Hisonotus notatus Eigenmann & Eigenmann, 1889

Martins, Fernanda O. & Langeani, Francisco, 2016, Redescription of Hisonotus notatus Eigenmann & Eigenmann, 1889 (Loricariidae: Hypoptopomatinae), the type species of the genus, and description of a new species from coastal drainages of southeastern Brazil, Neotropical Ichthyology 14 (2), No. e 150100, pp. 1-18 : 10-16

Hisonotus notatus Eigenmann & Eigenmann, 1889

Figs. 6-7

Otocinclus maculicauda Steindachner, 1877: 222 (partim, specimens without adipose fin).

Hisonotus notatus Eigenmann & Eigenmann, 1889: 41 (original description; partim, specimens from Santa Cruz). - Eigenmann & Eigenmann, 1890: 391 (catalogue; cited as minutus (lapsus) referring to notatus ). - Eschmeyer, 1998: 1198 (catalogue). - Schaefer, 2003: 323 (catalogue). -Gauger & Buckup, 2005 (phylogenetic relationships). - Ferraris, 2007: 248 (catalogue). - Reis & Carvalho, 2007: 84 (catalogue). - Martins et al., 2014: 864 (phylogenetic relationships).

Otocinclus notatus . - Regan, 1904: 266 (identification key), 268 (catalogue). -Miranda-Ribeiro, 1911: 91 (identification key); 93 (catalogue; Rio Grande do Sul State erroneously cited as type-locality). - Fowler, 1954: 130 (catalogue).

Diagnosis. Hisonotus notatus differs from H. aky , H. brunneus , H. carreiro , H. charrua , H. heterogaster , H. laevior , H. megaloplax , H. montanus , H. nigricauda , H. notopagos , H. ringueleti , H. taimensis , and H. vireo by having the anterior portion of snout completely covered by odontodes ( Fig. 2 ) (vs. anterior portion of snout with an odontode-free band between the dorsal and ventral series of odontodes). It distinguishes from H. alberti , H. depressicauda , H. depressinotus , H. francirochai , H. maculipinnis , H. packysarkos , H. paulinus , and H. prata by having the anterior portion of abdomen covered by large plates arranged in three longitudinal series without naked spaces between them (vs. abdominal plates, when present, not arranged in three longitudinal series, or when arranged with naked spaces between the lateral and median series). It differs from H. acuen , H. bockmanni , H. chromodontus , and H. vespuccii by having an ovoid to rectangular spinelet (vs. spinelet V -shaped, with lateral projections anteriorly directed). It can be distinguished from H. iota and H. leucophrys by the absence of well-developed odontodes at posterior tip of supraoccipital (vs. presence). It differs from H. armatus and H. hungy by having 28 vertebrae (vs. 25-26 in H. hungy and 29 in H. armatus ). It distinguishes from H. leucofrenatus by having the clear longitudinal stripe of head ending near the vertical through distal tip of opercle (vs. clear longitudinal stripe longer, bifurcating at the tip of compound pterotic and running parallel to each other; the inferior stripe over the canals of the lateral line, reaching the vertical through the middle of dorsal-fin base); bifid neural spine of seventh vertebra present, dorsolaterally projected (vs. bifid neural spine absent); and basipterygia contacting along midline until anterior margin (vs. anterior portion of basipterygia with halves slightly apart from each other). Finally, H. notatus differs from H. thayeri by having the mid-dorsal series of plates generally interrupted, with a total of 4-13 plates (mode 5), 5-8 lacking plates in the middle of the series ( Fig. 3 ) (vs. mid-dorsal series of plates generally continuous, with 15-18 plates (mode 17), rarely one plate lacking in the middle of the series).

Description. Morphometric and meristic data in Tables 4-7. Dorsal body profile ascending from snout to vertical through posterior edge of eye; slightly convex to dorsalfin insertion; descending at dorsal-fin base; almost straight to caudal-fin origin, except by small elevation in region of dorsal procurrent rays. Males with dorsal profile generally flattened, sometimes straight from vertical through posterior edge of nostril to caudal-fin origin ( Fig. 4 ). Ventral body profile almost straight from snout to pelvic-fin insertion; slightly ascending at pelvic-fin base; straight to caudal-fin origin, except by slight descent in region of ventral procurrent rays. Greatest body depth at dorsal-fin origin. Greatest body width at opercular opening, gradually tapering towards snout and caudal fin. Caudal peduncle almost ellipsoid in transverse section.

