Hyphessobrycon comodoro, Dagosta & Seren & Ferreira & Marinho, 2022

Dagosta, Fernando Cesar Paiva, Seren, Thomaz Jefrey, Ferreira, Anderson & Marinho, Manoela Maria Ferreira, 2022, The emerald green tetra: a new restricted-range Hyphessobrycon (Characiformes: Characidae) from the upper rio Juruena, Chapada dos Parecis, Brazil, Neotropical Ichthyology (e 210119) 20 (1), pp. 1-15 : 3-9

Hyphessobrycon comodoro , new species urn:lsid:zoobank.org:act:2F8D142C-C2D3-4CB2-AD15-D746BB4F90E4

( Figs. 1–2 ; Tab. 1)

Holotype. MZUSP 125904 , 29.6 mm SL. Brazil, Mato Grosso State, Municipality of Comodoro, lagoon at tributary of the rio Mutum, formed due to the construction of a road, tributary of rio Camararé , upper rio Juruena basin, rio Tapajós basin, 13°12’47.6”S 59°54’13.8”W, 567 m a.s.l., 19 Oct 2018, F. Dagosta, A. Ferreira & H. Lenza.

Paratypes. All from Brazil, Mato Grosso State, Municipality of Comodoro, rio Mutum drainage, upper rio Juruena basin. MZUSP 125215 , 4 c&s, 211, 16.8–38.6 mm SL, UFPB 12086 , 10 , 24.0– 31.2 mm SL, INPA 59651 , 5 , 26.2–31.1 mm SL, collected with holotype. MZUSP 115698 , 22 , 18.2 –34.0 mm SL, rio Mutum at the Fazenda Mutum , at the bridge of the road between Comodoro and Vilhena, 13°05’09.2”S 59°53’33.8”W, 502 m a.s.l., 29 Aug 2013, O. Oyakawa, F. Dagosta, M. Marinho & P. Camelier. MZUSP 125217 , 63 , 13.9–32.1 mm SL, lagoon at tributary of the rio Mutum , formed due to the construction of a road, tributary of rio Camararé , upper rio Juruena basin, rio Tapajós basin, 13°13’23.2”S 59°54’41.8”W, 551 m a.s.l., 19 Oct 2018, F. Dagosta, A. Ferreira & H. Lenza. MZUSP 125221 , 136 , 14.3–29.7 mm SL, rio Mutum at the bridge of the road BR –364, 13°05’05.3”S 59°53’30.7”W, 504 m a.s.l., 20 Oct 2018, F. Dagosta, A. Ferreira & H. Lenza .

Diagnose. The new species can be distinguished from all congeners, except Hyphessobrycon . cachimbensis Travassos, 1964 , H. cyanotaenia Zarske & Géry, 2006 , H. fernandezi Fernández-Yépez, 1972 , H. melanostichos , H. nigricinctus Zarske & Géry, 2004 , H. paucilepis García-Alzate, Román-Valencia & Taphorn, 2008 , H. petricolus Ohara, Lima & Barros, 2017 , H. piranga Camelier, Dagosta & Marinho, 2018 , H. psittacus Dagosta, Marinho, Camelier & Lima, 2016 , H. scholzei Ahl, 1937 , H. sovichthys Schultz, 1944 , H. stegemanni Géry, 1961 , H. taphorni García-Alzate, Román-Valencia & Ortega, 2013 , H. tuyensis García-Alzate, Román-Valencia & Taphorn, 2008 , and H. vilmae Géry, 1966 by the presence of a well-defined and relatively narrow dark midlateral stripe on body, extending from head to the middle caudal-fin rays (vs. well-defined longitudinal stripe absent, or stripe wider than the orbit, or stripe starting approximately vertically through the origin of the dorsal fin or stripe blurred posteriorly). The new species is distinguished from the aforementioned species, except H. cachimbensis , H. cyanotaenia , H. melanostichos , H. nigricinctus , and H. petricolus , by the possession of a humeral blotch (vs. humeral blotch absent). It is distinguished from H. cachimbensis and H. cyanotaenia by having the distal profile of the anal fin falcate in males (vs. approximately straight or convex) and from H. cachimbensis , H. petricolus , and H. nigricinctus by having 13–16 branched anal-fin rays (vs. 17–26). It can be further distinguished from H. cyanotaenia by lacking concentration of black pigmentation on longest rays of dorsal, pelvic, and anal fins (vs. pigmentation present). It is readily distinguished from H. melanostichos , the most similar congener, by having 11 or 12 horizontal scale rows around caudal peduncle (vs. 14), fewer branched pelvic-fin rays (6 vs. 7), humeral blotch wider than deep, with pigmentation much more intense than the dark midlateral band, with well-defined edges (vs. humeral blotch deeper than wide, with pigmentation similar to the dark midlateral band, without well-defined edges). Another useful character in distinguishing H. comodoro from H. melanostichos is the presence of 13–15, mode 14, rarely 16 (only 3 of 30 specimens), branched anal-fin rays (vs. 16–18, mode 16).

