Two new species of Characidium Reinhardt (Characiformes: Crenuchidae) from northeastern Brazilian coastal drainages

Two new species of Characidium , one from the rio Pardo basin, and another from the rio Paraguaçu basin, Bahia, Brazil, are described. The first new species is distinguished from its congeners by having conspicuous black vertical traces on body, formed by the concentration of melanophores along posterior margin of scales. The species further differs from most congeners by the presence of a conspicuous 3-shaped black blotch on the caudal fin and isthmus not covered by scales. The other new species is distinguished from congeners by having irregular dark blotches on dorsum alternating elongation to one or the other side of body, usually not connected to lateral blotches. The species can be further characterized by the absence of conspicuous blotches or bars on fins and the presence of secondary sexual dimorphism, such as pelvic fins of mature males longer than in females and with bony hooks. , não conectada às manchas laterais. A espécie pode ser ainda caracterizada pela ausência de manchas ou barras conspícuas nas nadadeiras e pela presença de dimorfismo sexual secundário, tais como nadadeiras pélvicas dos machos maduros mais longas que em fêmeas e com espinhos ósseos.


Introduction
Characidium Reinhardt comprises 59 valid species of small Neotropical fishes distributed from Argentina to Panama (Eschmeyer, 2015). Half of these species were described before 1950 and about 15 species were described after the year 2000 (e.g., Melo & Buckup, 2002;Taphorn et al., 2006;Silveira et al., 2008;Lujan et al., 2013;Peixoto & Wosiacki, 2013;Leitão & Buckup, 2014;Zanata & Camelier, 2014), indicating recent efforts to increase the taxonomic knowledge of the genus. Characidium is currently considered a monophyletic group based on the presence of a black spot near the base of the middle caudal-fin rays (Buckup, 1993a). Limitations of the diagnosis of the genus, in addition to the need for further investigation on its monophyly and phylogenetic relationships, were highlighted by Melo & Buckup (2002).
Here we describe two additional species, from rivers draining the Bahia State, northeastern Brazil. The first, a mountain-dwelling form with morphological characteristics possibly related to the inhabitance of fast flowing streams (e.g., a naked isthmus, a streamlined body, and paired-fins modifications), was collected in the lower rio Pardo basin within the domain of the Atlantic Forest. The other species has conspicuous secondary sexual dimorphic characters (e.g., mature males with longer and more pointed pelvic fins than females reaching the analfin origin and bony hooks on the pelvic fins) and was collected in tributaries of the upper rio Paraguaçu basin, on the west side of the Chapada Diamantina National Park, within the domain of the Cerrado-Caatinga ecotone.

Material and Methods
Measurements and counts were performed according to the methods of Buckup (1993b). Measurements were taken with a digital caliper to the nearest 0.1 mm and expressed as percent of standard length (SL) for body parts and head length (HL) for parts of head. Frequencies are recorded (in parentheses), after the respective characteristic, and an asterisk indicates values for the holotype. Observations on vertebrae, ectopterygoid teeth, branchiostegal rays, procurrent caudal-fin rays, epural bones, and other osteologic observations were made only from cleared and stained (c&s) paratypes prepared according to the method of Taylor & Van Dyke (1985). The sex of some specimens was confirmed by dissection. The pseudotympanum morphology was assessed by removal of the overlying skin, adipose tissue, and lateralline nerve of alcohol-preserved specimens. Color in life was described on the basis of photographs of live specimens taken in the field. Specimens examined belong to the following institutions: Museu de Zoologia da Universidade de São Paulo (MZUSP), São Paulo; Museu Nacional da Universidade Federal do Rio de Janeiro (MNRJ), Rio de Janeiro; Museu de Zoologia da Universidade Federal da Bahia UFBA, Salvador.