Anterior margin of snout rounded in dorsal view; tip of snout with single large rostral plate, its posterior margin with U -or V -shaped concavity; well-developed odontodes completely covering ventral and dorsal portions of rostral plate, postrostral plate 1, and lateroventral margin of head ( Figs. 3a, c ). Remaining odontodes of head and body small, randomly distributed, not forming conspicuous rows, crests or tufts. Eye small, dorsolaterally placed, not visible in ventral view. Iris operculum present. Compound pterotic fenestrae variable in size, small on laterodorsal and large on lateroventral portions; posterior extension of compound pterotic medium-sized and rounded, not surpassing rib of sixth vertebra; infraorbital canal entering infraorbital series via sphenotic. Parieto-supraoccipital not forming part of dorsal wall of swimbladder capsule.

Body entirely covered by dermal plates, except on ventral part of head, region overlying opening of swimbladder capsule, pelvic-fin origin, and urogenital pore. Abdomen completely covered by large plates; anterior plates arranged in three longitudinal rows, lateral row with 2-5(4) plates; posterior plates, between pelvic fins, randomly distributed.

Lips oval, papillose; lower lip fringy, larger than upper, falling short of pectoral girdle; papillae gradually smaller towards lip edge. Maxillary barbel reduced, free from oral disk. Teeth slender and bifid; median cusp larger and rounded, lateral smaller and pointed. Premaxillary and dentary accessory teeth absent, even in smallest examined specimen (12.2 mm SL).

Dorsal fin originating approximately at vertical through end of pelvic-fin base; tip of adpressed rays surpassing vertical line at end of anal-fin base. Spinelet small, ovoid, inserted in notch in nuchal plate; locking mechanism non-functional. Nuchal plate exposed area rectangular to pentagonal. Anterior portion of compound supraneural first dorsal-fin proximal radial contacting neural spine of seventh vertebra. Pectoral fin originating immediately behind opercular opening; tip of adpressed rays almost reaching vertical through urogenital opening; well-developed odontodes on unbranched ray, gradually enlarged toward tip. Cleithrum and coracoid almost totally exposed, with many odontodes, except for arrector fossa region covered by skin only. Arrector fossa almost completely enclosed by ventral lamina of coracoid and cleithrum, opening restricted to small anterior area near midline. Pectoral axillary slit present in juveniles and adults, large, about 1.5-2 times in orbital diameter, at angle of 45° with body axis. Pelvic-fin unbranched ray shorter than branched ones. Anal-fin first proximal radial contacting haemal spine of 13th vertebra. Caudal fin concave, lower lobe slightly longer than upper. Adipose fin and azygous plates absent.

Five lateral series of plates ( Fig. 3a ). Dorsal series complete from posterior edge of supraoccipital to caudalpeduncle end. Mid-dorsal series short, from posterior edge of compound pterotic to near vertical through middle of dorsal-fin base; occasionally longer, with many intermediate plates lacking. Median series from compound pterotic to caudal-fin base; sometimes 1-3 plates lacking; 1-11 non-perforated plates in middle portion of series, near vertical through dorsal-fin base, and 1-8 non-perforated plates at end of series; first plate, sometimes also second, restricted to sensorial canal, occasionally fused to compound pterotic. Mid-ventral series long, from lateral process of cleithrum to vertical through tip of adpressed anal fin. Ventral series from near middle or end of pelvicfin length to caudal-peduncle end.

Color in alcohol. Dorsal profile medium brown; dorsal area of head dark brown from tip of snout to median portion of supraoccipital. Three dorsal inconspicuous saddles: first at dorsal-fin base; second at end of dorsal-fin length; third at end of caudal peduncle. Clear stripe extending from tip of snout to near vertical through distal tip of opercle, passing by dorsal margin of postrostral plates 1 and 2, external edge of nostril, limits between prefrontal and infraorbitals 2 and 3, and dorsal margin of orbit. Lateral profile of body homogeneously medium brown, except for yellowish lateroventral portion of head and lateral process of cleithrum, sometimes with spots forming vermiculated pattern. Ventral portion of body yellowish.

Membranes of dorsal, anal, pectoral, and pelvic fins hyaline, pigmented areas of rays arranged in interspersed bars forming transversal bands. Caudal fin densely pigmented, except for slender unpigmented edge and hyaline areas in both lobes: superior lobe with oblique blotch from posteromedial portion of unbranched ray to distal portion of median rays, and other at superior tip of lobe, these two areas separated by dark inclined line; inferior lobe with small posteromedial area restricted to unbranched ray and last branched ray, and another at inferior tip of lobe.

Sexual dimorphism. Males commonly smaller and with dorsal profile more depressed than females ( Fig. 4 ). Males have conspicuous urogenital papilla immediately posterior to anus present, expanded flap of skin on dorsal surface of the first pelvic-fin ray present, and tip of adpressed pelvic fin generally reaching anal-fin origin. Nasal chamber of males enlarged, its width 12.5-17.1% in HL (vs. 8.6-12.3% in females), and its length 15.7-21.7% in HL (vs. 10.2-15.6% in females).

Distribution. Restricted to the rio São João drainage and other small coastal drainages running to the Baía de Guanabara and to the Baía de Sepetiba in the Rio de Janeiro State ( Fig. 5 ).

