Cynodon gibbus Agassiz, 1829

TOLEDO-PIZA, MÔNICA, 2000, The Neotropical Fish Subfamily Cynodontinae (Teleostei: Ostariophysi: Characiformes): A Phylogenetic Study and a Revision of Cynodon and Rhaphiodon, American Museum Novitates 3286, pp. 1-1 : 1-

Cynodon gibbus Agassiz, 1829

Rhaphiodon gibbus Agassiz, 1829: 77 , pl. XXVII (plate labeled Cynodon gibbus ) (original description, type locality: Brazil). c Lasso , 1988: 132 ( Venezuela, lower Río Orinoco, identification based on location).

Cynodon gibbus : Cuvier, 1829: 312 (named in a footnote to the description of the genus Hydrocyon ; nomen nudum). c Valenciennes, 1849: 333 (Brazilian Amazon; description). c Kner, 1859: 46 ( Brazil, Rio Branco). c Günther, 1864: 359 (based on Valenciennes, 1849). c Cope, 1878: 688 ( Peru; identification based on location). c Steindachner, 1883: 15 ( Peru, Río Huallaga). c Ulrey, 1895: 296 ( Brazil, Rio Tocantins specimen in poor condition; identification based on location). c Eigenmann and Eigenmann, 1891: 59 ( Peru, list of species). c Fowler, 1906: 467 ( Peru; description; identification based on location); 1945: 158, fig.50 ( Peru; list of species); 1950: 330 (literature compilation, references in part); 1975: 277 (literature compilation). c Eigenmann, 1910: 444 (literature compilation). c Eigenmann and Allen, 1942: 271 ( Peru, Yurimaguas; common name). c Campos, 1945: 473 ( Brazil, Rio Amazonas; description). c Schultz, 1950: 48 (references, in part). c Lowe­McConnel, 1964: 110 ( Guyana, Essequibo River, Dadanawa ponds). c Ovchynnyk, 1967:Appendix A (list of freshwater fishes of Ecuador). c Howes, 1976: 204 (specimens at the BMNH). c Mendes dos Santos et al., 1984: 40 ( Brazil, Rio Tocantins). c Taphorn and Lilyestrom, 1984:70 ( Venezuela, Río Apure drainage). c Lauzanne and Loubens, 1985: 56 ( Bolivia, Río Mamore´, Trinidad). c Géry, 1986: 66 (key to cynodontine species). c Ortega and Vari, 1986: 10 (list of freshwater fishes of Peru). c Barriga, 1991: 30 (list of freshwater fishes of Ecuador, common name). c Taphorn, 1992: 436 ( Venezuela, Río Apure drainage). (Not Eigenmann, 1912; c Pellegrin, 1909; Di Caporiacco, 1935; Boeseman, 1952).

Raphiodon gibbus : (genus name misspelled): Müller and Troschel, 1844: 94 ( Brazil); 1845: 19 (identical with Müller and Troschel, 1844).

Cynodus gibbus : (genus name misspelled) Machado­Allison, 1987: 134 ( Venezuela, Llanos, identification based on location).

DIAGNOSIS: Cynodon gibbus can be distinguished from Cynodon septenarius by the presence of a band of dark pigmentation that covers the base of the caudal­fin rays ( fig. 21 ), the presence of 8 (versus 7) branched pelvic­fin rays, and by a relatively smaller orbital diameter (24.9–33.8 versus 30.1–34.4 of HL) ( fig. 22 ). Cynodon gibbus differs from C. meionactis by the relative smaller orbital diameter (24.9–33.8, mean 29.2 versus 29.8–34.4, mean 31.8, respectively) and higher number of branched anal­fin rays (68– 80, 2 specimens with 65 rays, versus 63–67, respectively). See also comments under Remarks, previous comments on C. meionactis , and Géry et al. (1999).