Description. Morphometric data in Tab. 1. Body compressed, moderately elongate. Greatest body depth at dorsal-fin origin. Dorsal profile of head convex from upper lip to vertical through posterior nostril; slightly convex from that point to base of supraoccipital spine Dorsal profile of body convex along predorsal region, slightly convex along dorsal-fin base, straight from terminus of dorsal-fin base to adipose-fin origin, and slightly concave to straight from that point to origin of anteriormost dorsal procurrent caudal-fin ray. Ventral profile of head and body convex from tip of lower lip to pelvic-fin origin, slightly concave between latter point to anal-fin origin, somewhat straight to convex (see Sexual Dimorphism section) along anal-fin base, and concave from the terminus of anal fin to origin of anteriormost ventral procurrent caudal-fin ray.

Jaws vertically aligned, mouth terminal. Premaxillary teeth in two distinct rows. Outer row with 2(1), 3*(21), or 4(9) tri- to pentacuspid teeth. Inner row with 5*(31) trito heptacuspid teeth. Posterior tip of maxilla at vertical through posterior half of second infraorbital. Maxilla with 1(2), 2*(28), or 3(1) conical to pentacuspid teeth. Dentary with 5*(31) larger penta- to heptacuspid teeth followed by series of 5 to 9 diminutive conical to tricuspid teeth. Central median cusp in all teeth longer than lateral cusps. Branchiostegal rays 4(4). Gill-rakers 8(2) or 9(2) in the lower and 7(1) or 8(3) in the upper branch.

Cycloid scales, with 5–7 radii from focus to posterior border, and conspicuous circulii anteriorly. Lateral line incomplete, with 6(1), 7(1), 8*(26), 9(2), or 10(1) perforated scales, and 29*(6), 30(16), or 31(7) total scales on longitudinal series. Longitudinal scale rows between dorsal-fin origin and lateral line 4(1) or 5*(30). Longitudinal scale rows between lateral line and pelvic-fin origin 3*(27) or 4(4). Scales along middorsal line between posterior tip of supraoccipital process and dorsal-fin origin 9*(13), 10(11), or 11(7). Horizontal scale rows around caudal peduncle 11(6) or 12*(25). Base of anteriormost anal-fin rays covered by series of 3 or 4 scales. Caudal fin not scaled.

Supraneurals 4(2) or 5(2). Dorsal-fin rays ii*(29), iii(2), 7(1), 8(10), or 9*(20). Base of last dorsal-fin ray at vertical anterior to anal fin. Pectoral-fin rays i*(31), 9(16), or 10*(15). Pelvic-fin rays i*(31), 6*(31). Adipose fin frequently present, of variable size, present in 27 specimens, absent in four specimens. Anal fin falcate, with iv*(4), 13(3), 14*(18), 15(7), or 16(3) branched rays. Principal caudal-fin rays i,9,8,i*(27), i,8,8,i(1), i,10,8,i(1), i,9,7,i(1); caudal fin forked, lobes somewhat pointed, of similar size. Dorsal procurrent caudal-fin rays 10(4); ventral procurrent caudal-fin rays 9(4). Total vertebrae 32(2) or 33(2): precaudal vertebrae 14(1) or 15(3) and caudal vertebrae 17(2) or 18(2).

Color in alcohol. Overall ground coloration of head and body beige ( Fig. 1 ). Some specimens retaining guanine on opercular region. Dorsal portion of head and dorsal midline of body dark. A reticulated pattern on first three to four horizontal scale rows, formed by concentration of chromatophores on posterior margin of scales. Snout, jaws and 1 st and 2 nd infraorbitals with concentration of dark chromatophores, 3 rd and 4 th infraorbitals with scattered dark pigmentation and 5 th and 6 th infraorbitals densely pigmented with dark chromatophores, continuing with dark midlateral stripe. Roughly inverted teardrop-shaped humeral blotch formed by two layers of pigmentation. Superficial layer darker and conspicuous, overlapping midlateral stripe and encompassing approximately four scales horizontally and one or two vertically. Subjacent layer with scattered pigmentation encompassing approximately three scales vertically and forming a ventral projection to the humeral spot with diffuse borders. Dark midlateral stripe on body, extending from upper half of posterior portion of eye to tip of middle caudal-fin rays. Abdominal region with few scattered chromatophores. Sparse dark chromatophores above anal fin, mainly near anal-fin base. Caudal-peduncle blotch absent. Adipose fin with scattered dark chromatophores. All fins with dark chromatophores scattered along edge of lepidotrichia. Dorsal and anal fins with dark pigmentation on interadial membranes. Some specimens with sparse dark pigmentation on pelvic-fin interadial membranes.

Color in life. Middorsal area olive green ( Figs. 1C , 2 ); abdominal region silvery to yellow, with some specimens with orange pigmentation in the ventral portion. Upper portion of eye yellow to red, upper-posterior region dark pigmented. First and second infraorbitals, maxilla, lower jaw, gular area and preopercle with yellow pigmentation and scattered orange chromatophores. Remaining infraorbitals mostly silvery and with sparse orange cromatophores. Some specimens with lower portion of opercle lacking guanine, exposing red branchial filaments inside branchial chamber. Bright green midlateral stripe above and below the dark midlateral stripe, thicker at region above anal-fin base. All fins vivid orange to red coloration, more intense in caudal and anal fins. Adipose fin pale hyaline to pale yellow.

