Probolodus heterostomus Eigenmann, 1911

Santos, Osmar & Castro, Ricardo M. C., 2014, Taxonomy of Probolodus Eigenmann, 1911 (Characiformes: Characidae) with description of two new species, and comments about the phylogenetic relationships and biogeography of the genus, Neotropical Ichthyology 12 (2), pp. 403-418 : 405-408

Probolodus heterostomus Eigenmann, 1911 Figs. 3-4

Probolodus heterostomus Eigenmann, 1911 , monotypic [original description] (type locality: rio Paraíba do Sul basin, Campos, Rio de Janeiro, Brazil). Paratypes [CM 2974, 3, 48- 64 mm SL]. - Eigenmann, 1915:3-22 [in part] (type-material). - Jordan, 1920: 538 (citation). - Pearson, 1937: 108 (list). - Myers, 1942: 91 [in part] (distribution). - Roberts, 1970: 384- 89 (dentition and systematic relationships). Géry, 1977: 298, 543, 575-79 (identification key; systematic of Cheirodontinae and comments about dentition - Probolodini tribe). - Sazima, 1977: 510-12 [in part] (distribution; feeding habits). - Géry, 1980: 1-8 (systematic relationships). - Sazima, 1983: 2-13 (lepidophagous habits). - Vari, 1986: 329 (systematic relationships). -Ibarra & Stewart, 1987: 70 [in part] (typematerial). - Jégu et al., 1991: 773 (dentition and systematic relationships). - Bizerril, 1994: 58, 65 [in part] (distribution and identification key).-L. Malabarba, 1998:230 (comments). - Lucena, 1998: 23, 30, 32, 33, 34 (dentition and systematic relationships).- Bizerril, 1999:241 (citation).-Lima etal., 2003: 154 [in part] (type-material; type locality and distribution). -Zanata & Akama, 2004: 48-49, 52 (comments). - Teixeira et al., 2005:351 (list).- Pinto et al., 2006:272, 273 (list). - Nelson, 2006:157 (comments). - Buckup et al., 2007: 61 [in part] (type locality and distribution). - Menezes et al., 2007: 105 [in part] (type locality; distribution; systematic and ecology). - Mirande, 2007: 20 (systematic relationships). - Mirande, 2009: 580, 583 (systematic relationships). - Azevedo, 2010: 470 (comments). - Mirande, 2010: 385-568 (systematic relationships).- Mirande et al., 2011: 14 (comments).- Oliveira et al., 2011: 21 (systematic relationships). -Mattox & Toledo- Piza, 2012: 847 (dentition and systematic relationships).

Diagnosis. Probolodus heterostomus differs from its two congeners, P. oyakawai (new species) and P. sazimai (new species) by the following attributes: 45-56 perforated scales on the lateral line (vs. 41-43 and 36-43 perforated scales, respectively); 18-21 scale series around the caudal peduncle (vs. 14-16 scale series around the caudal peduncle); symplectic with bone projection posteroventrally developed (vs. sympletic without bone projection) ( Fig. 4a ); process extending posteriorly along the dorsal margin of the hyomandibular (vs. hyomandibular with flat margin, without process) ( Fig. 4a ), and anterior portion of urohyal not bifurcated, with central orifice (vs. anterior portion of urohyal bifurcated) ( Fig. 4b ).

Description. Morphometrics of holotype and non-type specimens presented in Table 1 . Body moderately compressed and deep, less so in individuals of less than 150 mm SL, greatest body depth within region delimited anteriorly by vertical through insertion of pelvic fin and posteriorly by vertical through origin of dorsal fin. Average body depth variable among population samples, but with broad overlap in ranges among examined samples. Dorsal profile of head distinctly convex from margin of upper lip to vertical through posterior nostril, straight to very slightly convex from latter point to tip of supraoccipital spine. Dorsal profile of body moderately convex from tip of supraoccipital spine to origin of dorsal fin, straight and posteroventrally-slanted along base of dorsal fin, straight to slightly convex from posterior terminus of base of dorsal fin to adipose fin, and slightly concave along caudal peduncle. Broad middorsal ridge present along predorsal region of body, with ridge less obvious anteriorly. Dorsal region of body between posterior terminus of dorsal fin and adipose fin transversely rounded overall, but slightly flattened middorsally in some individuals. Ventral profile of head strongly convex anteriorly from margin of lower lip approximately to vertical through anterior nares, then slightly convex from that point to vertical through posterior margin of eye. Ventral profile of body convex to insertion of pelvic fin, nearly straight but slightly posteroventrally-aligned from that point to origin of anal fin, straight to slightly convex and posterodorsally-slanted along base of anal fin, and slightly concave along caudal peduncle. Prepelvic region of body somewhat flattened transverselly.

