Trichomycterus ipatinga, Reis & Pinna, 2023

Reis, Vinícius & Pinna, Mário De, 2023, Diversity and systematics of Trichomycterus Valenciennes 1832 (Siluriformes: Trichomycteridae) in the Rio Doce Basin: iterating DNA, phylogeny and classical taxonomy, Zoological Journal of the Linnean Society 197, pp. 344-441 : 408-411

TRICHOMYCTERUS IPATINGA SP. NOV.

( FIGS 7, 29)

Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: BE65375F-FE39-4F4D-BD8D-1FC7EB4002BB

Holotype: MZUSP 112279 , 67.6 mm SL; Brazil, state of Minas Gerais, Conceição do Mato Dentro, Meloso Creek, tributary Rio Santo Antônio (19°4’35.98”S 43°20’28.84”W); col. M. V. Loeb , 12 January 2011.

Paratypes: All from Brazil, state of Minas Gerais. MZUSP 87814, 11, 39.2–103.5 mm SL, 2 c&s, 102.5– 114.9 mm SL; Serro, creek tributary of Rio Doce Basin (18°34’50.11”S 43°23’31.49”W); col. A. Carvalho Filho; 27 August 2004. MZUSP 104682, 4, 31.3–46.1 mm SL; Conceição do Mato Dentro, Axupé Creek (19°06’41”S 43°16’02”W), col. I Fichberg & M.V. Loeb, 22 March 2009. MZUSP 104699, 6, 25.2–52.6 mm SL; Conceição do Mato Dentro, São João Creek, tributary of Santo Antônio River (19°02’29”S 43°20’34”W), col. I. Fichberg & M.V. Loeb, 19 March 2009. MZUSP 104700, 2, 42.8– 45.0 mm SL; Conceição do Mato Dentro, creek on the road between Conceição do Mato Dentro and Meloso District (19°2’58.00”S 43°21’45.00”W), col. I. Fichberg & M.V. Loeb, 18 March 2009. MZUSP 104701, 10, 26.4–39.7 mm SL; Conceição do Mato Dentro, creek on the road that crosses the Meloso Municipality, Rio Doce Basin (19°04'33.0"S 43°20'26.0"W); col. I. Fichberg & M.V. Loeb, 21 March 2009. MZUSP 104702, 6, 27.0– 78.9 mm SL, 1 c&s, 50.13 mm SL; Conceição do Mato Dentro, Faia Creek, tributary of São João River (19°01’19”S 49°20’39”W); col. I. Fichberg & M.V. Loeb, 19 March 2009. MZUSP 104706, 1, 52.3 mm SL; Conceição do Mato Dentro, Axupé Creek, Santo Antonio River (19°6’36.00”S 43°17’55.00”W); col. I. Fichberg & M.V. Loeb, 18 March 2009. MZUSP 109370, 2, 47.8– 56.4 mm SL, 1 c&s, 56 mm SL; Brazil, Minas Gerais, Santa Barbara; Ribeirão Preto Creek, Piracicaba River (20°5’36.00”S 43°39’26.00”W); col. B.P. Maia, 31 July 2010. MZUSP 109385, 1, 100.5 mm SL; Santa Barbara; São João River, Piracicaba River (20°2’28.00”S 43°40’2.00”W); col. B. P. Maia, 31 July 2010. MZUSP 109393, 2, 50.1–112.6 mm SL; Brazil, Minas Gerais, Santa Barbara; Ribeirão Preto Creek, Piracicaba River (20°3’57.00”S 43°40’16.00”W); col. B.P. Maia, 31 July 2010. MZUSP 112237, 5, 26.5–31.6 mm SL; Conceição do Mato Dentro, Axupé Creek, Santo Antônio River (19°6’44.10”S 43°16’4.65”W), col. M.V. Loeb, 6 January 2011; MZUSP 112241, 2, 27.8–32.6 mm SL; Conceição do Mato Dentro, Axupé Creek, Santo Antônio River (19°6’44.47”S 43°16’44.68”W), col. M.V. Loeb, 6 January 2011; MZUSP 112253, 1, 25.7 mm SL; Conceição do Mato Dentro, Ponte Nova Creek, Santo Antônio River (18°59’24.67”S 43°23’1.62”W); col. M.V. Loeb, 10 January 2011; MZUSP 112260, 6, 29.7–58.4 mm SL; Conceição do Mato Dentro, Antonieta Creek, Santo Antônio River (19°0’42.07”S 43°22’20.42”W); col. M.V. Loeb, 10 January 2011; MZUSP 112270, 7, 28.8–63.9 mm SL, 3 c&s, 29.0– 41.2 mm SL; Conceição do Mato Dentro, São João River, Santo Antônio River (19°2’30.77”S 43°20’34.02”W); col. M.V. Loeb, 11 January 2011; MZUSP 112271, 4, 39.3–103.8 mm SL, 1 c&s, 39.1 mm SL; Conceição do Mato Dentro, São João Creek, Santo Antônio River (19°1’21.73”S 43°20’38.60”W); col. M.V. Loeb, 11 January 2011. MZUSP 112277, 1, 94.7 mm SL; Conceição do Mato Dentro, São João Creek, Santo Antônio River (19°1’57.18”S 43°22’42.57”W); col. M.V. Loeb, 12 January 2011. All from state of Espírito Santo —MBML 4337, 4, 31–60.9 mm SL; Iúna, José Preto River in the National Park of Caparaó, Manhuaçu River (20°22’9.50”S 41°51’27.50”W); col. L.M. Sarmento-Soares, M.R. Britto, V.C. Espíndola, F.M.R.S. Pupo, R.F.M. Pinheiro & M.M.C. Roldi, 10 September 2011. MBML 4340, 1, 73.7 mm SL; Iúna, Córrego Feio Creek, Manhuaçu Basin (20°22’9.40”S 41°51’28.70”W); col. L.M. Sarmento-Soares, M.R. Britto, V.C. Espíndola, F.M.R.S. Pupo, R.F.M. Pinheiro & M.M.C. Roldi, 10 September 2011. MBML 6223, 13, 30.1–95.4 mm SL; Afonso Cláudio, Rio Guandu (20°4’12.00”S 41°13’44.00”W); col. Researches from the BIOdiversES Project, 11 August 2012. MBML 6825, 1, 52.4 mm SL; Santa Teresa, Vinte Cinco de Julho River, Santa Maria do Rio Doce River (19°50’14.60”S 40°33’18.80”W); col. L.M. Sarmento-Soares, R.F. Martins Pinheiro, M.M.C. Roldi & R. Becalli, 5 May 2013. MBML 6844, 34, 40.7–100.5 mm SL; Santa Teresa, Vinte e Cinco de Julho River, tributary of Santa Maria do Rio Doce (19°50’20.70”S 40°34’4.30”W); col. L.M. Sarmento-Soares, R.F. Martins Pinheiro, M.M.C. Roldi & R. Becalli, 5 May 2013. MNRJ 52979, 1, 53.9 mm SL; came from MZUSP 112271. MNRJ 52980, 3, 30 - 34.5 mm SL; came from MZUSP 104701.