DESCRIPTION: (table 1) Body compressed laterally, deep anteriorly, greatest body depth approximately at vertical through pectoral­fin base, depth decreasing posteriorly. Dorsal profile of head concave at interorbital region. Predorsal body profile strongly convex, forming pronounced hump at vertical through middle of orbit; straight and slightly posteroventrally slanted at dorsal­fin base, proportionally less slanted and almost straight in region of body extending from that point to vertical through last anal­fin ray; concave between latter point and origin of dorsalmost procurrent caudal­fin ray. In a small specimen 35 mm SL, dorsal profile of head straight, dorsal profile of body convex anterior to dorsal­fin origin, straight posteriorly. Ventral profile of body convex to posterior tip of coracoids; straight and posterodorsally slanted (sometimes slightly convex) to pelvic­fin base; straight from that point to anal­fin origin; straight and posterodorsally slanted along anal­fin base, concave from rear of anal fin to caudal­fin origin. Ventral surface of body with keel from isthmus to pelvic fin­base; keel anteriorly supported by expanded coracoids.

Infraorbitals and opercular bones with laterosensory canal system highly branched; canals more developed in larger individuals. Mouth obliquely aligned relative to horizontal axis of body, with upper jaw very long relative to head length; posterior tip of maxilla extending to vertical through posterior tip of second infraorbital; relatively more elongate in smaller individuals. Third infraorbital not in contact with preopercle ventrally. Adipose eyelid with notch in region of orbital margin where second and third infraorbitals meet.

Teeth in both jaws conical, in single row, varying in size. Premaxilla with 3 small canines, similar in size, one at the anterior and one at the posteriormost portion; third canine sometimes slightly smaller, located anterior to posteriormost canine and separated from it usually by 2 or 3 small conical teeth; several small conical teeth between anteriormost and middle canines. Maxilla with slightly enlarged conical teeth separated by smaller teeth of similar size; teeth gradually becoming smaller posteriorly. Dentary with well­developed canine, extending up into snout when mouth is closed, tip of canine reaching nostrils anteriorly. Dentary with one smaller canine anterior to largest canine; smaller canine about half the size of the largest dentary canine and preceded by another smaller conical tooth anteriorly; dentary canines posterior to largest canine separated by conical teeth of varying size; teeth gradually decreasing in size posteriorly. Teeth on ectopterygoid and mesopterygoid very small and conical. No teeth on metapterygoid.

Scales without distinct serration, scales small on dorsal portions of body, scale size increasing toward lateral line; largest scales along lateral line; scales on region dorsal to anal fin small. Scales along predorsal midline very small, arranged in somewhat irregular rows. Row of scales forming keel from posterior portion of coracoid to pelvic­fin base less rounded in shape than those covering rest of body. Scales below lateral line obliquely arranged. Lateral­line scales with many divergent side branches from main lateral­line canal. Divergent branches more developed in larger individuals; no side branches of lateral­line canal present in specimens under 80 mm SL. Lateral­line canal extending to posterior tip of middle caudal­fin ray.

Dorsal­fin rays ii,10. Dorsal­fin origin slightly posterior to vertical through anal­fin origin. First basal dorsal­fin pterygiophore inserting behind neural spine of 19th or 20th vertebra. Distal margin of dorsal fin straight to somewhat concave. First anal­fin pterygiophore inserting behind hemal spine of 22nd to 24th vertebrae. Distal margin of anal fin straight. Scales covering one­third to one­half length of anal­fin rays, less so in specimens smaller than 80 mm SL. Pectoral­fin rays pointed distally. Posterior tip of longest pectoral­fin ray extends beyond vertical through anal­fin origin, and reaches vertical through dorsal­fin origin. Pelvic fin short, rays i,8 (7 in three specimens, see comments under Remarks). Pelvic­fin base inserted at level of ventral profile of abdomen. Caudal fin forked, middle caudal­fin ray elongate, slightly longer than rays immediately dorsal and ventral to it, but its tip not extending to, or beyond, vertical through tip of dorsalmost principal ray; distal margin of upper lobe somewhat concave, and of lower lobe round­ ed; scales covering only basal portion of fin rays, not extending onto their branched portions.

