Hypostomus khimaera, Tencatt & Zawadzki & Froehlich, 2014

Tencatt, Luiz F. C., Zawadzki, Cláudio H. & Froehlich, Otávio, 2014, Two new species of the Hypostomus cochliodon group (Siluriformes: Loricariidae) from the rio Paraguay basin, with a redescription of Hypostomus cochliodon Kner, 1854, Neotropical Ichthyology 12 (3), pp. 585-602 : 597-600

Hypostomus khimaera , new species

Figs. 3c , 4c , 5c , 6c , 13 , 14

Hypostomus cochliodon Armbruster, 2003: 21 (partim; redescription).

Holotype. MZUSP 111129, 139.1 mm SL, Brazil, Mato Grosso State, Serra das Araras, Porto Estrela, córrego Salobo , rio Paraguay basin, 15°39’03"S 57°12’54"W, 2-3 Aug 1999, O. A. Shibatta.

Paratypes. CPUFMT 1449 , 2 , 112.2 - 126.9 mm SL; INPA 37744, 1, 125.5 mm SL; MNRJ 40185, 2 , 105.5 - 128.1 mm SL; MZUEL 5821, 16 , 37.5-113.2 mm SL; and NUP 14506, 4 , 125.7 - 141.5 mm SL, collected with holotype .

Non-type material. 169 specimens. Brazil. rio Paraguay basin. Mato Grosso. LBP 5825 , 1 , 95.8 mm SL, Cuiabá, rio Coxipó. LBP 8496 , 10 , 47.5-104.5 mm SL, Porto Estrela, rio Salobra. MCP 15621 , 1 , 86.5 mm SL; and MCP 15785 , 3 , 85.4 -113.0 mm SL, unnamed stream. MZUSP 44313 , 4 , 30.3-113.9 mm SL, Nova Olímpia, unnamed stream. MZUSP 78741 , 5 , 51.7-101.3 mm SL, Reserva do Cabaçal , ribeirão Sete de Setembro. MZUSP 78783 , 7 of 8, 13.2-96.0 mm SL (13.2-96.0 mm SL), Indiavaí, rio Jaurú. MZUSP 78785 , 4 , 56.5-66.3 mm SL, Reserva do Cabaçal , rio Cabaçal. MZUSP 78853 , 1, 156.7 mm SL, Diamantino, rio Paraguay. MZUSP 79135 , 2 , 69.6- 88.8 mm SL, Cuiabá, rio Cuiabá. MZUSP 82036 , 1 , 109.0 mm SL, rio Sepotuba. MZUSP 90458 , 1 , 94.5 mm SL, rio Sepotuba. NUP 915 , 12 , 82.7-116.1 mm SL; and NUP 12393 , 1, 146.6 mm SL, Chapada dos Guimarães, Manso Reservoir. NUP 2843 , 2 , 75.8-89.5 mm SL, Chapada dos Guimarães, rio Quilombo. NUP 3000 , 2 , 114.9 - 122.5 mm SL; and NUP 12014 , 1 , 27.2 mm SL, Santo Antônio do Leverger , rio Cuiabá. NUP 3037 , 1 , 89.2 mm SL, Chapada dos Guimarães, rio Casca. NUP 9723 , 2 , 61.8-72.4 mm SL, Cáceres, rio Piraputanga. NUP 11825 , 1 c&s, 69.5 mm SL, Cáceres, córrego Piraputanga. NUP 12005 , 1 , 139.0 mm SL; and NUP 12495 , 1, 108.5 mm SL, Rosário Oeste, rio Manso. NUP 12006 , 2 , 91.8-107.1 mm SL, Barão de Melgaço , rio Cuiabá. NUP 12013 , 1, 112.7 mm SL, Chapada dos Guimarães, rio Cuiabá. NUP 12015 , 1 , 95.9 mm SL, Barão de Melgaço , baia de Chacororé. NUP 12016 , 1 , 93.6 mm SL, Santo Antônio do Leverger. NUP 12121 , 1 , 91.4 mm SL, Nova Brasilândia, rio Manso. NUP 13399 , 4 , 136.2 - 163.8 mm SL, Tangará da Serra , córrego Rico. NUP 13400 , 1 , 59.1 mm SL, Rondonópolis, córrego do Esparramo. NUP 13401 , 1 , 61.8 mm SL, Rondonópolis, córrego Pitaluga. NUP 13423 , 3 , 86.2-96.1 mm SL, Chapada dos Guimarães, rio Quilombo. NUP 13480 , 11 , 50.0- 130.2 mm SL, Jangada, rio Jangada. Mato Grosso do Sul State. NUP 10982 , 1 , 99.1 mm SL; and NUP 11819 , 3 , 76.4-103.7 mm SL, Coxim, córrego da Onça. NUP 13269 , 3 , 64.1- 81.5 mm SL, Rochedo, córrego Formiga. NUP 13270 , 9 , 43.4 -93.0 mm SL, Rochedo, córrego Tamanduá. NUP 13494 , 4 , 61.2-73.1 mm SL, Terenos. ZUFMS-PIS 1316 , 11 , 27.5 -71.0 mm SL, Aquidauana, córrego das Antas. ZUFMS-PIS 1978 , 1, 115.7 mm SL, São Gabriel do Oeste , rio Coxim. ZUFMS-PIS 3539 , 20 , 39.0-73.0 mm SL, Jaraguari, córrego Furnas do Dionísio. ZUFMS-PIS 3557 , 32 , 26.0- 77.0 mm SL, Corguinho, tributary to rio Aquidauana. ZUFMS-PIS 3738 , 5 , 8.8-10.6 mm SL, Terenos, rio Aquidauana .