Diagnosis: The combination of the following traits distinguishes T. ipatinga from congeners: (1) body randomly covered by roundish maculae, either far larger or far smaller than eye, evenly and densely spaced; (2) horizontal dark stripe on the caudal fin extending from base to tip of middle rays (vs. absent); and (3) pectoral-fin rays I + 7 (I + 5, I + 6 or I + 8); (4) two or, rarely, three lateral line pores (vs. always three or more). Among congeners in south-eastern South America, character 1 distinguishes T. ipatinga from all species except for some colour morphs of T. brasiliensis , T. lauryi and T. vinnulus ; character 2 from all except for T. melanopygius , young stages of T. immaculatus , T. reinhardti and T. tantalus ; character 3 distinguishes T. ipatinga from all species in the T. brasiliensis and T. reinhardti species complex ( Barbosa & Costa, 2010; Costa, 2021; Costa & Katz, 2021), plus T. trefauti (all preceding with I + 6 or fewer) and from T. astromycterus , T. caipora , T. giganteus , T. immaculatus , T. lauryi , T. nigricans and T. tantalus (with I + 8 or more); character 4, when three lateral line pores are present, from all except T. astromycterus , T. aff. caipora , T. nigricans and T. vinnulus . Among congeners in the Rio Doce Basin , T. ipatinga is most similar to T. vinnulus . In addition to characters above, T. ipatinga can be further distinguished from T. vinnulus by more numerous premaxillary teeth (10– 14 vs. 8); more numerous interopercular odontodes (25–38 vs. 25–26). The two species are separated by a barcoding distance of 3.8%.

