A new species of Peckoltia from the Upper Orinoco (Siluriformes, Loricariidae)

Abstract A new species of the suckermouth armored catfish genus Peckoltia is described from the lower Ventuari River, a tributary of the upper Orinoco River in Amazonas State, Venezuela. Specimens of this species were formerly included in the wide-ranging Amazonian species Peckoltia vittata, but a recent molecular phylogeny found Orinoco individuals to be distantly related to Amazon Basin individuals spanning the range of Peckoltia vittata syntypes. Detailed morphological examination confirmed distinctiveness of Orinoco specimens, and found them to be diagnosable from true Peckoltia vittata by having generally greater than 25 teeth (vs. less), spots on the nape (vs. nape lacking spots), the upper lip with two to three black bar-shaped markings in a line like a moustache (vs. lips generally with a hyaline wash), and by the snout having a medial black line disconnected from the moustache markings (vs. medial snout stripe connected to a bar just above the lip). Peckoltia wernekei displays remarkable genetic similarity to its sister species, Peckoltia lujani, but differs morphologically by having dentary tooth rows meet at an angle less than 90° (vs. >90°), by having large faint blotches on the abdomen (vs. abdomen with no blotches), by a smaller internares width (21.2–26.6% vs. 28.5–46.5% of interorbital width), and a larger dorsal spine (148.1–178.6% vs. 80.1–134.5% of abdominal length).


Introduction
Peckoltia Miranda Ribeiro, 1912 is a genus of suckermouth armored catfishes (Loricariidae) with 18 currently described species . Armbruster (2004;2008) had restricted Peckoltia to those species of Ancistrini that had dentary tooth rows meeting at an angle of 90° or less and that lacked the synapomorphies of similar genera like Hypancistrus and Panaqolus (the latter then the Panaque dentex group); however, this arbitrary definition was not supported by the molecular analysis of Lujan et al. (2015), so Armbruster et al. (2015) recognized an expanded Peckoltia that currently lacks a morphological diagnosis, but is strongly monophyletic based on molecular evidence (Lujan et al. 2015). Armbruster (2008) had recognized a wide-ranging Peckoltia vittata (Steindachner, 1881) that included specimens from the Maranhão to the Madeira and upper Orinoco, but suggested that this putative range of P. vittata included multiple species. The syntype series of Peckoltia vittata itself contains specimens spanning more than 600 km of the main channel of the Amazon River, from the Xingu River to the Madeira River, making it difficult to know where one might reliably find the true P. vittata. Specimens from the Xingu, Madeira and Orinoco that were morphologically consistent with Peckoltia vittata were found to be polyphyletic in Lujan et al. (2015) and Lujan et al. (in review, Fig . 1). In addition, P. greedoi was recognized as distinct from P. vittata by Armbruster et al. (2015; specimens of P. greedoi were originally included among the specimens of P. vittata examined by Armbruster 2008). Lujan et al. (2015) found the putative specimens of Peckoltia vittata from the Orinoco to be strongly supported as sister to another Orinoco species, P. lujani Armbruster, Werneke and Tan, and part of a clade with another undescribed species known as Peckoltia sp. n. Meta L147. In this study, we re-examine specimens identified as P. vittata from the upper Orinoco and describe them as a new species clearly distinguishable from Amazon Basin P. vittata. In addition, we provide a key to all of the current species of Peckoltia. Armbruster (2003) with the addition of counts of mid-dorsal and mid-ventral plates (the number of plates in these series from the head to caudal fin and excluding the last, triangular plate, which is beyond the hypural). Institutional abbreviations are as in Sabaj Pérez (2014). Names of skeletal characteristics are as in Schaefer (1987) and Geerinckx et al. (2007) and of plate rows as in Schaefer (1997). Full morphometric dataset is presented in Suppl. material 1, locality information for species described below is presented in Suppl. material 2.  