Two new species of the Hypostomus cochliodon group ( Siluriformes : Loricariidae ) from the rio Paraguay basin , with a redescription of Hypostomus cochliodon Kner , 1854

Hypostomus cochliodon group is a monophyletic clade of 20 valid species of Neotropical armored catfishes that is widely distributed throughout South America. Recently, specimens identified as H. cochliodon from the type locality and nearby localities were examined, and found to include representatives of more than one species. A redescription of H. cochliodon is provided, with a description of two new species, one from the Bodoquena Plateau and another from several localities of the rio Paraguay basin. A lectotype for H. cochliodon is designated herein, since the previous designation is invalid. Hypostomus cochliodon is diagnosed from all other species of the H. cochliodon group by having the opercle almost completely covered laterally by thick layer of skin, the absence of buccal papilla, weak to moderately developed keels on the lateral plates of the body and by the color pattern of its body and fins. Hypostomus basilisko, new species, is distinguished from the remaining species of the H. cochliodon group by the absence of spots on the body, highly developed keels and spoon-shaped teeth. Hypostomus khimaera, new species, is distinguished from the other species of the H. cochliodon group by having a dark tan stripe along the midline of the flank, black spots on the body and/or fins and teeth with mesial cusp and not spoon-shaped.

Hypostomus cochliodon Kner was described from the rio Cuiabá basin, based on five syntypes collected by Natterer.Armbruster (2003) reported that Hypostomus cochliodon was found exclusively in the rio Paraguay basin, but Weber (2003) noted that its distribution included the middle rio Paraná basin.More recently, H. cochliodon was also reported from the upper rio Paraná basin, due to flooding of the Sete Quedas falls after the construction of the Itaipu reservoir (Zawadzki et al., 2005;Graça & Pavanelli, 2007).
In the original description, Kner (1854) described the color pattern of Hypostomus cochliodon based on his observations of the syntypes and remarks in Natterer's field notes.The author noted a concentration of small black spots on the dorsal portion of the head, which are scarce along the trunk.Kner (1854) also mentioned the presence of black spots on the fins as well as the bicolored pattern of the fins, which present their proximal basis at the same color as the body and distal tips darker.Armbruster (2003) performed a comprehensive taxonomic review of the H. cochliodon group, providing redescriptions of the previously described species and describing four new species.In the same paper, Armbruster stated that H. cochliodon possesses color pattern of the body generally entirely dark brown, with a dark tan stripe in the midline of the flank; stripe sometimes crossed by dark saddles or with dark spots anteriorly.Hollanda Carvalho & Weber (2004) raised some issues in the redescription of H. cochliodon made by Armbruster (2003).Initially, there was a contradiction in color patterns described by Armbruster (2003) versus those mentioned in the original description by Kner (1854), mainly by the presence of a dark tan stripe in the midline of the flank in H. cochliodon, reported by Armbruster (2003) but which was not mentioned in Kner's description.
Other point in Armbruster's (2003) paper commented by Hollanda Carvalho & Weber (2004) were the diagnostic characters, which have very large variation, such as the number of teeth ranging from 6 to 27.In Kner's (1854) description, the number of teeth ranged from seven to eight.Hollanda Carvalho & Weber (2004) suggested the possibility that in the redescription of Hypostomus cochliodon made by Armbruster (2003) the author had not examined what would be the true H. cochliodon, with exception of two syntypes (NMW 46277 and NMW 44101).In addition, the authors commented that the designation of the H. cochliodon lectotype by Armbruster (2003) was not valid since it is not in accordance with the Declaration 44, amendment of Article 74.7.3 of the International Commission on Zoological Nomenclature.Hollanda Carvalho & Weber (2004) also highlighted the need of further studies encompassing several additional populations of H. cochliodon from the rio Paraguay basin.Armbruster (2003) and Hollanda Carvalho & Weber (2004) suggested that H. cochliodon from the rio Paraguay basin is likely a complex of species.
From the examination of several recent collected specimens from the rios Paraná and Paraguay basins it was possible to confirm that more than one species of the Hypostomus cochliodon group coexist not only in the rio Cuiabá (the type locality of H. cochliodon), but also in other regions of the rio Paraguay basin.From the analysis of fish from several localities within the rio Paraguay basin, specimens having a dark tan stripe mentioned by Armbruster (2003) were revealed to be a new species, which is described herein.
Additionally, specimens from the Bodoquena Plateau, Mato Grosso do Sul State, Brazil, revealed another undescribed species of the Hypostomus cochliodon group, whose description is also presented herein.The redescription of Hypostomus cochliodon with the designation of a lectotype is also provided.