VERTEBRAE: 51 (2); 52 (9); 53 (13); 54 (1); 55(1).

COLOR IN ALCOHOL: Specimens retaining guanine on scales with silver coloration on sides of body and head (including lower jaw, except for tip) to horizontal through dorsal margin of orbit, darker dorsally, including tip of lower jaw. In many specimens dark pigmentation of head extends to dorsal half of opercle and around infraorbitals. Specimens lacking guanine with yellowish­tan ground coloration (dark tan in some specimens) on sides of body and head, slightly darker dorsally. Specimens show varying degrees of guanine retention. Spot of dark pigmentation on posteriormost portion of supracleithrum. Specimens retaining pigmentation on fins with dorsal fin dusky; distal half of pelvic fins and dorsal portion of pectoral fins (especially unbranched pectoral­fin ray) covered with dark chromatophores. Distal half of anal fin with band of dark chromatophores. Base of caudal­fin rays with dark pigmentation forming vertically elongate blotch, less conspicuous on ventral portion of caudal­fin base. Adipose fin hyaline.

GEOGRAPHIC DISTRIBUTION: Cynodon gibbus is widely distributed throughout the rivers of the Amazon basin ranging from the westernmost portions of the basin in the Ríos Marañon and Ucayali east to the drainages of the rios Purus , Madeira , Branco , Amazonas , Trombetas, Xingu, and Tocantins basins ( fig. 23 ). Three specimens ( MZUSP 43613 ) were collected in Rio Pindare´, Maranhão state, Brazil representing the only record of a Cynodontinae in a drainage of northeastern Brazil. Cynodon gibbus also occurs in the middle and lower portions of the Río Orinoco basin, and in the Rupununi River, in the upper portions of the Essequibo River, Guyana .

Cynodon gibbus is found in sympatry with C. septenarius in Rio Uatuma˜, a tributary of the Rio Amazonas, Brazil. In the Rio Branco, a tributary of Rio Negro, the two species are found in proximate localities: Cynodon gibbus (MZUSP 32595) at Marara´, and C. septenarius (MZUSP 32596) at the confluence of Rio Branco and Rio Xeriuni. In the Rio Trombetas drainage samples of Cynodon gibbus were examined only from localities below the cataracts of Cachoeira da Porteira, at the mouth of the Rio Mapuera, whereas specimens of C. septenarius examined were collected in the Rio Mapuera (above Cachoeira da Porteira).

REMARKS: The features that distinguish Cynodon gibbus from its congener, C. septenarius , seem consistent throughout the samples examined. However, in a few instances some incongruences were observed. Table 2 shows that three specimens (AMNH 12542, MZUSP 32595, and MCNG 19340) assigned to Cynodon gibbus have 7 branched pelvic­fin rays on the left side (they have 8 branched rays on the right side). In 11 specimens, pelvic­fin ray counts could not be taken because of fin damage.

In spite of the significant difference in orbital diameter ( fig. 22 ) this feature show a slight overlap between the two species (table 1). Specimens of Cynodon gibbus with relative orbital diameters larger than 30.5 mm SL are found in the Río Orinoco drainage and in Rios Madeira, Xingu, Branco, and Ucayali in the Amazon basin, not conforming, however, to any geographic pattern. In a few instances the band of dark pigmentation at the base of the caudal fin was faint, in many cases evidently a preservation artifact.

The problems mentioned above made species determination difficult in a few instances. In most of the cases such specimens belonged to lots with a number of other specimens that consistently showed all the features diagnostic for Cynodon gibbus . In other cases (e.g., MCNG 19340) the specimens originated in a region where C. septenarius does not occur. Given these facts and because these specimens showed some of the distinguishing features of Cynodon gibbus , they were assigned to that species.

