Aspidoras lakoi Miranda Ribeiro, 1949

Tencatt, Luiz Fernando Caserta, Britto, Marcelo R., Isbrücker, Isaäc Jan Hendrik & Pavanelli, Carla Simone, 2022, Taxonomy of the armored catfish genus Aspidoras (Siluriformes: Callichthyidae) revisited, with the description of a new species, Neotropical Ichthyology (e 220040) 20 (3), pp. 1-159 : 76-85

Aspidoras lakoi Miranda Ribeiro, 1949

( Fig. 39 )

Aspidoras lakoi Miranda Ribeiro, 1949:143 (original description; type locality: stream at the do Grotão Forest , da Cachoeira Farm, Minas Gerais State, Brazil). —Nijssen, Isbrücker, 1976:113 (redescription). —Reis, 2003:292 (listed). —Ferraris, 2007:109 (listed). —Wosiacki et al., 2014:311 (morphological comparison). —Leão et al., 2015:585 (listed as comparative material). —Tencatt, Bichuette, 2017:8 (morphological comparison).

Diagnosis. Aspidoras lakoi can be distinguished from all of its congeners by having the following features: anterodorsal portion of infraorbital 1 with a pointed process ( Figs. 40A,B ) (vs. anterodorsal portion of infraorbital 1 slightly rounded, lacking a pointed process, Fig. 40C ) and parieto-supraoccipital fontanel slightly displaced towards anterior portion of parieto-supraoccipital (vs. located medially or slightly displaced towards posterior portion of parieto-supraoccipital in A. albater ; located close to origin of posterior process in A. velites ; located medially on parieto-supraoccipital in remaining congeners). Additionally, it differs from A. aldebaran , A. belenos , A. depinnai , A. poecilus , A. psammatides , A. raimundi , and A. velites by presenting relatively wide frontal bone, with width equal to or slightly larger than half of entire length (vs. narrow, with width slightly smaller than half of entire length in A. aldebaran , A. belenos , A. depinnai , A. poecilus , A. raimundi , and A. velites ; extremely narrow, with width conspicuously smaller than half of entire length in A. psammatides ); from A. aldebaran , A. belenos , A depinnai , A. gabrieli , A. kiriri , A. maculosus , A. raimundi , and A. velites it can be distinguished by having 6 to 13 preadipose platelets (vs. less than 6 platelets). Aspidoras lakoi further differs from A. azaghal , A. belenos , A. depinnai , A. fuscoguttatus , A. maculosus , A. mephisto , A. poecilus , A. psammatides , A. raimundi , and A. velites by having inner laminar expansion of infraorbital 1 extremely well developed (vs. well developed in A. azaghal and A. depinnai ; ranging from moderately developed to well developed in A. fuscoguttatus and A. poecilus ; moderately developed in A. belenos , A. maculosus , A. mephisto , and A. raimundi ; poorly developed in A. psammatides and A. velites ).

Description. Morphometric data presented in Tab. 6. Head compressed with convex dorsal profile; somewhat triangular or trapezoid in dorsal view. Snout moderately developed and relatively pointed; or more rounded. Head profile convex from tip of snout to anterior nares; region of frontal and/or parieto-supraoccipital slightly concave in some specimens; ascending slightly convex from this point to dorsal-fin origin. Profile slightly convex along dorsal-fin base. Postdorsal-fin body profile slightly concave to adipose-fin spine; slightly concave from this point to caudal-fin base. Ventral profile of body slightly convex from isthmus to pelvic-fin origin; region of gill opening slightly concave in some specimens; nearly straight from this point to anal-fin origin; slightly concave until caudal-fin base. Body roughly elliptical in cross section at pectoral girdle, gradually becoming more compressed toward caudal fin.