Material and Methods
Measurements were made with digital calipers to the nearest 0.1 mm.Methodology and terminology for measurements follow Boeseman (1968) with modifications of Weber (1985) and Zawadzki et al. (2008).Plate counts and nomenclature follow Schaefer (1997), with the modifications of Oyakawa et al. (2005).Standard length (SL) is expressed in millimeters and all other measurements are expressed as percentages of standard length or head length (HL).Vertebral and rib counts were taken from cleared-and-stained (c&s) specimens prepared according to Taylor & Van Dyke (1985).The vertebral complex of the Weberian apparatus and the compound caudal centra are each counted as a single element.Syntypes of Hypostomus cochliodon, NMW 46277 and NMW 59395, were examined through high definition photographs.In the species descriptions numbers indicated by an asterisk refer to counts of primary types.

Hypostomus cochliodon Kner, 1854
Figs. the presence of bicuspid teeth with a large spoon-shaped mesial cusp and inconspicuous lateral cusp that is generally fused to mesial cusp (vs.bicuspid teeth with mesial cusp conspicuously large and round but not spoon-shaped and with distinct lateral cusp).It further differs from H. basilisko and H. khimaera by the absence of a longitudinal dark stripe along midline of flank (vs.presence); from H. levis (Pearson) by the presence of an adipose fin (vs.absence).1. Overall view of body in Fig. 2, juvenile in Fig. 4a.Head broad, moderately deep and slightly compressed.Snout and anterior profile of head pointed in dorsal view.Eye moderate in size, laterally positioned.Dorsal margin of orbit not raised.Greatest body width at cleithrum, decreasing to caudal peduncle.Dorsal profile of head straight from snout tip to vertical through interorbital region, and forming angle of 45° with ventral region of head; convex from that point to dorsal-fin origin; sloped downward to first dorsal caudal-fin procurrent rays, then elevating again to caudal-fin insertion.Ventral profile almost straight from snout tip to insertion of pelvic-fin unbranched ray; slightly straight from pelvic-fin insertion to first ventral caudal-fin procurrent ray, then descending to caudal-fin insertion.Caudal peduncle laterally compressed, ellipsoid on its whole extension.Mesethmoid region rough.Supraoccipital bone with highlydeveloped median ridge; with short posterior process bordered by single plate.Moderate ridge originating lateral to nares, passing through supraorbital, and extending very slightly through superior portion of compound pterotic.Opercle small, almost not exposed and generally not supporting odontodes (Fig. 3a).Oral disk round, moderate in size, lower lip not reaching transversal through gill openings (Fig. 5a); ventral surface covered with numerous small papillae decreasing in size posteriorly.Maxillary barbel slightly smaller than eye diameter.Odontodes present on anterior surface of upper lip, just below snout.Buccal papilla (sensu Armbruster, 2003) absent.Dentaries acutely angled, averaging less than 80° between left and right dentary rami.Seven to 9 (mode 7, lectotype 8) teeth in premaxilla, 7 to 9 (mode 8, lectotype 7) in dentary.Teeth spoon-shaped, bicuspid with lateral cusp very reduced or fused to mesial cusp (see Armbruster, 2003, fig. 1c).Juveniles, up to 80 mm SL, with villiform bicuspid teeth, similar to those in most species of Hypostomus (see Armbruster, 2003, fig. 1c).

Description. Morphometric data in Table
Body dorsally covered with five rows of dermal plates with weak-developed odontodes, except on base of dorsal fin and small naked area on snout tip.Predorsal region with slight median keel.These keels slightly diverge posteriorly (Fig. 6a).Dorsal and mid-dorsal series of plates with very slight keels.Median series bearing lateral line and without keels.Mid-ventral series angled to fifth or to sixth plate; slightly bent ventrally on caudal peduncle region.Ventral series without keel.Ventral surface of head covered with platelets, with exception of region beneath lower lip.Abdomen covered with minute platelets in specimens larger than 80 mm SL, with exception of very small areas around pectoral-and pelvic-fin insertions and at urogenital opening.Preanal plate present.Median series of plates with 27-29 (mode 28*), three predorsal plates, plates between dorsal and adipose fins 7*-9 (mode 8), plates between adipose and caudal fins 7*-9 (mode 8); plates below dorsal-fin base 7-8* (mode 7).Dorsal fin II,7, its origin at vertical through midpoint between pectoral and pelvic fins, or slightly posterior to that point.Dorsal-fin distal margin straight; dorsal-fin ray tips not reaching adipose spine.Adipose-fin spine compressed and curved inward.Pectoral fin I,6, its distal border straight.Pectoral-fin spine slightly curved inward, covered with moderately developed odontodes, more developed on its distal portion and in larger specimens.Tip of adpressed pectoral fin reaching to basal one-third of adpressed pelvic-fin spine.Pelvic fin i,5, its distal border convex; its adpressed unbranched ray surpassing anal-fin origin.Anal fin i,4, its tip reaching fifth to sixth plate after its origin.Rays of anal fin progressively increasing in size posteriorly, third branched ray generally longest.Caudal fin i,14,i, its margin falcate, with both lobes similar in length.

