Sternarchorhynchus curumim, Santana & Crampton, 2006

Santana, Carlos David De & Crampton, William G. R., 2006, Sternarchorhynchus curumim (Gymnotiformes: Apteronotidae), a new species of tube-snouted ghost electric knifefish from the low- land Amazon basin, Brazil, Zootaxa 1166, pp. 57-68 : 59-68

Sternarchorhynchus curumim new species

Figure 1 , Table 1

Holotype. MCP 38304 ( WGRC 50.231099 , female, 163 mm), Brazil, Amazonas , Rio Tefé , Toco Preto, trawl sample, Municipality of Tefé, 03°47.31’S, 64°59.91’W, collected by W. Crampton, 23 Oct 1999.

Paratypes. INPA 25256 , (1 female c&s, 211 mm), same locality as holotype, collected by W. Crampton, 24 Oct 1999 . MCP 38305 (2: female 181 mm, male 183 mm), same locality as holotype, collected by W. Crampton, 24–25 Oct 1999 .

Diagnosis. Sternarchorhynchus curumim is diagnosed as a member of the genus Sternarchorhynchus by anguloarticular, and endopterygoid bones elongate, five to 10 times longer than deep in specimens larger than 100 mm TL; anterior process of maxilla unossified; orbitosphenoid narrow, with unossified anterior margin; five branchiostegal rays; and Meckel’s cartilage lost or greatly reduced ( Campos­da­Paz, 2000). Sternarchorhynchus curumim is diagnosed from congeners by the following combination of characters: head and mid­dorsum as dark as dorsolateral areas (four specimens examined) ( Fig. 1 ) (vs. white or yellow pigments along head and mid­dorsum forming long pale stripe in S. roseni ; this character appears to be polymorphic in S. britskii , S. curvirostris , and S. mesensis (Campos­da­Paz, 2000: 527)); anal and pectoral fins translucent, without conspicuous distal dark margins (vs. dark margins in S. mormyrus , S. oxyrhynchus , and S. roseni ); 10–11 scales above lateral line at mid­body (vs. 11–17 in S. britskii , S. curvirostris , S. mesensis , and 5–8 S. oxyrhynchus ); 23–24 anterior unbranched anal­fin rays (vs. 18–22 in S. britskii ); 179–189 total anal­fin rays (vs. 213–227 in S. mormyrus , 209–221 S. oxyrhynchus , and 187–215 S. roseni ); greatest body depth 9.0– 10.0% of length to end of anal fin (LEA) (vs. 10.0–14.5% in S. britskii and S. mesensis ); mouth length 3.5–5.6% of head length (HL) (vs. 5.9–9.6% in S. britskii and S. mormyrus ); internarinal distance 2.4–2.8 % of HL (vs. 3.1–5.8 in S. curvirostris , S. mesensis , and S. mormyrus ); branchial opening 11.7–12.9% of HL (vs. 13.1–17.9% in S. britskii ); postocular distance 33.6–39.2% of HL (vs. 40.0–50.5% in S. britskii and S. mormyrus ); prepectoral distance 18.3–20.6% of LEA (vs. 21.4–23.8% in S. mesensis ); tail length (CL) 19.5–25.2% of LEA (vs. 5.9–14.3% in S. britskii and S. mesensis ); tail depth 10.6–11.9% of CL (vs. 18.9–25.0% in S. britskii ); and 15 precaudal vertebrae (vs. 16–17 in S. britskii , S. mesensis , and S. mormyrus ). Additional characters used to diagnose all valid described species of Sternarchorhynchus are summarized in Table 2 .