Eye rounded, located dorso-laterally on head; orbit delimited dorsally by lateral ethmoid, frontal and sphenotic, ventrally by infraorbitals. Anterior and posterior nares close to each other, only separated by flap of skin. Anterior naris tubular. Posterior naris close to anterodorsal margin of orbit, separated from it by distance generally slightly smaller than naris diameter. Mouth small, subterminal, width larger than bony orbit diameter. Maxillary barbel moderate to large in size, ranging from not reaching to slightly surpassing anteroventral limit of gill opening. Outer mental barbel slightly larger than maxillary barbel. Inner mental barbel fleshy, with base close to its counterpart.

Lower lip moderately developed, forming small semicircular or triangular fleshy flap. Small rounded papillae covering entire surface of all barbels, upper and lower lips, snout and isthmus.

Mesethmoid short; anterior tip relatively long, equal to or slightly larger than 50% of entire bone length (see Britto, 2003:123, ch. 1, state 0; fig. 1A); posterior portion wide, generally partially exposed; relatively large exposed area in some specimens. Nasal slender, curved laterally, inner margin generally with moderately-developed laminar expansion; outer margin with reduced laminar expansion; mesial border contacting only frontal; contacting frontal and mesethmoid in some specimens.

Frontal elongated, relatively wide, with width equal to or slightly larger than half of entire length ( Fig. 3B ); anterior projection ranging from short, with size smaller than nasal length, to long, with size larger than nasal length; some areas of anterior margin covered by thick layer of skin in some specimens. Frontal fontanel relatively small, ellipsoid or somewhat rhomboid; posterior tip extension not entering anterior margin of parieto-supraoccipital. Sphenotic somewhat trapezoid, contacting parieto-supraoccipital dorsally, pterotic-extrascapular posteriorly, second infraorbital ventrally and frontal anteriorly. Pterotic-extrascapular roughly pipe-shaped, with posteriormost portion contacting first lateral-line ossicle, and ventral margin contacting opercle and cleithrum; posterior expansion almost entirely covering lateral opening of swimbladder capsule, leaving slender pseudotympanic area on its dorsal margin covered only by thick layer of skin. Parieto-supraoccipital wide, posterior process poorly developed; not contacting nuchal plate. Parieto-supraoccipital medial keel expanded ventrally; laminar, with posterior portion at same level as posterior process tip; or expanded posteriorly, slightly surpassing tip of posterior process. Parieto-supraoccipital fontanel small, roundish; slightly displaced towards anterior portion of parieto-supraoccipital; fontanel occluded, reduced to a small fossa, in some specimens.

Two laminar infraorbitals with minute odontodes; infraorbital 1 large, ventral laminar expansion generally moderately developed; poorly developed in specimens with about 20.0 mm SL or less; relatively well developed in some specimens; anterior portion with laminar expansion ranging from poorly developed, slightly surpassing posterior margin of nasal capsule, to moderately developed, reaching middle of nasal capsule; anterodorsal portion with a pointed process ( Figs. 40A,B ); inner laminar expansion extremely well developed ( Figs. 5A , 40A,B ); external surface partially covered by thick layer of skin; infraorbital 2 small, slender to more compact; with posterior laminar expansion ranging from moderately to well developed; inner laminar expansion ranging from moderately to well developed; posteroventral margin generally contacting posterodorsal ridge of hyomandibula; close but not directly contacting in some specimens; dorsal tip contacting only sphenotic; or contacting sphenotic and pterotic-extrascapular; presence of secondary laminar expansion on its posterodorsal portion in some specimens; small portions of external surface covered by thick layer of skin ( Figs. 40A,B ). Posterodorsal ridge of hyomandibula, close to its articulation with opercle, oblong, relatively slender; exposed; dorsal ridge of hyomandibula, between pterotic-extrascapular and opercle, exposed or covered by thick layer of skin; covered by thinner layer of skin, externally visible; exposed areas generally bearing small odontodes. Interopercle with posterior portion exposed; almost entirely exposed in some specimens; somewhat triangular, anterior projection moderately developed. Preopercle relatively slender, elongated, minute odontodes sparse on external surface. Opercle compact in shape, width clearly larger than half of its length; free margin convex; posterodorsal region variably with smoothly concave area; without serrations and covered by small odontodes; some portions of bony distal margin irregular in some specimens.