Color in alcohol.
Ground color of head and trunk grayish brown; ventral surface of body yellowish brown.Spots at least in some part of body and fins in all specimens.Presence of many small dark spots on head, mainly on top of head and compound pterotic; spots on trunk sparce, more faded and generally larger than those in head and widely spaced (Fig. 7a) in some specimens from rio Paraguay basin.Spots closely spaced on ventral surface of body in some specimens from rio Paraguay basin.Caudal peduncle generally without spots.All fins with spots on spines, unbranched and branched rays and membrane.Proximal region of fins with same color to ventral surface of body, becoming dark brown towards distal portions (Fig. 7b) in some larger specimens from both rios Paraguay and Paraná basins; uniform ground color on fins in some specimens.Larger and more widely spaced spots on dorsal portion of body and head; spots generally more closely spaced on ventral surface of body in some specimens from upper rio Paraná basin.

Color in life.
Color pattern of live specimens is very similar to that of preserved ones (Fig. 8).

Sexual dimorphism. No sexual dimorphism was observed.
Distribution.Hypostomus cochliodon is known from the rio Paraguay basin, as well as from the middle and upper rio Paraná basins (Fig. 9).In the upper rio Paraná basin, it is known from downstream of the Porto Primavera reservoir, which is the first reservoir upstream of the Itaipu reservoir, suggesting that the species colonized this region after the flooding of the Sete Quedas falls by the construction of the Itaipu reservoir in 1982.No records of the species in the upper rio Paraná are known before this period.1c).Inner portion of anterior and posterior jaws supporting agglomerated well-developed papillae, usually more developed on inner posterior jaws (Fig. 5b).Body dorsally covered with five rows of spinulose dermal plates, except on base of dorsal fin and small naked area on snout tip.Odontodes more developed on whole head surface; conical in shape.Predorsal region medially keeled; area between keels concave.These keels, which support hypertrophied odontodes, slightly diverge posteriorly (Fig. 6b).Dorsal and mid-dorsal series of plates with keels also supporting hypertrophied conical odontodes.Median series bearing lateral line and without keels; most plates support medially aligned slightly hypertrophied odontodes.Mid-ventral series highly angled to sixth or seventh plate, without keel posteriorly.Ventral series slightly bent ventrally on caudal peduncle.Ventral surface of head covered with platelets, except beneath lower lip.Abdomen covered with minute platelets in specimens larger than 80 mm SL, except for very small areas around pectoraland pelvic-fin insertions and at urogenital opening.Preanal plate present.Median series of plates with 27-28* (mode 28), three predorsal plates, plates between dorsal and adipose fins 7-8* (mode 8), plates between adipose and caudal fins 7-8* (mode 8) and plates below dorsal-fin base 7.
Dorsal fin II,7, its origin at vertical through midpoint between pectoral and pelvic fins, or slightly posterior to that point.Dorsal-fin distal margin straight; dorsal-fin posterior rays not reaching adipose spine.Adipose-fin spine compressed and curved inward.Pectoral fin I,6, its distal border straight.Pectoral-fin spine slightly curved inward, covered with moderately developed odontodes, slightly more developed on its distal portion in larger specimens.Tip of adpressed pectoral fin reaching one-third of adpressed pelvicfin spine.Pelvic fin i,5, its distal border straight to slightly convex; its adpressed unbranched ray surpassing anal-fin origin.Anal fin i,4, its tip reaching fifth to sixth plate after its origin.Rays of anal fin progressively increasing in size, third branched ray generally longer.Caudal-fin margin falcate, i,14,i, with ventral lobe slightly longer than dorsal one.