Description. Morphometric data for holotype and paratypes are presented in Table 1 . Body laterally compressed, with greatest body depth at abdominal cavity or a little posterior to this area. Dorsal profile nearly straight. Lateral line extending to tail, but absent on caudal fin. First anterior perforated scale of lateral line above pectoral­fin origin ( Fig. 1 ). Head laterally compressed, widest at opercular region and deepest at nape; snout elongate, compressed and curved downward. Eyes small, located laterally on head, and completely covered by a thin membrane. Anterior nares at end of a small tube, close to tip of snout; posterior ones ellipsoid, without a tube and closer to tip of snout than to eyes. Branchial opening slightly anterior to pectoral­fin origin; branchial membranes joined at isthmus. Anus and urogenital papilla adjacent, ventral, located in a vertical posterior to eyes, does not noticeable move anteriorly with age. Neurocranium partially reticulated. Infraorbital series not ossified. Mesethmoid long and narrow. Lateral ethmoid absent. Premaxillae of small size, somewhat rounded, seven to 10 teeth (n=1). Dentary elongate, a row of seven curved conical teeth (n=1). Meckel’s cartilage greatly reduced. Coronomeckelian bone absent. Anguloarticular elongate. Mouth terminal, rictus not passing a vertical through anterior nares. Endopterygoid thin and long, without teeth or an ascending process connecting orbitosphenoid. Five branchiostegal rays, first, second and third almost filamentous, ventromedial branchiostegals large and broad. Urohyal with trapezoidal head, and well­developed at posterior laminar portion. Basihyal elongate, narrow at base and broad posteriorly, about same size or bigger than first ceratobranchial. First and second basibranchial ossified, posterior ones cartilaginous. Epibranchials one to four ossified, fifth one cartilaginous. Lower pharyngeal tooth plates with six teeth (n=1); upper pharyngeal tooth plates with seven to eight teeth (n=1). Four ossified independent proximal pectoral radials; third postcleithrum not ossified; anterior portion of coracoid reaching anterior edge of cleithrum. Absence of medial ridge on cleithrum, scapula without scapular foramen; supracleithrum and postemporal fused. Pectoral fin elongate, broad and pointed distally, with ii+11–12 rays (n=4). Anal­fin origin anterior to opercular region; 23–24 (n= 2) anterior unbranched anal­fin rays and 179–189 (n= 3) total anal­fin rays. 10–11 (n=4) scales above lateral line at mid­body. Dorsal mid­sagittal electroreceptive filament origin on posterior half of body, and inserted into a narrow middorsal groove, almost extending to, or slightly passing end of anal fin. Tail compressed and short, ending in a small and elongate caudal fin, 13–15 rays (n=3). Number of precaudal vertebrae 15 (12 anterior, three transitional), (n= 4).

Secondary sexual dimorphism. Single male specimen with wider snout than in all three female specimens (see Fig. 1 ). External teeth resembling those known from S. roseni from the Orinoco basin (Mago Leccia, 1994) and S. cf. roseni from the Amazon (Py­ Daniel & Cox­Fernandes, 2005: 105, fig. 5) were not present in the male specimen. No sexual differences in size or post­cranial morphology were evident.

Coloration in alcohol. Body dark brown; pectoral­fins hyaline to translucent; anal­fin hyaline to translucent; caudal­fin black. Coloration in life is similar, with brown pigments less faded and with a purplish hue.

Electric organ discharge. Known from a single sexually mature female (the holotype). Continuous periodic wave­type EOD with biphasic waveform and stable repetition rate of 1168 Hz. Downward inflection in rising voltage above zero line. The EOD of S. curumim has a harmonic spectral content, with energy concentrated into the fundamental frequency (F 0) and higher harmonics (at integer multiples of F 0) ( Fig. 2 ). No spontaneous amplitude modulations (‘chirps’) or other EOD modulations ( Zakon et al., 2002) were observed during the recording.

Ecology. Sternarchorhynchus curumim is known only from the type series captured at depths of 5–14 m in the Rio Tefé towards the end of the low­water period. The Rio Tefé is a typical nutrient poor blackwater river with low electrical conductivity (6–20 Scm­1). All four specimens were in reproductive condition. The females possessed swollen ovaries containing large yellow globular eggs typical of spawning fish. The male specimen had enlarged white testes typical of a spawning specimen. The stomachs of all specimens contained only autochthonous invertebrates, mainly the larvae of Chironomidae, Coleoptera and Plecoptera.

Distribution. Known only from the type series collected in the lower Rio Tefé, Amazonas, Brazil.

Etymology. The specific epithet is from curumim , the Brazilian Portuguese derivate of the Tupi­Guarani for child, curumi, or kurumí; referring to the small size of this species. A noun in apposition.

Material examined

Data are arranged alphabetically by country, state, museum abbreviation, and museum lot number. Each museum number is followed by number of specimens and size range in mm TL, locality, collector and date of capture (when available).