Four branchiostegal rays decreasing in size posteriorly. Hypobranchial 2 somewhat triangular, tip ossified and directed towards anterior portion, posterior margin cartilaginous; ossified portion well developed, about twice size of cartilaginous portion. Five ceratobranchials with expansions increasing posteriorly; ceratobranchial 1 with small process on anterior margin of mesial portion; process strongly reduced in some specimens; ceratobranchial 3 with continuous postero-lateral margin; ceratobranchial 5 toothed on postero-dorsal surface, 22 to 30 (3) teeth aligned in one row. Four epibranchials with similar size; epibranchial 2 slightly larger than others, with small pointed process on laminar expansion of posterior margin; epibranchial 3 with triangular uncinate process on laminar expansion of posterior margin. Two wide pharyngobranchials (3 and 4), pharyngobranchial 3 with triangular laminar expansion on posterior margin; triangular laminar expansion with notches in some specimens. Upper tooth plate oval, with 29 to 34(2) teeth aligned in two rows on postero-ventral surface.

Lateral-line canal entering neurocranium through pterotic-extrascapular, branching twice before entering sphenotic: pterotic branch with single pore; preoperculomandibular branch conspicuously reduced, with single pore opening close to postotic main canal; more developed, with pore opening closer to anteroventral border of pterotic-extrascapular in some specimens; postotic main canal widens just posterior to pterotic branch. Sensory canal continuing through pterotic-extrascapular, entering sphenotic as temporal canal, which splits into two branches: one branch giving rise to infraorbital canal, other branch entering frontal through supraorbital canal, both with single pore. Supraorbital canal branched, running through nasal bone. Epiphyseal branch of supraorbital canal relatively long, with pore opening close to frontal fontanel. Nasal canal with three openings, first on posterior edge, second on posterolateral portion and third on anterior edge; second pore generally fused with first pore. Infraorbital canal running through entire second infraorbital, extending to infraorbital 1 and generally opening into two pores. Preoperculomandibular branch giving rise to preoperculomandibular canal, which runs through entire preopercle with three openings, leading to pores 3, 4, and 5, respectively; pore 3 opening between suture of preopercle and posterodorsal ridge of hyomandibula in some specimens.

Dorsal fin somewhat triangular, located just posterior to third or fourth dorsolateral body plate. Dorsal-fin rays II,8(14), posterior margin of dorsal-fin spine smooth. Nuchal plate poorly to moderately developed in length; generally, with posterior portion exposed; almost entirely exposed in some specimens; minute odontodes in exposed area ( Fig. 41 ); spinelet extremely short or short, and generally partially exposed; spine ranging from poorly developed, with adpressed distal tip not reaching middle portion of dorsal-fin base, to moderately developed, with adpressed distal tip slightly surpassing middle portion of dorsal-fin base; anterior margin with small odontodes. Pectoral fin roughly triangular, its origin just posterior to gill opening. Pectoral-fin rays I,9*(16), I,10(1); posterior margin of pectoral spine with nine to 21 poorly- or moderately-developed serrations along almost its entire length; small region just posterior to origin of spine lacking serrations; serrations only on distal half of pectoral-spine posterior margin in some specimens; some serrations directed towards origin of spine, perpendicularly directed or directed towards tip of spine; presence of bifid serrations in some specimens ( Fig. 42 ). Anteroventral portion of cleithrum partially exposed; posterolateral portion of scapulocoracoid reduced, generally externally visible. Pelvic fin oblong, generally located just below third or fourth ventrolateral body plate, and at vertical through fourth dorsal-fin branched ray. Pelvic-fin rays i,5*(17). Adipose fin roughly triangular, separated from posterior origin of dorsal-fin base by nine to 11 dorsolateral body plates. Anal fin somewhat triangular, generally located just posterior to 15 th ventrolateral body plates, and at vertical through region of preadipose platelets. Anal-fin generally with eight rays (16); some specimens with ii,5,i(2) or ii,6(3). Caudal-fin rays generally i,12,i(4); caudal fin smoothly bilobed, dorsal lobe generally slightly larger than ventral lobe; nearly truncated in some specimens.