Conservation status. Despite of the relatively small extent of occurrence (approximately 2,661 km 2), a threat criterion according to IUCN, Hisonotus notatus is a common species, being well-represented in fish collections and usually abundant in the sampling sites. In addition, no current risk was recognized that may endanger the species. Thus, according to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2014), Hisonotus notatus can be classified as Least Concern (LC).

Remarks. The original description of Hisonotus notatus was based on specimens of two different lots: MCZ 8177, with a single specimen from the rio Paraíba do Sul drainage in Juiz de Fora, Minas Gerais State; and MCZ 7764, from Santa Cruz, Rio de Janeiro State. The latter lot originally had 95 specimens and today has 79 specimens, since 12 were exchanged: six to the fish collection of ANSP (ANSP 166924) and six to the MNRJ (MNRJ 28882). The remaining four specimens were not found during the last counting by the staff of MCZ in the year of 2012, according to information on online data base of the fish collection of MCZ. The specimens of lots MCZ 7766 and MCZ 7768 are erroneously referred as cotypes of H. notatus in the catalog book of MCZ, since they are not mentioned by Eigenmann & Eigenmann (1889) in the original description. Our observations revealed that the type series of Hisonotus notatus is mixed, and the specimens from the two original lots belong to two different species, one of them (MCZ 8177) described herein as new. Based on that, we restricted H. notatus to the specimens originally from MCZ 7764, and in order to clarify the taxonomic status of this nominal species, following the article 74 of the International Code of Zoological Nomenclature (ICZN, 1999), we designate here a specimen as a lectotype. Although the material has been sampled in 1865, the specimens are all well preserved, and we chose as the lectotype the specimen in best condition from the lot MNRJ 28882, representing the most abundant original sampling. Thus, H. notatus is herein restricted to the rio São João drainage and to other small coastal drainages running to the Baía de Sepetiba and to the Baía de Guanabara, such as rio Grande drainage and rio Macacu drainage, while H. thayeri occurs in coastal basins of rio Paraíba do Sul, Lagoa Feia, rio Macaé, rio Itabapoana, rio Itapemirim, rio Novo, rio Benevente, and rio Doce.

The data from the type locality of H. notatus are controversial. In the MCZ record book, the only information is Santa Cruz for the locality, and Dom Pedro for the collector. Later, in a paper that provides details of the collecting sites of the Thayer Expedition, Higuchi (1996) presented the following information for this sample point (field number Thayer 114): Rio de Janeiro, Santa Cruz, rio Grande (arroio Fundo), in the urban area of Rio de Janeiro Municipality, Santa Cruz farm – Emperor Pedro II’s farm, ca. 22º56’S 43º12’W, Apr 1865, D. Pedro II, D. Bourget. Curiously, Higuchi (1996) gave the same geographical coordinates for point Thayer 156, for which the original label reads “rio Quenda” or “rio Quendu” in handwritting. He proposed the handwritten locality as an error, and pointed that the collection probably was made near or at Emperor Pedro II’s Fazenda Santa Cruz, as well as Thayer 114. However, the old Emperor Pedro II’s farm, in Santa Cruz, is about 50 km straight west to the geographical coordinate suggested by Higuchi (1996), today an urban area. At the farm there is no reference to rio Grande, being this area drained by the rio Guandu basin, probably referred by collectors in the original label as “rio Quendu”. Based on this, we propose 22º54’40”S 43°41’7”W as the geographical coordinate representing Thayer 114 and 156 collection points, and consequently the type locality for H. notatus . This location is at the old Emperor Pedro II’s farm, more specifically at the farm headquarters, today a building used by the Brazilian Army.

