Hisonotus dinizae, Ribeiro-Silva & Silva & Venere & Silva & Roxo, 2020

Ribeiro-Silva, Luís R., Silva, Gabriel S. C., Venere, Paulo C., Silva, Hugmar Pains Da & Roxo, Fábio F., 2020, Description of a new species of Hisonotus (Loricariidae: Siluriformes) from rio Araguaia basin, Zootaxa 4860 (4), pp. 553-562 : 554-557

Hisonotus dinizae , new species

Fig. 1 , Table I

“ Hisonotus sp.”— Venere & Garutti, 2011 [inventory], pg 132.

Holotype. MZUSP 125790 (female, 23.3 mm SL), Brazil, Mato Grosso state, municipality of Barra do Garças, córrego Grande, drainage of rio Pindaíba , rio Araguaia basin (-15.7417; -52.0936), 08/24/2014, col. P. C. Vênere & V. Garutti.

Paratype. All specimens from Brazil, Mato Grosso state, municipality of Barra do Garças, drainage of rio Pindaíba , rio Araguaia basin (n = 11); LBP 4932 (4, 19.1– 17.3 mm SL, 1 c&s, 20.2 mm SL), rio Corrente , tributary of ribeirão Ínsula (-15,4997; -52,2033), 03/22/2007, col. P. C. Vênere & V. Garutti; LBP 29173 (4, 16.9–19.4 mm SL), collected with holotype ; MZUSP 125791 (2, 18.8–19.0 mm SL), collected with holotype .

Non-types. All specimens from Brazil, Mato Grosso state, municipality of Barra do Garças, drainage of rio Pindaíba , rio Araguaia basin ( Fig. 2 ) (n = 6). LBP 1572 (3, 19.5–23.1 mm SL, 1 c&s, 20.0 mm SL), rio Corrente , tributary of ribeirão Ínsula (-15.4992; -52.2028), 12/09/2002, col. C. Oliveira ; LBP 1856 (2, 22.9– 21.1 mm SL), ribeirão Ínsula (-15.5483; -52.2047), 08/27/2003, col. C. Martins.

Diagnosis. Hisonotus dinizae differs from all congeners, except H. acuen , H. bockmanni , H. chromodontus , H. jumaorum and H. vespuccii by having a V -shaped spinelet (vs. rounded, rectangular or triangular-shaped spinelet). The new species can be distinguished from H. chromodontus and H. jumaorum by having yellowish teeth (vs. reddish-tipped teeth in H. chromodontus and H. jumaorum ); from H. bockmanni by the absence of unpaired platelets at typical adipose fin position (vs. presence of the unpaired platelets); H. acuen , H. chromodontus and H. vespuccii by having the caudal-fin color hyaline with three transverse dark bars, Fig. 1 (vs. two hyaline rounded areas on the upper and lower lobes in H. chromodontus or a dark brown chromatophores largely concentrated on rays near lower caudal spine in H. acuen and H. vespuccii , see Fig. 2 in Roxo et al. (2015a) for these characters). Moreover, the new species differs from H. acuen and H. chromodontus by having one abdominal median plate series (vs. three or more abdominal medial plate series); from H. acuen and H. vespuccii by having lower caudal-peduncle length (14.6– 21.0% of SL vs. 25.5–33.0 % of SL in H. acuen and 34.0–40.3% of SL in H. vespuccii ) and higher snout length (60.5–68.8 % of HL vs. 34.2–57.2 % of HL in H. acuen and 45.5–50.6 % of HL in H. vespuccii ); from H. jumaorum by having higher pelvic-fin unbranched ray length (20.2–21.9% of SL vs. 14.8–15.7% of SL), lower caudal-peduncle length (14.6–21.0% of SL vs. 25.3–30.4% of SL), lower head width (49.5–56.7% of HL vs. 57.8–63.5% of HL), higher snout length (60.5–68.8% of HL vs. 57.4–59.1% of HL), higher interorbital width (38.3–45.1% of HL vs. 32.9–35.8% of HL) and higher orbital diameter (15.5–22.4% of HL vs. 11.0–14.2% of HL).

Description. Morphometric and meristic data presented in Table.1 Small size loricariid (16.9–19.3 mm SL, mean 18.7 mm SL); depressed and elongated body.

In lateral view, dorsal profile of head straight from tip of snout to middle portion of parieto-supraoccipital, concave at area between nostril, straight to posterior margin of parieto-supraoccipital to dorsal fin insertion. Ventral profile of head slightly convex from tip of snout to gill opening. Head completely covered by bony plates, except on ventral portion of head at mouth region, between lower lip and scapular bridge. Bony plates covered by odontodes randomly arranged; odontodes form poor defined aligned rows. Supraoccipital process not elevated and without tuft of odontodes in specimens of all size. Snout long (60.5–68.8% HL), slightly pointed, its tip rounded. Eye of median size (15.5–22.4% HL), situated almost laterally in midpoint of head. Iris operculum present. No ridge between eyes and nares. Nostril relatively large. Lower lip rounded, not reaching transversal line through gill opening. Small papillae randomly distributed through lower and upper lips, increasing in size proximally. Buccal papilla absent. Yellowish teeth, slender and bicuspid; medial cusp larger than lateral. Premaxillary teeth 18–19. Dental teeth 14–16. Maxillary beard small and attached to lower lip.

