Characidium fleurdelis, Zanata & Oliveira-Silva & Ohara, 2023

Zanata, Angela Maria, Oliveira-Silva, Leonardo & Ohara, Willian M., 2023, A new sexually dichromatic miniature Characidium (Characiformes: Crenuchidae) from the rio Guaporé, rio Madeira basin, Brazil, with remarkable morphological novelties to the genus, Neotropical Ichthyology (e 220059) 21 (1), pp. 20-20 : 20

Characidium fleurdelis , new species

urn:lsid:zoobank.org:act:8D2995F6-A0DD-4FFA-8977-46327C995DA4

( Figs. 1–5 ; Tab. 1 )

Holotype. MZUSP 126956 , 21.6 mm SL, Brazil, Rondônia, Corumbiara town, Vitória da União district, stream tributary of rio Oimerê , rio Corumbiara , rio Guaporé sub basin, rio Madeira basin, 12°59’56.32”S 61°08’51.09”W, 197 m above sea level, 23 Jan 2022, W. Ohara.

Paratypes. All from Brazil, Rondônia, Corumbiara town, Vitória da União district , stream tributary of rio Oimerê, tributary of rio Corumbiara, rio Guaporé sub basin, rio Madeira basin, 12°59’56.32”S 61°08’51.09”W. UFBA 9231 *, 3, 20.3–21.7 mm SL , 1 c&s, 20.3 mm SL, 6 May 2021, W. M. Ohara & W. C. S. Tomicha. INPA 59849, 5, 16.3–24.4 mm SL; UFBA 9233, 21, 14.5–22.2 mm SL; MZUSP 126957, 12, 15.1–21.3 mm SL, 19 Aug 2021, W. Ohara & V. O. Alves. UFBA 9234 *, 22, 20.2–24.1 mm SL, 4 c&s, 20.2–23.5 mm SL; MZUSP 126958,12, 18.4–23.3 mm SL; INPA 59848, 24, 19.3–24.1 mm SL collected with holotype.

;

Non-types. All from Brazil, Rondônia, Corumbiara town, Vitória da União district, stream tributaries of rio Corumbiara, rio Guaporé sub basin, rio Madeira basin. INPA 59850, 1, 21.5 mm SL, stream tributary of rio Oimerê , 12°59’56.32”S 61°08’51.09”W, 5 May 2021, W. M. Ohara & W. C. S. Tomicha. INPA 59851 , 2 , 15.9–19.6 mm SL, stream tributary of rio Oimerê, 13°00’47.92”S 61°08’28.04”W, 6 May 2021, W. M. Ohara & W. C. S. Tomicha. INPA 59852 , 10 , 13.7 –17.0 mm SL, rio Bocão , 13° 5’14.16”S 61°10’7.50”W, 6 May 2021, W. M. Ohara & W. C. S. Tomicha. INPA 59853 , 1 , 15.5 mm SL, stream tributary of rio Bocão , 13°03’43.00”S 61°03’47.00”W, 6 May 2021, W. M. Ohara & W. C. S. Tomicha.