Sternarchorhynchus curvirostris . Equador: MCZ 486776 , 1 , Río Putuno , Tributary of Río Bobonoza, R. Olalla, Oct 1957 .

Sternarchorhynchus cf. curvirostris . Brazil: Amazonas: INPA 4834 , 1 , 189 , Rio Uatumã, Balbina near of dam, J. Zuanon, et al., 24 Oct 1987 . INPA 11523 , 1 , 291 , Paraná Afoia, 10 Km west of the community ‘mouth of Mamirauá’, Alvarães, Rio Solimões , 03°2’S 64°51’W . INPA 11331 , 1 , 137 , Rio Negro, Lago do Prato , Novo Airão, M. Garcia, 17 Mar 1991 . INPA 19992 , 1 , 222 , Rio Amazonas , Paraná do Tapará, C. Cox­Fernandes, 0 3 Nov 1992 . Pará: INPA 3931 , 2 , 170–184 , Rio Xingu, Cachoeira de Kaituká , L. R. Py­Daniel & J. Zuanon, 0 9 Oct 1990 . INPA 3934 , 3 , 99–130 , Rio Xingu, Cachoeira de Kaituká , L. R. Py­Daniel & J. Zuanon, 0 9 Oct 1990 .

Sternarchorhynchus mesensis . Brazil: Goias: MNRJ 11611 , paratypes 4 c&s, Rio Tocantins, local of the future hydroelectric dam Serra da Mesa, Minaçu, Cavalcante , 13°50’S 48°19’W, D. F. Moraes et al., 24–31 Jul 1988 . MNRJ 11613 , paratypes 7, 115– 250, Rio Tocantins, local of the future hydroelectric dam Serra da Mesa, Minaçu, Cavalcante , 13°50’S 48°19’W, D. F. Moraes et al., 24–31 Jul 1988 .

Sternarchorhynchus mormyrus . Brazil: Amazonas: INPA uncat., 1, 213, Costa do Morimba , Ilha do Careiro, C. Cox­Fernandes, Jan 1998 . INPA uncat., 1, 375, Rio Purus , C. Cox­Fernandes, 20 Oct 1992 . INPA uncat., 1, 275, Rio Solimões , Xiborena, C. Cox­ Fernandes, 2 Dec 1998 . INPA uncat., 1, 382, Rio Solimões , Xiborena, C. Cox­Fernandes, 0 6 Feb 1998 . INPA uncat., 3, 240–250, Paraná do Rei , Ilha do Careiro, C. Cox­Fernandes, 22 Jan 1998 . INPA 4899 , 2 , 378–413 , Rio Amazonas , Ilha do Careiro, Paraná do Rei , M. Jégu, 0 5 Apr 1986 . INPA 4900 , 1 , 505 , Rio Amazonas , Ilha do Careiro, P. Grenand, Apr 1987 . INPA 15823 , 253–286 , Mamirauá Lake System, Paraná Maiana, Alvarães, 03º06.74'S, 64°47.53'W, W. G. R. Crampton, 02–22 Feb 2000 . INPA 17608 , 1 , 342 , Costa do Marimba , Ilha do Careiro, C. Cox­Fernandes, 1987. INPA 17609 , 3 , 310–350 , Ilha da Machantaria , C. Cox­Fernandes, 23 Apr 1998 . INPA 17610 , 1 , 240 , Rio Solimões , Xiborena, 16 Dec 1998 . INPA 17611 , 1 , 180 , Paraná do Curari , C. Cox­Fernandes, 13 May 1998 . INPA 18295 , 1 , 248 , Rio Japurá at mouth of Lago Caxinguba, Alvarães, 03º06.17'S, 64º45.84'W, W. G. R. Crampton, 0 4 Feb 1999 . Venezuela: CU 80960, 2, 250– 275, Río Orinoco , Caño Anabata, 08º37’20”N, 061º47’33”W, D. Stewart, 15 Nov 1979 .

Sternarchorhynchus cf. mormyrus . Brazil: Pará: INPA uncat., 2, 293–348, Cametá market, Jan 1987.