Head obtusely rounded anteriorly in lateral profile. Mouth terminal. Upper jaw with maxilla distinctly posteroventrallyangled relative to ventral margin of premaxilla and extending ventral of orbit to point somewhat short of, or reaching, vertical through anterior margin of pupil. Nares of each side of head very close together; anterior opening circular, posterior crescent-shaped with distinct flap between nares. Eye relatively large and lacking distinct adipose eyelid. Median fronto-parietal fontanel extending from mesethmoid to supraoccipital spine. Width of fontanel approximately onefifth distance across bony interorbit. Infraorbital series complete with third infraorbital by far largest. All infraorbitals carrying laterosensory canal segments proximate to margin of orbital rim. Supraorbital absent. Branchiostegal rays four. Gill-rakers long and setiform; 10-12+1+6-9 rakers present on first gill-arch.

Teeth on premaxillary, maxillary, and dentary in one row. Premaxilla with three (159) or four (1) teeth [three] somewhat directed outward; each tooth with three points in angles of a nearly isosceles triangle; middle point, which is also the anterior one, much larger. Maxilla with two to five (commonly four) teeth [four] with two cusps of similar size, first two or three directed outward. Dentary with four large teeth, first three directed outward, fourth, and one or more smaller ones following it, directed upward; larger teeth of lower jaw heavy, conical, with a minute cusp on each side; in overall, dentary has five to seven (commonly five) tricuspidate or biscupidate teeth [five].

Scales cycloid, relatively small, firmly implanted. Lateral line decurved anteriorly approximately to vertical through origin of dorsal fin, then slightly posterodorsally-angled to caudal peduncle, and then running horizontally to terminus of scale series. Lateral line completely pored from supracleithrum to base of caudal fin and followed posteriorly by ossified tubular extension running along lateral margin of membrane joining middle rays of caudal fin. Lateral-line scales 45 (18), 46 (10), 47 (10), 48 (52), 49 (8), 50 (26), 51 (7), 52 (4), 53 (9), 54 (4), 55 (4), or 56 (3) [47]; scales in transverse series from origin of dorsal fin to lateral line 8 (7), 9 (108), or 10 (42) [9]; scales in transverse series from insertion of pelvic fin to lateral line 7 (75) or 8 (82) [8]; scales in transverse series from origin of anal fin to lateral line 7 (1), 8 (38), 9 (117), or 10 (1) [9]; scales along middorsal line between tip of supraoccipital process and origin of dorsal fin 12 (80), 13 (69), or 14 (6) [12]; scales along middorsal line between posterior termination of base of dorsal fin and adipose fin 14 (3), 15 (47), 16 (87), or 17 (20) [14]; horizontal scale rows around caudal peduncle 18 (94), 19 (41), 20 (17), or 21 (3) [20]. Vertebrae 34 (n = 13) or 35 (n = 23).

Dorsal-fin rays ii,9 (159) [ii,9].Anal-fin rays iii (2), iv (43) or v (114), 23 (2), 24 (6), 25 (14), 26 (43), 27 (45), 28 (34), 29 (12), 30 (2), or 31 (1) [iii,26]. Pectoral-fin rays i,10,i (2), i,11 (9), i,11,i (54), i,12 (68), i,12,i (18), or i,13 (6) [i,12]. Pelvic-fin rays i,6 (3), i,6,i (2), i,7 (153), or i,8 (1) [i,7]. Principal caudal-fin rays i,17,i (159).