Diagnosis. Characidium fleurdelis differs from congeners, except C. longum , C. pellucidum , and C. pteroides by having teeth in the premaxilla and outer series of dentary strongly tricuspid, with three well developed and similar sized cusps ( Fig. 2 ) (vs. teeth uni- or if tricuspid with median cusp distinctly larger; e.g., Agudelo-Zamora et al., 2020, Fig. 4 ; Melo et al., 2021; Figs. 3A,B ). The new species differs from the aforementioned congeners by the presence of a dark (occasionally interrupted) narrow midlateral stripe on the body (vs. absence of dark midlateral stripe), the presence of a black midventral dashed line extending from area between contralateral pectoral fins to at least the anal-fin origin ( Fig. 1B ) (vs. absence of interrupted black line throughout ventral midline of body in C. longum and C. pteroides , and midventral black line restricted to the area posterior to pelvic fins in C. pellucidum ), and the presence of sexual dichromatism, with females having narrow dark bars on laterals of body and males without it ( Figs. 1 , 5 ) (vs. sexual dichromatism absent). Characidium fleurdelis also differs from the three aforementioned species and remaining congeners, except C. bahiense Almeida, 1971 , C. cacah Zanata, Ribeiro, Araújo-Porto, Pessali & Oliveira-Silva, 2020 , C. chicoi Graça, Ota & Domingues, 2019 , C. interruptum Pellegrin, 1909 , C. laterale (Boulenger, 1895) , C. mirim Netto-Ferreira, Birindelli Buckup, 2013 , C. nana Mendonça & Netto-Ferreira, 2015 , C. nupelia Graça, Pavanelli & Buckup, 2008 , C. rachovii Regan, 1913 , C. stigmosum Melo & Buckup, 2002 , and C. xavante Graça, Pavanelli Buckup, 2008 , by having a short lateral line with 6–8 perforated scales (vs. lateral line with more than 14 perforated scales). The new species can be distinguished from C. cacah , C. chicoi , C. mirim , C. nana , C. nupelia , C. stigmosum , and C. xavante by the presence of adipose fin (vs. absence), from C. bahiense and C. laterale by having two dentary teeth rows (vs. one), from C. rachovii by the absence of roundish black marks on the pelvic, dorsal, and anal fins (vs. presence) and from C. interruptum by having 12 circumpeduncular scales (vs. 14). Other features useful to diagnose the new species from most congeners includes: first pleural rib with a rounded process posteriorly directed near the vertebra ( Fig. 3A ) (vs. absence of such a process or, if present, triangular or L shaped); neural and haemal spines of the antepenultimate vertebra not reaching origins of dorsal and ventral procurrent rays, respectively, nor the origin of the caudal-fin rays ( Fig. 3B ) (vs. neural and haemal spines of the antepenultimate vertebra reaching origins of procurrent rays or the origin of the caudal-fin rays); and three to four haemal spines of caudal vertebrae anterior to the anal fin flattened and distinctly elongate ( Figs. 3C, D ) (vs. haemal spines anterior to the first anal-fin proximal radial with tapered tip, comparatively shorter than the neural spine of the same vertebra and similar in length or rarely longer than the haemal spines situated above the anal fin). See “Discussion” for additional comments.

Description. Morphometric data of holotype and paratypes in Tab. 1 . Largest specimen reaching 24.4 mm SL. Body elongate. Highest body depth at vertical through dorsal-fin origin. Anterior portion of head convex in lateral view; dorsal profile convex from snout to posterior tip of supraoccipital, straight or slightly convex from supraoccipital to origin of dorsal-fin base, convex along dorsal-fin base, slightly concave or straight from that point to origin of anteriormost dorsal procurrent caudal-fin rays. Ventral profile of body nearly straight or slightly convex from dentary symphysis to isthmus, straight or slightly concave from that point to pelvic-fin origin in males, nonreproductive females, and immature specimens ( Fig. 1 ), convex in mature females ( Fig. 5 ). Profile straight or concave from pelvic-fin insertion to anal-fin origin, straight or slightly concave along anal-fin base, and straight or slightly concave from end of anal-fin base to anterior most ventral procurrent caudal-fin ray.

Snout triangular-shaped in lateral view. Mouth subterminal, aligned or slightly superior than ventral margin of orbit. Distal tip of maxilla barely reaching anterior margin of orbit. Orbit approximately round, distinctly larger than snout length. Cheek narrow, its depth approximately one fifth of orbit diameter. Nares separated, without distinctly raised margins; posterior naris distinctly closer to orbit than anterior naris. Supraorbital broad, roughly triangular-shaped, outer border somewhat concave and inner border with angle. Nasal bones restricted to ossified canal. Parietal fontanel limited anteriorly by frontals and laterally by parietals. Parietal branch of supraorbital canal absent.

Dentary teeth in two rows; outer row with 7(1), 8(1), 9(1), or 10(2) teeth; majority of teeth tricuspid, pointed cusps well developed and similar in size ( Fig. 2 ), and posteriormost teeth smallest and conical; inner row with several small conical teeth inserted on edge of replacement tooth trench. Premaxilla with single row of 8(3) or 9(2) teeth tricuspid with cusps well developed and similar in size; teeth decreasing in size from symphysis, posteriormost tooth unicuspid in one c&s specimen. Maxillary edentulous. Ectopterygoid with one row of 7(2) or 8(3) teeth, minute and conical. Endopterygoid teeth absent. Branchiostegal rays 4(5), 3 connected to anterior ceratohyal, 1 connected to posterior ceratohyal.