In lateral view, dorsal profile of trunk slightly convex and descending from dorsal-fin insertion to upper caudalfin ray insertion. Ventral profile of trunk slightly convex from gill opening to first anal-fin ray insertion, concave from that point to lower caudal-fin ray insertion. Cross-section of caudal peduncle ellipsoid; rounded laterally and almost flat dorsally and ventrally. Trunk completely covered by bony plates, except at areas around pectoral, pelvic, dorsal and anal fins origins. Cleithrum and coracoid completely exposed, covered with pointed odontodes. Arrector fossae partially enclosed by ventral lamina of coracoids. Lateral median plate series ranging from 20 to 22 plates; lateral line incomplete. Abdominal region entirely covered by plates; lateral abdominal plate series with about four plates; median abdominal plate series with about five plates; one large plate at anal region.

Dorsal-fin rays ii,7; spinelet V -shaped and dorsal fin locking mechanism functional; first dorsal fin ray insertion posterior to pelvic fins origins; dorsal-fin rays tips almost reaching middle of anal-fin base. Pectoral-fin rays i,6; almost reaching end of pelvic fins unbranched rays when adpressed; pectoral spine covered by odontodes on dorsal and ventral surfaces; pectoral-fin axillary slit present. Pelvic-fin rays i,5; not reaching anal-fin insertion when adpressed; pelvic-fin spine covered by odontodes, curved inward on ventral surface. Anal-fin rays i,5; distal fin margin slightly convex; anal-fin spine completely covered by odontodes. Caudal-fin rays i,14,i; forked, fin forked, all rays covered with odontodes. Caudal fin emarginated.

Coloration in alcohol. Background coloration, in dorsal and lateral view yellowish; dorsal portion darker than ventral. Mid-lateral dark-brown stripe extending from tip of snout to caudal peduncle. Dorsal and lateral portion of body covered with small dark; dots smaller than eye diameter. Dorsal, pectoral, pelvic and anal fins with dark brown, irregularly-distributed chromatophores almost forming bands. Caudal fin hyaline, possessing three transverse dark bars: first at origin of branched rays, second at middle portion of caudal fin, and third at distal portion of rays.

Sexual Dimorphism. Adults males have a papilla at urogenital opening (this character is absent in females).

Distribution and Habitat. Hisonotus dinizae is known from two localities around municipality of Barra do Garças, Mato Grosso state, Brazil. Found at córrego Grande (type-locality) and at rio Corrente, both tributaries of rio Pindaíba, rio Araguaia basin. A non-type locality is found at ribeirão Ínsula, tributary to rio Pindaíba, rio Araguaia basin ( Fig. 3 ). The three localities are small size streams, with about 0.5–2.0 m depth with marginal vegetation, and shallow, clear and fast-flowing water. Specimens were associated with marginal submerged vegetation, but absent at the river bottom (see Fig. 4 for type locality).

Specimens of H. dinizae appear to be relatively rare along the collection sites. We have performed eight collection expeditions in the municipality of Barra do Graças hydrographic systems and collected only 12 specimens. However, a potentially undescribed species Parotocinclus is found sympatrically with this new Hisonotus species and appears to be abundant (i.e., we have collected more than 200 specimens of the new Parotocinclus along rio Corrente and ribeirão Ínsula). We also have collected samples of the following species on type-locality of H. dinizae : Moenkhausia phaenota , Pamphorichthys araguaiensis , Ochmacanthus sp., Serrapinnus cf. micropterus , Poptella sp., Jupiaba polylepis , Aphyocharax anisitsi , Iguanodectes spilurus , Acestrorhynchus sp., Moenkhausia pyrophthalma , Charax aff. leticiae and Thayeria boehlkei .

Etymology. The specific epithet is a tribute to Professor Débora Diniz from the State University of Southwest Bahia (Uesb) in recognition of the work carried out and her contribution to cytogenetic studies of neotropical freshwater fish.

Figures

FIGURE 1. Hisonotus dinizae, MZUSP 125790, holotype, female, 23.3 mm SL. Brazil, Mato Grosso state, córrego Grande, drainage of rio Pindaíba, rio Araguaia basin (-15.7417; -52.0936).

FIGURE 2. Hisonotus dinizae, LBP1572, non-type specimen from rio Corrente, tributary of ribeirão Ínsula (-15.4992; - 52.2028).

FIGURE 3. Map showing the collection sites of Hisonotus dinizae at rio São Araguaia basin. Black-star shows the type-locality at córrego Grande sub-basin (light-grey), black-square the paratype locality at rio Corrente sub-basin (dark-grey), and blackcircle the non-paratype locality at ribeirão Ínsula sub-basin (mid-grey).

FIGURE 4. Habitat of H. dinizae at type-locality of córrego Grande, drainage of rio Pindaíba, rio Araguaia basin, municipality of Barra do Garças, Mato Grosso state, Brazil.