Sternarchorhynchus oxyrhynchus . Brazil: Amazonas : INPA uncat., 1, 353 , Ilha do Careiro, Paraná do Rei , Feb 1987 . INPA uncat., 5, 344–384, Januaca, Solimões, W. Heiligenberg, 12 Sept 1976 . INPA uncat., 1, 244, Rio Juruá , mouth of Lago Mamiraua, W. G. R. Crampton, 7 Dec 1999 . INPA uncat., 1, 370, Rio Amazonas , Ilha do Careiro, Paraná of Lago do Rei , B. Merona et al., 27 Feb 1986 . INPA 4435 , 3 , 180–303 , Rio Negro , near Manaus, J. Lundberg & L. Chao, Dec 1990 . INPA 4833 , 1 , 337 , Rio Uatumã, Balbina , near of dam, J. Zuanon et al., 29 Oct 1987 . INPA 12551 , 2 , 176–217 , Rio Jaú , mouth of Jaú, M. Garcia, 0 3 Nov 1994 . INPA 1256 , 1 , 191 , Rio Jaú, mouth of Rio Preto , M. Garcia, 0 3 Nov 1994 . INPA 17104 , 2 , 175–212 , Rio Purus , 4º53’47.1”S, 62º54’51.3”W, L. Py­ Daniel, 0 6 Jun 2001 . INPA 19991 , 1 , 203 , Rio Amazonas , Paraná do Tapará, C. Cox­ Fernandes, 0 3 Nov 1992 . INPA 11355 , 1 , 184 , Rio Jaú , curve of Jaú, M. Garcia, 9 Nov 1994 . INPA 15821 , 6 , 311–369 , Rio Tefé , toco Preto, W. G. R. Crampton, 22–23 Oct 1999 . INPA 16636 , 1 , 357 , Rio Solimões , Xiborena, 0 6 Feb 1998 . INPA 17633 , 4 , 285– 336 , Costa do Morimba , Ilha do Careiro, C. Cox­Fernandes, 1997. INPA 17637 , 1 , 347 , Paraná do Rei , Ilha do Careiro, C. Cox­Fernandes, 0 5 Feb 1998 . INPA 18194 , 1 , 248 , Rio Japurá , West bank at mouth of Lago Mamirauá, Alvarães , 03º07.13'S 64º47.30'W, W. G. R. Crampton, 0 7 Dec 1999 . INPA 18274 , 1 , 334 , Rio Japurá , W. G. R. Crampton, 9 Feb 1991 . INPA 20221 , 28 , 230–313 , Rio Amazonas, below mouth of Rio Madeira , J. Lundberg, 20 Oct 1994 . Roraima: MCZ 46887, 1 c&s; Rio Negro, near of the confluence with Rio Branco , 1º24’S, 61º27’W, Alpha Helix Expedition, Mar 1967 . MCZ 98428, 1 c&s, no data available . Venezuela: FMNH 100722 , 1 c&s, Rio Suripa , Barinas, B. Chernoff et al., 11 Jan 1991 .

Sternarchorhynchus roseni . Venezuela: Apure: CU 72165, 1, 147, Matiyuri River, Orinoco River , just S of village of Achaguas, C. D. Hopkins, 25 May 1989 .

Sternarchorhynchus cf. roseni . Brazil: Amazonas: INPA 15822, 6, 223–374, Rio Tefé, Toco Preto, 03°47.31’S, 64°59.91’W, W. G. R. Crampton, 22–25 Out 1999. INPA 17601, 3, 310–326, C. Cox­Fernandes, 0 7 Jan 1998. INPA 17602, 1, 370, Rio Purus, Bacia da Ressaca, C. Cox­Fernandes, 20 Oct 1992. INPA 17603, 2, 337–373, Rio Purus, Bacia da Ressaca, C. Cox­Fernandes, 20 Oct 1992. INPA 17604, 1, 305, Rio Purus, C. Cox­ Fernandes, 20 Oct 1992. INPA 17605, 3, 192–279, Costa do Morimba, Careiro, C. Cox­ Fernandes, 0 7 Jan 1998. INPA 17606, 1, 243, Rio Amazonas, C. Cox­Fernandes, 14 Nov 1992. INPA 17607, 1, 238, Rio Solimões, Machantaria, C. Cox­Fernandes, 26 Oct 1992. INPA 17098, 1, 180, Rio Purus, 4º17’0.1”S, 61º54’9.7”W, L. Py­Daniel, 11 Jun 2001. UF 146954, 1, 295, Rio Tefé, Toco Preto, 03°47.31’S 64°59.91’W, W. G. R. Crampton, 23 Out 1999.