Two or three laterosensory canals on trunk; first ossicle tubular, second ossicle laminar, third lateral-line canal, if present, encased in third dorsolateral body plate. Body plates with conspicuous line of relatively large odontodes confined to posterior margins; dorsolateral body plates 26*(6), 27(11); ventrolateral body plates 23*(3), 24(14); dorsolateral body plates along dorsal-fin base 6*(14), 7(3); dorsolateral body plates between adipose-fin spine and caudal-fin base 7*(8), 8(9); preadipose platelets 6(3), 7(1), 8(3), 9(1), 10(3), 11(2), 12*(3), 13(1); small platelets covering base of caudal-fin rays; small platelets disposed dorsally and ventrally between junctions of lateral plates on posterior portion of caudal peduncle. Region between nuchal plate and posterior process of parieto-supraoccipital with relatively large platelets in some specimens.

Vertebral count 24(1); ribs 7(1), first pair conspicuously large; parapophysis of complex vertebra moderately developed ( Fig. 8C ).

Coloration in alcohol. Ground color of body light or brownish yellow, with top of head dark brown. Posterodorsal portion of head, region below eye, opercle and cleithrum with scattered dark brown or black chromatophores. Snout covered by dark brown or black chromatophores on its dorsal surface; chromatophores densely disposed in some specimens; with dark brown or black diffuse stripe from anteroventral portion of orbit to upper lip lateral area in some specimens; ventrolateral portion of snout variably with dark brown or black chromatophores. Upper lip and maxillary barbel with dark brown or black chromatophores; area of lateral portion of upper lip with conspicuous concentration of dark brown or black chromatophores in some specimens. Dorsal series of three to five dark brown or black blotches, first on anterior portion of dorsal-fin base, second on posterior portion of dorsal-fin base, third on adipose-fin base, fourth, if present on middle portion of caudal peduncle, and fifth, if present, on caudal-fin base; blotches variably diffuse. Dorsal portion of body with conspicuous concentration of dark brown or black chromatophores between counterparts of dorsolateral body plates in some specimens. Ventral surface of trunk, generally on region close to origins of pectoral and pelvic fins, and region posterior to urogenital opening with dark brown or black chromatophores in some specimens. First dorsolateral body plate with conspicuous concentration of dark brown or black chromatophores; posterior margin of some dorso- and ventrolateral body plates, and lateral line pores with conspicuous concentration of dark brown or black chromatophores in some specimens. Midline of flank with longitudinal series of generally four to five medium- to large-sized conspicuous dark brown or black blotches; blotches rounded, oblong or irregular; blotches variably diffuse. Dorsal half of dorsolateral body plates with dark brown or black chromatophores; region of anterior and posterior portions of dorsal-fin base, between dorsal and adipose fins, adipose-fin base, between adipose and base of caudal peduncle and base of caudal peduncle with more concentrated chromatophores, forming conspicuous blotches in some specimens. Ventral half of dorsolateral body plates and dorsal half of ventrolateral body plates with concentration of dark brown or black chromatophores, forming conspicuous blotches in some specimens; blotches generally more evident on anterior portion of body and on area of flank midline blotches. Mid-ventral portion of ventrolateral body plates on area of flank midline blotches with concentration of dark brown or black chromatophores; variably forming conspicuous blotches; blotches generally more evident posteriorly to pelvic-fin origin; fused to flank midline blotches in some specimens; ventral portion of ventrolateral body plates with concentration of dark brown or black chromatophores, generally more evident posterior to anal-fin anterior origin, in some specimens. Dorsal fin with dark brown or black spots; aligned spots, forming longitudinal or oblique bars in some specimens; region of first and second branched rays with concentration of dark brown or black chromatophores on membranes in some specimens; dorsal-fin base with conspicuous concentration of dark brown or black chromatophores, generally more concentrated on bases of first and last branched rays; spine covered by dark brown or black chromatophores. Pectoral fin with dark brown or black chromatophores on its dorsal surface, generally more evident on spine and first branched rays; region of body around dorsal portion of pectoral-fin origin with concentration of dark brown or black chromatophores in some specimens. Pelvic fin generally with sparse dark brown or black chromatophores on its dorsal surface; region of body around dorsal portion of pelvic-fin origin with concentration of dark brown or black chromatophores in some specimens. Adipose-fin membrane with dark brown or black chromatophores; conspicuous concentration of dark brown or black chromatophores in some areas of membrane, generally more evident close to spine; adipose-fin spine generally with dark brown or black chromatophores. Anal fin with conspicuous concentrations of dark brown or black chromatophores in some areas, generally more evident on its middle portion and bases of last branched rays; with one or two dark brown or black blotches in some specimens. Middle portion of caudal-fin base, posteriorly to last flank midline blotch, generally with small- to medium-sized dark brown or black blotch; blotch variably diffuse or fused with last midlateral blotch. Caudal fin with three to six transversal dark brown or black and generally slender bars.