Lujan et al. (in review). Results based on analysis of a 4293 base pair alignment consisting of two mitochondrial (16S, Cyt b) and three nuclear loci (RAG1, RAG2, MyH6). Node support values given in order as Bayesian posterior probability, maximum likelihood bootstrap and maximum parsimony bootstrap. Diagnosis. Peckoltia wernekei can be separated from all other Peckoltia by having a broken black line of pigment on the upper jaw (vs. solid line of pigment along snout edge or snout uniformly colored or mottled). Peckoltia wernekei can be further separated from P. vittata by generally having 25 or more teeth in at least one dentary or one premaxilla (vs. generally 24 or fewer; one specimen of P. wernekei had both upper and lower jaws with <25 teeth/ramus), by having a largely naked abdomen (abdomen with a few plates below pectoral girdle, between pelvic fins and along sides of abdomen; vs. most of ventral surface from the throat to the anus with small plates), and by having large, faint blotches on the abdomen (vs. abdomen uniform). Peckoltia wernekei can be further separated from upper Orinoco congeners as follows: from P. brevis and P. lineola by lacking short lines and spots on the head (vs. lines and spots present), from P. brevis, P. caenosa and P. lineola by having a largely naked abdomen (vs. abdomen fully plated), and by generally having 25 or more teeth per jaw ramus (vs. 22 or fewer in P. brevis, 21 or fewer in P. caenosa, and 19 or fewer in P. lineola); from P. lujani by having the dentaries meet at an angle less than 90° (vs. >90°), by having large, faint  blotches on the abdomen (vs. abdomen with no blotches), by a smaller internares width to interorbital width ratio (21.2-26.6% vs. 28.5-46.5%), and a larger dorsal spine to abdominal length ratio (148.1-178.6% vs. 80.1-134.5%); and from P. sabaji by having bands in the dorsal and caudal fins (vs. spots) and prominent dorsal saddles on the body (vs. large spots).

Peckoltia wernekei
Description. Morphometrics in Table 1. Counts and measurements based on 23 specimens. Small to medium-sized loricariids, largest specimen examined 104.6 mm SL. Body stout, but slightly narrower than P. vittata. Head gently sloped to supraoccipital. Supraoccipital with tall, rounded crest. Supraoccipital crest raised slightly above nuchal region. Nuchal region rises slightly to nuchal plate. Dorsal slope decreasing in straight line to insertion of dorsal procurrent caudal-fin rays then ascending to caudal fin. Body depth greatest at anteriormost insertion of dorsal fin. Ventral profile flat to caudal fin. Caudal peduncle trapezoidal in cross section with dorsal surface flattened. Body widest at insertion of pectoral fins, narrowest at insertion of caudal fin. Snout rounded.
Eye moderately sized (orbit diameter 18.9 ± 1.0% of head length), dorsal rim of orbit forming tall crest that continues forward to area just anterior of nares as low, rounded ridge. Iris operculum present. Interorbital space with slight, rounded, median hump that is contiguous with ridge of parieto-supraoccipital. Parieto-supraoccipital pointed posteriorly with posterior point raised above nuchal region in small crest. Infraorbitals, frontal, nasal, compound pterotic and parieto-supraoccipital supporting odontodes. Preopercle generally supporting a single column of odontodes that gener- ally decrease in number with increasing body size; largest specimen with some odontodes located posterodorsally on preopercle and two individuals without preopercular odontodes. Opercle with one to three rows of odontodes with numbers of rows and numbers of odontodes generally decreasing with increasing body size; largest individual without odontodes.
Lips covered with short, wide papillae. Lower lip wide, reaching just to or slightly short of pectoral girdle; upper lip narrow. Edge of lower lip smooth. Maxillary barbel only barbel present, reaching about two-thirds of distance to gill opening from base of barbel.
Median plates 24-26 (mode 24). Plates unkeeled, but first four or five plates of mid-ventral series bent to form slight ridge. Five caudal peduncle plate rows. Plates on all dorsolateral surfaces of body. Throat naked. Abdomen mostly naked except for a line one to three platelets wide along and slightly posterior to anterior margin of pectoral girdle, few uneven rows of platelets ventral to ventral plate series, patch of platelets below posterior section of pelvic girdle; number of platelets on abdomen increases with body size. Evertible cheek plates supporting hypertrophied odontodes evertible perpendicular to head. Cheek odontodes 17-40 (mode 33). Longest evertible cheek odontode almost reaching vertical through posterior edge of pectoral-fin spine. Hypertrophied cheek odontodes relatively weak. Odontodes slightly longer than average body odontodes present along dorsal-, adipose-, pelvic-, caudal-, and pectoral-fin spines; larger individuals with hypertrophied odontodes at tip of pectoral spine.