Color in alcohol.
Ground color brown yellowish to brown reddish.Region between mid-dorsal and mid-ventral keels with faint tan stripe, more evident below dorsal-fin base.Fins lighter and slightly more reddish than trunk.Region around base of dorsal fin darker.Darker coloration around dorsal-fin base extends medially along dorsal portion of caudal peduncle, forming inconspicuous stripe on dorsal profile in some specimens.Spots on body, head or fins absent.
Color in life.Ground color of body reddish brown with faint tan stripe between mid-dorsal and mid-ventral keels in most specimens, with stripe more evident below dorsal-fin base (Fig. 11a); or yellowish brown overall in other specimens (Fig. 11b).Spots absent on trunk, head or fins.Fins lighter than trunk.Eye color golden with black pupil.Sexual dimorphism.Males with middle region of pelvic-fin spine thickened on ventral surface (Fig. 12).
Distribution.Hypostomus basilisko is known from rio Salobra basin of the rio Paraguay basin, Bodoquena Plateau, Mato Grosso do Sul, Brazil (Fig. 9).Ecological notes.Hypostomus basilisko was collected and observed while snorkeling in clear-water streams and rivers of the Bodoquena Plateau.Larger individuals were easily observed during the day, lying on soft-bottom patches (mainly on sand, sometimes on leaf litter) at deeper sites.Those individuals foraged mainly during the night, when they sought shallower areas with rocky bottom.Occasionally, they were seen grazing during the day.Small individuals were observed foraging during the day and night, always in shallower areas.
Although, Hypostomus basilisko is part of a group of species that are usually reported as wood-eaters, individuals were observed foraging mainly on rocky substrates, as a periphyton grazer.Individuals also explored submerged logs and branches, but not to a noticeably greater extent than other species of Loricariidae that coexist with H. basilisko.The high degree of tooth abrasion that is usually observed in this species seems to support the idea that it does not use wood as its main food source.
Etymology.The Basilisk (from the Greek, basiliskoς [= basiliskos], diminutive of basileuς [= basileus], meaning "little king") is a mythical creature known as the king of snakes, which is often represented with a crown on his head.This crown makes an allusion to the three strong ridges at the top of head of the new species.A noun in apposition.

Remarks.
The most conspicuous characteristics used to recognize Hypostomus basilisko are its overall reddish brown color pattern that lacks spots, the rough and spiny body odontodes, and the conspicuous keels.Until now, the only species of the H. cochliodon group totally lacking spots is H. soniae and some specimens of H. pagei Armbruster.In fact, H. soniae is the most similar species to H. basilisko.However the new species is differentiated from H. soniae by having large spoon-shaped teeth, with the lateral cusp, when present, almost imperceptible versus bicuspid non spoon-shaped teeth, with mesial cusp larger than lateral cusp, but with the lateral one being clearly visible in H. basilisko.Another remarkable feature of H. basilisko is the presence of hypertrophied odontodes, which are conspicuous all over the body and even more remarkable on anterodorsal region of body in specimens up to 150.0 mm SL.

Color in life.
Color in life is similar to that in alcohol preserved specimens, except for more visible stripes and more yellowishbrown ground color (Fig. 14).
Sexual dimorphism.No sexual dimorphism was observed.

Ecological notes.
Hypostomus khimaera occurs syntopically with H. cochliodon in all aforementioned localities.However, in ichthyological surveys of headwater streams of rio Aquidauana basin, H. khimaera was more commonly found in small streams than in larger streams.In the rio Aquidauana basin streams, H. khimaera was collected generally along the margins of deeper sites with sandy bottoms.
Etymology.The epithet khimaera derives from the Greek, cimaira or khímaira, a mythological creature with hybrid body, formed essentially by three animals, a lion, a snake and a goat.The new species belongs to the Hypostomus cochliodon group, a group commonly associated with relatively few, spoon-shape teeth, but has, instead, numerous teeth that are not spoonshaped, very similar to that found in H. plecostomoides or H. soniae.However, its general body morphology is similar to H. cochliodon.The epithet khimaera makes an allusion due to the new species possess features of conspicuously distinct species.A noun in apposition.
Remarks.Some morphological differences were observed between the specimens from the rio Cuiabá and those from streams of rio Paraguay basin.Characters such as mesial cusp morphology (round to oblong), development of lateral cusp (moderate to well developed), development of keels (moderate to well developed) and roughness of the body plates (moderate to well developed odontodes on lateral body plates) usually show some degree of variation even among specimens collected at the same site.Due to the presence of such variations, only the specimens from the rio Salobo were designated as paratypes.However, some degree of morphological variation is more common among loricariid populations inhabiting small to medium rivers than in populations of species inhabiting channels of larger rivers (C.H. Zawadzki, pers.obs.).Probably, because the sedentary characteristics of most of the species of Hypostomus, any degree of geographical isolation can result in gradual levels of morphological variation from each small stream population to the neighboring ones.