Dorsal-fin margin distally rounded to slightly truncate; first unbranched ray approximately 40-50% length of second unbranched ray. Dorsal-fin origin situated along vertical located approximately at middle of SL. Origin of adipose fin located slightly anterior of vertical through posterior terminus of base of anal fin. Profile of adpressed pectoral fin distinctly acute. Tip of pectoral fin extending approximately to vertical through insertion of pelvic fin. Profile of expanded pelvic fin pointed, with first branched ray either longest in fin or subequal to unbranched ray. Insertion of pelvic fin located distinctly anterior to vertical through origin of dorsal fin. Tip of adpressed pelvic fin extending approximately to vertical through insertion of anal fin. Some larger, apparently male, specimens with posteriorly-directed hooks along posterior margins of second through seventh pelvic-fin rays; hooks rarely also present on first ray. Hooks limited to posterior branch of hook-bearing rays. Each hook-bearing segment typically with one hook, although two hooks occasionally present on some segments. Distal margin of anal fin slightly concave in which fourth or fifth unbranched and first and second branched rays longest and subequal or first through third branched rays longest with subsequent branched rays gradually decreasing in length. Some larger, apparently male, individuals with hooks present on various rays gradually of anal fin. Hooks most often arise along posterior margin of posterior branch of second through seventh branched rays. Hooks extending onto unbranched segments of some rays. Caudal fin forked, with distal margins of lobes obtusely pointed.

Color in alcohol. Overall ground color of body in specimens fixed in formalin yellowish brown. Guanine remaining on lateral and ventral portions of head and on ventral and, to a variable degree, lateral surfaces of body. Snout and dorsal portion of head relatively dark. Middorsal and immediately adjoining portions of body relatively dark. Distinct, wedge-shaped, ventrally-attenuated humeral blotch with irregular margins extending from approximately five scales dorsal of lateral line to about two scales ventral of lateral line. Pigmentation of humeral blotch typically most intense in region dorsal of lateral line, with pigmentation of remaining ventral portion of blotch variably lighter, but still quite obvious. Dark midlateral pigmentation more conspicuous on portion of body beginning at vertical through anterior portion of dorsal fin, with stripe widening posteriorly on caudal peduncle into distinct, horizontally-elongate, ovoid blotch. Pigmentation of blotch more intense than that of remainder of stripe. Chromatophores of dorsal portion are concentrated at the base and middle region of the scales, its margins being free of chromatophores. Region below the lateral line decreases the concentration of chromatophores, and, between the anal fin and caudal peduncle, sparse chromatophores are present in greater proportion.

Dorsal, anal, and caudal fins with interradial membranes covered by small dark chromatophores, with chromatophores often more concentrated proximate to margins of fin rays. Dark pigmentation on caudal fin more intense along middle fin-rays in most specimens and forming stripe variably continuous anteriorly with midlateral dark blotch on caudal peduncle. Anal fin with unbranched rays and all branched rays pigmented. Distal half of remainder of fin with dark chromatophores in all individuals, with fields of chromatophores extending nearly to base of fin membranes. Adipose fin lightly colored overall, but often freckled with small dark spots. Pectoral and pelvic fins with small, dark spots located both along fin-ray margins.

Distribution. Probolodus heterostomus is known to occur in the tributaries of rio Paraíba do Sul basin, southeastern Brazil ( Fig. 2 ).

Ecological notes. Probolodus heterostomus was studied by Sazima (1977; 1983) because of its habit of tearing off and eating scales of other fishes. Pieces of leaves, insects and scales were observed in the mouth of many specimens preserved in alcohol (MZUSP 44110, 5, 40.2-46.7 mm SL; MZUSP 7904, 6, 42.3-56.6 mm SL). However, ctenoid and many cycloid fish scales were found in the stomach contents and between gill rakers of the cleared and stained specimens (LIRP 6296, 2, 72.7-88.5 mm SL; ZUEC 5498, 2, 77.3-100.8 mm SL).

