Tetranematichthys barthemi, Peixoto & Wosiacki, 2010

Peixoto, Luiz Antônio Wanderley & Wosiacki, Wolmar Benjamin, 2010, Description of a new species of Tetranematichthys (Siluriformes: Auchenipteridae) from the lower Amazon basin, Brazil, Neotropical Ichthyology 8 (1), pp. 69-75 : 70-73

Tetranematichthys barthemi new species Figs. 1-2

Holotype. MPEG 11081, 154.2 mm SL, sexually mature male, Brazil, Pará, Oriximiná, rio Araticum, rio Trombetas basin, 1°45’34.7”S 56°22’35.5”W, 22 Oct 2007, W. B. Wosiacki, L. A. W. Peixoto & T. O. B. Ruffeil.

Paratypes. Brazil, Pará: MPEG 11013 , 2 , 158.2 - 164.4 mm SL, collected with the holotype. MPEG 14565 , 1, 175.7 mm SL , Pará, Oriximiná, rio Saracá, rio Trombetas basin, 1°48’39.2”S 56°16’20”W, 18 Oct 2007, W. B. Wosiacki, L. A. W. Peixoto & T. O. B. Ruffeil . Amazonas: INPA 14163 , 1, 123.3 mm SL, Manaus, igarapé Gavião, rio Urubu , rio Negro basin, Esteio Farm , Reserve 1401, 2º30’S 60°59’W, 29 Oct 1996, C. Bührnheim .

Diagnosis. Tetranematichthys barthemi is distinguished from T. wallacei and T. quadrifilis by a serrated margin on the distal portion of the mandibular barbel ( Fig. 3 ) (vs. presence of conspicuous digitiform elaboration); by the length of the mandibular barbel, 4.5-6.0% HL (vs. 6.3-23.5% in T. quadrifilis and 7.4-24.6% in T. wallacei ); by a pale ventral region with sparse chromatophores (vs. uniformly brown with darkened spots); by a large pale stripe, more evident in females, immediately above the lateral line, extending from the humeral region to the transverse line above the end of the adipose fin (vs. narrow pale stripe in both sexes or absent); by the presence of irregular patches, which can form a pale distinct stripe in the medial portion of the pelvic fin (vs. uniform dark pigmentation); by the absence of darkened spots on the anal fin in females (vs. presence in both sexes); by the absence of irregular dark patches along the body (vs. patches present); by the two pale distinct vertical stripes on the caudal fin in specimens over 160 mm SL (vs. only irregular patches or vertical stripe followed by irregular patches). It can be further distinguished from T. wallacei by the small size of the snout, 28.8-34.5% HL (vs. 41.2-49.3%) and by the width of the body at the insertion of the pectoral fin, 82.1-88.7% HL (vs. 69.2- 79.3%). Tetranematichthys barthemi can be further distinguished from T. quadrifilis by the reduced size of principal unbranched ray of the upper caudal-fin lobe, 15.6- 16.9% SL (vs. 18.1-19.9%), by the length of head, 24.4-28.2% SL (vs. 28.5-32.3%) and by the width of the body at the insertion of the pectoral fin, 91.6-111.3% HO (vs. 117.0-125.0%).

Description. Morphometric data given in Table 1. Body tall anteriorly, more slender after pectoral-fin insertion. Portion of dorsal-fin insertion taller than pre-dorsal region, more pronounced in mature males than in females and sexually immature males. In lateral view, dorsal profile of head straight or slightly concave from upper lip to transverse line that passes along posterior margin of eyes, ascending gradually in females and abruptly in mature males, until dorsal-fin origin. Dorsal profile of trunk slightly concave anteriorly, becoming slightly convex immediately anterior to adipose fin. Base of adipose fin descending from origin to beginning of dorsal profile of slightly concave caudal peduncle. Ventral profile of head straight from lower lip to point over transverse line at base of pectoral fin, sharply convex until anus, concave from anterior margin of anus to anal-fin origin. Base of anal fin slightly convex from its insertion to its end. Ventral profile of caudal peduncle straight or slightly concave and short, noticeably smaller than dorsal profile.