Cynodon gibbus was described on the basis of a single specimen collected by Spix and Martius and originating from the rivers of Brazil (‘‘Brasiliae fluviis’’ in Agassiz, 1829: 78). Many specimens on which Agassiz’s descriptions were based are housed at the MHNN, Neuchâtel (see, Rhaphiodon vulpinus , below). The rest of Spix and Martius’s specimens remained at the Zoologische Staatssammlung München but were destroyed during a bombing raid in 1944 (Terofal, 1983 and Kottelat, 1988). I was unable to locate any specimen of Cynodon gibbus potentially used by Agassiz as a basis for his description and it may have been destroyed. The number of nine pelvic­rays (‘‘pinnae pectoralis ventrales 9’’, Agassiz, 1829: 78) reported in the original description can be used to identify the specimen Agassiz examined as Cynodon gibbus . As discussed above, Cynodon gibbus has i,8 pelvic­fin rays (total of nine) and C. septenarius has i,7 (total of eight). A few specimens of Cynodon septenarius also have a total of nine pelvic­fin rays (see discussion under Remarks of that species). The areas in Brazil sampled by Spix and Martius (Papavero, 1971, map 7 following page 66), where Cynodon occurs, encompass the distribution of Cynodon gibbus and C. septenarius . Therefore, we cannot absolutely determine that the specimen examined by Agassiz was Cynodon gibbus or C. septenarius with an aberrant number of pelvic­fin rays. Agassiz did not mention any pigmentation associated with the caudal fin, so this feature cannot be used to resolve the problem. But since only three out of 45 specimens of C. septenarius had nine pelvic­fin rays, the nine pelvic­fin rays reported by Agassiz (in Agassiz, 1829: 78) can be argued as evidence that the specimen he was dealing with was indeed Cynodon gibbus .

In light of the discussion above and in or­ der to stabilize the nomenclature of Cynodon gibbus , a specimen MZUSP 6539, 146.0 mm SL is herein designated as neotype of Cynodon gibbus Agassiz, 1829 . Agassiz ( 1829) reported the specimen of Cynodon gibbus as originating from the rivers in Brazil (‘‘Brasiliae fluviis’’). Papavero (1971, map following page 66) described the itinerary of Spix and Martius’s collecting trip. The specimen herein designated as neotype of Cynodon gibbus originated from Lago Manacapuru, Amazonas State, located within the region from which the Spix and Martius collections were made.

MATERIAL EXAMINED: 226 specimens (72, 77.0­ 280):

TYPE MATERIAL: MZUSP 6539 (1, 146.0) Lago Manacapuru; NEOTYPE (present designation); see discussion above under Remarks.