Sexual dimorphism. Males with anal-fin base slightly convex (vs. somewhat straight in females). Dark midlateral stripe in males wider and blurred (vs. midlateral stripe relatively narrow and with more defined edges in females), a type of sexual dichromatism involving the larger concentration of melanophore-based pigments in males (Pastana et al., 2017). Bony hooks on fins not present.

Geographical distribution. The new species is so far known from headwater of the rio Mutum, tributary of the rio Camararé, upper rio Juruena basin at Chapada dos Parecis, Mato Grosso State, Brazil ( Fig. 3 ).

Ecological notes. Two collection sites of Hyphessobrycon comodoro are impoundments of tributaries of the rio Mutum formed by the road building ( Fig. 4 ). In these habitats, the water is transparent, with maximum widths ranging 50–60 m and depth 0.3– 2 m. The substrate is formed by sand, silt, and organic matter, with the presence of submerged aquatic macrophytes and large amounts of filamentous algae. The only other species collected syntopically was Hoplerythrinus unitaeniatus (Spix & Agassiz, 1829) , probably a predator of the new species. The streams that form the lagoons are small, 2–4 m wide and 0.5–2 m deep, with clear rapid waters and a bottom composed of sand and leaf litter. Local vegetation is composed of secondary forest. The other known locality lies at the rio Mutum itself, downstream to the other two. At that point, the new species occurs syntopically with Hyphessobrycon hexastichos Bertaco & Carvalho, 2005 and Hasemania nambiquara Bertaco & Malabarba, 2007 . The diet was mainly composed of resources autochthonous (91.6% of the volume of food items), mainly vegetable fragments (57.7%) and aquatic insects (32.7%). The vegetable fragments were composed of aquatic macrophyte structures and aquatic insects (fragments of adults, larvae, and pupae of Diptera and larvae of Trichoptera, and Odonata).

Specimens analyzed were sampled in a region under moderate anthropogenic pressure, which may influence the diet of fish species. Further, damming streams to road buildingchanges the taxonomic and functional of fish assemblages and limits the longitudinal dispersion (Brejão et al., 2020). The transformation from lotic to lentic environments, with an increase in the width of the canopy-opening channel, creates pelagic and benthic areas that allow the proliferation of macrophytes and algae (Brejão et al., 2020). Biological data taken from regions impacted by human action has high scientific value, but in the case of this species, it is crucial that data also be available from less impacted environments.

Etymology. The name comodoro is in reference to the Municipality of Comodoro, Mato Grosso State, where all the specimens were collected. It is also the name of a senior naval rank used in many navies, which inspired the municipality’s name. A noun in apposition.

Conservation status. Hyphessobrycon comodoro is endemic to Brazil and is a restricted-range species, a common pattern among endemic characids of the ‘Chapada dos Parecis’ biogeographic region (Dagosta et al., 2020). Despite such biogeographic region was considered by those authors as one of the Endemic Amazonian Fish Areas (EAFAs), i.e., regions that should be considered as conservation priorities in the basin by presenting imminent threats and a low cover of protected areas, the new species is endemic to one of the most preserved river basins draining the Cerrado biome – the rio Mutum drainage. Hyphessobrycon comodoro is so far known by three localities, but its EOO (Extent of occurrence) is likely underestimated since only the headwater of the rio Mutum basin was sampled. Most of the rio Mutum basin lies within the Nambikwara indigenous territory, where H. comodoro is likely to occur. Despite it has been exported in the aquarium trade it remains abundant in collection sites, which, as far as we know, are the same as those fished by the professional fishermen. Therefore, this species is assessed as Least Concern (LC) according to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2019).

Figures

FIGURE 1 | Hyphessobrycon comodoro, Brazil, Mato Grosso State, Municipality of Comodoro, rio Mutum, upper rio Juruena basin: A. Holotype, MZUSP 125904, 29.6 mm SL, male; B. Paratype, MZUSP 125215, 25.3 mm SL, female; C. Aquarium specimen, not measured or preserved.

FIGURE 2 | Live coloration of Hyphessobrycon comodoro, Brazil, Mato Grosso State, Municipality of Comodoro, rio Mutum, upper rio Juruena basin: A. Holotype, MZUSP 125904, 29.6 mm SL, male; B. Paratype, MZUSP 125215, 27.4 mm SL, male lacking adipose fin; C. Paratype, MZUSP 125215, 29.8 mm SL, female.

FIGURE 3 | Distribution of Hyphessobrycon comodoro in the upper rio Mutum, rio Juruena basin, Brazil. Red star (type locality), black dot (occurrence of other paratypes). Symbol can represent more than one collection event.

FIGURE 4 | Lagoon at the rio Mutum headwater due to the construction of a road, tributary of rio Camararé, upper rio Juruena basin, rio Tapajós basin, Comodoro, Mato Grosso, Brazil.