Dorsal fin ii,7; dorsal spinelet V-shaped, dorsal-fin locking mechanism present, last ray of dorsal fin not reaching or just reaching preadipose plate when adpressed. Adipose fin with single preadipose plate and moderately long spine. Caudal fin i,14,i; caudal fin forked, ventral lobe longer than dorsal lobe; dorsal and ventral procurrent caudal-fin rays five. Pectoral fin i,6; pectoral-fin spine reaching just posterior to pelvic fin when adpressed ventral to pelvic fin. Pelvic fin i,5; pelvic-fin spine extending one to two plates posterior to anal fin when adpressed. Anal fin i,4; unbranched anal-fin ray slightly shorter than first branched ray.
Teeth bicuspid with lateral lobe one-half to three-quarters length of medial lobe and lateral cusp half width of medial cusp. Eighteen to 32 left dentary teeth (mode 31; 1 of 23 with less than 25); 22-35 left premaxillary teeth (mode 32; 1 of 23 with less than 25); all specimens with at least one jaw ramus having 25 or more teeth.
Color. Base color reddish brown. Head and nape mottled dark brown with distinct, medial dark line along mesethmoid and slightly less distinct lines from lateral portion of naris to lip mark. Parieto-supraoccipital crest darker than surrounding areas. Lip with dark mark consisting of two or three ovoid dashes of brown, lateral portions continue as line to lateral portions of nares (Fig. 6). Dark portion of lips separated from mesethmoid line by distinctly lighter C-shaped region (Fig. 6), which may continue less distinctly between mesethmoid line and lines lateral to nares. Lips may also have other spots. Head colors less distinct in larger specimens. Body with four distinct, oblique bars, first below anterior of dorsal fin, second below posterior end of dorsal fin and anterior part of interdorsal space, third beginning at preadipose plate to about posterior edge of adipose spine, and fourth at end of caudal peduncle; first and second bars fade into a dark wash ventrally connecting the two bars; third and fourth bars continuing around caudal peduncle; bars connected at median plate series. Secondary bars sometimes present between any two primary bars, but generally not as dark, darker ventrally than dorsally; posterior secondary bars darker than anterior; secondary bars may connect across caudal peduncle. Pectoral-fin spine dark brown with alternating, similarly-sized dark and light spots, spots continuing as bands on fin; two to five dark bands on fin with number increasing with body size. Pelvic fin as pectoral but with two to four dark bands. Dorsal fin as pectoral but with dark bands distinctly wider than light bands, three or four dark bands. Anal and caudal fins as pectoral, but with light bands wider than dark bands (one to three dark bands in anal and three to five bands in caudal). Adipose spine with dorsal section of third dark bar covering base in all specimens, with some also having dark spot at tip of spine; in largest individual (holotype) basal and distal spots combine along posterior margin of spine, with ante-  rior edge having light space between spots. Abdomen mostly light, but with four to six large, faint blotches laterally and occasionally with one or two median faint blotches.
Sexual dimorphism. None observed. Distribution. Known only from the Ventuari River, a right-bank tributary of the upper Orinoco River in Amazonas State, Venezuela (Fig. 7).
Etymology. Patronym honoring David C. Werneke, Collection Manager of Fishes at the Auburn University Museum, for his diligence, camaraderie and humor during three expeditions to the upper Orinoco Basin and for his long service as a Collection Manager at Auburn University.
