontodes along lateral margins of head including snout; odontodes small on tip of snout, increasing gradually in length from anterolateral margin of snout to cheeks; longest odontodes on posterior most portion of non-evertible cheek plates. Eyes small (orbital diameter 14.5−18.8% of HL), dorsolaterally positioned. Oral disk transversely ellipsoid. Lower lip not reaching transverse line between gill openings. Lower lip covered with numerous small papillae. Maxillary barbel developed. Mouth relatively large. Premaxillary teeth 40−61 per ramus; dentary teeth 28−69 per ramus. Teeth bifid, medial cusp large and rounded, lateral cusp minute and pointed. Wide jaws, dentary bones forming an oblique angle, premaxillary bones almost co-linear.

Dorsal fin II,7, origin approximately at midpoint between pectoral- and pelvic-fin origins, last dorsal-fin ray reaching adipose fin when depressed. Pectoral fin I,6, spine tip curved inward, covered with enlarged odontodes distally; depressed tip reaching one-third length of pelvic-fin spine. Pelvic fin I,5, spine tip curved inward, almost reaching anal-fin origin when depressed. Anal fin I,5, spine tip straight, reaching sev enth plate posterior to its origin. Caudal fin I,7−I,7, distal margin concave, inferior lobe longer than superior. Adipose fin with lightly curved spine, preceded by single median preadipose plate.

Color in life.

Ground color dark greenish-brown on dorsum and sides of body, becoming dark brown posteriorly, and lighter brown ventrally. Anterior portion of head to posterior margin of orbits with many small, crowded, yellow spots; spots becoming abruptly larger on posterior portion of head, continuing on body, becoming slightly and gradually larger towards caudal peduncle. Dorsal plate series usually with two large spots per plate. Mid-dorsal plates usually with one large spot per plate. Lateral median plates with one large spot per plate. Mid-ventral plates and ventral plates with one large spot per plate. Dorsal-fin spine, rays and membranes with large round large spots. Adipose-fin with two large spots on spine and membrane. Pectoral, pelvic, anal and caudal fin with numerous and similarly sized yellow spots. Hypertrophied odontodes along head margin yellowish (Fig. 3).

Color in alcohol.

Similar to pattern described for living individuals, but with ground color dark brown, and spots pale tan (Fig. 1).

Sexual dimorphism.

Males possess a papilla posterior to urogenital opening, an attribute absent in females. Both sexes in Pseudancistrus zawadzkii exhibit highly hypertrophied odontodes along snout margin, similar to others species of Pseudancistrus ( Armbruster 2004b). In some loricariid species of genus Pareiorhaphis those hypertrophied odontodes may be sexually dimorphic (Pereira et al. 2007), an attribute not observed in the new species Pseudancistrus zawadzkii .

Etymology.

Specific name is in honor of Cláudio Henrique Zawadzki, professor at Universidade Estadual de Maringá (UEM), Maringá, Paraná State, Brazil, in recognition of his dedication and remarkable contributions to the study of the family Loricariidae .

Distribution.

Pseudancistrus zawadzkii is known from rio Tapajós (04°33'10"S, 56°18'W) and rio Tracuá (04°28'11"S, 56°17'01"W), municipality of Itaituba, all from rio Tapajós basin, Pará State, Brazil. (see Fig. 4 for distribution map of type species localities).

Ecological notes.

The rio Tapajós, and rio Tracuá where Pseudancistrus zawadzkii occurs are clear water rivers, varying from medium to large size, with rocky outcrops forming small waterfalls and substrates of rocks and sand (Fig. 5).