Paratypes. All from Brazil, Bahia, rio Pardo basin. UFBA 7563, 5, 38.7-46.2 mm SL, collected with holotype. MNRJ 42132, 6, 39.8-47.2 mm SL, MZUSP 115008, 6, 34.7-53.7 mm SL, UFBA 5679, 14, 1 c&s, 29.6-55.3  oiticicai Travassos, C. pterostictum Gomes, C. schubarti Travassos, C. timbuiense Travassos, C. vidali Travassos, and members of the C. fasciatum Reinhardt clade, by lacking scales on isthmus. Characidium kamakan further differs from these congeners by the absence of conspicuous vertically elongated bars or blotches on body (vs. presence in C. alipioi, C. declivirostre, C. fasciatum, C. gomesi, C. grajahuensis, C. lauroi, C. oiticicai, C. timbuiense, and C. vidali), presence of a conspicuous black blotch at midlength of caudal-fin rays shaped like a 3 and unpigmented rounded A. M. Zanata & P. Camelier 489 areas close to the base of the lobes (vs. two or more dark bars on caudal fin and/or absence of rounded clear areas at the base of caudal-fin lobes in C. gomesi, C. grajahuensis, C. japuhybense, C. lauroi, C. oiticicai, C. pterostictum, C. schubarti, and C. timbuiense), having only the anteriormost portion of isthmus naked (vs. naked area broader, from isthmus to the vertical through contralateral bases of last pectoral-fin ray in C. macrolepidotum; from isthmus to median area of belly in C. crandellii and C. declivirostre), and presence of small foramen for the ophthalmic nerve bordered by a well-developed bony crest (vs. exceptionally large pterosphenoid foramen for the ophthalmic nerve, not usually bordered by bony crests in C. boavistae). More specifically, from congeners known to occur in rivers draining northeastern Brazil, C. kamakan further differs by having all fins with conspicuous dark bars or blotches (vs. absence of blotches on fins, except by an inconspicuous dark bar crossing dorsal-fin midlength of C. bahiense, C. deludens new species, and C. samurai, or a well-marked dark bar at base of dorsal-fin rays and a second faded bar at distal portion of fin in C. bimaculatum).
Description. Morphometric data for holotype and paratypes presented in Table 1. Body fusiform and moderately compressed. Greatest body depth at vertical through dorsal-fin origin. Dorsal profile convex from upper lip to vertical through nares, slightly convex from this point to end of occipital process, slightly convex or straight from this point to dorsal-fin base origin, slightly convex or straight along dorsal-fin base, straight between end of dorsal-fin base and adipose fin, and slightly concave from this point to origin of anteriormost dorsal procurrent caudal-fin ray. Ventral profile straight along length of head, slightly convex from isthmus to pelvic-fin origin, straight from latter point to origin of anal fin, and slightly concave from this point to origin of anteriormost ventral procurrent caudal-fin ray. Snout triangular-shaped from lateral view. Mouth subterminal, aligned with or slightly lower than ventral edge of orbit. Distal tip of maxilla barely reaching anterior margin of orbit. Orbit rounded, approximately with same length as snout. Cheek thin, its depth about a third of orbit diameter. Nares separated, both with skin flaps and raised margins; posterior naris closer to eye than to anterior naris. Supraorbital somewhat drop-shaped in dorsal view, medial margin convex abutting frontal and lateral margin straight to slightly concave, anterior portion directed away from frontal bone, somewhat wider than posterior portion. Parietal fontanel limited anteriorly by parietals. Parietal branch of supraorbital canal present, not trespassing frontal-parietal border. Orbithosfenoid slightly rectangular in lateral view, connected anteriorly to rhinosphenoid. Pterosphenoid foramen for ophthalmic nerve relatively small, formed by a tunnel crossing diagonally pterosphenoid and bordered by bony crest preventing direct lateral view of brain cavity through foramen. Dentary teeth in two rows; outer series with 7(9), 8*(12), 9(8), or 10(4) teeth; anterior teeth tricuspid, posterior conical; teeth decreasing in size from symphysis; inner series, with several minute conical teeth inserted on edge of replacement tooth trench. Premaxilla with single series of 5(2), 6*(19), or 7(14) tricuspid teeth, decreasing in size from symphysis; lateral cusps very small, central somewhat elongate. Maxillary edentulous. Ectopterygoid teeth 20(1), conical, in a patch of two or three somewhat disorganized series. Mesopterygoid teeth absent.

Color in alcohol.
