Trichomycterus araxa, Costa & Mattos & Sampaio & Giongo & Almeida & Katz, 2022
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publication ID |
https://dx.doi.org/10.3897/zse.98.83109 |
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publication LSID |
lsid:zoobank.org:pub:F75C5C03-4C7E-4AF6-BD19-AF4182AFC24A |
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persistent identifier |
https://treatment.plazi.org/id/367D112A-6969-4316-8456-D7AA9DE987AE |
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taxon LSID |
lsid:zoobank.org:act:367D112A-6969-4316-8456-D7AA9DE987AE |
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treatment provided by |
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scientific name |
Trichomycterus araxa |
| status |
sp. nov. |
Trichomycterus araxa sp. nov.
Figs 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 8A-C View Figure 8
Holotype.
UFRJ 7029, 53.6 mm SL; Brazil: Minas Gerais State: Araxá Municipality: stream tributary to Rio Capivara, a tributary of Rio Quebra Anzol, a tributary of the Rio Araguari subdrainage, Rio Paranaíba drainage, Rio Paraná basin, at Reserva Particular do Patrimônio Natural São Sebastião, 19°40'26"S, 47°02'24"W, about 970 m asl; A.M. Katz et al., 3 November 2021.
Paratypes.
All from Brazil: Minas Gerais State: Araxá Municipality: Rio Araguari subdrainage, Rio Paranaíba drainage, Rio Paraná basin. UFRJ 7030, 18 ex., 28.1-60.7 mm SL; CICCAA 05603, 10 ex., 28.5-56.3 mm SL; all collected with holotype. - UFRJ 7031, 3 ex. (C&S), 36.7-57.7 mm SL; about 1.7 km below the type locality, 19°40'02"S, 47°01'34"W, about 940 m asl; W.M.S. Sampaio et al., 5 August 2021. - MZUSP 114937, 9 ex., 19.6-64.0 mm SL; stream tributary to Rio Quebra Anzol, 19°36'27"S, 46°54'57"W, about 983 m asl; O.T. Oyakawa et al., 26 June 2013. - MZUSP 114925, 15 ex., 14.4-55.2 mm SL; stream tributary to Rio Quebra Anzol at Araxá City, 19°35'37"S, 46°52'57"W, about 963 m asl; O.T. Oyakawa et al., 25 June 2013. - MZUSP 114918, 13 ex., 16.4-52.4 mm SL; stream tributary to Rio Quebra Anzol near Santuário Nossa Senhora de Fátima, 19°35'56"S, 46°54'51"W, about 1020 m asl; O.T. Oyakawa et al., 26 June 2013.
Additional specimens (non-types).
MZUSP 109239, 2 ex.; Domo de Salitre; L.F. Salvador & M.J. Pozza, no date.
Diagnosis.
Trichomycterus araxa is distinguished from all other species of the subgenus Trichomycterus Cryptocambeva by the presence of a black median longitudinal stripe on the caudal fin in juvenile specimens below about 40 mm SL (Fig. 6 View Figure 6 ; vs. black median longitudinal stripe always absent). Trichomycterus araxa differs from all other species of Cryptocambeva , except T. macrotrichopterus , by having a long pectoral-fin filament, its length about 40-60% of pectoral-fin length in specimens about 50 mm SL or larger (vs. short, about 5-20%). Trichomycterus araxa is also distinguished from T. macrotrichopterus by the presence of the anterior infraorbital canal, supported by an elliptical antorbital (Fig. 8A View Figure 8 ; vs. anterior infraorbital canal absent, antorbital circular, Fig. 8D View Figure 8 ), a moderately deep opercular odontode patch (Fig. 8B View Figure 8 ; vs. slender, Fig. 8E View Figure 8 ), posterior margin of the metapterygoid, anterior margin of the hyomandibula anterior outgrowth and dorso-posterior margin of the quadrate slightly curved (Fig. 8B View Figure 8 ; vs. strongly waved, Fig. 8E View Figure 8 ), and absence of a prominent projection on the lateral margin of the lateral ethmoid, ventrally overlapping the sesamoid supraorbital (Fig. 8A View Figure 8 ; vs. presence, Fig. 8C View Figure 8 ).