Head conspicuously compressed in pre-orbital portion, rounded in dorsal view. Opercular opening reduced, more apparent in lower portion, near pectoral-fin insertion. Orbits rounded, turned laterally, visible in dorsal and ventral view. Pair of maxillary barbels present. Maxillary barbels pronounced and ossified in mature males, extending until pectoral-fin insertion. Maxillary barbels with epidermal protrusions throughout, located on dorsal surface, less concentrated in anterior portion, extending beyond distal portion of barbel in mature males. Upward curve present on medial portion of maxillary barbel in mature males; females and immature males with short maxillary barbels, not ossified, without medial curve, size similar to orbital diameter. Pair of minute mandibular barbels, slightly serrated on anterior distal portion, or serrations absent; when serrations absent distal portion of barbel lanceolated. Length of mandibular barbel less than orbital diameter. Mandibular barbel aligned anteriorly in preserved specimens, towards posterior surface of jaw. Mouth terminal, opening between orbits. Pre-maxillary teeth small, pointed distally, with posterior curvature, arranged in 10*(4) or 11(1) irregular rows along surface of pre-maxilla. Dentary with 8(1) or 9*(4) irregular rows of teeth. Maxilla more prominent than dentary. Branquiostegal membrane attached to isthmus. Branchiostegal rays visible in radiographed specimens 6*(3) or 8(2). Opercular opening prominent, reaching from anterior pectoral-fin insertion to humeral portion. First gill arch with 14(1), 15*(1) or 16(3) gill rakers.

Lateral line complete, clear zig-zag pattern anteriorly, less pronounced after half of body, bifurcated posteriorly over caudal-fin base.Alignment of pectoral-fin insertion occurring parallel to operculum in ventral view.

Dorsal-fin rays I,6, second branched ray larger than other branched rays. Dorsal-fin spine beyond pelvic-fin insertion in mature males, reaching transverse line that passes over anal-fin insertion; in females and immature males spine not reaching transverse line that passes over pelvic-fin insertion; immature males and females with dorsal spine serrated on posterior surface (19-21 serrations), anterior surface slightly rough, without serrations, mature males with 48-50 serrations on anterior surface, posterior surface without rugosities. Adipose-fin size equivalent to orbital diameter in both sexes. Anal-fin origin posterior to middle of SL, margin convex, strongly convex posteriorly, rays progressively longer from posterior half, last rays minute, membrane joining caudal 72 Description of a new species of Tetranematichthys from the lower Amazon basin, Brazil Anterior surface with slight rugosities. Branched rays becoming progressively smaller, second ray longest.

Total vertebrae 39*(1), 40(2) or 41(2). Vertebrae 7-8 proportionally thicker. Hemal spines 13-15 larger than others. Pleural ribs 7. First anal-fin pterygiophore contacting anterior portion of 12 th hemal spine. Anal-fin pterygiophores 1-2 proportionally larger than others. Pterigiophore rays of mature males more deeply embedded in hemal spines than those of females and immature males.