Ground color of head and body whitish to pale yellow ( Fig. 1). Dark stripe from snout tip to anterior margin of orbit. Dark blotch posterior to orbit usually separated from it by narrow clear area; some specimens with blotch forming stripe aligned with that of snout, although somewhat broader. Opercle dark, mainly in its dorsal half. Dark irregular blotches on head dorsum. Area around nares somewhat clear. Ventral half of head clear, with sparse small melanophores. Scales with melanophores densely concentrated along posterior margin, forming short vertical black traces; some specimens with dark borders of scales aligned, forming traces somewhat longer; few scales on lateral surface of body without concentration of melanophores, resulting in small clear areas. Dark midlateral stripe inconspicuous, formed by underlying dark pigment, extending from rear of head to caudal peduncle. Dark humeral blotch on rear of opercle usually inconspicuous, merged with longitudinal band. Nine or 10 inconspicuous dark vertical bars formed by underlying pigment on lateral surface of body, usually more visible on area over longitudinal stripe; some specimens without vertical bars. Ventral portion of body yellowish; area anterior to pelvic fins usually without concentration of melanophores on scale margins, area posterior to pelvic fins with borders of scales dark. All fins with dark pigmentation pattern. Dorsal-fin base with a dark bar formed by melanophores over rays and interradial membranes, broader anteriorly; second dark bar around midlength of rays, usually broad anteriorly over two or three branched rays, divided into two bands posteriorly; or, in some specimens, continuous throughout fin, without division; distal borders of rays usually dark. Caudal fin with conspicuous 3-shaped black blotch covering basal portion of four or five median caudal-fin rays black and midlength of lobes; area of lobes anterior to blotch completely clear; distal margins of caudal-fin rays somewhat dark. Some specimens with 3-shaped blotch somewhat inconspicuous due to extra short dark traces on posterior half of fin. Pectoral fin with concentration of melanophores at dorsal portion of rays, usually more evident on distal half. Pelvic fin with dark bar over midlength of rays. Anal fin with similar dark bar, primarily at midlength of rays. Central portion or posterior half of adipose fin usually darkly colored.

Color in life.
Dark pattern on scales and fins similar to that of specimens in alcohol. Ground color of body and fins yellow or orange; dorsal and caudal-fins strongly pigmented, particularly with yellow marks at base of caudal-fin lobes. Lateral of head silvery. Sexual dimorphism. No hooks were observed on fins of the specimens examined. Mature males (around 50.0 mm SL) have the 3 rd and 4 th branched pelvic-fin rays somewhat longer than in females of similar standard length, reaching closer to anal-fin origin when adpressed. Furthermore, in some mature males the posterior border of the anal fin is somewhat more pointed due to the elongation of some branched rays (especially the 2 nd ), while in females the branched anal-fin rays usually have similar lengths and straight or rounded fin border. However, a more detailed analysis of a greater number of mature specimens is necessary for a precise evaluation of the dimorphic features described above.
Distribution. Characidium kamakan was sampled in the rio Água Preta and rio Panelão, tributaries of the lower portion of rio Pardo basin, Bahia State, Brazil (Fig. 3).
Habitat and ecological notes. The rio Pardo is an eastern coastal drainage with its upper and part of middle portions located in the state of Minas Gerais and its lower portion in the state of Bahia, within the domain of the Atlantic Forest. The new species occurs in the latter area and was captured in stretches of the rio Água Preta and rio Panelão (Fig. 4), at altitudes ranging from 162-184 m above sea level, with moderate to rapid water current, running over rock, pebbles and sand bottoms, 0.3-1.5 m deep, with rapids, pools, and meanders. Locally, the riparian vegetation has shrubs, trees, and grass. The surrounding original Atlantic Forest had been converted to cocoa plantations and more recently to cattle ranches, coffee, and rubber crops. Characidium kamakan inhabits places with fast water current over substrate composed of medium to somewhat large sized stones. The analysis of stomach contents of two specimens revealed the presence of allochthonous and autochthonous items, composed by fragments of vascular plants, organic debris, insect larvae (Diptera: Chironomidae and other unidentified orders), and fragments of unidentified arthropods.
Etymology. Named after the Kamakã indigenous people that originally inhabited the area. A noun in apposition.
