Heptapterus carmelitanorum sp. nov., Azevedo-Santos, Depra , Aguilera, Faustino-Fuster & Katz

Depra, Gabriel de Carvalho, Aguilera, Gaston, Faustino-Fuster, Dario R., Katz, Axel M. & Azevedo-Santos, Valter M., 2022, Redefinition of Heptapterus (Heptapteridae) and description of Heptapterus carmelitanorum, a new species from the upper Parana River basin in Brazil, Zoosystematics and Evolution 98 (2), pp. 327-343 : 327

Heptapterus carmelitanorum sp. nov., Azevedo-Santos, Depra, Aguilera, Faustino-Fuster & Katz

Figs 3 , 4

Heptapterus ' Heptapterus ' sp.: - Azevedo-Santos et al. (2019) (listed in a survey).

Holotype.

MNRJ 53174, 144.3 mm SL; Brazil: Minas Gerais State: limit of Carmo do Rio Claro and Ilicínea municipalities: Unknown named stream tributary of Itací stream, tributary of Sapucaí River (stretch flooded by Furnas reservoir), Grande River Drainage, Paraná River basin, ~ 20°54'57"S, 45°56'21"W, altitude about 830 m asl; A. M. Katz and V. M. Azevedo-Santos, 31 October 2021.

Paratypes.

LBP 26570, 1, 95.7 mm SL; same locality as holotype; V. M. Azevedo-Santos and P. N. Coelho, 22 July 2017; LBP 26575, 1, 89.1 mm SL, same locality as holotype; V. M. Azevedo-Santos and P. N. Coelho, 25 May 2018; LBP 23577, 1, 104.4 mm SL, same locality as holotype; V. M. Azevedo-Santos and P. N. Coelho, 10 April 2017.

Diagnosis.

Heptapterus carmelitanorum differs from all congeners by possessing the anal-fin insertion less than one eye diameter posterior to a vertical through the adipose-fin insertion (vs. more than one eye diameter posterior). From all congeners, except H. borodini , by an isognathous mouth (vs. slightly to moderately retrognathous). It differs from all other congeners except H. borodini and H. hollandi , by the keel formed by ventral procurrent caudal-fin rays shallow, far from reaching anal-fin base (vs. keel formed by ventral procurrent caudal-fin rays deep, continuing almost to the anal-fin base, even though its anterior portion is devoid of fin rays) (Fig. 5 ). It differs from both H. borodini and H. hollandi by having an almost elliptical caudal fin (vs. lanceolate in H. borodini , obliquely truncate to falcate in H. hollandi ; Fig. 6 ), the length of its dorsal lobe 18.3-19.3% SL (vs. 24.4-43.3% SL in H. borodini ). Additionally, H. carmelitanorum differs from all other congeners, except H. carnatus , H. mbya , H. qenqo , and some specimens of H. hollandi , by having inconspicuous dorsal bars (vs. conspicuous). From H. borodini , H. carnatus , H. exilis , H. hollandi , H. mustelinus , and H. ornaticeps , by having 14-15 anal-fin rays (vs. 10-12 in H. borodini and H. hollandi ; 18-21 in H. carnatus ; 16-19 in H. exilis ; 18-23 in H. mustelinus ; and 19 in H. ornaticeps ). Differs from H. exilis by the complete lateral line (in adults), continuous to base of hypural plate (vs. incomplete, not reaching dorsal-fin insertion). Heptapterus carmelitanorum further differs from H. hollandi by having i,6 dorsal-fin rays (vs. i,7).

Description.

General morphology (Figs 3 - 4 , 7 ; Suppl. material 1: Figs S1-S3). Available specimens (holotype and three paratypes) ranging from 89.1-144.3 mm SL; morphometric data in Table 1 . General shape of body presented in photographs of preserved and live specimens. Dorsal profile convex from premaxillary symphysis to end of dorsal-fin base; slightly convex from that point to adipose-fin insertion; slightly convex along adipose-fin base. Caudal-fin base rounded. Ventral profile convex from dentary symphysis to isthmus; straight or slightly convex from that point to anal opening; straight along anal-fin base; concave from its end to caudal-fin base. In dorsal view, mouth rim gently arched, convex; lateral profile of head convex due to well-developed adductor mandibulae muscle; lateral profile of body straight to slightly convex along abdomen, tapering gently to about half adipose-fin base, then tapering more abruptly to caudal-fin base.

