A taxonomic review of the Neotropical electric fish <i>Rhamphichthys</i> (Gymnotiformes: Rhamphichthyidae)

The species diversity and taxonomy of Rhamphichthys is reviewed and seven species are considered valid: Rhamphichthys apurensis from the Orinoco and Cuyuni river basins; R. drepanium from the Amazon and Orinoco river basins; R. hahni from the Paraná-Paraguay River system; R. heleios and R. lineatus from the Amazon River basin; R. pantherinus from theupper Orinoco, Essequibo, Amazon and coastal rivers of North Brazil,and R. rostratus from the upper Orinoco, Amazon and coastal rivers of Guianas. Based on the examination of specimens from nominal species, from across their geographic ranges, including specimen types, the previous synonymization of four species (R. blochii, R. reinhardti, R. schomburgki, and R. schneideri)with R. rostratus,and R. marmoratus with R. pantherinus is confirmed. Two other nominal species, R. atlanticus and R. longior, are proposed as junior synonyms of R. pantherinus.Species are redescribed and diagnosed based on color pattern, morphometric, meristic, and internal anatomy characters.Distribution maps and an identification key based on the examination of a comprehensive list of materials are also provided.

Keywords:
Identification key; Ostariophysi; Species diversity; Taxonomy

Authorship

Tiago P. Carvalho

Conceptualization

Data curation

Formal analysis

Project administration

Writing-original draft

Writing-review and editing

Laboratorio de Ictiología, Unidad de Ecología y Sistemática (UNESIS), Departamento de Biología, Facultad de Ciencias, Pontificia Universidad Javeriana, Carrera, Bogotá DC, Colombia. pitiago@javeriana.edu.co.Pontificia Universidad JaverianaColombiaCarrera, Bogotá DC, Colombia Laboratorio de Ictiología, Unidad de Ecología y Sistemática (UNESIS), Departamento de Biología, Facultad de Ciencias, Pontificia Universidad Javeriana, Carrera, Bogotá DC, Colombia. pitiago@javeriana.edu.co.

http://orcid.org/0000-0001-5901-1634

James S. Albert

Conceptualization

Formal analysis

Investigation

Methodology

Project administration

Writing-review and editing

University of Louisiana at Lafayette, Department of Biology, P.O. Box 42451, Lafayette, LA 70504, USA. jalbert@louisiana.edu University of Louisiana at LafayetteUSALafayette, LA, USA University of Louisiana at Lafayette, Department of Biology, P.O. Box 42451, Lafayette, LA 70504, USA. jalbert@louisiana.edu

http://orcid.org/0000-0001-5477-1749

Edited-by

William Crampton

Correspondence

Tiago P. Carvalhopitiago@javeriana.edu.co

Competing Interests

The authors declare no competing interests.

Ethical Statement

Not applicable.

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables

Figures (64)
Tables (10)

Characters	*R. apurensis*	*R. drepanium*	*R. hahni*	*R. heleios*	*R. lineatus*	*R. pantherinus*	*R. rostratus*
Snout length	long; 58.4–63.7% of HL	short; 49.5–54.6% of HL	short; 46.4–54.3% of HL	short; 50.5–55.1% of HL	short; 52.1–56.0% of HL	short; 51.4–59.1% of HL	long; 58.8–65.1% of HL
Caudal appendage length	long; 23.2–36.8% of LEA	short; 5.8–20.3% of LEA	short; 7.3–15.4% of LEA	short; 12.7–16.9% of LEA	short; often damaged	short; 9.1–28.0% of LEA	long; 18.4–35.6%o LEA
Anal fin rays	347–417	310–390	310–360	320–345	341–381	360–444	365–455
Saddles in the dorsum	intercalated saddles	sickle shaped paired saddles	sickle shaped paired saddles	dark, no saddles	clear, no conspicuous saddles	intercalated saddles	intercalated saddles
Anal fin pigmentation	Mostly clear	Mostly dark with reticulated clear areas	Mostly dark with reticulated clear areas	Reticulated dark areas	Mostly clear, sometimes with dark spots	Variable, clear to reticulated dark areas	Terminal dark band
Posterior gas bladder	small, membranous walls	Large, membranous, or thickened walls	Large membranous	Large, thickened walls	small, membranous walls	small, membranous walls	Small, membranous walls