Remarks. Roberts (1970) examining stomach contents of some lepidophagous characids, such as Catoprion , Exodon , Roeboides , and Roeboexodon , was the first author to observe a large number of scales in the stomachs of specimens of Probolodus heterostomus and commented on the absence, until then, of knowledge about the relationships among the lepidophagous genera aforementioned (see more details about the lepidophagous taxa in Sazima, 1977; Géry, 1980; Sazima & Uieda, 1980; Sazima & Machado, 1982; Sazima, 1983; Vari, 1986; Janovetz, 2005). Still, Roberts (1970) considered the genus P. heterostomus very similar to the tetras of the genus Astyanax .

Therefore, Géry (1977) based in Eigenmann (1911, 1915) and Roberts (1970), considered P. heterostomus morphologically very similar to the tetras of the genus Astyanax , especially A. fasciatus , but both with different dentitions. According to the cited author, the tricuspidate teeth of P. heterostomus are few in number and directed outward, especially on the prominent dentary, enabling it to remove rows of scales of other fishes, possibly from the bottom up. However, Sazima (1977) suggested that A. fasciatus is the main prey of P. heterostomus , which are externally very similar and sympatric species occurring in the drainage of the rio Paraíba do Sul. In addition, Sazima (1977; 1983) hypothesized that the similarity between these two genera is a form of disguise or aggressive mimicry.

