Mimagoniates barberi Regan, 1907

Menezes ¹, Naércio A. & Weitzman ², Stanley H., 2009, Systematics of the Neotropical fish subfamily Glandulocaudinae (Teleostei: Characiformes: Characidae), Neotropical Ichthyology 7 (3), pp. 295-370 : 330-334

Mimagoniates barberi Regan, 1907

Fig. 36

Mimagoniates barberi Regan, 1907: 402 (type locality: arroyo Yâcá, Estación Caballero, Paraguay, fig. 6). - Myers, in Eigenmann & Myers, 1929: 492-493 (distinction between M. barberi and M. microlepis unclear; uncertain of validity of M. barberi ). Pearson, 1937: 108 ( M. barberi as endemic to Paraguay basin). - Travassos, 1952: 93 (listed). - Schultz, 1959: 63 (designated lectotype; recognized as a distinct species). - Nelson, 1964a: 64 (recognized M. barberi as valid species). - Géry, 1964: 6 (recognized M. barberi as possible geographic form of M. microlepis ). - Géry, 1966: 228, 230 (recognized as distinct species). - Géry, 1977: 362 (recognized as distinct species). - Weitzman & Fink, 1985: 105 (in materials examined). - Weitzman et al., 1988: 404 (phylogeny, biogeography, figure). - Menezes & Weitzman, 1990: 385 (in key). - Houtan, 1990: 9 (aquarium description; color photograph). - Vari & Howe, 1991: 30 (listed in type catalog). - Pecio & Rafiñski, 1994: 180 (histological and ultrastructure of testes). - Weitzman & Menezes, 1994: 3 (general discussion for non-systematic readers). - Weitzman et al., 1996a: 209 (courtship behavior). - Weitzman et al., 1996b: 203, 204 (breeding and rearing). - Malabarba & Weitzman, 2000: 279 (listed in discussion). - Weitzman, 2003: 226 (maximum length; distribution; remarks and references). - Britski et al., 2007: 68 (diagnosis; figure). - Menezes et al., 2008: 38-42 (distribution; discussion of relationships and biogeography).

Mimagoniates microlepis Schultz, 1959: 11 (in part, 1 specimen of M. barberi in USNM 86296, misidentified as M. microlepis ).

Diagnosis. Males of Mimagoniates barberi , M. pulcher n. sp., and M. inequalis have a rudimentary caudal-fin ray pump ( Figs. 32 , 38 , and 47) and in this respect differ from males of their congeners which have a fully developed caudal-fin ray pump ( Figs. 58 , 67 , 75 , and 85). Mimagoniates barberi can be distinguished from M. inequalis by having more branched anal-fin rays (30-36 vs. 23-30), more scales in lateral series (41-48 vs. 34-41), fewer scale rows between dorsal-fin origin and anal-fin origin (13-15 vs. 15-18) and the mid-lateral dark stripe of adult males nearly black (vs. lateral body stripe of adult males diffuse, poorly developed, often not apparent). Mimagoniates barberi differs from M. pulcher by the number of branched anal-fin rays (30-36 vs. 26-30) and by the absence of spines on principal caudal-fin rays ( Fig. 38 ), present in M. pulcher ( Fig. 47 ).

Description. Table 7 presents morphometrics of the holotype, paratypes, and other specimens. Description refers to all population samples combined except where noted. These collections were treated statistically as one population sample to represent the species as a whole.