Description: Morphometric data for specimens examined is presented in Table 12. Body long and almost straight, trunk roughly round in cross-section near head, then slightly deeper than wide and gently compressed to caudal peduncle, tapering to caudal fin. Dorsal profile of body gently convex to dorsal-fin origin, then straight or slightly concave along caudal peduncle to caudal-fin origin. Ventral profile convex from gular region to vent, due partly to abdominal distension, then straight or slightly concave along anal-fin origin to caudal-fin base. Caudal peduncle nearly as deep as body at end of anal-fin base.

Head approximately 1/6 to 1/5 of SL, pentagonal, longer than wide and depressed. Mouth subterminal. Upper jaw slightly longer than lower. Upper lip wider than lower lip, and laterally continuous with base of maxillary barbel. Lower lip small, approximately 2/3 width of upper one, partly divided into right and left portions by median concavity. Lower lip with uniform covering of tiny villi, resulting in velvet-like surface and not clustered into large papillae. Region between upper and lower lips with slender fleshy lobe.

Dentary and premaxillary teeth similar to each other in shape. Dentary teeth conical, arranged in four irregular rows, first row with 10–14 teeth, extending from base to slightly up of coronoid process, with size of individual teeth increasing markedly towards symphysis and from posterior to anterior rows. Total area of premaxillary teeth slightly smaller than that of dentary, with teeth arranged irregularly in four rows, first row with approximately 11–14 teeth, over entire ventral surface of premaxilla. Premaxillary teeth conical.

Eye medium-sized, slightly protruding, positioned dorsally on head, without free orbital rim and covered with transparent skin. Eye located on anterior half of HL, closer to lateral border of head than to the midline in dorsal view. Anterior naris surrounded by tube of integument directed anterolaterally, continuous posterolaterally with nasal barbel. Posterior naris closer to anterior naris than to eyes, surrounded by tube of integument incomplete posteriorly. Maxillary barbel narrowing markedly towards fine tip, reaching from lateroposterior side of interopercle until base of pectoral fin. Rictal barbel inserted immediately ventral to maxillary barbel, its tip reaching from anterolateral to the middle of interopercle. Nasal barbel originating on posterolateral region of anterior naris, reaching from posterior border of eyes to anterior portion of opercle. Interopercular patch of odontodes large compared to head length, oval in shape and with well-developed odontodes, prominent in ventral aspect of head. Interopercular patch of odontodes extending from vertical through ventroposterior border of eye to ventroanterior to opercular patch of odontodes. Interopercular odontodes arranged in two or three irregular series, with those on mesial series much longer than those on lateral one; odontodes gradually larger posteriorly in both series, with those posteriorly on mesial row largest. Interopercular odontodes 25–38. Opercular patch of odontodes on dorsolateral surface of posterior part of head, positioned anterodorsally to pectoral-fin base, roundish in shape and larger than eye in dorsal aspect of head. Opercular odontodes 13–18, sunk in individual slits of integument, progressively larger posteriorly, all with fine tips, with largest ones curved distally and claw-like. Entire patch surrounded by rim of integument.

Pectoral fin with its base immediately posterior and ventral to opercular patch of odontodes. Pectoral-fin rays I + 7. First pectoral-fin ray (unbranched) longer, prolonged as filament beyond fin margin. Other rays progressively less long, their tips following continuous line along fin margin. Pelvic fin with convex distal margin, its origin slightly posterior to middle of SL and anterior to vertical through dorsal-fin origin, anteriorly touching anal and urogenital openings in adults but never covering them. Bases of pelvic fins separated by less than eye diameter close to each other. Pelvic-fin rays I + 4, first ray unbranched. Anterior process of basipterygium long and laterally curved. Dorsal fin long, its distal profile sinusoidal. Dorsal-fin origin closer to base of caudal fin than to tip of snout. Dorsal-fin rays ii + II + 7 (2); iii + II + 7 (5). Anal fin slightly smaller than dorsal fin, its distal profile gently convex. Anal-fin origin posterior to vertical through end of dorsal-fin base. Anal-fin rays ii + II + 5 (2) or iii + II + 5 (5). Caudal fin rounded shape, with 6 + 7 principal rays. Adipose fin absent or modified into low integumentary fold extending between end of dorsal fin and caudal-fin origin. Post-Weberian vertebrae 37 (7). First dorsal-fin pterygiophore immediately anterior to neural spine of 17 th (5) or 18 th (2) vertebra, first anal-fin pterygiophore immediately anterior to neural spine of 21 th (4) or 22 th (3) vertebra. Caudal-fin procurrent rays plus one segmented non-principal ray dorsally and ventrally. Procurrent caudal-fin rays, 16–21 dorsally and 11–15 ventrally, beginning anteriorly at 32 th (7) vertebrae. Pleural ribs 12 (5) or 13 (2). Branchiostegal rays 7 (1) or 8 (6). Dorsal-fin pterygiophores 8. Anal-fin pterygiophores 6.