NONTYPE MATERIAL: BOLIVIA. El Beni : AMNH 77340 (1, 85.7) mouth of Río Ibarre ; USNM 305368 (2, 169.0–261.0) Ballivia, Río Cuiraba at 10 km NE El Porvenir Biological Station, at 40 air km E San Borja ; MNHN 1989 1457 (4, 119.7–180.0), Trinidad, Santa Rosa. BRAZIL. Amazonas : BMNH 1913.7.7:5 (1, 225.0) ; BMNH 1970.4.2:2 (1, 159.0) Manaus ; USNM 229138 (1, 86.8) embayment of Ilha da Marchantaria ; USNM 229139 (1, 157.0) near Manaus, Lago Terra Preta , Janauari ; MCZ 21389 (1, 171.0) Manaus and environs ; MCZ 21331 (2, 217.0–220.0) Lago Janauari ; INPA 5328 (3, 191.0–200.0) Rio Amazonas, Ilha do Caieiro, Lago do Rei ; INPA 5348 (1, 221.0) Rio Uatuma ˜ ; MCZ 21411 (1, 112.6) SERPA, Rio Amazonas at Itacoatiara ; MZUSP 13497 (1, 226.0) Rio Amazonas , Itacoatiara ; MZUSP 21489 (1, 130.0) Pauini ; MCZ 21392 (2, 82.6–189.0) Rio Javari ; MCZ 21403 (4, 122.4–133.7) Río Putumayo near the Brazilian­Colombian border ; MCZ 21380 (1, 98.4) Lago Coari ; MZUSP 27340 (3, 144.0–157.0) Costa do Capacete, Rio Solimões, Município of Tabatinga ; MZUSP 35550 (1, 124.0) Igarapé Joari , Humaita´ ; MZUSP 6972 (1, 100.0) Rio Madeira ; Pará : CAS 53414 (1, 134.1) Lago Grande, into Rio Amazonas ; CAS 69890 (1, 200.0) ‘‘ Santarém River’ ’; CAS 79320 (2, 219.0–226.0) Santarém Market ; INPA 5340 (1, 122.0) Rio Mapuera, Cachoeira São Francisco , Cachoeira Porteira ; INPA 5341 (1) Rio Mapuera, Cachoeira da Égua ; INPA 5326 (1, 167.0) ; INPA 5327 (1, 163.0), Rio Tocantins , Icangui ; MZUSP 32588 (1, 176.0) ; MZUSP 32589 (1, 226.0) Rio Itacaiunas , Caldeirão ; MZUSP 32587 (1, 149.9) Rio Xingu , Belo Monte; Rondônia : INPA 14528 (1, 128.0) Rio Mamore´, below Surpresa , and the mouth of Rio Guapore´ ; INPA 14529 (2, 230.0) Rio Guapore´, Pimenteiras ; INPA 14530 (1, 280.0) Rio Jamari , below Samuel dam ; MZUSP 32592 (5, 159.0–193.0) ; MZUSP 32593 (31, 170.0–258.0) Rio Madeira , Calama; Roraima : NMW 68729 (2, 183.0– 198.0) ; NMW 57862 (1, 186.0) Rio Branco ; MZUSP 32594 (1, 215.0) Rio Branco, Cachoeira do Bem­Querer ; MZUSP 32595 (4, 132.0–160.0) Rio Branco , Marara´ ; NMW 57112 (1, 226.0) Conceição, Rio Branco ; NMW 57113 (1, 238.0) Rio Branco , Boa Vista; Goiás : MZUSP 40401 (1, 185.0) Rio Macacos , tributary of Rio Parana ˜, Fazenda Fortaleza, Flores de Goiás ; MZUSP 40737 (1, 157.0) Rio Parana ˜, above mouth of Rio Atalaia, Village of Porto Real , Monte Alegre de Goiás ; MZUSP 4840 (1, 98.0) Rio Araguaia, Aruana ˜; Acre : AMNH 223194 (2, 127.9–134.7) vicinity of Rio Macaua, tributary of Rio Iaco, a tributary of Rio Purus , near Sena Madureira ; MCZ 33512 (1, 131.6) vicinity of Rio Macaua, tributary of Rio Iaco (tributary of Rio Purus ); Maranhão : MZUSP 43613 (3, 208.0–280.0) Lago do Viana, Rio Pindaré system ; MNHN 1683 (1, 211.0) Brazil , ‘‘ Amazone’ ’; MZUSP 3119 (1, 216.0) Pará and Amazonas ; MNHN 1994 –0170 (2) Brazil, Rio Solimões ; NMW 57110 (1, 140.4) Rio Purus. COLOMBIA. Meta . ANSP 128216 (1, 194.0) Laguna Mozambique at Mozambique Ranch ; NE portion of lake ; ANSP 128257 (1, 155.0) Laguna Mozambique , central