Diagnosis. Hypostomus khimaera is distinguished from all other Hypostomus species, except those belonging to the H. cochliodon group, by having the following unique combination of features: notch between metapterygoid and hyomandibula absent (vs. notch present) and strongly angled dentaries, less than 80° (vs. shallow angle between dentaries, generally more than 80°). Hypostomus khimaera can be distinguished from all other species of the H. cochliodon group, except from H. basilisko and H. soniae , by the presence of a dark tan stripe along the flank (vs. absence). The new species can be distinguished from H. basilisko and H. soniae by the presence of black spots on the body and fins or at least in one of these (vs. absence of spots). It can be additionally distinguished from H. basilisko in having moderately developed keels (vs. highly developed keels) and more vertebrae (28 vs. 27). The new species is additionally distinguished from H. cochliodon by having comparatively more teeth (12-27 vs. 7-9), externalized opercle, exposed region easily visible ( Fig. 3 b-c) (vs. almost entire internalized opercle, exposed region not easily visible ( Fig. 3a ) and fewer vertebrae (28 vs. 29).

Description. Morphometric data in Table 1. Overall view of body in Fig. 13 , juvenile in Fig. 4c . Head broad, rough, moderately deep and slightly compressed. Snout and anterior profile of head pointed, sometimes slightly round, in dorsal view. Eyes moderate in size, laterally positioned. Dorsal margin of orbit slightly elevated. Compound pterotic covered by well-developed odontodes in some specimens. Greatest body width at cleithrum, then decreasing to caudal peduncle. Dorsal profile of head straight from snout tip to supraocciptal 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 rays, then descending to caudal-fin insertion. Caudal peduncle laterally compressed, broad on anterior region to very compressed on posterior region. Body dorsally covered with spinulose dermal plates, except of dorsal fin and small naked area on snout tip. Mesethmoid region covered by odontodes, more conspicuous anteriorly to nares. Moderate ridge originating laterally to nares, passing through supraorbital and extending through superior portion of compound pterotic. Exposed region of opercle ellipsoid and moderate in size; odontodes more developed distally. Opercle completely surrounded by thin layer of skin ( Fig. 3c ); covered by numerous odontodes. Oral disk round, relatively small in size, lower lip not reaching transversal through gill openings; ventral surface covered with numerous small papillae decreasing in size posteriorly ( Fig. 5c ). Maxillary barbel equal to or slightly larger than eye pupil. Odontodes present on anterior surface of upper lip, just anterior snout. Buccal papilla (sensu Armbruster, 2003) absent. Dentaries acutely angled, averaging less than 80° between left and right dentary rami. Twelve to 27 teeth (mode 19, holotype 21) in maxilla, twelve to 27 teeth (mode 22*) in dentary. Teeth shovel-shaped, bicuspid; mesial cusp round to oblong in ventral view and conspicuously more developed than lateral cusp; lateral cusp distinct and generally well-developed, sometimes fused to mesial cusp (similar to condition found in Hypostomus hemicochliodon , see Armbruster (2003, 2004) and H. soniae , see Hollanda Carvalho & Weber, 2004). Juveniles with tooth morphology similar to adult specimens.