	n	Range	Mean	SD
Length to end of anal fin (LEA)	14	252–520	401.0	–
Percents of LEA
Anal-fin length	14	86.1–92.5	88.9	1.7
Body depth	14	7.7–9.4	8.4	0.4
Pectoral-fin length	14	4.1–5.5	4.8	0.4
Head length	14	12.9–15.1	13.8	0.6
Caudal filament length	14	23.2–36.8	30.6	4.0
Caudal filament depth	14	1.8–2.3	2.1	0.1
Percents of head length
Interorbital distance	14	9.3–11.6	10.2	0.5
Snout length	14	58.4–63.7	60.9	1.6
Postorbital length	14	34.4–38.1	36.3	1.1
Eye diameter	14	4.2–6.7	5.0	0.6
Post. nares length	14	13.2–17.8	14.8	1.1
Branchial Opening	14	13.2–18.2	15.1	1.4
Meristics
Anal-fin rays	14	347–417	387.1	22.5
Pectoral-fin rays	14	17–21	18.4	1.2

PCV	18	19	20	21	CV	90	92	93	94	100	101	106	109	111	113	116	117
R. apurensis	3	9									1	2	2
R. drepanium	2	7	1				1	1	1
R. hahni		2	4	1		2	1	1
R. heleios		1
R. lineatus	5	1
R. pantherinus	4	3	2						1	1
R. rostratus		6	1											1	1	1	1

	H	H1	H2	H3	n	Range	Mean	SD
Length to end of anal fin (LEA)	730	–	690	850	52	285–850	452.5	–
Percents of LEA
Anal-fin length	92.8	–	89.8	89.4	52	74.6–101.4	89.7	3.9
Body depth	8.4	–	7.6	5.9	52	4.8–10.8	8.6	1.2
Pectoral-fin length	4.1	–	4.2	3.5	52	3.6–6.5	5.0	0.6
Head length	10.7	–	12.2	9.1	53	9.2–15.2	12.6	1.3
Caudal filament length	–	–	–	–	19	9.1–28.0	16.3	5.7
Caudal filament depth	2.6	–	2.0	2.2	44	1.5–2.7	2.0	0.2
Percents of head length
Interorbital distance	14.0	11.3	10.5	13.4	53	9.5–14.3	12.0	1.2
Snout length	53.6	52.6	58.1	54.5	53	51.4–59.1	55.7	1.8
Postorbital length	44.9	43.5	40.0	43.3	53	37.5–46.7	41.9	1.9
Eye diameter	5.2	5.2	4.1	5.3	53	4.1–7.4	5.6	0.7
Post. nares length	15.1	15.5	15.8	16.0	53	14.4–18.6	16.3	1.0
Branchial opening	20.2	19.6	22.1	24.4	53	16.5–26.1	20.7	2.3
Meristics
Anal-fin rays	369	381	430	395	32	360–455	396.7	23.3
Pectoral-fin rays	20	18	19	19	32	17–22	18.4	1.3

	H1	H2	H3	H4	n	Range	Mean	SD
Length to end of anal fin (LEA)	600	630	700	510	32	270–700	446.9	–
Percents of LEA
Anal-fin length	90	88.9	87.5	94.1	32	80.6–94.1	88.2	2.4
Body depth	6.6	8.9	8.1	8.6	32	6.1–8.9	7.6	0.6
Pectoral-fin length	4.1	4.7	3.6	5.3	32	3.7–5.6	4.8	0.5
Head length	12.4	14.0	15.7	15.9	32	12.4–15.9	14.3	0.9
Caudal filament length	18.5	23.8	–	23.3	26	18.4–35.6	26.6	4.9
Caudal filament depth	1.8	1.9	1.4	1.5	32	1.0–3.0	2.0	0.4
Percents of head length
Interorbital distance	10.3	9.7	8.1	9.3	32	8.1–12.5	9.7	0.9
Snout length	60.7	63.2	65.1	60.3	32	58.8–65.1	62.3	1.2
Postorbital length	36.8	36.3	34.1	37.2	32	33.1–38.2	35.6	1.1
Eye diameter	4.4	3.4	2.9	3.7	32	2.9–5.8	4.4	0.6
Post. nares length	13.3	13.2	12.4	–	31	12.5–18.4	14.8	1.2
Branchial opening	–	15.8	12.6	15.5	31	12.6–19.6	16.0	1.6
Meristics
Anal-fin rays	405	403	417	394	28	365–455	400.0	22.7
Pectoral-fin rays	18	19	22	21	32	17–39	62.9	119.3