Sternarchorhynchus sp. Brazil: Amazonas: INPA uncat. 1, 126, Cachoeira da Ponte , Balbina, M. Jégu, 23 Nov 1985 . INPA 4227 , 1 , 96 , Rio Solimões, Januacá, Lago do Castanha , J. Donath, 17 Mar 1978 . Brazil: Pará : INPA 4829 , 1 , 246 , Rio Tocantins, Tucuruí near of dam , INPA Icthyology Team , Dec 1984 . INPA 6811 , 1 , 109 , Rio Jamamxim, afluent of Rio Tapajós, Ilha de Terra Preta , L. Py­Daniel & J. Zuanon, 20 Oct 1991 . Roraima : INPA 10578 , 1 , 178 , Rio Mucajaí , E. Ferreira & M. Jégu, 18 Feb 1987 . INPA 10590 , 1 , 200 , Rio Mucajaí mouth of igarapé Traira, E. Ferreira & M. Jégu, 21 Feb 1987 .

Acknowledgements

WGRC thanks Instituto Mamirauá for field support. CDS is indebted to the Georgia Museum of Natural History for hosting him and the Lakeside Fellowship offered by the California Academy of Sciences; to grants offered by PRONEX/UNISOL/Projeto Piaba/ PNOPG (466098/2001­4 and 550367/2001­2), provided by L. N. Chao; and to an Ernst Mayr Grant offered by the Museum of Comparative Zoology, Harvard University. WGRC was funded by the Conselho Nacional de Pesquisas e Desenvolvimento Tecnológico (CNPq) (38062/96­2 and 381597/97­0 plus extensions). This paper was benefited with the criticism of three anonymous reviewers. Collecting was authorized by IBAMA permit 0492/99­12 and extensions to WGRC. All specimens were deposited at MCP, which is an officially registered depositary (fiel depositário) of Brazilian fish specimens. Animal care protocols follow CNPq guidelines.

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Figures

FIGURE 1. Photographs of preserved specimens of Sternarchorhynchus curumim n. sp.: A: holotype, MCP 38304, mature female showing lateral and dorsal views, and close up of head. B: head of paratype, MCP 38305, mature male. Scale bars = 10 mm. Note the slightly wider snout in the male.

FIGURE 2. Electric Organ Discharge (EOD) waveform (left) and Fourier Power Spectrum (right) of Sternarchorhynchus curumim n. sp., MCP 38304 (WGRC 50.231099, female). EOD plotted with head­positivity upwards, voltage on the vertical axis (dashed line = 0 volts) and time on the horizontal axis (scale bar = 1 msec). Power spectrum computed by 65536 point Fast­Fourier­ Transform from a 3 sec digital recording with a sample rate of 96 kHz. The Peak Power Frequency (PPF), which is equivalent to the fundamental frequency, is scaled to 0 dB.

Tables

TABLE 2. Characters used to identify species of Sternarchorhynchus: 1, yellow or white band on head and mid­dorsum; 2, dark distal margins; 3, cranial dimorphism (type 1 = males with external teeth, type 2 = males with wider snout than females); 4, fundamental frequency of the Electric Organ Discharges; 5, number of scales above lateral line; 6, number of anterior unbranched anal­fin rays; 7, number total of anal­fin rays; 8, number of precaudal vertebrae; 9, number of transitional vertebrae; 10, habitat preference. Data from: * Campos­da­Paz (1992; 2000); ** Crampton (1998); *** Mago­Leccia (1994).

Taxon	1	2	3	4	5	6	7	8	9	10
S. britskii *	present/ absent	absent	absent	?	11­13	18­22	166­178	16­17	3	channels
S. curumim	absent	absent	?	1.168	10­11	23­24	179­189	15	3	channels
S. curvirostris	present/ absent	absent	?	?	13­15	18	174­185*	?	?	?
S. mesensis *	present/ absent	absent	absent	?	11­13	23­28	171­189	16­17	3	caves
S. mormyrus	absent	present	type 2	?	10­15	23­25* 213­227*		17	3­4	channels
S. oxyrhynchus	absent	present	absent	1.321­1.390**	5­8	21­27	209­221	15­16	2	channels
S. roseni ***	present	present	type 1	?	11­13	?	187­215	11	?	channels