Parotocinclus dani, Roxo, Fabio F., Silva, Gabriel S. C. & Oliveira, Claudio, 2016

Roxo, Fabio F., Silva, Gabriel S. C. & Oliveira, Claudio, 2016, Description of a new species of Parotocinclus (Siluriformes, Hypoptopomatinae) from the rio Tapajos basin, ZooKeys 634, pp. 125-136 : 126-131

Taxon classification Animalia Siluriformes Loricariidae

Parotocinclus dani sp. n. Fig. 1, Table 1

Holotype.

MZUSP 120737, 27.3 mm SL, municipality of Peixoto de Azevedo, Mato Grosso State, small tributary of rio Peixoto de Azevedo, drainage of rio Teles Pires, rio Tapajós basin, 10°23'10"S, 54°18'22"W, 18 August 2007, coll. JLO Birindelli, AL Netto-Ferreira & LM Souza.

Paratypes.

All from Brazil, Mato Grosso State, rio Tapajós basin. MZUSP 96785, 126, 17.8-26.7 mm SL, collected with holotype. LBP 22089, 1, 26.9 mm SL, 1 c&s, 27.3 mm SL, collected with holotype. MZUSP 96194, 18, 16.7-24.7 mm SL, municipality of Paranaíta, rio Teles Pires, 09°27'31"S, 56°29'19"W, 30 September 2007, coll. LM Souza, AL Netto-Ferreira. MZUSP 96225, 5, 17.3-24.1 mm SL, municipality of Paranaíta, rio Teles Pires, 09°25'44"S, 56°32'36"W, 29 September 2007, coll. LM Souza, AL Netto-Ferreira.

Diagnosis.

The new species Parotocinclus dani can be distinguished from all congeners, except Parotocinclus amazonensis , Parotocinclus bidentatus , Parotocinclus britskii , Parotocinclus eppleyi , Parotocinclus longirostris , Parotocinclus polyochrus , and Parotocinclus variola by one character proposed by Lehmann et al. (2014, 2015): the presence of a triangular dark blotch at the anterior base of the dorsal fin, Fig. 2a (vs. absence Fig. 2b). The new species can be distinguished from Parotocinclus amazonensis , Parotocinclus britskii , Parotocinclus collinsae , Parotocinclus eppleyi , Parotocinclus halbothi , Parotocinclus longirostris , Parotocinclus polyochrus , and Parotocinclus variola by the absence of an adipose fin but presence of one small platelet at typical adipose-fin region, Fig. 3 (vs. presence of a poorly developed to well-developed adipose fin); from Parotocinclus bahiensis , Parotocinclus cearensis , Parotocinclus cesarpintoi , Parotocinclus jumbo , Parotocinclus prata , Parotocinclus robustus , and Parotocinclus spilosoma by the abdomen completely covered by dermal plates (vs. abdomen totally exposed or with few small and dispersed platelets); from Parotocinclus cearensis , Parotocinclus cesarpintoi , Parotocinclus jumbo , Parotocinclus prata , Parotocinclus robustus , Parotocinclus spilosoma , and Parotocinclus spilurus by having the pectoral girdle totally exposed (vs. the pectoral girdle medially covered by skin and exposed only laterally); from Parotocinclus bidentatus by the presence of a single series of bicuspid teeth (vs. the presence of a series of unicuspid teeth behind the series of bicuspid teeth of the dentary and premaxilla), and by the higher number of bicuspid premaxillary teeth 15-25, mode 21 (vs. 6-12, mode 9) and bicuspid dentary teeth 15-22, mode 21 (vs. 4-10, mode 7).

Description.

Morphometric and meristic data shown in Table 1. Small size Loricariidae , holotype 27.3 mm SL; paratypes 20.7-27.3 mm SL. Dorsal profile in lateral view straight from snout tip to anterior portion of parieto-supraoccipital, slightly convex to dorsal-fin origin. Dorsal-fin base straight, slightly concave and descending from posterior end of dorsal-fin base to caudal peduncle. Ventral profile in lateral view slightly concave from snout tip to anal-fin origin, slightly convex from anal-fin base to caudal-fin origin. In dorsal view body progressively narrowing posteriorly from cleithrum to caudal peduncle and anteriorly to snout tip. Greatest body depth at dorsal-fin origin. Cross-section of body between pectoral and pelvic fins dorsally rounded and ventrally flat; cross-section of caudal peduncle ellipsoid, round laterally, flat dorsally and ventrally.

Top of head in parieto-supraoccipital region and between orbits convex; superior margin of orbits elevated. Eyes moderately small (9.7-17.0% of HL), and dorsolaterally positioned. Snout pointed and rounded in dorsal view. Nostril small. Body and almost all head plates covered with minute, uniformly sized and evenly distributed odontodes. Absence of tufts of hypertrophied odontodes at posterior medial portion of parieto- supraoccipital or crests on head. Dorsal and ventral anterior margin of snout covered with larger odontodes compared to rest of head. Lips moderately developed and rounded; lower lip far from reaching pectoral girdle. Papillae uniformly distributed on base of dentary and premaxilla, getting smaller distally. Lower lip larger than upper. Maxillary barbel present and poorly developed. Teeth slender and bicuspid; medial cusp larger than lateral cusp. Left premaxillary teeth 15-25 (mode 21). Left dentary teeth 15-22 (mode 21).