Cephalic lateral line canals with simple, non-dendritic tubes ending in single pores. Supraorbital canal mostly in frontal bone. Supraorbital pores invariably present: s1 mesial to nasal-barbel base and autopalatine, s3 mesial to posterior nostril and anterior to frontal and paired s6 posteromedial to eye and at midlength of frontal. Infraorbital latero-sensory canal incomplete with four pores, i1 and i3 anteriorly and i10 and i11 posteriorly. This canal extending from sphenotic posteriorly to terminal pore located ventroposteriorly to eye. Infraorbital pore i1 located ventro-lateral to nasal-barbel base and autopalatine, i3 ventrolateral to posterior nostril and anterior to frontal, i10 and i11 posterior to eye. Otic canal without pores. Postotic pores po1, anteromedial to opercular patch of odontodes, and po2, mesial to opercular patch of odontodes. Lateral line of trunk anteriorly continuous with postotic canal and reduced to short tube. Lateral line pores ll1 and ll2, in some specimens the ll3 is present dorsomedial to pectoral-fin base.

Coloration in ethanol: Body covered with small to large round to amoeboid dark maculae. Individual maculae rarely fusing with each other, varying bimodally in size and number, creating two extreme colour patterns ( Fig. 7). At one extreme, maculae mostly twice eye diameter. At the other extreme, maculae smaller than eye diameter and more numerous. Head and base of all fins, except for caudal fin, following colour pattern of body. Caudal fin with dark stripe extending from the base of middle principal caudal-fin rays to nearly margin of fin, evident in young specimens and gradually fading or masked by additional caudal-fin pigmentation in larger individuals. Ventral part of body without dark pigmentation.

Etymology: The name honours Ipatinga, a city located in the state of Minas Gerais where the Piracicaba River joins the Rio Doce. It is a noun in apposition.

Remarks: Trichomycterus ipatinga varies in colour pattern, a situation common in species of the genus ( Arratia et al., 1978; Triques & Vono, 2004; Castellanos-Morales, 2007; Lima et al., 2008; Silva et al., 2010; Ferrer & Malabarba, 2013; Buckup et al., 2014; Nascimento et al., 2017). The overall colour pattern of T. ipatinga may resemble the well-known T. brasiliensis or other species in the T. brasiliensis complex ( Barbosa & Costa, 2010). However, the species is highly divergent from T. brasiliensis both in other morphological traits and in DNA sequences ( Table 2). Contrastingly, T. tantalus and T. melanopygius (both outside of the T. brasiliensis complex) display low DNA barcoding divergence relative to T. ipatinga . Nevertheless, those two species are distinct phenotypically from each other and from T. ipatinga (cf. Remarks, T. tantalus ). In the phylogenetic hypothesis, samples of T. ipatinga form a monophyletic group and are included in a clade with T. aff. caipora , T. melanopygius and T. tantalus , but its closest relative is unresolved.

Geographical distribution: Trichomycterus ipatinga is distributed in headwaters throughout the entire Rio Doce Basin ( Fig. 30), but not in the main channel. The same phenomenon happens with T. melanopygius according to Reis et al. (2020). As with the latter species, such absence is not a result of the destruction of the main channel by the Samarco Dam rupture, because older collection records from the main channel also fail to reveal the species. Thus, the species distribution seems to be a result of habitat preferences, with the main channel serving as a dispersion corridor only.