Head much depressed, flat dorsally and ventrally, rounded laterally. Mouth isognathous. Mouth rictus fleshy, folding ventrally, with large sub-labial groove beneath it (Fig. 7a ). Lips double, i.e., divided by deep labial slit into outer and inner lip (Fig. 7b ). Outer dorsal lip thickly and abundantly plicate; outer lower lip thickly, but scarcely plicate; inner dorsal and ventral lips finely and abundantly plicate (Fig. 7b ). Tubular anterior nostril not reaching mouth rim. Deep skin fold surrounding entire posterior nostril, but with deep posterior notch (Fig. 7c ). Maxillary barbel groove extending from base of barbel almost to the eye; in dorsal view, rim of groove almost parallel with body axis. Dorsal surface of snout with shallow depression posteriorly to posterior nostril, and elongate depression marking anterior cranial fontanel (Fig. 7b ). Bulging eyes covered in thick skin with no free rim, almost completely dorsal. Base of inner mental barbel slightly anterior to that of outer mental barbel, distinctly posterior to base of maxillary barbel. Maxillary barbel reaching anterior margin of first pectoral-fin ray. Shallow cleithral skin fold immediately posterior to branchial aperture, posterior terminus medial to base of first pectoral-fin ray (Fig. 7a ). Abdominal region depressed, distinctly broader than deep; in cross section, something between elliptic and rectangular. Cross section at dorsal-fin base approximately as broad as deep, between round and square. Body compressed from adipose-fin insertion to caudal fin, cross-section distinctly deeper than broad. Vertebrae 43. Ribs 9 (Suppl. material 1: Fig. S4).

Dorsal fin distal margin convex; i,6*(4) rays (first ray rigid only basally); each branched ray with, at least, tertiary branches; thin membrane between rays. Pelvic-fin insertion at same vertical as base of second (first branched) dorsal-fin ray (2 specimens) or between bases of first and second rays (2*). Adipose fin continuous (i.e., connected) with the anteriormost ray of dorsal portion of caudal fin, originating slightly anteriorly to vertical through anal-fin insertion (distance less than one eye diameter); margin slightly convex. Caudal fin approximately elliptical, rays of dorsal half little longer than ventral ones; xiii,8,8,xi*(1) xv,7,8,xv(1), xvii,6,7,xiv(1), xvii,6,7,xvi(1) rays (Suppl. material 1: Fig. S5); thin membrane between rays. Pectoral fin approximately elliptical, with anterior rays longer than posterior ones; i,7,i(2), i,8*(2) rays on left side (first ray rigid only basally); on right side, i,7,i*(4); each branched ray with, at least, tertiary branches; thin membrane between rays. Pelvic fin approximately elliptical, with anterior rays longer than posterior ones; i,5 (4) rays on both sides; each branched ray with, at least, tertiary branches; thin membrane between rays.

Premaxillary toothplate about twice as wide as long, length of lateral margin slightly higher than symphyseal margin; small posterolateral projection present; about six rows of conical teeth (tooth plate virtually identical to the one in Mees 1967, fig. 1c). External gill rakers on first arch 1+6*(3), 1+7(1). Branchiostegal rays 8(2) (Suppl. material 1: Fig. S5).

Laterosensory system. Cephalic laterosensory pores as Bockmann and Miquelarena (2008) described for Rhamdella cainguae Bockmann & Miquelarena, 2008, except in following details (Fig. 8 ): s2+i2 pore much closer to anterior nostril (vs. at about middle of the distance between anterior and posterior nostrils); s4 pore distinctly more medial than s3 pore (vs. slightly more medial); s8 with two pores (s8a and s8p; vs. s8 with one pore); po3 with two pores (po3a and po3p; vs. po3 with one pore); pm1 pore only slightly posterior to transversal line across pm2 pore (vs. much posterior to it); pm1 directed medially, facing antimere (vs. directed ventrally); pm2 and pm3 pores facing anteroventrally (vs. posteroventrally and ventrally, respectively); pm4 and pm5 pores anteromedial to rictus (vs. posteromedial and posterior to it, respectively); pm10 pore slightly closer to po1+pm11 pore than to pm9 pore (vs. much closer to pm9 pore). Eye also more distant from i5, i6, s6, s7, and s8 pores than in R. cainguae , seemingly due to anterior displacement of eye in Heptapterus carmelitanorum . Lateral line continuous to hypural plate, with 43(1), 46(1), 63(1) pores, or ending on hypural plate, but with large gap between anterior and posterior portions, with 23(1) total pores (smallest specimen, LBP 26575).