Dorsal fin ii,7; its origin slightly posterior to pelvic-fin origin; when depressed reaching beyond vertical line through anal-fin insertion. Tip of branched dorsal-fin rays reaching vertical line slightly posterior of anal-fin origin. Dorsal-fin spinelet V-shaped, laterally extended; dorsal-fin locking mechanism functional. Pectoral fin i,6; tip of longest pectoral-fin ray almost reaching vertical line through center of horizontal pelvic-fin length when depressed. Pectoral axial slit present between pectoral-fin base and lateral process of cleithrum. Lateral margin of pectoral spine possessing odontodes increasing in size posteriorly. Pelvic fin i,5; tip not exceeding anal-fin origin when depressed. Males with flap along dorsal margin of unbranched pelvic-fin ray, absent in females. Anal fin i,5; tip of unbranched anal-fin ray reaching 7th to 9th plate from anal-fin origin. Adipose-fin absent but with small unpaired plates in typical adipose fin region. Caudal fin i,14,i; distal margin forked. Lateral plate series formed by 24-26 (mode 25) plates. Lateral line with one or two unperforated plates in line of pores along mid length of body, terminating in two plates preceding last lateral plate. Abdomen completely covered by dermal plates. Cleithrum partly enclosed by ventral lamina of coracoids.

Color in alcohol.

Background color dark yellowish-brown in dorsal portion of body and yellowish tan in ventral portion. Dorsal surface of head dark brownish, except for striking V-shaped yellowish tan mark from rostral plate passing through nares to orbital margins. Irregular and conspicuous dark brownish longitudinal stripe along lateral line. Four dark brownish bars crossing dorsum, reaching longitudinal stripe on sides of trunk: first below dorsal-fin origin, second at end of dorsal-fin base, third at adipose fin region, and fourth more inconspicuous at end of caudal peduncle. Dorsal, pectoral, and pelvic fins with dark chromatophores, forming irregular sets of bands: five on dorsal and pectoral fins, three to four on pelvic-fin, and four on anal fin. Dorsal-fin with triangular dark blotch at anterior base. Unpaired plates in typical adipose-fin region yellowish tan. Caudal-fin hyaline, except for one black spot at its origin extending to ventral lobe, and two almost inconspicuous bands. Entire body covered with irregularly distributed chromatophores.

Sexual dimorphism.

Adult males can be distinguished from females by presenting two characters: (1) presence of a papilla at urogenital opening (vs. papilla absent in females), and (2) unbranched pelvic-fin ray supporting a dermal flap on proximal dorsal surface (vs. dermal flap absent in females).

Distribution.

The new species is known from three drainages of rio Tapajós in Mato Grosso State, Brazil (Fig. 4). Two from the rio Teles Pires, in the municipality of Paranaíta and from a small tributary of rio Peixoto de Azevedo, in the municipality of Peixoto de Azevedo.

Etymology.

The specific name " dani " is in honor of Daniela Fernandes Roxo, FF Roxo’s sister.

Discussion.

Lehmann et al. (2014, 2015) proposed that the species Parotocinclus amazonensis , Parotocinclus britskii , Parotocinclus collinsae , Parotocinclus eppleyi , Parotocinclus halbothi , Parotocinclus longirostris , Parotocinclus polyochrus , and Parotocinclus variola should be part of a new genus of Otothyrini based on the following synapomorphies (1) presence of a triangular dark blotch at the anterior base of the dorsal fin, (2) canal cheek plate on the ventral surface of the head elongated posteriorly and contacting the cleithrum, and (3) head and snout elongated and with a Y-shaped, white or cream colored mark dorsally. The first character is apparently conserved and may help to diagnose a new genus within Otothyrini . However, it is also present in Parotocinclus bidentatus (see the holotype picture in Gauger and Buckup 2005, Fig. 5). The second character is absent in Parotocinclus dani and the third character is present not only in Parotocinclus dani and species of this possible new genus proposed by Lehmann et al. (2014, 2015), but also in species of Hisonotus - e.g., Hisonotus acuen and Hisonotus chromodontus , species of Curculionichthys - e.g., Curculionichthys luteofrenatus , Curculionichthys paresi , and species of Epactionotus - e.g., Epactionotus bilineatus , Epactionotus itaimbezinho and Epactionotus gracilis . Given the above information, it is clear that new analyses are necessary to recognize this putative new genus more accurately.

Carvalho and Datovo (2012) described a new Otothyrini species, Hisonotus bockmanni , from small tributaries of the rio Teles Pires, drainages of the rio Tapajós. This species lacks an adipose fin as the new species Parotocinclus dani , and presents several small platelets at typical adipose-fin region. Furthermore, Hisonotus bockmanni shows a triangular dark blotch at the anterior base of the dorsal-fin suggesting that this species may also be part of the new genus proposed by Lehmann et al. (2014, 2015). However, we could not examine the clear and stained specimens of Hisonotus bockmanni to verify if this species presents the first character proposed by Lehmann et al. (2014, 2015), i.e., a canal cheek plate on the ventral surface of the head elongated posteriorly and contacting the cleithrum. Hisonotus bockmanni and the new species Parotocinclus dani could be part of the same monophyletic genus and may be closely related. Notwithstanding, Hisonotus bockmanni can be distinguished from its congeners by the presence of the following characters of coloration pattern proposed by Carvalho and Datovo (2012): (1) the snout with unpigmented, rostrocaudally elongate ellipse anterior to each naris; (2) the dark-brown pigmented pre-dorsal region with five unpigmented white spots arranged as an anteriorly chevron-shaped blotch with three spots anteriorly of dorsal-fin and two posterior spots lateral to and coequal with insertion of dorsal-fin spine; and (3) the caudal-fin lacking pigments on half of membrane and rays.