Material examined: Holotype. FMNH 54328 [ex CM 2973 ], 49.0 mm SL, Brazil , Rio de Janeiro, município de Campos, rio Paraíba do Sul basin, 13 Jun 1908, J. D. Haseman . Paratypes. FMNH 54329 [ex CM 2974 ], 2, 36- 38 mm SL, Brazil , Rio de Janeiro, município de Campos, rio Paraíba do Sul basin, 13 Jun 1908, J. D. Haseman . Non-type specimens. All specimens from Brazil. São Paulo State: LIRP 6296 , 2 , 72.7-88.5 mm SL (2 c&s), município de Guararema, rio Paraíbuna basin, 23°24’59’’S 46°02’59’’W ; MZUSP 14743 , 1 , 49.9 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°17’59’’S 45°58’00’’W ; MZUSP 44097 , 14 , 38.8-62.5 mm SL, município de Natividade da Serra, rio Paraíbuna basin, rio do Peixe at bairro of Laranjal, 23°25’59’’S 45°17’59’’W ; MZUSP 44108 , 1 , 55.3 mm SL, município de Redenção da Serra, rio Paraíbuna basin, rio Paraitinga between the Mineiros bridge and sítio of Mr. Ismael, 23°15’59’’S 45°32’59’’W ; MZUSP 44110 , 20 , 30.5-49.3 mm SL, município de Natividade da Serra, rio Paraíbuna basin, unnamed stream at bairro of Volta Comprida, 5 km after the bairro Alto, 23°25’59’’S 45°17’59’’W ; MZUSP 44114 , 7 , 27.0- 58.5 mm SL, município de Natividade da Serra, rio Paraíbuna basin, unnamed stream at bairro of Volta Comprida, 5 km after the bairro Alto, 23°25’59"S 45°17’59"W ; MZUSP 45920 , 1 , 58.4 mm SL, município de Guararema, rio Paraíbuna basin, rio Itapeti , 23°24’59"S 46°02’59"W ; MZUSP 45922 , 15 , 32.3-47.3 mm SL, município de Paraíbuna, rio Paraíbuna basin, unnamed stream at bairro of Volta Comprida, 6 km after the bairro Alto, 23°25’59’’S 45°17’59’’W ; MZUSP 7904 , 30 , 40.2-58.8 mm SL, município de Santa Branca, rio Paraíba do Sul basin, represa de Santa Branca, 23°21’S 45°49’59’’W ; MZUSP 93978 , 1 , 52.8 mm SL, município de Paraíbuna, rio Paraíbuna basin, 23°25’59’’S 45°17’59’’W ; ZUEC 2239 , 1 , 63.4 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35’’W ; ZUEC 2240 , 1 , 70.4 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35’’W ; ZUEC 2241 , 1 , 62.7 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35’’W ; ZUEC 2242 , 1 , 61.4 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35’’W ; ZUEC 2243 , 1 , 57.5 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35’’W ; ZUEC 2244 , 1 , 57.1 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35’’W ; ZUEC 2245 , 1 , 55.7 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35’’W ; ZUEC 2246 , 1 , 53.7 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35’’W ; ZUEC 2247 , 1 , 56.8 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35’’W ; ZUEC 2248 , 1 , 57.9 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35’’W ; ZUEC 2249 , 1 , 49.4 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35’’W ; ZUEC 2250 , 1 , 49.0 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35’’W ; ZUEC 2251 , 1 , 50.8 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35’’W ; ZUEC 2252 , 1 , 51.2 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35’’W ; ZUEC 3559 , 3 , 49.1-83.7 mm SL, município de Paraíbuna, rio Paraíbuna basin, 23°22’48’’S 45°39’35’’W ; ZUEC 4086 , 4 , 61.5-78.4 mm SL, município de Paraíbuna, rio Paraíbuna basin, 23°22’48’’S 45°39’35’’W ; ZUEC 4603 , 2 , 66.2-71.9 mm SL, município de Paraíbuna, rio Paraíbuna basin, 23°22’48’’S 45°39’35’’W ; ZUEC 4667 , 2 , 16.3-17.1 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35’’W ; ZUEC 4823 , 1 , 71.3 mm SL, município de Paraíbuna, rio Paraíbuna basin, 23°22’48’’S 45°39’35’’W ; ZUEC 4824 , 1 , 70.8 mm SL, município de Paraíbuna, rio Paraíbuna basin, rio Parateí , 23°22’48’’S 45°39’35’’W ; ZUEC 5501 , 1 , 26.5 mm SL, município de Jacareí, rio Paraíba do Sul basin, 23°18’S 45°57’35"W ; ZUEC 5498 , 17 , 77.3-100.8 mm SL (2 c&s), município de Paraíbuna, rio Paraíbuna basin, 23°22’48’’S 45°39’35’’W . Rio de Janeiro State: MNRJ 10942 , 3 , 35.5-62.8 mm SL, município de Itatiaia, rio Paraíba do Sul basin, ribeirão Santo Antônio, vale do Paraíba, 22°29’29"S 44°33’33"W ; MNRJ 13864 , 5 , 32.2-83.8 mm SL, município de Silva Jardim / Araruama, rio Paraíba do Sul basin, Jaturnaíba small lake, 22°39’03"S 42°24’20"W ; MNRJ 15382 , 1 , 94.8 mm SL, município de Três Rios, rio Paraíbuna basin, left hand tributary of rio Paraíba do Sul , 22°07’00"S 43°12’33"W ; MNRJ 17874 , 17918 , 4 , 72.2-89.4 mm SL, município de Barra Mansa, rio Paraíba do Sul basin, rio do Turvo, 22°32’38"S 44°10’15"W ; MNRJ 19251 , 10 , 35.2-49.6 mm SL, rio Paraíba do Sul basin, rio Pirineus or Crubixais (left hand tributary of rio São José ), under bridge near the fazenda Novo Horizonte, 22°30’26’’S 42°29’14’’W ; MNRJ 25988 , 1 , 47.9 mm SL, rio Paraíba do Sul, unnamed small stream near of Quatis, approximately 7 km, left hand tributary of rio Paraíba do Sul , 22°24’26"S 44°15’29"W .

Figures

Fig. 3. Probolodus heterostomus, holotype, FMNH 54328, 49.0 mm SL, Brazil, Rio de Janeiro, município de Campos, rio Paraíba do Sul basin.

Fig. 4. Suspensorium, lateral view (a) and of the urohyal, dorsal view (b) of Probolodus heterostomus, LIRP 6296, 70.7 mm SL. HYO: hyomandibula, MSP: mesopterygoid, MTP: metapterygoid, OPE: opercle, QUA: quadrate, SYM: symplectic. Scale bars = 1 mm.

Fig. 2. Geographic distribution of Probolodus oyakawai (squares), P. heterostomus (circles), and P. sazimai (triangle); star indicates type locality. 1) rio Ribeira de Iguape, 2) rio Tietê, in upper rio Paraná basin, 3) rio Paraíba do Sul, 4) rio Itapemirim, 5) rio Doce, 6) rio Mucuri, 7) rio Jequitinhonha. Symbols may represent more than one locality.