Description.
General morphology (Figs 4 View Figure 4 - 7 View Figure 7 ). Morphometric data appear in Table 1 View Table 1 . Body moderately slender, subcylindrical, slightly depressed anteriorly, compressed posteriorly. Greatest body depth at vertical immediately anterior to pelvic-fin base. Dorsal and ventral profiles of head and trunk slightly convex, about straight on caudal peduncle. Anus and urogenital papilla at vertical just anterior to middle of dorsal-fin base. Head sub-trapezoidal in dorsal view. Anterior profile of snout slightly convex in dorsal view. Eye small, dorsally positioned in head, about equidistant from mouth and posterior border of opercle. Posterior nostril nearer anterior nostril than orbit. Tip of nasal barbel posteriorly reaching opercle or area slightly posterior to it; tip of maxillary barbel posteriorly reaching pectoral-fin base; rictal barbel posteriorly reaching area between interopercular patch of odontodes and pectoral-fin base. Mouth subterminal. Jaw teeth irregularly arranged, pointed, 35-49 in premaxilla, 32-45 in dentary. Head and trunk skin with minute skin papillae.
Dorsal and anal fins subtriangular, distal margin slightly convex; total dorsal-fin rays 10 or 11 (i-ii + II + 7), total anal-fin rays 9 (ii + II + 5); anal-fin origin at vertical through base of 5th branched dorsal-fin ray. Pectoral fin subtriangular in dorsal view, posterior margin slightly convex, first pectoral-fin ray terminating in long filament, reaching about 40-60% of pectoral-fin length in specimens above about 50 mm SL; total pectoral-fin rays 7 (I + 6). Pelvic fin subtruncate, its posterior extremity at vertical through middle of dorsal-fin base and posterior to urogenital aperture; pelvic-fin bases medially in contact; total pelvic-fin rays 5 (I + 4). Caudal fin subtruncate, posterior corners rounded; total principal caudal-fin rays 13 (I + 11 + I), total dorsal procurrent rays 20-23 (xix-xxii + I), total ventral procurrent rays 16 or 17 (xv-xvi + I).
Laterosensory system. Supraorbital sensory canal continuous, posteriorly connected to posterior section of infraorbital canal. Supraorbital pores 3, all paired: s1, adjacent to medial margin of anterior nostril; s3, adjacent and just posterior to medial margin of posterior nostril; s6, at transverse line through posterior half of orbit. Pores s6 nearer its symmetrical homologous pore than orbit. Infraorbital sensory canal arranged in 2 segments; anterior section isolated, with two pores: i1, at transverse line through anterior nostril, i3, at transverse line just anterior to posterior nostril; posterior segment posteriorly connected to postorbital canal, with 2 pores: i10, adjacent to ventral margin of orbit, i11, posterior to orbit. Postorbital canal with 2 pores: po1, at vertical line above posterior portion of interopercular patch of odontodes, po2, at vertical line above posterior portion of opercular patch of odontodes. Lateral line of body short, with 1 pore just posterior to head.
Osteology (Fig. 8A-C View Figure 8 ). Mesethmoid T-shaped in dorsal view, cornu extremity rounded. Antorbital elliptical, short, dorso-posteriorly carrying thin latero-sensory canal. Sesamoid supraorbital slender, without processes. Premaxilla sub-rectangular in dorsal view, slightly narrowing laterally. Maxilla boomerang-shaped, shorter than premaxilla. Autopalatine sub-rectangular in dorsal view when excluding its postero-lateral process, its width about half its length including anterior cartilage; medial margin slightly sinuous, lateral margin about straight; posterolateral process well-developed, subtriangular, its length slightly shorter than autopalatine length excluding anterior cartilage. Lateral ethmoid with minute lateral projection. Metapterygoid sub-triangular, slightly longer than deep. Quadrate L-shaped, vertical branch wider, dorsoposterior margin in close proximity to hyomandibula outgrowth.