Body covered by five rows of rough and spiny dermal plates. Odontodes more concentrated on dorsal surface of head and medially on dermal plates. Dorsal-fin base naked. Predorsal region medially keeled; these keels moderate developed, slightly diverging posteriorly ( Fig. 6c ). Dorsal and mid-dorsal series of plates with moderate developed keels. Median series bearing lateral line and without keels. Mid-ventral series angled to fifth first plates, without keel posteriorly. Ventral series smooth angled ventrally towards posterior portion of caudal peduncle. Ventral surface of head covered with platelets, with exception to 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 26-28 (mode 27*), three predorsal plates, plates between dorsal and adipose fins 7*-9 (mode 7), plates between adipose and caudal fins 7*-8 (mode 7) and 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 posterior rays not reaching adipose-fin spine. Adipose 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 distal portion in larger specimens. Tip of adpressed pectoral fin reaching to one-third of adpressed pelvic-fin 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 sixth plate after its origin. Unbranched and fifth branched rays smaller than second, third, and fourth rays; third branched ray generally longest. Caudal fin i,14,i; distal margin falcate, with ventral lobe slightly longer than dorsal one.

Color in alcohol. Ground color generally yellowish-brown, some specimens tan. One faint stripe between mid-dorsal and mid-ventral keels. Color of fins equal to ground color of trunk, sometimes lighter; some specimens with ventral lobe of caudal fin slightly darker than dorsal lobe. Region around dorsal-fin base darker, extending medially along dorsal portion of caudal peduncle, usually forming inconspicuous dark stripe on dorsal region; anal fin color pattern similar to that of dorsal fin. Spots at least in some part of body and fins in all specimens. Body generally with sparse and small spots, concentrated on anterior portion of body; some specimens have few or even lack spots altogether. All fins generally covered by small spots, closely spaced; spots diffuse or absent in some specimens. Color pattern of juvenile specimens similar to adults; diffuse spots on body and fins in some juvenile specimens.

Color in life. Color in life is similar to that in alcohol preserved specimens, except for more visible stripes and more yellowish-brown ground color ( Fig. 14 ).

Sexual dimorphism. No sexual dimorphism was observed.

Distribution. Hypostomus khimaera is known from several localities of rio Paraguay basin, such as rios Cuiabá, Manso, Quilombo, Coxipó, Coxim, baía de Chacororé, rios Vermelho and Aquidauana basins ( Fig. 9 ).

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 spoon-shaped, 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.

Figures

Fig. 3. Opercle morphology of (a) Hypostomus cochliodon, NUP 10809, 215.8 mm SL, showing indistinct opercle without odontodes; (b) Hypostomus basilisko, holotype, MZUSP 111110, 182.5 mm SL and (c) Hypostomus khimaera, holotype, MZUSP 111129, 139.1 mm SL, showing layer of skin surrounding opercle that supports odontodes.

Fig. 4. Lateral view of juvenile in (a) Hypostomus cochliodon, NUP 11956, 92.8 mm SL, (b) Hypostomus basilisko, paratype, ZUFMS-PIS 3083, 64.2 mm SL and (c) Hypostomus khimaera, NUP13494,68.8 mmSL.

Fig. 5. Mouth and teeth of (a) Hypostomus cochliodon, NUP 10807, 208.0 mm SL, showing one series of papillae in inner face of upper and lower jaws; (b) Hypostomus basilisko, holotype, MZUSP 111110, 182.5 mm SL, showing the agglomerated papillae on inner face of upper and lower jaws; and (c) Hypostomus khimaera, MZUSP 111129, holotype, 139.1 mm SL, showing weakly developed papillae not forming series.

Fig. 6. Keels, ridges and odontodes of (a) Hypostomus cochliodon, NUP 10807, 208.0 mm SL, showing two weakly developed ridges in compound pterotic, weakly developed keels, few and weakly developed odontodes and predorsal keels weakly developed; (b) Hypostomus basilisko, holotype, MZUSP 111110, 182.5 mm SL, showing the three ridges on top of head, strongly developed keels, numerous welldeveloped odontodes on plates covering body and head and strong V-shaped predorsal keels; (c) Hypostomus khimaera, holotype, MZUSP 111129, 139.1 mm SL, showing moderately developed keels and dermal plates supporting moderately developed odontodes.

Fig. 13. Hypostomus khimaera, holotype, MZUSP 111129, 139.1 mm SL, from córrego Salobo, rio Paraguay basin, Mato Grosso State, Brazil; dorsal (top), lateral (middle), and ventral (bottom) views.

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

Fig. 9. Type locality of Hypostomus basilisko (yellow star), Hypostomus cochliodon (dark star) and Hypostomus khimaera (red star). The dark triangles represent areas of co-occurrence of Hypostomus cochliodon and Hypostomus khimaera; dark diamonds represent area of occurrence of Hypostomus cochliodon in the upper rio Paraná basin.