Material examined. Types. MNRJ 42969 , lectotype, PRESENT DESIGNATION, 31.3 mm SL, Brazil, Rio de Janeiro State, Santa Cruz, rio Guandu , Santa Cruz farm – Emperor Pedro II’s farm, 22º54’40”S 43º41’7”W, Apr 1865, D. Pedro II & D. Bourget . MCZ 7764 , paralectotypes, 79 (17, 24.4-32.2 mm SL) ; MNRJ 28882 , 5 (2, 28.8-32.2 mm SL), collected with lectotype. Non-types. All from Brazil, Rio de Janeiro State. Rio Cação drainage : MZUSP 10315 , 22 , 22.4 -31.0 mm SL, Itaguaí, córrego of Lagoa Nova, km 7 on the road Itaguaí-Raiz da Serra . MZUSP 10316 , 28 , 22.6-34.2 mm SL, Itaguaí, ribeirão of Ponte do Teixeira, km 5 on the road Itaguaí-Raiz da Serra. Rio Grande drainage : MZUSP 23767 , 20 , 23.6-34.8 mm SL, Rio de Janeiro, Jardim Palmares , km 52 on the road Rio-Santa Cruz. Rio Macacu drainage : MNRJ 13737 , 31 , 14.2-26.55 mm SL, Cachoeiras de Macacu, affluent to rio Soarinho , near Papucaia . MNRJ 15741 , 124 (4 c&s), 16.1-38.3 mm SL (28.4- 38.3 mm SL), Cachoeiras de Macacu, rio Macacu . MNRJ 18033 , 2 , 29.2-30.8 mm SL, Guapimirim, rio Paraíso . MNRJ 19386 , 15 , 19.3-36.1 mm SL, Cachoeiras de Macacu, rio Guapiaçu . MNRJ 20286 , 1 , 32.9 mm SL, Guapimirim, rio Paraíso . MNRJ 20346 , 51 , 16.7 -39.0 mm SL, rio Macacu. Rio São João drainage: DZSJRP 13836, 1, 34.9 mm SL, Silva Jardim, affluent to rio São João . DZSJRP 13852 , 46 (3 c&s), 14.3-39.4 mm SL (27.6-39.4 mm SL), Silva Jardim, affluent to rio São João . DZSJRP 13874 , 22 , 13.8- 43.5 mm SL (31.6-43.5 mm SL), Silva Jardim, affluent to rio São João . DZSJRP 13889 , 23 (1 c&s), 20.4-45.2 mm SL (35.2-45.2 mm SL), Silva Jardim, affluent to rio São João . MBML 2089 , 10 , 24.3 -40.0 mm SL, Silva Jardim, córrego Bananeiras . MBML 2104 , 4 , 29.1-30.8 mm SL, Silva Jardim, rio São João . MNRJ 13552 , 30 (2 c&s), 12.2-31.5 mm SL, Silva Jardim, rio São João . MNRJ 19253 , 12 , 30.3-36.1 mm SL, Silva Jardim, rio Pirineus / Crubixais . MNRJ 19262 , 5 , 21.0- 34.7 mm SL, Silva Jardim, córrego Água Fria affluent to rio Pirineus . MNRJ 19267 , 5 , 23.8-31.1 mm SL, Silva Jardim , rio do Ouro . MNRJ 19277 , 10 , 21.8-26.1 mm SL, Rio Bonito , rio dos Índios . MNRJ 37448 , 6 , 14.0- 41.40 mm SL, Silva Jardim, rio Aldeia Velha . MNRJ 37500 , 30 , 21.8-44.8 mm SL, Casimiro de Abreu , córrego Aldeia Velha . MNRJ 37826 , 5 , 22.8 - 31.0 mm SL, Casimiro de Abreu , córrego Ipiabas . MNRJ 37855 , 1 , 34.2 mm SL, Silva Jardim, rio Iguape . MNRJ 38097 , 2 , 31.2-33.3 mm SL, Silva Jardim, rio São João . MNRJ 38103 , 3 , 29.3-36.1 mm SL, Casimiro de Abreu, rio Lontras . MNRJ 38114 , 24 , Rio Bonito, rio Bacaxa . MNRJ 38147 , 10 of 42 (1 c&s), 28.1-39.9 mm SL, Silva Jardim rio Maratua. Other drainages : MNRJ 17703 , 44 , 20.6 -34.0 mm SL, Magé, rio Suruí . MNRJ 39003 , 7 , 27.3 - 3.8 mm SL (27.3-35.8 mm SL), Piabetá, affluent to rio Inhomirim .

Types not examined. ANSP 166924 , 6 , collected with lectotype .

Figures

Fig. 6. Hisonotus notatus, MCZ 7764, paralectotype, 29.2 mm SL, female, Brazil, Rio de Janeiro, Santa Cruz district.

Fig. 7. Hisonotus notatus, DZSJRP 13874, non-type, 43.5 mm SL, female, Brazil, Rio de Janeiro, Silva Jardim Municipality, rio São João drainage.

Fig. 2. Scanning electron micrographs of tip of snout of Hisonotus notatus, DZSJRP 13852, 34.6 mm SL (a, c) and Hisonotus thayeri, MNRJ 14752, 38.4 mm SL, paratype (b, d).

Fig. 3. Lateral plates of trunk of Hisonotus notatus, DZSJRP 13852, 31.5 mm SL, male (a) and Hisonotus thayeri, DZSJRP 20157, paratype, 32.4 mm SL, female (b), left side. Scale bars = 1mm.

Fig. 4. Sexual dimorphism in body depth in Hisonotus notatus, MNRJ 38147, female, 37.2 mm SL (above), and male 32.3 mm SL (below).

Fig. 5. Geographic distribution of Hisonotus notatus (black squares, and star for type locality) and Hisonotus thayeri (red dots, and triangle for type locality) in southeastern Brazilian costal drainages. Symbols can represent more than one sampling locality.