A remarkable new <i>Characidium</i> (Characiformes: Crenuchidae) from tributaries of río Marañón, Loreto, Peru, with unique fin bony processes in both sexes

Zanata, Angela Maria; Britzke, Ricardo; Meza-Vargas, Vanessa; Hidalgo, Max H.; Faustino-Fuster, Dario; Oliveira-Silva, Leonardo

doi:10.1590/1982-0224-2025-0047

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Original Article • Neotrop. ichthyol. 23 (03) • 2025 • https://doi.org/10.1590/1982-0224-2025-0047 linkcopy

A remarkable new Characidium (Characiformes: Crenuchidae) from tributaries of río Marañón, Loreto, Peru, with unique fin bony processes in both sexes

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Abstract

A new species of Characidium from tributaries of the río Marañón, Loreto, Peru is described.The new species is promptly distinguished from congeners and also remaining species of Crenuchidae by two exclusive features: females and males with bony processes along length of the pectoral-fin rays, including immature and mature specimens, and paired fins with black longitudinal bands that extend along the total length of a few unbranched and branched rays. The species is further differentiated from most congeners, with the exception of some psammophilous species, by the presence of strongly tricuspid teeth on the premaxilla and dentary, with three well developed and similar sized cusps, and a black dashed midventral line extending from area between pectoral fins to caudal peduncle. Characidium sp. n. is externally similar to psammophilous species such as C. fleurdelis and C. pteroides, but a definition of its relationships depends on future comprehensive phylogenetic studies of Characidium.

Keywords:
Amazon fishes; Dark fins; Fin hooks; Psammophily; Tricuspid teeth

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Sociedade Brasileira de Ictiologia Neotropical Ichthyology, Departamento de Biologia Animal e Vegetal, CCB, Universidade Estadual de Londrina, Rodovia Celso Garcia Cid, Km 380, Cidade Universitária, 86055-900, Londrina, Paraná, Brazil, Phone +55(43)3371-5151 - Londrina - PR - Brazil
E-mail: neoichth@nupelia.uem.br

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	Holotype	Range	Mean	SD
Total length (mm)	38.6	31.3–44.4	-	-
Standard length (mm)	30.2	24.7–35.6	-	-
Percents of standard length
Depth at dorsal-fin origin	19.9	16.8–20.8	19.2	1.1
Depth at anal-fin origin	12.3	11.6–14.2	12.7	0.5
Caudal-peduncle depth	8.6	8.0–9.4	8.6	0.3
Caudal-peduncle length	19.2	16.8–19.6	18.3	0.9
Snout to dorsal-fin origin	41.7	40.2–44.3	42.7	1.0
Snout to pectoral-fin origin	24.5	23.6–26.0	24.9	0.7
Snout to pelvic-fin origin	47.4	47.1–49.5	48.4	0.7
Snout to anal-fin origin	75.5	74.0–76.2	75.2	0.7
Anal-apex distance	93.4	91.1–94.8	93.0	1.1
Dorsal-fin adpressed	29.5	28.1–31.9	29.4	0.8
Distance end of dorsal/adipose	10.6	8.9–12.7	10.6	0.8
Pectoral-fin length	27.2	25.1–28.8	26.7	1.1
Pelvic-fin length	23.2	22.3–25.6	23.8	1.0
Anus to anal-fin origin	13.6	12.4–15.2	14.1	0.8
Body width	12.3	9.6–12.3	10.7	0.9
Head length	21.9	20.8–24.3	23.2	0.9
Percents of head length
Horizontal eye diameter	30.3	30.3–35.1	33.2	1.3
Snout length	22.7	21.1–23.5	22.3	0.7
Snout to maxillary tip	24.2	20.3–24.6	21.8	1.1
Anterior naris to orbit	12.1	9.7–12.2	10.8	0.8
Posterior naris to orbit	4.5	3.1–6.1	4.4	0.7
Cheek depth	6.1	4.5–6.8	6.2	1.0
Least interorbital width	21.2	19.2–21.9	21.4	0.8