Trichomycterus brucutu, Reis & Pinna, 2023

TRICHOMYCTERUS BRUCUTU SP. NOV.

( FIG. 19)

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: 0E3EC319-DA7C-4D01-BE1F-C704D3347A2C

Holotype: MZUSP 87834, 103 mm SL; Brazil, state of Minas Gerais, Santo Antônio de Itambé, Lajeado Creek , tributary of Rio Mãe d’Água (18°30’0.00”S 43°17’60.00”W); col. A. Carvalho Filho, 30 August 2004. GoogleMaps

Paratypes: MZUSP 126757 View Materials , 2 View Materials , 24.6–71.8 mm SL; collected with holotype GoogleMaps . MNRJ 48472 View Materials , 1, 120.6 mm SL; Brazil, state of Minas Gerais, Conceição do Mato Dentro Municipality: unamed creek, tributary of left margim of Ribeirão Santo Antônio or Cruzeiro at headwater region (18 o 46’46”S 43 o 33’21”W); col. S.A. Santos, M GoogleMaps . R. Britto & D.F. Moraes, 30 July 2016 .

Diagnosis: The combination of the following traits distinguishes T. brucutu from congeners: (1) body depth 19.0–19.9% SL (vs. 18.3% or lower); (2) long and deep dorsal and ventral integument folds from end of dorsal and anal fins to base of caudal-fin, with elongate procurrent rays (vs. dorsal and ventral integument folds beginning at middle of caudal peduncle length); (3) colour pattern consisting of tiny spots, round to vermiculate, homogeneously distributed over entire body; and (4) pectoral-fin rays I + 7 (vs. I + 5, I + 6 or I + 8). Among congeners in south-eastern South America, character 1 and 2 distinguish T. brucutu from all congeners; character 3 from all congeners except T. laury and species in the T. brasiliensis species complex; character 4 from 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. giganteus , T. immaculatus , T. lauryi , T. nigricans , T. pradensis and T. tantalus (with I + 8 or higher). Among congeners in the Rio Doce Basin , T. brucutu is most similar to T. argos and T. brunoi and it can be distinguished from those two species, in addition to characters mentioned above, by the pelvic-fin bases spaced out (vs. closely set).

Description: Morphometric data for specimens examined is presented in Table 7. Body long and almost totally 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 long, wide and as deep as body at beginning of anal-fin base, with a long and wide dorsal and ventral integumentary folds from end of dorsal and anal fin to caudal fin, with long proccurent rays.

Head approximately 1/6 of SL, pentagonal, longer than wide and depressed. Mouth subterminal. Upper jaw slightly longer than lower jaw. 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 extending from base to slightly up of coronoid process, 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 over entire ventral surface of premaxilla. Premaxillary teeth conical.

Eye small sized, 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. Extensor tentaculi and dilatator operculi hypertrophied, creating crest-like elevation dorsal to eyes. 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 the base of pectoral fin. Rictal barbel inserted immediately ventral to maxillary barbel, its tip reaching lateroposterior border of interopercle. Nasal barbel originating on posterolateralregionofanteriornaris, reachinganterior border of opercle. Interopercular patch of odontodes oval in shape and with well-developed odontodes, prominent in ventral aspect of head. Interopercular patch of odontodes extending from vertical through posteroventral border of eye to anteroventral of 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 37–47. Opercular patch of odontodes on dorsolateral surface of posterior part of head, positioned anterodorsally to pectoral-fin base, roundish in shape in dorsal aspect and with same size as eye diameter. Opercular odontodes 18–21, 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 shorter, their tips following continuous line along fin margin. Pelvic-fin with convex distal profile, its origin slightly posterior to middle of SL and anterior to vertical through dorsal-fin origin, touching the anterior border of anal and urogenital openings in adults, but not beyond. Bases of pelvic fins separated by one eye diameter. Pelvic-fin rays I + 4, first ray. Dorsal fin long, its distal margin sinusoidal. Dorsal-fin origin closer to base of caudal-fin than to tip of snout. Dorsal-fin rays ii + II + 7 (2). Anal fin slightly smaller than dorsal fin, its distal margin gently convex. Anal-fin origin posterior to vertical through end of dorsal-fin base.Anal-fin rays ii + II + 5 (2). Caudal fin subtruncate with 6 + 7 principal rays. Adipose fin, if present, incorporated or modified into deep integumentary fold extending between end of dorsal fin and caudal-fin origin. Post-Weberian vertebrae 37 (2) and 38 (1). First dorsal-fin pterygiophore immediately anterior to neural spine of 17 th (2) and 18 th (1) vertebrae, first anal-fin pterygiophore immediately anterior to neural spine of 21 st (2) and 22 nd (1) vertebrae. Caudal fin procurrent rays plus one segmented non-principal ray dorsally and ventrally. Procurrent caudal-fin rays, 24–25 (2) dorsally and 14–17 (2) ventrally, beginning anteriorly at 28 th (2) vertebra. Ribs 12 (2) or 13 (1). Branchiostegal rays 8 (3). 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, paired s6, closer to mesial line than to eyes, 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. Canal extending from sphenotic posteriorly to terminal pore located ventroposteriorly to eye. Infraorbital pore i1 located ventrolateral 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 dorsomedial to pectoral-fin base.

Coloration in ethanol: Dark chromatophores distributed on inner and outer skin layers throughout entire body. Margin of integumentary fold of opercular patch of odontodes darkly pigmented. Interopercular patch of odontodes white (no pigmentation). Base of nasal barbels surrounded with concentration of dark pigment, extending posteriorly as an elongate dark field to anterior margin of eyes. Tiny brownish round to amoeboid maculae shortly spaced covering entire body, except ventral part. Individual maculae rarely fusing to each other. Head darkest on region corresponding to neurocranium, outlined by brain pigment seen by transparency. Area of levator operculi and adductor operculi muscles on the cheeks with few chromatophores. Tiny round dark spots laterally on head, mainly anterolaterally to opercle. Spots limited to base of fins, with rays outlined in dark.

Etymology: The word brucutu is Brazilian Portuguese slang for rustic, rough or brute, in allusion to the thick deep body and caudal peduncle of this species. The name is used for the Brazilian version of the main character of American cartoon character Alley Oop and it is also the name of the second largest iron cave in Brazil, located in the state of Minas Gerais, in the drainage area of the Rio Doce. It is a noun in apposition.

Remarks: Trichomycterus brucutu has a remarkably deep body when adult. A small specimen (24.7 mm SL) has been found, but was not deep-bodied to the same degree and thus the character is only useful to diagnose adult specimens. A second conspicuous diagnostic character for T. brucutu is the length and depth of dorsal and ventral integumentary folds on the caudal peduncle. Such traits accentuate the depth of the caudal peduncle and makes it externally even (in depth) from the level of dorsal- and anal-fin ends to slightly beyond the caudal-fin base. Such a condition is only shared by Cambeva crassicaudata (Wosiacki & de Pinna 2008) and Cambeva stawiarski (Miranda Ribeiro 1968) among the Trichomycterus lineage (sensu Ochoa et al., 2020). In all other species with deep caudal peduncles (e.g. T. brasiliensis ), the posterior part of caudal peduncle flares towards its fusion with the caudal fin. Material of the species suitable for sequence analysis is not currently available.

Geographical distribution: Trichomycterus brucutu is endemic to Lajeado Creek, in the headwaters of Rio Santo Antônio , a tributary of the Middle Rio Doce Basin ( Fig. 20).