Conservation status. Characidium kamakan is so far known from localities in the lower rio Pardo basin, with a relatively restricted distribution. The species occurs in rapid water stretches within domain originally covered by the Atlantic Forest, posteriorly converted to cocoa plantations and more recently to cattle ranches, coffee, and rubber crops. However, since no imminent threats to the species were detected C. kamakan could be classified as east Concern (LC) according to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2014). Additional collecting efforts should be conducted in that region in order to better understand biological aspects and distribution of the species.    Graça, Pavanelli & Buckup, C. xavante, and C. zebra Eigenmann), and presence of adipose fin (vs. absent in C. mirim, C. nupelia, C. stigmosum, C. xavante, and absent or reduced in C. vestigipinne). Characidium deludens differs further from C. satoi Melo & Oyakawa, by having one or two scales between anus and origin of anal fin (vs. 4-7 scales), area between pelvic and anal-fin origin straight (vs. area moderate to strongly convex), and absence of sexually dimorphic coloration (vs. presence). More specifically, from congeners known to occur in rivers draining northeastern Brazil and adjacent drainages to south of Bahia, C. deludens further differs from C. bahiense by the presence of parietal branch of supraorbital canal (vs. absence); from C. bimaculatum by having a higher number of lateral line scales (35-37 vs. 32-34), one faded dark bar on proximal half of dorsal-fin rays (vs. a well-marked dark bar at proximal portion of rays and a second faded bar on distal portion); from C. fasciatum by having one series of dentary teeth (vs. two). In addition to distinctive color pattern, C. deludens can be further distinguished from C. kamakan by having 5 series of scales between lateral line and insertion of pelvic fin (vs. 3 or 4); from C. samurai by the presence of dark marks on ventral half of body and the presence of a narrow dark stripe on lateral of body (vs. ventral half of body without dark marks and presence of a broad dark stripe on lateral of the body), dentary with one series of 6-10 teeth (vs. dentary with two series of teeth, outer series with 10-13 teeth), and premaxilla with 5-7 teeth (vs. 7-10); and from C. timbuiense by having one faded dark bar on proximal half of dorsal-fin rays (vs. two dark bars crossing dorsal fin). Table 2. Body fusiform and moderately compressed. Greatest body depth at vertical through dorsalfin origin. Dorsal profile convex from upper lip to vertical through nares, slightly convex to nearly straight from this point to end of occipital process, slightly convex from this point to origin of dorsal-fin base, convex along dorsal-fin base, almost straight between end of dorsal-fin base and adipose fin and slightly concave from this point to origin of anteriormost dorsal procurrent caudal-fin ray. Ventral profile straight to slightly convex along length of head, slightly convex from isthmus to origin of pelvic-fin origin, straight from latter point to origin of anal-fin, and slightly concave from this point to origin of anteriormost ventral procurrent caudal-fin ray. Snout triangular-shaped from lateral view. Mouth subterminal, aligned with or slightly lower than ventral edge of orbit. Distal tip of maxilla barely reaching anterior margin of orbit. Orbit approximately rounded, horizontal length similar to or slightly longer than snout length. Cheek thin, its depth about a third to a quarter of orbital diameter. Nares separated; anterior naris with raised margins; posterior naris considerably closer to orbit than to anterior naris, usually without skin flaps. Supraorbital elongated in dorsal view, medial margin abutting frontal, slightly convex on posterior half and concave on anterior; lateral slightly straight; anterior portion directed away from frontal bone, somewhat narrower than posterior portion. Parietal fontanel limited anteriorly by frontals. Parietal branch of supraorbital canal present, slightly exceeding frontal-parietal border. Orbithosfenoid slightly rectangular from lateral view, connected anteriorly to rhinosphenoid. Pterosphenoid foramen for ophthalmic nerve relatively small, formed by a tunnel crossing pterosphenoid diagonally, bordered by bony crest that prevents direct lateral view of brain cavity through foramen.