Olfactory organ . One specimen (LBP 23577) dissected with two longitudinal series of flat, triangular lamellae on right olfactory canal, each series with 32 lamellae (Fig. 9 ).

Epidermal papillae . In LBP 23577, external surface of body covered with densely packed, flexible, perpendicularly protruding epidermal Epidermal papillae (except lips; distal half of barbels, tubular portion of anterior nostril and skin flap of posterior nostril; center of eye; distal margin of branchiostegal membrane; and nearly entire fins). Distance between adjacent Epidermal papillae ~0.15 mm, equal to their maximum length. Papillae slender, rod-like on most of body (Fig. 10a, b ); short, club-like, apparently with widened distal extremity on ventral surface of head (Fig. 10c ; widened portion possibly attached mucus). Very small Epidermal papillae on anterior face of first pectoral- and pelvic-fin ray; on base of caudal-fin rays; on margin of eye; on base of tubular portion of anterior nostril; on base of skin flap of posterior nostril; on ventral half of adipose fin. Scarce, but well-developed Epidermal papillae on urogenital papilla and anus. All epidermal Epidermal papillae visible only after removal of body mucus.

Color in alcohol (Fig. 3 , Suppl. material 1: Figs S1, S2). Background color greyish-brown, grading to white towards belly and to white beige towards region between anus and anal fin, and ventral side of head; transition between brown and light beige more abrupt on head than in remainder of body. Caudal spot very faint, small, at base of dorsalmost branched caudal-fin ray; DB8 and 7 absent; DB6 through 4 inconspicuous, dark-brown (respectively, at adipose-fin insertion; midway between dorsal and adipose fins; and terminus of dorsal-fin base); DB3 present as roundish dark-brown spot immediately anterior to dorsal fin; DB2 very faint, little posterior to supraoccipital, at vertical through posterior end of pectoral-fin base; DB1 dark brown, extending to opercle; interorbital bar indistinct. Pre-orbital stripe very diffuse, dark-brown. Diffuse, dark-brown humeral spot; faint midlateral stripe present in LBP 26570 specimen; laterodorsal stripe absent.

Color in life (Fig. 4 , Suppl. material 1: Fig. S3). General pattern of body dark brown, yellowish in the holotype (Fig. 4 ). Ventral region from isthmus to anal-fin insertion paler than remainder of body and somewhat pinkish, as well as cheek, branchiostegal membrane, cleithrum and lateral line. All fin rays dark brown. Adipose fin brownish yellow or dark yellowish brown. Interradial membranes of pectoral, anal and caudal fins yellow. Dorsal-fin interradial membrane hyaline, with scattered melanophores on basal third. Barbels dark brown dorsally and beige ventrally.

Ontogeny.

Strong positive allometry in cleithral width (R2 = 0.997), head length (0.742), fleshy interorbital distance (0.809), mouth width (0.633), and dorsal caudal-fin lobe length (0.593; compare Fig. 3 , Suppl. material 1: Figs S1, S2); moderate positive allometry in ventral caudal-fin lobe length (0.362); moderate negative allometry in bony interorbital distance (0.392), maxillary-barbel length (0.313), first dorsal-fin ray length (0.259), and maximum adipose-fin height (0.317); strong negative allometry in dorsal-adipose distance (0.656), first pectoral-fin ray length (0.993), and first pelvic-fin ray length (0.918). Positive allomery present in the number of branched rays in the dorsal caudal-fin lobe (R2 = 0.5712) and in the number of lateral-line pores (0.899).

Etymology.

The specific name is a noun in apposition derived from Carmelitanos (in Portuguese), the local appellation of people born or living in Carmo do Rio Claro (Minas Gerais, Brazil), the city where the species was discovered. The name is in honor of Carmelitanos , especially Ana Maria Vilela Soares, José Cândido de Mello Carvalho, Moara Lemos, and Carlos Roberto Bueno Júnior, for their contributions to biological science.

Geographical distribution and ecological notes.

