Aspidoras depinnai Britto, 2000

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 : 53-63

Aspidoras depinnai Britto, 2000

( Fig. 28 )

Aspidoras depinnai Britto, 2000:1049 (original description; type locality: creek at Amaraji-Primavera road). —Reis, 2003:292 (listed). —Ferraris, 2007:109 (listed). —Wosiacki et al., 2014:311 (morphological comparison). —Tencatt, Bichuette, 2017:21 (listed as comparative material).

Diagnosis. Aspidoras depinnai can be distinguished from its congeners, with exception of A. albater , A. azaghal , A. fuscoguttatus , A. gabrieli , A. kiriri , A. poecilus , and A. raimundi by having dorsal fin with conspicuous concentration of dark brown or black chromatophores on its middle portion, forming large dark brown or black blotch (vs. blotch absent); it can be distinguished from A. albater , A. azaghal , and A. gabrieli by having narrow frontal bone, with width slightly smaller than half of its entire length (vs. relatively wide, with width equal to or slightly larger than half of entire length in A. albater and A. gabrieli ; relatively wide, with width equal to half of entire length in A. azaghal ); from A. fuscoguttatus by lacking small spots on dorsal fin (vs. spots present); from A. kiriri by the presence of parapophysis of complex vertebra moderately developed (vs. well developed); from A. poecilus it differs by the presence of the following combination of features: dark brown or black stripe from anteroventral portion of orbit to upper lip lateral area, when present, less evident (vs. generally present and more evident), and flanks generally with fewer and/or less evident dark brown or black markings, not considering the number of blotches in the series along flank midline (vs. markings generally more numerous and/or more evident); and from A. raimundi it can be distinguished by the dorsal-fin color pattern (dark brown or black blotch on middle portion of dorsal fin less pigmented vs. dark brown or black blotch on middle portion of dorsal fin generally present and intensely pigmented; variably with obliquely fragmented blotch, forming two smaller blotches; region of blotch(es) with almost entirely hyaline membranes in some specimens, forming series of dark brown or black spots; presence of non-aligned dark brown or black small spots in some specimens), and by having inner laminar expansion of infraorbital 1 well developed (vs. moderately developed).

Description. Morphometric data of type specimens in Britto (2000), data on additional examined specimens presented in Tab. 4. Head compressed with convex dorsal profile; triangular or somewhat trapezoid in dorsal view. Snout moderately developed and rounded. Head profile convex from tip of snout to anterior nares; ascending slightly convex from this point to dorsal-fin origin; region of parieto-supraoccipital process slightly concave in some specimens. 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; 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 equal to or slightly smaller than naris diameter. Mouth small, subterminal, width larger than bony orbit diameter. Maxillary barbel moderate to large, ranging from not reaching to 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 one or two triangular fleshy flaps. Small rounded papillae covering entire surface of all barbels, upper and lower lips, snout and isthmus.

Mesethmoid short; anterior tip poorly developed, slightly smaller than 50% of bone length (see Britto, 2003:123, ch. 1, state 1; fig. 1B); posterior portion wide, covered by thick layer of skin. Nasal slender, curved laterally, inner margin with moderately-developed laminar expansion; outer margin with reduced laminar expansion; mesial border generally contacting only frontal.

Frontal elongated, narrow, with width slightly smaller than half of entire length ( Fig. 3A ); anterior projection short, size smaller than nasal length; anterior margin partially covered by thick layer of skin. 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 not reaching tip of posterior process. Parieto-supraoccipital fontanel small, roundish; located medially on parieto-supraoccipital.

Two laminar infraorbitals with minute odontodes; infraorbital 1 large, ventral laminar expansion from poorly to moderately developed; anterior portion with well-developed laminar expansion, slightly surpassing middle of nasal capsule ( Fig. 29 ); inner laminar expansion well developed ( Fig. 5B ); small portions of external surface covered by thick layer of skin; infraorbital 2 small, slender; with posterior laminar expansion generally poorly developed; conspicuously reduced in some specimens; inner laminar expansion moderately developed; posteroventral margin close but not directly contacting posterodorsal ridge of hyomandibula, dorsal tip contacting only sphenotic; external surface partially covered by thick layer of skin ( Fig. 29 ). Posterodorsal ridge of hyomandibula, close to its articulation with opercle, oblong, relatively slender; exposed, generally bearing small odontodes; dorsal ridge of hyomandibula, between pterotic-extrascapular and opercle, covered by thin layer of skin. Interopercle covered by thick layer of skin on its anterior portion; or entirely covered by thick layer of skin; somewhat triangular, anterior projection moderately developed. Preopercle relatively slender, elongated, minute odontodes sparse on external surface. Opercle compact in shape, width 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; ceratobranchial 3 with continuous postero-lateral margin; ceratobranchial 5 toothed on postero-dorsal surface, 27 to 28 (2) 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; process absent in some specimens; 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 generally with rounded notch. Upper tooth plate oval, with 30 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; 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, another 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; or slightly shorter, with pore opening closer to supraorbital main canal. Nasal canal with three openings, first on posterior edge, second on posterolateral portion, generally fused with the first pore, and third on anterior edge. Infraorbital canal running through entire second infraorbital, extending to infraorbital 1 and opening into two or three pores. Preoperculomandibular branch giving rise to preoperculo-mandibular canal, which runs through entire preopercle with three openings, leading to pores 3, 4, and 5, respectively; pore 3 opening at posterodorsal ridge of hyomandibula in some specimens.