Dorsal-fin rays ii,9*(30); distal margin of dorsal fin slightly rounded. Adipose fin present. Pectoral-fin rays highly variable iii,6,ii(2), iii,6,iii(6), iii,7,i*(1), iii,7,ii(5), iii,8,1(7), iii,8ii(1), iii,9,i(3), iv,7,i(1) or iv,8,i(1); 1 st and 2 nd branched pectoral-fin rays longest; posterior tip of pectoral fin not reaching pelvic-fin insertion. Pelvic-fin rays i,6,ii(3), i,7,i*(26), or i,7,ii(1); 2 nd to 4 th branched pelvic-fin rays longest; posterior tip of pelvic fin usually not reaching anal-fin origin. Anal-fin rays ii,6(1) or ii,7*(28); posterior margin of anal fin straight or slightly rounded. Caudal-fin rays i, 9,8,i*(26). Dorsal procurrent caudal-fin rays 8(1); ventral procurrent caudal-fin rays 7(1). Total number of vertebrae 34(1); precaudal vertebrae 19(1); caudal vertebrae 15(1). Supraneural bones 6(1), one anterior to neural spine of 5 th centrum. Epural bones 2(1). Uroneural bones 1(1). Branchiostegal rays 4(1); 3 connected to anterior ceratohyal, 1 connected to area between anterior and posterior ceratohyal. Color in alcohol. Ground color of head and body yellowish (Fig. 5). Dorsal half of head darker due to concentration of small melanophores. Majority of specimens with dark band from tip of the snout to anterior margin of orbit. Ventral half of head clearer, with sparsely distributed melanophores; fewer or no melanophores at isthmus, contrasting the dotted pattern around it. Scales on dorsal half of body with melanophores concentrated on exposed margin, resulting in a somewhat reticulated aspect; some of these scales darker overall, forming blotches that extend partially lateroventrally (Fig. 5b); blotches observed in dorsal view usually alternating elongation to one or the other side of body and not conforming continuous bars through the lateral of body. Vertically elongated dark blotches on lateral of body, usually not corresponding in number and position with middorsal blotches; usually 8 to 12, although variable; lateral blotches centered mainly over narrow dark longitudinal stripe that extends from rear of head to caudal peduncle, though some of them are positioned exclusively ventral or dorsal to dark median stripe. Small and somewhat inconspicuous vertically elongated dark humeral blotch on rear of opercle. Body yellowish in ventral view, without dark bars or spots, except by a narrow dark band in the median area between pelvic and anal fins, formed by underlying pigment. Fins with sparsely-distributed melanophores on border of rays and between ray segments. Fins without blotches, except by a faded dark band that may occurs below midlength of dorsal-fin rays. Small rounded black spot near base of middle caudal-fin rays. Adipose fin somewhat dark, with sparse melanophores.

Color in life.
Pattern of coloration similar to that of specimens in alcohol, except for a well-defined yellow background.
Sexual dimorphism. Small bony hooks on pelvic fins were observed in 18 mature males of Characidium deludens, around 34.0 mm SL or larger (Fig. 6a). Welldeveloped hooks are distributed usually over distal half of 2 nd to 4 th branched rays but four specimens have also hooks on 1 st branched ray. In large mature males hooks are more numerous on 3 rd and 4 th rays, with around 20 hooks dorsally directed; 1 st and 2 nd with a few similar hooks. Hooks on maturing males occur in lower number and are distributed solely on distal 3 rd of pelvic rays. The mature females examined had no bony hooks on any of fins. Along with the presence of hooks, mature males have 3 rd to 5 th branched pelvic-fin rays somewhat more elongate than in females, reaching or almost reaching anal-fin origin when adpressed (Fig. 6a). Females of similar size possess a more rounded pelvic-fin border, distant from anal-fin origin when adpressed (Fig. 6b). Distribution. Characidium deludens is known from the rio Cochó and rio Santo Antônio, tributaries of upper rio Paraguaçu basin, Bahia State, Brazil (Fig. 3).