Hyomandibula long, with well-developed anterior outgrowth; middle portion of dorsal margin of hyomandibula slightly concave. Opercle slender, with moderately deep odontode patch with 12-16 odontodes transversely arranged. Opercular odontodes pointed, anterior odontodes narrow and straight, posterior odontodes slightly broader, slightly curved. Dorsal process of opercle short. Opercular articular facet for hyomandibula with prominent rounded extension, articular facet for preopercle well developed, rounded. Interopercular patch of odontodes long, about four fifths of hyomandibula length, with 26-31 odontodes. Interopercular odontodes pointed, arranged in irregular longitudinal rows. Preopercle slender, narrowing anteriorly.
Parurohyal robust, lateral process subtriangular, latero-posteriorly directed, tip pointed; parurohyal head well-developed, with prominent anterolateral paired process; middle foramen oval circular; posterior process long, slightly shorter or equal to distance between anterior margin of parurohyal and anterior insertion of posterior process. Branchiostegal rays 8. Vertebrae 35. Ribs 12 or 13. Dorsal-fin origin at vertical through centrum of 19th vertebra; anal-fin origin at vertical through centrum of 22nd or 23rd vertebra. Two dorsal hypural plates, corresponding to hypurals 4 + 5 and 3, respectively; single ventral hypural plate corresponding to hypurals 1 and 2, and parhypural.
Colouration (Figs 4 View Figure 4 - 7 View Figure 7 ). Colouration of preserved specimens in alcohol similar to colouration in live specimens, except for yellow colouration being paler after preservation. Flank, dorsum and head side pale yellow, with variably shaped dark brown to black marks in adults. Smaller specimens (14.4-21.8 mm SL) with unspotted colouration and black narrow stripe along flank longitudinal midline. In specimens above about 25 mm SL, dark marks variably arranged and shaped, gradually changing in larger specimens, becoming more spotted and longitudinal midline stripe becoming fragmented or disappearing. Some specimens with dark marks arranged in three longitudinal zones (Fig. 7A-C View Figure 7 ), often forming large, coalesced blotches along dorsal region. In other specimens, longitudinal zones little or not distinct (Figs 4 View Figure 4 , 5 View Figure 5 , 7D, E View Figure 7 ), with spots being smaller and more scattered on flank in some specimens (Fig. 7E View Figure 7 ). Venter always white to yellowish white, paired fins hyaline. In smaller juveniles, about 14-40 mm SL (Fig. 6 View Figure 6 ), fins hyaline, caudal fin with broad median black stripe anteriorly joined to flank midline stripe; in larger specimens, unpaired fins gradually becoming faintly spotted on their bases, and caudal black stripe becoming inconspicuous in larger specimens (Figs 4 View Figure 4 , 5 View Figure 5 , 7 View Figure 7 ).
Etymology.
The name Trichomycterus araxa is a reference to the occurrence of the new species in the region of Araxá, a historical Brazilian city founded in the 18th century, during the colonial period. The word Trichomycterus araxa is possibly derived from the Tupi-Guarani to designate some native people formerly inhabiting the region.
Distribution and habitat notes.
Trichomycterus araxa occurs in the Rio Quebra Anzol drainage, which is part of the Rio Paranaíba drainage, a main tributary of the upper Rio Paraná basin, in altitudes about 940-1020 m asl (Fig. 2 View Figure 2 ). In the type locality area, the new species was collected in shallow, moderate fast-flowing streams, about 40-50 cm deep, and about 3-5 m wide, with a well-preserved marginal vegetation. The stream bottom comprised gravel, sand and pebbles. The new species was collected buried in the stream bank, but smaller specimens were sporadically seen swimming above gravel substratum. See Costa et al. (2022a) for a list of species occurring in this area, where this species is identified as Trichomycterus sp.
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