Scales cycloid; circuli on exposed portion of scales absent; up to seven divergent radii present on exposed portion of scales. Lateral line reduced, with 6(17), 7*(12), or 8(1) perforated scales; total scales along lateral line series 32(1), 33*(12), 34(12), or 35(2); horizontal scale rows 8*(11) or 9(19). Scales along middorsal line between supraoccipital and origin of dorsal fin 8(16) or 9*(14). Scale rows around caudal peduncle 12*(30). Three (4), 4*(22), or 5(4) scales between anus aperture and anal-fin insertion. Isthmus and belly completely covered with scales. Pseudotympanum present, limited dorsally by lateralis superficialis, anteriorly and posteriorly by obliquus inferioris, and ventrally by obliquus superioris. Humeral hiatus divided into anterior and posterior chambers by pleural rib of fifth vertebra ( Fig. 4 ). Swimbladder with two well-developed chambers, both with anterior and posterior extremities rounded, without pointed tip in the second chamber. Total length of swimbladder 20.1–24.8% of SL in four specimens of 20.5–22.9 mm SL; anterior chamber of females 41.7–50.0% and posterior chamber 50.0%–58.3% of swimbladder length; anterior chamber of males 46.1–46.6% and posterior chamber 53.8%–57.1% of swimbladder length.

Fins broad with fragile rays. Dorsal-fin rays ii,9*(30); distal margin of fin nearly straight or somewhat concave. Adipose fin well-developed, somewhat aligned vertically with end of anal-fin base. Pectoral fin with 7–10 total rays; iii,3,i(1), iii,4,i(1), iii,5,i*(17), iii,6(5), or iii,6,i(6); last unbranched and first branched fin rays longest, first branched ray distinctly elongate, posterior tip of fin usually reaching beyond pelvic-fin origin. Postcleithrum 1 absent. Pelvic-fin rays i,6,ii(4) or i,7,i*(26); second branched fin ray elongated, posterior tip of fin reaching anal-fin ray origin ( Figs. 1 , 5 ). Anal-fin rays ii,6,i*(18) or ii,7(12) visible in alcohol (2 of the c&s specimens with com iii rays); posterior margin of fin straight or slightly concave, without distinctly elongate rays. First anal-fin radial inserts behind 21 st (2) or 22 th (3) vertebra, behind the fourth (1) or fifth (4) caudal vertebra; fin elements on last pterygiophore 1(5). Anal-fin proximal radials of males with distinctly developed plate-like bony expansions anteriorly and posteriorly directed ( Fig. 3 C ), meeting each other at midline between adjacent radials; radials of females without distinctly developed bony expansions ( Fig. 3 D ). Caudal-fin rays i,9,8,i*(30). Dorsal procurrent caudal-fin rays 6(5); ventral procurrent caudal-fin rays 5(4) or 6(1). Total vertebrae 33(5); precaudal vertebrae 16(3) or 17(2); caudal vertebrae 16(1) or 17(4). First pleural rib with two distinctly developed processes (5), one dorsally positioned, close to vertebra, posteriorly directed and with rounded posterior margin ( Fig. 3A ), and a second process more ventrally positioned, approximately at midlenght of rib, thumblike or somewhat triangular-shaped, directed towards swimbladder (see Buckup 1993b, fig. 11). Haemal spines of first three or four caudal vertebrae distinctly elongate almost reaching ventralmost portion of body ( Fig. 3 C, D ; distal portion of haemal spines flattened laterally with rounded tip in males ( Fig. 3 C ) and pointed in females ( Fig. 3D ). Supraneural bones 2(1), 3(1), or 4(3). Epural bones 2(4) or 3(1). Uroneural bone 1(5).