Coloration in life. Similar to that observed in preserved specimens but with ground color of body grayish yellow in some specimens. Body covered by whitish yellow and green iridescent coloration ( Fig. 43A ).

Geographical distribution. Aspidoras lakoi is known only from the rio Grande basin, a tributary to the upper portion of the rio Paraná basin in Minas Gerais State,

Brazil ( Fig. 10 ).

Ecological notes. The typical habitat of Aspidoras lakoi at a stream with unknown name tributary to the rio Grande basin. The small stream presents transparent slightly brownish water, with up to one meter depth, moderate current, and substrate composed by clay, sand, gravel, larger rocks, submerged logs, and leaf litter ( Fig. 43B ). The species was found in syntopy with two unidentified species, Rhamdiopsis sp. and Trichomycterus sp.

Conservation status. Aspidoras lakoi is currently known only from its type locality and two additional records located in its surrounding area, both from the rio Grande basin, upper rio Paraná drainage in Minas Gerais State. Although the currently available material show that the species occurs in both left and right bank tributaries of the rio Grande, recent survey efforts (2022) in the region of the type locality, led to the capture of this species in a single site (of 14 sampled), in which only five specimens were captured so far (Naraiana Benone, 2022, pers. comm.), suggesting that A. lakoi may present a relatively restricted geographic distribution and low abundance. Additionally, the whole area is severely impacted by anthropic action, especially for agricultural and cattle raising purposes. Furthermore, the Extent of Occurrence of A. lakoi was roughly estimated to be 363 km 2 (as the coordinates of the type locality remain unknown, we adopted the coordinates of Passos City as a reference, which is the municipality of the type locality). According to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2019), Aspidoras lakoi can be classified as Near Threatened (NT), approximating the Endangered (EN) category by criterion B1b(iii).

Material examined. In addition to the material examined by Nijssen, Isbrücker (1976:113), except by the preparation of 3 CS specimens (disarticulated, indeterminate size) from MNRJ 5293, the following specimens were analysed. MNRJ 31639, 6, 16.3‒38.5 mm SL, stream tributary to the left margin of the ribeirão do Turvo, Minas Gerais, rio Grande basin.