Habitat and ecological notes. The rio Cochó has part of its headwaters in Piatã, around 1,200 m above sea level, and runs on the eastern slopes of the Serra do Sincorá, on the west side of the Chapada Diamantina National Park. Included in the Cerrado-Caatinga ecotone, the area of the rio Cochó is dominated by Cerrado vegetation, usually composed of scattered small trees, shrubs and grasses. The stretch of the rio Cochó sampled is 5-10 m wide, up to one m deep, characterized by relatively slow water current and clear water running over portions of rocky bed alternating with sandy substrate (Fig. 7). The river is perennial in Piatã, but may become intermittent in several sections downstream, suffering considerable impact along its course due to frequent burning cycles of native vegetation, impoundment of the river associated with irrigation, and use of pesticides for coffee, sugar cane and fruit farming (Rocha, 2002). The stretch sampled in the rio Santo Antônio is around 7 m wide, a few centimeters to 1.5 m deep, surrounded by trees and shrubs, and with clear water running on sandy bottom with rocks and pebbles. The analysis of stomach contents of two specimens of C. deludens revealed the presence of allochthonous and autochthonous items, composed by fragments of vascular plants, organic debris, insect aquatic larvae and shelters (Trichoptera: Hydroptilidae), Crustacea, and fragments of unidentified arthropods. Etymology. From the Latin delude, which means false, deceive, alluding to the deceitful vertical bars on body, in comparison to those common in congeners as Characidium fasciatum.
Conservation status. Characidium deludens is so far known only from two localities on the upper rio Paraguaçu basin, one of them represented by a small intermittent river, suffering considerable impact along its course due to frequent burning cycles of native vegetation, impoundment of the river associated with irrigation, and use of pesticides for coffee, sugar cane, and fruit farming. However, given the absence of studies on population biology and on geographical range reductions for the species, we are unable to assess the effect of these putative threats on the conservation of C. deludens and on the maintenance of its populations. Thus, C. deludens could be classified as data deficient (DD) according to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2014). Additional collecting efforts should be conducted in that region in order to better understand biological aspects and distribution of the species.

Discussion
Characidium kamakan shares the potential synapomorphies proposed by Buckup (1993a) to Clade C1: poscleithrum 1 reduced or absent (absent in the species), a scaleless area on the isthmus, and reduction of the fontanel with exclusion of the frontals from its anterior margin. According to the author, within Clade C1, the Clade C2 (composed by C. boavistae, C. bolivianum Pearson, C. fasciatum, C. gomesi, and C. purpuratum Steindachner) is diagnosed by having an exceptionally large foramen on the pterosphenoid for the ophthalmic nerve usually not bordered by bony crests and a second vertebral centrum with a pair of ventral processes, extending anteroventrally along the connective tissue surrounding the dorsal aorta and the anterior wall of the swimbladder. Characidium kamakan has the processes of the second vertebral centrum similar to the condition described for members of Clade C2 but does not share the large pterosphenoid foramen. Instead, the foramen for the ophthalmic nerve in C. kamakan is relatively small and bordered by a welldeveloped bony crest. The diagnostic features proposed by Buckup (1993a) for the second subgroup of C1, named Clade C3 (composed by C. crandellii and C. declivirostre and diagnosed by having scaleless area of isthmus extending onto the ventral body surface located posterior to the pectoral girdle, branchiostegal membranes united across the isthmus, independent dermal flaps surrounding the anterior and posterior naris but touching each other distally, and the posterior process of the coracoid reduced to a squarish protuberance), are not observed in C. kamakan. The basicaudal spot, whose absence was attributed by the author as diagnostic to Clade C3, is also not evident in C. kamakan, being possibly overlapped by the black blotch on the anterior portion of median caudal-fin rays. Buckup & Reis (1997) suggested that C. alipioi, C. japuhybense, C. pterostictum, and C. timbuiense could be provisionally assigned also to Clade C1, based on the shared absence of scales at the isthmus. Of these four species, C. timbuiense was examined herein in detail and along with the naked isthmus it shares the other two diagnostic features for Clade C1 (poscleithrum 1 reduced, reduction of the fontanel, and exclusion of the frontals from its anterior margin). However, C. timbuiense does not share any of the synapomorphies of Clade C2 or C3, and thus, differs from C. kamakan by the absence of a pair of ventral processes extending anteroventrally from the second vertebral centrum.