Discussion
Hollanda Carvalho & Weber (2004) pointed out certain problems in the redescription of Hypostomus cochliodon made by Armbruster (2003), especially regarding the color pattern described by Armbruster, which differed from that described by Kner (1854), and also due to the large variation reported by Armbruster for some characters (e.g., number of teeth and color pattern).In the present work, some specimens from the rio Manso and rio Cuiabá (the type locality of H. cochliodon), exhibited a color pattern similar to that described by Armbruster (2003), while other specimens exhibit the color pattern described by Kner (1854) for H. cochliodon.Specimens that have the color pattern (with a dark brown stripe) which Armbruster (2003) described in his redescription of H. cochliodon can be clearly distinguished from those specimens showing the pattern described by Kner for H. cochliodon by the differences in the number and morphology of jaw teeth as well as the extent of development of keels along laterals of body and morphology of the opercle.Specimens with the dark brown stripe are named herein as H. khimaera and have been found in the type locality of H. cochliodon, and other nearby sites of the rio Paraguay basin.Therefore, Armbruster's redescription of H. cochliodon, appears to be a combination of these two species and that the "true" H. cochliodon has only a minimum of morphological and color variation through its whole geographical distribution.
Nuptial body odontodes were used by Armbruster (2003, fig. 4b) to diagnose his "odontodeless opercle group" (composed by Hypostomus cochliodon, H. ericius, H. levis, H. oculeus, H. pyrineusi, and H. taphorni), from the remaining species of the H. cochliodon group.Nuptial body odontodes sensu Armbruster (2003) are absent in H. cochliodon, H. basilisko, and H. khimaera.Even the well-developed odontodes of H. basilisko present conical shape (vs.triangular), which may signify that the "odontodeless opercle group" is not natural, since H. cochliodon (internalized opercle) and both new species (externalized opercle) present only conical-shaped odontodes on the body.Armbruster (2003) stated that the variation in the number of opercular odontodes in Hypostomus cochliodon does not seem correlated with other morphological variations, and for this reason he maintained all his examined material as a single species (as mentioned by Hollanda Carvalho & Weber, 2004).Despite the opercle of Hypostomus cochliodon generally does not support odontodes, while the two new species do, what really seems to determine the difference from H. cochliodon to H. basilisko and H. khimaera is not the number of odontodes supported by the opercle, but its own morphology.In H. cochliodon the opercle resembles that observed in H. ericius and H. pyrineusi (Fig. 3a; see also Armbruster, 2003), whereas in H. basilisko and H. khimaera, the opercle resembles that seen in H. plecostomoides and H. soniae (Fig. 3b-c; see also Armbruster, 2003).
In contrast, Hypostomus khimaera has numerous bicuspid teeth that are not spoon shaped, a dark stripe and exposed opercle bearing odontodes.Similar to what Armbruster (2004: 51) described for H. hemicochliodon, the teeth in H. khimaera also tends toward the spoon-shaped pattern found in most species of the H. cochliodon group.Despite the common association of the spoon-shaped teeth pattern with H. cochliodon species group, Armbruster (2003: 17) had already alluded to the presence of species without spoon-shaped teeth within this group by the time of his first revisionary study.

Fig. 7 .
Fig. 7. Spots and color pattern of fins in Hypostomus cochliodon; (a) NUP 12071, 151.1 mm SL, showing spots smaller and closely spaced on head and larger and widely spaced on the body; (b) NUP 12768, 241.1 mm SL, the base of fin with same color of body, becoming dark brown in tip; and uniform spot pattern in ventral portion of body.

Fig. 14 .
Fig. 14.Color pattern of live specimen of Hypostomus khimaera, ZUFMS-PIS 3738, 10.6 mm SL, rio Aquidauana, Mato Grosso do Sul, Brazil, showing the dark tan stripe along midline of flank and diffuse spots on the body.
mm SL, collected with holotype.