Heptapterus carmelitanorum is recorded only from a single unnamed stream. The watercourse is a tributary of Itací stream - ribeirão Itací, in Portuguese - which is an affluent of Furnas reservoir (in the Sapucaí River arm), Grande River basin, in the upper Paraná River system, in Minas Gerais State, Brazil (Figs 11 , 12 ).

The stream in which specimens of H. carmelitanorum were collected has its source on a mountain known as “Chapadão” (in Portuguese), approximately 1,300 meters a.s.l. Its cannel crosses successive falls (forming waterfalls), including one over 50 meters high. The type locality lies downstream from the waterfalls. According to the classification proposed by Strahler (1954), the stream may be classified as third order. The water was extremely clear (small characids readily observed) and well oxygenated. The stream depth was shallow (not exceeding 1 meter), and its bed was completely formed by rocks. Light penetration was low during samplings. In the reach, submerged tree roots and accumulated leaves and fruits (especially Fabaceae ) formed some microhabitats for some species, notably Trichomycterus candidus (Miranda Ribeiro, 1949) and Cetopsorhamdia iheringi Schubart & Gomes, 1959. The specimens of H. carmelitanorum were captured in environments that combined rocks (generally juxtaposed) and a more turbulent flow (see Fig. 12 ). Observation during sampling suggests that the species is demersal.

Species collected with H. carmelitanorum include C. iheringi , Hoplias malabaricus (Bloch, 1794), Knodus moenkhausii (Eigenmann & Kennedy, 1903), Odontostilbe weitzmani Chuctaya, Bührnheim, & Malabarba, 2018, Oligosarcus argenteus Günther, 1864, Pareiorhina sp., Psalidodon sp., T. candidus , T. septemradiatus Katz, Barbosa & Costa, 2013 ( Azevedo-Santos et al. 2019). New collections in the same reach resulted in the capture of additional species, such as Apareiodon sp. (CICCAA06610) and Rhamdiopsis sp. (CICCAA06611). In addition to fishes, aquatic spiders (e.g., Tetragnatha sp.) and insects, including specimens of the order Trichoptera in cases formed by small gravels, were captured in the stretch.

Figures

Figure 3. Heptapterus carmelitanorum, new species, holotype, MNRJ 53174, 144.3 mm SL; a. Dorsal view; b. Lateral view; c. Ventral view.

Figure 4. Heptapterus carmelitanorum, new species, holotype, coloration in life.

Figure 5. Schematic representation of the different degrees of proximity between the anal and caudal fins in Heptapterus. a. Keel formed by rigid connective tissue with imbedded ventral procurrent caudal-fin rays not much developed, its anterior end distant from anal-fin base (Heptapterus borodini, H. carmelitanorum and H. hollandi); b. Keel well developed, its anterior end reaching or almost reaching anal-fin base (remaining Heptapterus species).

Figure 6. Different caudal-fin shapes in Heptapterus. a. H. borodini, NUP 14882, 74.3 mm; b. H. hollandi, young; c. H. hollandi, adult, NUP 5978, 199.1 mm SL.

Figure 7. Superficial structures in Heptapterus carmelitanorum; a. Sub-labial groove (blue arrowhead) and cleithral skinfold (black arrowhead); b. Labial slit (blue arrowheads) and plicae on the outer (lemon arrowheads) and inner (pink arrowheads) lips; c. Posterior nostril, evidencing shape of posterior notch (red arrowhead).

Figure 8. Cephalic laterosensory system of Heptapterus carmelitanorum, new species (based on LBP 23577); abbreviations as in Bockmann and Miquelarena (2008).

Figure 9. Heptapterus carmelitanorum, LBP 23577, dissected to show the olfactory Olfactory organ (anterior side to the right). Some of the lamellae in the outer (red arrowhead) and inner (green arrowhead) series are outlined in blue to better evidence their shape.

Figure 10. Epidermal papillae in Heptapterus carmelitanorum, LBP 23577, paratype. a, b. Slender, rod-like Epidermal papillae are distributed on most of body, such as on the dorsum, between the head and dorsal fin (a) and on the head (b. arrow shows s 6 + s 6 pore); c. Short, club-like Epidermal papillae are distributed on ventral surface of head.

Figure 11. Distribution of Heptapterus carmelitanorum.

Figure 12. Partial view (i. e., stretch) of the stream where the type specimens of Heptapterus carmelitanorum were sampled.