Color in alcohol. Female ( Figs. 1 , 5A ). Ground color of head and body pale yellow. Dorsal surface of head darker than lateral, with a distinct dark patch of pigmentation, usually forming a heart-shaped large blotch behind eyes; melanophores distributed in smaller inconspicuous blotches between eyes or anterior to it. A dark stripe from anterior margin of snout to anterior margin of eye and a more diffuse posterior to eye, with few and large scattered melanophores, somewhat aligned with stripe of snout and continuous with midlateral stripe of body. Ventral half of head without melanophores, except by a few sparsely distributed in parts of opercle. Ventral surface of head pale, without melanophores. Humeral region without humeral blotch apart from longitudinal stripe. A dark line or narrow stripe extending from rear of opercle to end of caudal peduncle; stripe somewhat homogeneous in form and continuous along its extension or with irregular borders; stripe slightly enlarged at end of caudal peduncle; specimens up to 18.0 mm SL with stripe usually interrupted or dashed, separated by less pigmented or unpigmented short stretches. Laterals of body with 7(1), 8(1), 10 (5), 11(5), 12(2), 13(3), 14(3), 15*(3), 16(1), 19(1) narrow and vertically elongated dark bars ( Figs. 1 , 5 ); some main bars with shorter bars between them ( Fig. 1E , 5 ); position and form of bars also variable, reaching ventral half of body in some specimens ( Figs. 1A, E , 5B ) or centered along midlateral line in others ( Fig. 1B ); some specimens with area of bars close to dorsum roughly connected with each other resulting in a somewhat continuous dark area ( Fig. 1B ). Dorsum with up to 11 blotches, continuous or not with lateral bars; Basicaudal spot well marked. Ventral surface of body pale yellow with few, small and scattered chromatophores, except by a black dashed midventral line extending from area between pectoral fins to caudal peduncle ( Fig. 1B ). All fin-rays with tinny melanophores along its borders, forming or not inconspicuous dark lines bordering rays. Proximal portion of caudal fin usually with inconspicuous narrow black blotch on its ventral half, resembling a less elongation of the basicaudal spot. Adipose fin hyaline or with tinny sparse melanophores.

Male ( Figs. 1D , 5A ). Overall head, background and fins colorations similar to described above. A very conspicuous dark narrow stripe extending from rear of opercle to end of caudal peduncle; specimens up to 18.0 mm SL with stripe usually interrupted or dashed, separated by less pigmented or unpigmented short stretches. Body conspicuously pigmented with melanophores equally distributed, including on ventral half of body, mainly on area posterior do pelvic fins. Flanks without dark bars, with melanophores concentrated on border of one or two dorsalmost longitudinal series of scales, resulting in an inconspicuous reticulate pattern. Black dashed midventral line conspicuous from area between pectoral fins to anal-fin origin, but absent or less evident on caudal peduncle.

Coloration in life. Ground color pale brown in males and pale yellow in females, with silvery belly ( Fig. 5B ). Dark pattern of stripe and bars similar to the condition observed in preserved specimens. Males usually darker than females. Ventral half of head pale and opercle silvery. Pigmentation on fins similar to preserved specimens but with pale brown dorsal-, anal-, and caudal-fin rays; pectoral and pelvic fins pale.

Sexual dimorphism. Males can be readily distinguished from females by the absence of dark bars or blotches on laterals and dorsum of body, possessing instead a more homogeneously dark coloration on body ( Figs. 1 , 5 ). Males and females of C. fleurdelis possess elongated haemal spines of first caudal vertebrae situated anterior to the anal fin, with the distal portion of the elongated spines distinctly flattened in males (3) and pointed in females (2) ( Figs. 3C, D ; see Discussion). Males of C. fleurdelis also have proximal radials of the anal fin with distinctly developed plate-like bony expansions (3), anteriorly and posteriorly directed, meeting each other at midline between adjacent radials ( Fig. 3C; see Discussion). No similar expansion was observed in females (2; Fig. 3D ).

Geographical distribution. Characidium fleurdelis is known to occur in tributaries of the rio Corumbiara, rio Guaporé sub basin, rio Madeira basin, Corumbiara, Rondônia State, Brazil ( Fig. 6A ).

Ecological notes. Characidium fleurdelis was observed and captured only in backwater areas, near the substrate, predominantly composed by sand and mud and covered by leaves, in small clear water and slow current streams, approximately 1–2 m wide, 0.4–1.3 m deep, and bordered by aquatic vegetation and grass ( Fig. 6B ). The type locality is surrounded by large cultivated farmlands (e.g., soy, cotton and corn). Other species sampled syntopically near the bottom includes Apistogramma linkei Koslowski , 1985, A. staecki Koslowski, 1985 , Brachyrhamdia marthae Sands & Black, 1985 , Corydoras caudimaculatus Rössel, 1961, Characidium aff. zebra Eigenmann, 1909 and Mikrogeophagus altispinosus (Haseman, 1911). A dissected mature female of 24.1 mm SL had a total of 500 mature ovocytes.