Apart from the putative groups cited in the literature, C. kamakan shares the presence of the dark blotch crossing the caudal fin and similar overall body morphology with a series of species occurring along coastal Brazilian drainages, such as C. alipioi, C. grajahuensis, C. japuhybense, C. lauroi, C. oiticicai, C. pterostictum, C. timbuiense, and C. vidali. In fact, these species share a naked isthmus, a streamlined body, and paired-fins modifications possibly related to the inhabitance of fast flowing streams . Characidium kamakan is also a fast water current dwelling fish and possess body features possibly related to that life style. Along with a streamlined body, C. kamakan possess the 4 or 5 first pectoral-fin rays and the 2 or 3 first pelvic-fin rays covered with thick skin and the distal portion of the 4 first pectoral-fin rays protruded beyond the margin of the inter-radial membrane. Similar conditions were previously described for C. cf. timbuiense by Buckup et al. (2000: 275, fig. 3) as putative adaptations for waterfall climbing. Furthermore, examination of c&s specimen of C. kamakan revealed 4 or 5 anterior rays of the pectoral-and pelvicfin thick rays and formed by shorter ray segments, when compared to posterior rays of these fins. Similar enlargement of anterior rays and different length among ray segments of the fin was also observed herein in C. timbuiense. A distinct condition, without enlargement pectoral-and pelvic-fin rays, was observed in the species of Characidium that inhabit more lentic environments, as C. bahiense, C. bimaculatum, and C. samurai. No waterfall climbing was observed so far for C. kamakan and the described adaptations possibly provide adherence, resistance, and strength to avoid being swept downstream in the fast flowing water where the species inhabits.
Characidium deludens, on the other hand, does not appear to fit in any group of Characidium previously proposed in the literature (e.g., Buckup & Reis, 1997;Buckup & Hahn, 2000;Netto-Ferreira et al., 2013) and does not share any of the synapomorphies proposed by Buckup (1993a) for any particular group of the proposed Clade C. Although possessing a streamlined body, somewhat wide paired-fins and some of the adaptations observed in C. kamakan (e.g., first rays protruded beyond the margin of the inter-radial membrane and formed by shorter rayssegments), examined specimens of C. deludens do not have thick skin over the leading-edge pectoral and pelvic-fin rays or enlargement of these rays.
Patterns of sexual dimorphism in species of Characidium previously cited in the literature are a conspicuous black band along the distal margin of pelvic and anal fins in males, an enlarged anal fin with a rounded distal profile in adult males, brightly colored fins with orange or red chromatophores in live adult males (Buckup & Hahn, 2000 for C. occidentale, C. orientale, C. rachovii, and C. vestigipinne), a distinct color pattern of fins, conspicuously marked or dark in males (Melo & Buckup, 2002 for C. stigmosum;Graça et al., 2008 for C. nupelia and C. xavante), hooks on the rays of pelvic and pectoral fins of mature males (Almeida, 1971 for C. bahiense; Graça et al., 2008 for C. nupelia and C. xavante;Silveira et al., 2008 for C. xanthopterum;Netto-Ferreira et al., 2013 for C. mirim), and a less intensely colored dorsum coloration in mature males (Netto-Ferreira et al., 2013 for C. mirim). Mature males of C. deludens have longer pelvic fins than females, reaching the anal-fin origin, and bony hooks on the pelvic fins (Fig. 6). The somewhat elongated and pointed pelvic fins observed for mature males of C. deludens is reported for the first time as a dimorphic feature for species of Characidium. Although some mature males of C. kamakan have elongation of pelvic-fin rays, not observed in mature females, a more detailed analysis of a greater number of mature specimens is necessary to confirm this putative dimorphic feature. Hooks were not observed in the species.
The presence of pseudotympanum in species of Characidium was cited in the description of a few species and in phylogenetic studies including few species of the genus (e.g., Géry, 1977;Silveira et al., 2008;Peixoto & Wosiacki, 2013;Mirande, 2010). Recently, Zanata & Camelier (2014) provided a somewhat detailed description of the pseudotympanum of C. bahiense, C. bimaculatum, C. samurai, and C. timbuiense. The pseudotympana of C. deludens and C. kamakan are similar to the overall structure described previously for those four species. However, in these species the pseudotympanum has oval hiatus with anterior and posterior margins somewhat pointed (Fig. 2), instead of having the triangular overall form and more rounded apertures present in C. bahiense and C. samurai or the elongate form present in C. timbuiense (see Zanata & Camelier, 2014).