Characidium deludens, Zanata & Camelier, 2015

Zanata, Angela M. & Camelier, Priscila, 2015, Two new species of Characidium Reinhardt (Characiformes: Crenuchidae) from northeastern Brazilian coastal drainages, Neotropical Ichthyology (Neotrop. Ichthyol.) 13 (3), pp. 487-498 : 492-495

Characidium deludens , new species u r n:l s i d:z o o b a n k.o r g:a c t: 63 6 8 7 D 43-13B3 - 42F 3 -9 76 4 - 604B4716EDF6

Fig. 5

Holotype. MZUSP 115009 , 48.3 mm SL, Brazil, Bahia, Piatã, rio Cochó, tributary of the upper rio Paraguaçu , 13°00’37”S 41°53’14”W, 1,231 m above sea level, 15 Sep 2007, A. M. Zanata, P. Camelier & A. B. A. Góes.

Paratypes. MNRJ 42133 , 8 , 27.3-45.1 mm SL , MZUSP 115010 , 9 , 26.6-40.8 mm SL , UFBA 3850 , 22 , 1 c&s, 27.0- 47.8 mm SL, collected with holotype . UFBA 7720 , 14 , 34.7-39.1 mm SL, same locality as holotype, 1 Dec 2013, A . T. da Silva, S. B. Barreto & L. Argôlo . UFBA 7815 , 4 , 35.0- 44.7 mm SL, Brazil, Bahia, Palmeiras, rio Santo Antônio, tributary of the upper rio Paraguaçu , 12°22’17.3”S 41°31’05”W, 641 m above sea level, 28 Jan 2014, A. M. Zanata , R. Burger, L. Sales & R. Abreu .

Diagnosis. Characidium deludens can be distinguished from congeners by having dark blotches irregular in form along dorsum, alternating elongation to one or other side of body and usually not connected to lateral blotches. The new species further differs from congeners that occur in Brazilian rivers by having isthmus completely covered by scales (vs. naked isthmus or partially covered by scales in C. alipioi , C. boavistae, C. crandellii, C. declivirostre , C. fasciatum , C. gomesi , C. grajahuensis , C. japuhybense , C. kamakan new species, C. lauroi , C. macrolepidotum, C. oiticicai , C. pterostictum , C. schubarti, C. timbuiense , and C. vidali ), lateral line complete (vs. incomplete in C. bahiense , C. interruptum Pellegrin , C. laterale (Boulenger) , C. mirim Netto-Ferreira, Birindelli & Buckup, C. nupelia da Graça, Pavanelli & Buckup , C. rachovii Regan , C. stigmosum Melo & Buckup , and C. xavante da Graça, Pavanelli & Buckup ), 14 scales around caudal peduncle (vs. 10 or 12 in C. bahiense , C. brevirostre Pellegrin, C. gomesi Travassos , C. heirmostigmata da Graça & Pavanelli , C. lagosantense Travassos, C. litorale Leitão & Buckup, C. macrolepidotum (Peters), C. mirim, C. nupelia , C. occidentale Buckup & Reis, C. orientale Buckup & Reis, C. papachibe Peixoto & Wosiacki, C. rachovii , C. serrano Buckup & Reis, C. tenue (Cope) , C. xanthopterum Silveira, Langeani, da 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).

Description. Morphometric data of holotype and paratypes presented in Table 2. 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 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.

Dentary with a single series of 6(2), 7(13), 8*(12), 9(1), or 10(1) teeth; anterior three or four teeth from the symphysis usually tricuspid, posterior teeth triangular or conical; teeth decreasing in size from symphysis. Dentary teeth usually inclined anteriomedially; distal portion of symphyseal tooth overlapping its contralateral in some specimens. Premaxilla with a single series of 5(1), 6*(21), or 7(8) tricuspid teeth, decreasing in size from symphysis; smaller specimens with some conical teeth. Maxillary edentulous. Ectopterygoid teeth 12(1), conical, distributed in one or two series somewhat disorganized. Mesopterygoid teeth absent.

Scales cycloid; circulii absent on posterior field of scales located immediately below 10 th scale of lateral line, 10 to 16 radii present. Lateral line complete, perforated scales 35(4), 36*(22), or 37(1); horizontal scale rows above lateral line 4*(30); horizontal scale rows below lateral line 5*(30). Scales along middorsal line between supraoccipital and origin of dorsal fin 10(11), 11*(13), or 12(3) in a single row. Scales rows around caudal peduncle 14*(30). Axillary scale absent. Isthmus completely covered by scales. Pseudotympanum present, represented by muscular hiatus at vertical through anterior portion of swimbladder; hiatus situated between ribs of 5 th and 6 th vertebrae ( Fig. 2b ).

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 ). Well-developed 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.

Figures

Fig. 5. Characidium deludens, holotype, MZUSP 115009, 48.3 mm SL, female, Brazil, Bahia, Piatã, rio Cochó, tributary of upper rio Paraguaçu basin: (a) lateral and (b) dorsal views.

Fig. 2. Pseudotympanum of (a) Characidium kamakan, paratype, UFBA 5679, 45.7 mm SL, and (b) C. deludens, paratype, UFBA 3850, 41.9 mm SL. Number corresponds to the pleural rib of the 5th vertebra. Left side, anterior to left. Overlying skin, adipose tissue, and lateral-line nerve removed.

Fig. 6. Pelvic and anal fins of Characidium deludens, paratypes, UFBA 3850: (a) male, 35.3 mm SL, and (b) female, 36.1 mm SL.

Fig. 3. Map of distribution of Characidium kamakan (black and white symbols) and C. deludens (red symbols) in middle and lower rio Pardo basin and upper rio Paraguaçu basin, respectively, Bahia State, northeastern Brazil; type localities indicated by stars.

Fig. 7. Type locality of Characidium deludens, Bahia, Piatã, rio Cochó, upper rio Paraguaçu basin.