Key to the species of Peckoltia (after Armbruster (2008) and the present paper) Posterior margin of lower lip with finely branched fimbriate papillae (Fig. 2)  Dark blotch between eyes and on snout, head mottled or with a bold patch of pigment in the form of an E on the snout with the central branch of the E located mid-dorsally and the top and bottom branches located just lateral to the nares, all three branches extending anteriorly and the main stem of the E running transversely centered on the nares; none of the plates of the head or nape Cheek odontodes evertible to less than 45° from head, 0-10 hypertrophied cheek odontodes, cheek odontodes very short, not extending to cleithrum (no longer than 15× length of those on lateral plates)...... Peckoltia relictum - Cheek odontodes evertible to greater than 80° from head, 20 or more evertible cheek odontodes, cheek odontodes very long, extending to at least middle of cleithrum (much greater than 15×

Discussion
The disparity between the morphological and molecular phylogenies of Armbruster (2004;2008) and Lujan et al. (2015) and Lujan et al. (in review) are likely due to homoplasy and convergence in the morphological dataset, and nowhere is this more obvious than in the upper Orinoco clade containing Peckoltia lujani, P. wernekei and Peckoltia sp. n. Meta L147 (Fig. 1). Peckoltia wernekei was included in Peckoltia sensu Armbruster (2008) because of its stocky body and dentaries forming an angle of less than 90° (Fig. 6). The molecular phylogeny found P. wernekei to be sister to P. lujani, a species with dentary tooth rows forming almost a straight line and a more elongate body (Fig. 5a). Despite the differences in jaw angle, which likely has ecological and functional repercussions (Lujan and Armbruster 2012), P. wernekei and P. lujani differ from one another by only one of approximately 600 base pairs (bp; <0.2%) sequenced from the mitochondrial 16s gene and three of approximately 1150 bp (<0.3%) sequenced from the mitochondrial cytochrome b gene, whereas P. wernekei has 9.6% cyt b sequence divergence from P. vittata in the Xingu and 7.5% divergence from P. vittata in the Madeira (Lujan et al. in review). Given the nested phylogenetic position of Peckoltia wernekei among two other species with relatively straight tooth rows (P. lujani and P. n.sp. Meta L147; Fig. 1), its highly-angled dentary tooth row angle is likely derived and an example of convergence upon the condition observed in many other Peckoltia. Given the limited sequence divergence between P. wernekei and P. lujani, this jaw evolution has either occurred very quickly or there has been very recent mitochondrial introgression. Mitochondrial introgression was observed between the sympatric Panaqolus koko and Peckoltia otali (Fisch Muller et al., 2012) where the two species had similar sequences for the mitochondrial COI gene suggesting close relationships, but sequences in the nuclear F-Reticulon4 gene showed no such close relationship. In this case, P. wernekei and P. lujani are not known to be sympatric and nuclear genes are also very similar (≤0.3% divergence in RAG1, RAG2 and MYH6; Lujan et al., in review), so we believe that the genetic similarity between these species is indicative of close evolutionary relationships and not hybridization. If such a pattern can be seen among closely related species, then many elements of jaw morphology are likely to be convergent across the phylogeny. Indeed, highly-angled jaws were seen in several clades even within the morphological phylogeny (Armbruster 2004;2008). We are now testing this hypothesis with a phylogenetically explicit examination of jaw morphological diversity across the Hypostominae.
Peckoltia wernekei is illustrative of an increasingly clear biogeographical pattern in which the fish fauna of the Orinoco River upstream of its confluence with the Ventuari undergoes replacement or turnover between this confluence and the large Autures Rapids downstream. We hypothesize that this is due to an environmental filter similar to that documented by Winemiller et al. (2008) in the nearby Casiquiare Canal. The limnology of the Casiquiare Canal displays a gradient from relatively neutral or slightly acidic pH with few tannins at its origin in the upper Orinoco, to highly acidic pH with high tannin load at its confluence with the Negro River. Likewise, the physicochemical parameters of the clearwater upper Orinoco River shift a short distance downstream from the Ventuari River in response to its confluence with one major blackwater tributary (the Atabapo River) and one major whitewater river (the Guaviare/Inirida River) along its left-bank.
Many loricariid species are known only from the Ventuari River and nearby reaches of the Orinoco main channel.  (Armbruster 2008, Lujan and Armbruster 2011, Lujan and Birindelli 2011, 2009, Werneke et al. 2005. At least two other species have a disjunct distribution inclusive of the Ventuari River and the Caura River but are absent from intervening reaches of the Orinoco River main channel (Limatulichthys nasarcus, and Pseudolithoxus anthrax; Birindelli 2011, Londoño-Burbano et al. 2014), and in four of these instances there is strong morphological or molecular evidence that sister species are allopatrically distributed upstream vs. downstream of the confluence of the Orinoco and Atabapo/Guaviare/Inirida rivers. In addition to the Peckoltia lujani/P. wernekei pair, there is Hypancistrus debilittera and H. furunculus, Pseudolithoxus kelsorum and P. tigris, and Hemiancistrus sp. n. L128 (Dignall 2014) and Hemiancistrus subviridis.