Etymology. Named in allusion to the similarity of the three pointed flower-like teeth of the species with a stylized flower called fleur-de-lis. Géry (1960) was the first author, apparently, to point out the resemblance of such form of teeth with a fleur-de- lis in his description of Microcharacidium eleotrioides (Géry, 1960) . Lily or iris, the flower upon which the emblem fleur-de-lis is historically related, was the flower of Hera, the Greek moon goddess, being the symbol of purity. Also, the fleur-de-lis is often related with the sacred lotus symbol for “plant” meaning “Tree of Life”. A noun in apposition. Conservation status. The species is known from four localities, two in streams of the rio Oimerê, and two in the rio Bocão, both from the middle rio Corumbiara, tributary of rio Guaporé, rio Madeira basin. The area is strongly impacted by deforestation and severely converted in large cultivated farmlands of soybean, cotton, and corn, suffering effects of erosion, herbicides, pesticides, fertilizers, and silting. The Extension of Occurrence ( EOO) is 6.300 km 2. Therefore, we recommend that C. fleurdelis be classified as Near Threatened (NT) approaching of Vulnerable (VU) by criterion B1(biii), according to the guidelines published by the International Union for Conservation of Nature Standards and Petitions Committee ( IUCN, 2022).

Figures

FIGURE 1 | Characidium fleurdelis: A. Holotype, MZUSP126956, female, 21.6 mm standard length, lateral view; B. Paratype, UFBA 9234, female, 22.9 mm SL, lateral, dorsal and ventral views; C. Paratype, UFBA 9234, female, 23.8 mm SL, lateral view; D. Paratype, UFBA 9234, male, 20.6 mm SL, lateral view; E. Paratype, UFBA 9233, juvenile, 17.4 mm SL, lateral view. All from rio Guaporé sub basin, rio Madeira basin, Rondônia, Brazil.

FIGURE 2 | Dentary of Characidium fleurdelis, UFBA 9234, paratype, male, 21.0 mm SL, outer view.

FIGURE 3 | Osteological characteristics in cleared and stained specimens of Characidium fleurdelis, UFBA 9234, paratypes: A. Weberian apparatus and first ribs, black arrows indicate dorsal rounded processes on first ribs, female, 23.5 mm SL, dorsal view; B. Caudal-fin bony elements, black arrows indicate neural and haemal spines of the antepenultimate vertebra, posteriormost intermuscular bones removed, female, 23.5 mm SL, lateral view; C. Anal-fin radials and first haemal spines in male, 21.0 mm SL, asterisks indicate elongate and flattened haemal spines, black arrow indicates one radial with plate-like bony expansions, lateral view; D. Anal-fin radials and first haemal spines in female, asterisks indicate elongate haemal spines, black arrow indicates one radial without plate-like bony expansion, 23.5 mm SL, lateral view.

FIGURE 4 | Pseudotympanum of Characidium fleurdelis UFBA 9234, paratype, 20.6 mm SL, right side in lateral view. Overlying skin and adipose tissue removed. ls, lateralis superficialis; oi, obliquus inferioris; os, obliquus superioris. Asterisk indicates the rib of fifth vertebrae.

FIGURE 5 | Characidium fleurdelis, paratypes, INPA 59848, lateral view: A. Freshly preserved specimens, top male, 22.2 mm SL; bottom mature female with ovocytes seen by transparency on belly as a yellowish area, 24.1 mm SL; B. Live specimens, top male, 20.6 mm SL; bottom mature female, 24.0 mm SL. All from rio Guaporé sub basin, rio Madeira basin, Rondônia, Brazil.

FIGURE 6 | A. Map with part of the rio Madeira basin, Brazil, showing the type locality (black star) of Characidium fleurdelis; symbol may represent more than one locality or lot. B. Sampling locality of Characidium fleurdelis, Rondônia, Corumbiara town, Vitória da União district, stream tributary of rio Oimerê, tributary of rio Corumbiara, rio Guaporé sub basin, rio Madeira basin.