Figures

FIGURE 3 | Dorsal view of the head of CS specimens showing the three patterns of paired frontal bones (outlined in black) in Aspidoras: (A) narrow, with width of each frontal slightly smaller than half of its entire length (Aspidoras maculosus, UFBA 3291, 30.7 mm SL), (B) relatively wide, with width equal to or slightly larger than half of entire length (Aspidoras albater, MZUSP 40793, 29.4 mm SL), and (C) extremely narrow, with width clearly smaller than half of entire length (Aspidoras psammatides, UNT 9604, 27.3 mm SL). Scale bars = 1 mm.

FIGURE 5 | Dorsal view of the infraorbital series of CS specimens showing the four patterns of size and shape of the inner laminar expansion of infraorbital 1 (white arrows) in Aspidoras: (A) extremely well developed (Aspidoras albater, MNRJ 13080, 30.9 mm SL), (B) well developed (Aspidoras fuscoguttatus, NUP 12677, 36.1 mm SL), (C) moderately developed (Aspidoras poecilus, UNT 6249, 30.9 mm SL), and (D) poorly developed (Aspidoras psammatides, UNT 9604, 27.3 mm SL). Abbreviations: io1: infraorbital 1, io2: infraorbital 2. Scale bars = 1 mm.

FIGURE 8 | Ventral view of the complex vertebra in CS specimens of (A) Aspidoras belenos, paratype, UFRJ 4419 (ex-UFRJ 3861), 22.1 mm SL, with well-developed parapophysis, (B) Aspidoras albater, MNRJ 12571, 35.3 mm SL, with poorly-developed parapophysis, and (C) Aspidoras albater, MNRJ 12581 (disarticulated, indeterminate size), with moderately-developed parapophysis. Abbreviations: ccv: centrum of the complex vertebra, pcv: parapophysis of the complex vertebra. Scale bars = 1 mm.

FIGURE 10 | Map showing the geographical distribution of Aspidoras albater (type locality: red circle; non-type localities: black circles), A. aldebaran (type locality: red star; non-type localities: white stars), A. azaghal (purple triangle), A. belenos (type locality: purple diamond), A. brunneus (possible region of type locality: grey diamond), A. carvalhoi (type locality: purple circle), A. depinnai (type locality: red square; nontype localities: black squares), A. fuscoguttatus (type locality: red triangle; non-type localities: white triangles), A. gabrieli (type locality: red pentagon; non-type locality: white pentagon), A. kiriri (black cross), A. lakoi (type locality: red diamond; non-type locality: black diamond), A. maculosus (red cross), and A. mephisto (type locality: white cross). Each symbol may represent more than one locality.

FIGURE 39 | Aspidoras lakoi, holotype, MNRJ 5292, 30.8 mm SL, stream at the Grotão Forest, Minas Gerais State, Brazil. Dorsal (top), lateral (middle) and ventral (bottom) views. Photos by Victor de Brito.

FIGURE 40 | Infraorbital series of CS specimens of Aspidoras lakoi, MNRJ 5293, 30.0 mm SL, in lateral (A) and frontal (B) views, and A. albater, MNRJ 13080, 30.9 mm SL, in frontal (C) view. The white arrow and the black line in (A) and (B), respectively, show the pointed process on anterodorsal portion of infraorbital 1. The black line in (C) shows the anterodorsal portion of infraorbital 1 lacking a pointed process. Scale bar = 1 mm.

FIGURE 41 | Aspidoras lakoi, holotype, MNRJ 5292, 30.8 mm SL, showing predorsal region of trunk in dorsal view. Abbreviations: np: nuchal plate, pso: parieto-supraoccipital. Scale bar = 1 mm.

FIGURE 42 | Aspidoras lakoi, MNRJ 5293, CS, 30.0 mm SL, showing dorsal view of the pectoral-fin spine. Scale bar = 1 mm.

FIGURE 43 | Uncatalogued specimen of Aspidoras lakoi photographed alive (A), and its typical habitat, a stream with unknown name, 20°50’20”S 46°30’21”W, tributary to the rio Grande, Minas Gerais State, Brazil (B). Photo (B) by Naraiana Benone.