Color in alcohol. Dorsal region of body with brown background and irregular lighter areas. Mid-ventral region with light coloring in specimens larger than 123 mm SL. Back peduncle or caudal fin absent. Anterior five anal-fin rays characterized by changes in distal portion, ejaculatory duct structure in sexually mature males with reproductive purpose. Anal-fin rays iii,35*(2), iii,36(2), iii,37(1). Oblique caudal fin, upper lobe longer than lower lobe. Main caudal-fin rays i,7,7,i. Pelvic-fin rays i,6, second branched ray longest, extending posteriorly from anal-fin insertion. Distal margin convex. Pectoral-fin rays I,9*(2) or I,10(3). Spine well-developed, 21(1), 22 (1), 24*(2), 26 (1) twisted serrations in posterior margin. portion of head brown with irregular light areas in upper portion of orbit. Ventral region of head light colored. Upper and lower lips brown, upper lips darker. Lower lip covered by minute chromatophores, more concentrated at edge. Maxillary barbel distinctly lighter than upper lip, with blurred blotches throughout length. Maxillary barbels of females not pigmented. Mandibular barbel not pigmented. Horizontal stripe in pre- and post-orbital region with uniform pigmentation, extending from snout to pectoral-fin insertion. Slender light stripe on sagittal line, between end of dorsal-fin base and tip of adipose-fin. Cleithral portion with small chromatophages on specimens up to 160 mm SL. Distinct horizontal stripe with more prominent light colored area in mature females larger than 165 mm SL. Ventral region of abdomen with light color pattern, usually uniform, without blurred dark patches. Presence of horizontal dark stripe extending from posterior opercular region to beginning of caudal-fin.

Irregular humeral blotch, with dark center and blurred edge. Horizontal stripe extending from dorsal portion of humeral patch. Dorsal region of horizontal patch with large light colored area in specimens between 154 and 176 mm SL. In females with 165-176 mm SL humeral portion of light colored area more prominent than in males of similar size. Dorsal surface of caudal peduncle with light colored irregular patches and ventral surface with minute dispersed chromatophores. Less intense color pattern than in dorsal region of caudal peduncle. Dorsal fin with uniform pigmentation in males larger than 150 mm SL, including spine and branched rays; in females, dorsal spine with uniform pigmentation, surface of branched rays with irregular light colored areas; margin of dorsal-fin not pigmented in both sexes. Adipose-fin with brown pigmentation and light colored margin. Caudal-fin light brown; two distinct light colored stripes; second vertical stripe in specimens smaller than 155 mm SL may form irregular patches; margin not pigmented.Anal-fin light colored with dark rounded patches in males greater than 154 mm SL, absence of dark patches in females of 120 to 176 mm SL; dark brown color on margin, becoming less intense on upper part in both sexes. Pelvic-fin brown with light colored areas, forming distinct light colored stripe (in four specimens.); margin not pigmented. Pectoral-fin spine strongly pigmented; branched rays brown, with similar pattern on ventral portion, in specimens larger than 155 mm SL in both sexes. Margin not pigmented.

Distribution. Tetranematichthys barthemi is recorded from the lower Amazon, between the mouth of the rio Negro and the mouth of the rio Trombetas ( Fig. 4 ).

Sexual dimorphism. Presence of sexual dimorphism characterized by the increase in size of the dorsal-fin spine in males, which can reach slightly more than double the size of the dorsal spine in females. First dorsal-fin ray of males with minute serrations on anterior surface and, in females, protrusions on posterior region. Dorsum more prominent and noticeably taller in males. Maxillary barbels more pronounced in males, regularly reaching pectoral-fin insertion, and females with smaller maxillary barbels, extending until anterior margin of orbit.Anal-fin rays 1-5 in males modified to form copulatory organ in the distal portion.

Coloration pattern without dark irregular patches on analfin base of females, different from males in which patches are present. Presence of more obvious light colored area in humeral portion of the body in females, differing from the males, in which this area is less prominent or absent.

Etymology. The specific epithet barthemi is a tribute to Ronaldo Borges Barthem, researcher of the MPEG, for his contribution to the field of ichthyology, in particular to fisheries ecology in the Amazon.

Figures

Fig. 1. Tetranematichthys barthemi, holotype, male, MPEG 11081, 154.2 mm SL. (a) lateral, (b) dorsal, and (c) ventral views.

Fig. 2. Tetranematichthys barthemi, paratype, female, MPEG 14565, 175.7 mm SL. Lateral view.

Fig. 3. Mandibular barbel of Tetranematichthys barthemi, MPEG 14565, 175.7mm SL, showing the fleshy serrated distal portion. Scale bar = 1mm.

Fig. 4. Distribution of Tetranematichthys barthemi. 1 = type locality. Point 1 represents more than one locality.