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| Characidium fleurdelis Zanata, Oliveira-Silva & Ohara, 2023 |
Abstract
A new miniature species of Characidium is described from the midde rio Guaporé, rio Madeira basin, Rondônia, Brazil. The new species can be readily distinguished from all congeners by the sexual dichromatism, with females having narrow dark bars on body absent in males, and by the presence, in both sexes, of a black midventral dashed line extending from area between contralateral pectoral fins to at least the anal-fin origin. It can also be diagnosed from congeners by having strongly tricuspid teeth, with well developed and similar sized cusps in the premaxilla and outer series of dentary, and short lateral line with 6–8 perforated scales. Morphological novelties to Characidium observed in the new species include a rounded process on the first pleural rib near the vertebra, three or four haemal spines of the first caudal vertebrae distinctly elongate, neural and haemal spines of the antepenultimate vertebra not reaching origins of dorsal and ventral procurrent rays nor the origin of the caudal-fin rays.
Keywords: Amazon fishes; First rib; Haemal spine; Sexual dimorphism; Tricuspid teeth
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| 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. |
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| 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. |
Characidium fleurdelis, new species
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.
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| Dentary of Characidium fleurdelis, UFBA 9234, paratype, male, 21.0 mm SL, outer view. |
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.
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| 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. |
Angela Maria Zanata, Leonardo Oliveira-Silva and Willian M. Ohara. 2023. A New sexually dichromatic Miniature Characidium (Characiformes: Crenuchidae) from the rio Guaporé, rio Madeira Basin, Brazil, with Remarkable Morphological Novelties to the Genus. Neotrop. ichthyol. 21(1); DOI: 10.1590/1982-0224-2022-0059
Resumo: Uma nova espécie miniatura de Characidium é descrita do médio rio Guaporé, bacia do rio Madeira, Rondônia, Brasil. A nova espécie pode ser facilmente distinguida de todas as congêneres pelo dicromatismo sexual, com barras escuras estreitas no corpo das fêmeas ausentes nos machos, e por ter uma linha preta mediana ventral tracejada em ambos os sexos, que se estende da área entre as bases das nadadeiras peitorais até pelo menos a origem da nadadeira anal. A espécie também pode ser diagnosticada das congêneres por ter dentes fortemente tricúspides, com cúspides bem desenvolvidas e de tamanho semelhante no pré-maxilar e série externa do dentário, e linha lateral curta com 6–8 escamas perfuradas. Novidades morfológicas para Characidium observadas na nova espécie incluem presença de um processo arredondado na primeira costela pleural próximo à vértebra, três ou quatro espinhos hemais das primeiras vértebras caudais distintamente alongados, espinhos neurais e hemais da antepenúltima vértebra não atingindo as origens dos raios procorrentes dorsal e ventral, nem a origem dos raios da nadadeira caudal.
Palavras-chave: Dentes tricuspidados; Dimorfismo sexual; Espinho hemal; Peixes amazônicos; Primeira costela