pond, part of ox­bow N of and connecting with E current of laguna. ECUADOR. Napo : BMNH 1970.4 .3.6 (1, 100.4) Jatuncocha ; FMNH 103386 (2, 193.0–232.0) outflow of Laguna Jatuncocha ; FMNH 103387 (2, 171.0–218.0) Río Yasuni, 1–2 km downstream from confluence with Río Jatuncocha ; FMNH 103388 (1, 258.0) Río Yasuni , Laguna Jatuncocha ; FMNH 103389 (3, 86.9–189.0) mouth of Quebrada to the Río Tiputini. GUYANA . CAS 16076 (1, 107.2) Menari Ranch, near Lathan (= Lethem ?), border with Brazil ; BMNH 1972.7.27:43–45 (3, 211.0 from one specimen), Rupununi, Dadanawa ponds. PERU. Loreto : ANSP 136849 (2, 134.2–134.6) vicinity of Iquitos, Moronacocha outlet, right bank of Río Nanay ; CAS 134786 (2, 98.3– 99.1) near Pebas , caño Tuye ; CAS 134787 (1, 119.7) near Pebas, Río Ampiyacu ; CAS 166549 (1, 85.3) near Pebas ; USNM 167773 (2, 147.0–190.0) Lago Sanango , near Yurimaguas ; CAS 69886 (3, 156.0–208.0) Lago Sanango, large cutoff lake of Río Huallaga, above Yurimaguas , connected to river by narrow channel ; MZUSP 26107 (1, 151.0), Río Ucayali , Jenaro Herrera ; Ucayali : MZUSP 26176 (3, 102.0–105.0) Río Ucayali , Bagazan, Coronel Portillo ; MZUSP 26728 (1, 107.0) Río Ucayali , Pucallpa, Coronel Portillo, Departamento Ucayali ; Amazonas : LACM 39857–10 (1, 35.0) , LACM 39883–7 (1, 162.0) ; LACM 41724–12 (1, 94.9) Río Santiago at La Poza ; LACM 36343–3 (1, 208.0) Ayambis ; ANSP 21208 (2, 133.8–152.0) Peruvian Amazon ; VENEZUELA. Anzoátegui : ANSP 149475 (1, 78.8) river shore, N bank of río Orinoco, just downstream from Ciudad Bolivar; Delta Amacuro : CAS 50771 (1, 96.5) Delta Amacuro , in cove on shore; LACM 43295–89 (65, 100.0–144.0) Río Orinoco , on N shore at Isla Portuguesa ; LACM 43382–22 (11, 77.1–125.0) Río Orinoco , secondary caño about 500 m from its mouth in caño Guarguapo ; LACM 43399–25 (2, 102.0–104.0) Río Orinoco, Caño Chivera , Isla Chivera, near Barrancas ; UMMZ 211280 (1, 112.2) lagoon in Río Orinoco , 131 nautical miles from Sea Buoy ; USNM 222855 (2, 136.0) , USNM 233932 (1, 147.0) Río Orinoco, small caño near mouth of Caño Socoroco , 11 nautical miles upstream from sea buoy; Portuguesa : MCNG 19340 (1, 138.0) caño Igues ; Apure : USNM 258193 (1, 115.4) side channel of Río Apure ca. 5 km W of San Fernando de Apure ; ANSP 160097 (1,122.0) Río Orinoco at El Burro; Bolivar : USNM 222848 (1, 212.0) Río Orinoco, cove at W end of Islote Fajardo, 182 nautical miles upstream from Sea Buoy ; ANSP 166727 (6, 120.0–195.0) Caicara. Guarico : USNM 257564 (1, 208.0) Río Orituco where crossed by road from Calabozo .

Figures

Fig. 21. Cynodon gibbus, neotype, MZUSP 6539, 146.4 mm SL, Brazil, Amazonas, Lago Manacapuru.

Fig. 22. Plot of orbital diameter against head length, both in millimeters, for Cynodon gibbus (filled in circles) and Cynodon septenarius (open circles).

Fig. 23. Map of central and northern portions of South America showing geographic distribution of Cynodon gibbus. (Arrow indicates locality of neotype). Some symbols represent more than one lot of specimens or locality.