Dorsal fin somewhat triangular, located just posterior to third dorsolateral body plate. Dorsal-fin rays II,8(15), posterior margin of dorsal-fin spine smooth. Nuchal plate poorly to moderately developed in length; almost entirely exposed, with minute odontodes on exposed area; anterior tip covered by thick layer of skin ( Fig. 30 ); spinelet extremely short to short, partially exposed; spine poorly developed, adpressed distal tip generally not reaching middle portion of dorsal-fin base; or reaching 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(13), I,10(2); posterior margin of pectoral spine with nine to 22 moderately-developed serrations along almost its entire length; small region just posterior to origin of spine lacking serrations; some serrations directed towards origin of spine, perpendicularly directed or directed towards tip of spine; presence of bifid serrations in some specimens; base of branched rays with small laminar expansions on inner margin, generally more evident on first rays; laminar expansions variably with irregular margins ( Fig. 31 ). Anteroventral portion of cleithrum partially exposed; posterolateral portion of scapulocoracoid reduced, externally visible. Pelvic fin oblong, located just below third or fourth ventrolateral body plate, and at vertical through third dorsal-fin branched ray. Pelvic-fin rays i,5(15). Adipose fin somewhat triangular, separated from posterior origin of dorsal-fin base by generally eight dorsolateral body plates. Anal fin somewhat triangular, located just posterior to 13 th or 14 th ventrolateral body plates, and at vertical through region of preadipose platelets. Anal-fin rays, ii,6(11), ii,5,i(4). Caudal-fin rays i,12,i(15), generally five dorsal and/or ventral procurrent rays; caudal fin bilobed, dorsal and ventral lobes with similar size.

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 25(4), 26(7), 27(3), 28(1); ventrolateral body plates 22(1), 23(8), 24(6); dorsolateral body plates along dorsal-fin base 6(11), 7(4); dorsolateral body plates between adipose-fin spine and caudal-fin base 7(1), 8(4), 9(10); preadipose platelets 3(8), 4(6), 5(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. Anterior margin of orbit, above junction of frontal and lateral ethmoid, with small platelets. Ventral surface of trunk with small irregular platelets.

Vertebral count 22(1), 24(1); ribs 6(2), 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; variably forming dark brown or black rounded or irregular spots; with dark brown or black diffuse stripe from anteroventral portion of orbit to upper lip lateral area in some specimens; ventrolateral portion of snout with dark brown or black chromatophores in some specimens. 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; outer mental barbel with dark brown or black chromatophores, generally more evident on its proximal portion, in some specimens. Dorsal series of four 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, and fourth 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. First dorsolateral body plate with conspicuous concentration of dark brown or black chromatophores; posterior margin of some dorso- and ventrolateral plates, and lateral line pores with conspicuous concentration of dark brown or black chromatophores in some specimens. Midline of flank with longitudinal series of four to five medium- to large-sized conspicuous dark brown or black blotches; blotches rounded, oblong or irregular. Dorsal half of dorsolateral body plates with dark brown or black chromatophores; region of posterior portion of dorsal-fin base and adipose-fin base with more concentrated chromatophores, forming conspicuous blotches in some specimens; blotches variably fused to flank midline blotches. 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, forming conspicuous blotches in some specimens; blotches generally more evident posteriorly to pelvic-fin origin; variably fused to flank midline blotches; 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 lacking small spots; conspicuous concentration of dark brown or black chromatophores on its middle portion, forming large dark brown or black blotch; 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; covered by dark brown or black spots in some specimens; spots generally diffuse and more evident on first branched rays. Pelvic fin generally hyaline or with sparse dark brown or black chromatophores on dorsal surface. Adipose-fin membrane with dark brown or black chromatophores, generally more concentrated on posterior portion; spine generally with dark brown or black chromatophores. Anal fin with dark brown or black chromatophores on middle portion of branched rays; or lacking chromatophores in this region; chromatophores concentrated on bases of last branched rays. Middle portion of caudal-fin base, posteriorly to last flank midline blotch, generally with small- to medium-sized dark brown or black blotch; blotch diffuse or fused with last midlateral blotch in some specimens. Caudal fin with three to four transversal dark brown or black slender to wide 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. 32 ).

Geographical distribution. Aspidoras depinnai is known from the rio Ipojuca basin, its type locality, and from the rio Ipanema basin, a tributary to the lower rio São Francisco basin, both in the Pernambuco State, Brazil ( Fig. 10 ) .

Conservation status. Aspidoras depinnai is currently known from the rio Ipojuca and lower rio São Francisco drainage in Pernambuco. Although this species occurs in a relatively restricted area, as we currently know, it seems reasonable to conclude, considering the new records gathered herein, that the species may also occur in other tributaries of the lower rio São Francisco as well as in other coastal drainages surrounding the rio Ipojuca basin. Additionally, no threat to the species is suspected in the present moment. According to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2019), Aspidoras depinnai can be classified as Least Concern (LC).

Remarks. Britto (2000) pointed out two interesting and putatively exclusive features for A. depinnai : (I) an irregular row of minute pores on lateral portion of snout ( Britto,

2000:1051, fig. 3), and (II) a small cartilage between the upper principal and procurrent caudal-fin rays ( Britto, 2000:1052, fig. 5). Despite both features could be observed in the examined A. depinnai specimens, they were also simultaneously found in other

Aspidoras species, such as A. albater , A. poecilus and A. psammatides . As mentioned by

Britto (2000:1053), this small cartilage between the upper principal and procurrent caudal-fin rays ( Fig. 33 ) seems to be the opisthural cartilage (Monod, 1968; McDowall,

1999). Despite that it was not observed in all specimens and with exception of A. kiriri ,

A. lakoi , and A. maculosus , all examined species of Aspidoras presented this cartilage

( Fig. 33 ). Britto (2000) also stated that the presence of bifid serrations restricted to the distal portion of the pectoral spine posterior margin can distinguish A. depinnai from all its congeners. However, it was possible to observe some degree of variation in the

CS specimen examined herein (UFPB 6124), which showed the pattern mentioned by

Britto (2000) only on its left spine, whereas the right spine presents bifid serrations also on its proximal portion.

Aspidoras depinnai was described only from the rio Ipojuca basin, Pernambuco State. However, the analysis of material from the rio Ipanema basin in the lower portion of the rio São Francisco drainage, revealed the presence of A. depinnai . This can be explained by the relatively short distance between these basins, since the main channel of the rio Ipanema is about 10 km from the rio Ipojuca main channel at the region of Arcoverde, where most non-type specimens examined herein were captured.

Material examined. In addition to the material examined by Britto (2000:1049), the following material was analysed. All from Brazil, Pernambuco. Rio São Francisco basin. UFBA 3820, 1 of 2, 33.2 mm SL, small dam in the córrego do Meio. UFPB 6194, 6 of 7, 21.8‒35.5 mm SL, 1 CS of 7, 28.0 mm SL, córrego do Meio. UFPB 7231, 5 of 6, 21.1‒26.0 mm SL, unnamed stream. UFPB 9949, 2 of 3, 20.3‒21.7 mm SL, stream tributary to the rio Mimoso. Rio Ipojuca basin. UFPB 4382, 1 of 5, 22.1 mm SL, unnamed stream.

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 28 | Aspidoras depinnai, holotype, MZUSP 56214, 32.5 mm SL, stream at the Amaraji – Primavera Road, Pernambuco State, Brazil. Dorsal (top), lateral (middle) and ventral (bottom) views. Photo in lateral view by Eduardo Baena.

FIGURE 29 | Lateral view of the head of a CS specimen of Aspidoras depinnai, UFPB 6194, 28.0 mm SL, showing its general infraorbitals pattern. Abbreviations: io1: infraorbital 1, io2: infraorbital 2, sph: sphenotic, pes: pterotic-extrascapular. Scale bar = 1 mm.

FIGURE 30 | Aspidoras depinnai, MZUSP 56216, paratype, 20.6 mm SL, showing predorsal region of trunk in dorsal view. Dotted lines indicate the limits of the tip of the posterior process of the parietosupraoccipital and anterior tip of the nuchal plate. Abbreviations: np: nuchal plate, pso: parietosupraoccipital. Scale bar = 1 mm.

FIGURE 31 | Aspidoras depinnai, UFPB 6194, CS, 28.0 mm SL, showing dorsal view of the pectoral fin. Arrows indicate the small laminar expansions at the base of branched rays. Scale bar = 1 mm.

FIGURE 32 | Uncatalogued aquarium specimen of Aspidoras depinnai photographed alive. Photo by Ingo Seidel.

FIGURE 33 | Caudal fin of CS specimen of Aspidoras poecilus, UNT 12056, 31.5 mm SL, showing the small cartilage between the principal and procurrent rays (black arrow). Scale bar = 1 mm.