Body compressed, relatively elongate; body deepest at vertical through anal-fin origin. Predorsal body profile gently convex and slightly more arched in adult males. Body profile

Males Females and juveniles

Characters

Holotype N Range Mean SD N Range Mean SD dif. Standard length 33.1 36 19.0-33.2 25.1 38 17.4-27.0 22.6

Depth at dorsal-fin origin 26.3 36 31.0-28.0 24.7 1.7 38 21.4-27.7 23.6 1.5 – Snout to dorsal-fin origin 62.2 36 60.4-66.6 62.4 1.4 38 59.5-65.4 62.4 1.6 – Snout to pectoral-fin origin 25.7 36 23.4-28.6 25.7 1.0 38 23.4-26.3 25.0 0.8 – Snout to pelvic-fin origin 42.0 36 39.4-44.9 42.8 1.2 38 41.0-46.8 43.2 1.4 – Snout to anal-fin origin 54.4 36 52.1-57.7 54.7 1.3 38 51.9-58.7 55.4 1.4 – Caudal peduncle depth 16.0 36 11.3-16.0 12.6 1.6 38 08.8-12.4 10.5 0.9 + Caudal peduncle length 09.1 36 06.4-10.4 08.5 0.8 38 07.3-09.4 08.3 0.5 – Pectoral-fin length 21.8 36 20.0-24.4 21.5 1.1 38 18.9-22.7 20.9 0.9 – Pelvic-fin length 14.0 36 12.1-15.9 13.6 0.9 38 08.9-13.1 11.7 1.0 + Dorsal-fin base length 13.9 36 11.4-14.9 13.2 0.8 38 10.8-14.5 12.4 1.0 – Dorsal-fin height 29.6 35 20.5-30.9 25.2 2.7 34 18.0-25.7 22.1 1.9 + Anal-fin base length 39.0 36 36.0-40.9 39.0 1.2 38 37.2-41.6 38.8 1.0 – Anal-fin lobe length 19.9 36 14.5-21.4 18.4 2.0 35 16.0.21.1 18.3 1.2 – Eye to dorsal-fin origin 51.3 35 48.0-53.8 50.1 1.5 38 45.7-51.3 49.7 1.4 – Dorsal-fin origin to caudal-fin base 43.5 36 37.8-43.5 40.8 1.6 38 36.0-43.9 40.0 1.8 – Bony head length 24.8 36 21.7-26.8 24.7 1.1 38 21.7-25.8 24.1 1.0 – Horizontal eye diameter 35.4 36 34.2-45.8 40.5 3.4 38 36.6-47.6 42.9 2.8 – Snout length 25.6 36 18.6-26.4 23.0 1.8 38 19.2-26.9 22.8 1.9 – Least interorbital width 31.7 36 31.7-38.4 36.1 1.6 38 32.2-40.4 36.6 1.8 – Upper jaw length 42.7 36 38.1-44.2 42.2 1.8 38 38.3-44.9 41.6 1.7 –

slightly elevated at dorsal-fin origin. Dorsal profile of body nearly straight along dorsal-fin base and to adipose fin. Body profile posterior to adipose fin slightly concave dorsal to caudal peduncle, ending at origin of procurrent caudal-fin rays. Dorsal-fin origin nearer to caudal-fin base than to snout tip. Ventral profile of body convex in adults from tip of lower jaw to origin of pelvic fins, somewhat less convex in juveniles. Abdominal profile in adult males slightly concave between pelvic-fin origin and anal-fin origin, straight or nearly so in females and juveniles. Body profile along anal-fin base nearly straight in all specimens. Ventral profile of caudal peduncle convex in adult males; slightly concave or nearly straight in females and juveniles.

Lower jaw protruding beyond upper jaw. Lower jaw of adults thick and heavy compared to that of juveniles. Mouth slightly angled posteroventrally. Maxilla long, extending to point well ventral to horizontal through ventral border of eye in all specimens. Maxilla extends posteriorly to point anterior to vertical through anterior border of pupil of eye.

Dorsal-fin rays ii in all specimens, branched rays 7-8 (8), 8, n = 77; posterior ray not split to its base and counted as 1. Adipose fin elongate, slender ( Figs. 36 and 37 ). Anal-fin unbranched rays iv or v, usually iv, branched rays 31-36 (33), 33.1, n = 74); posterior ray split to its base and counted as 1. Anal fin with moderately developed lobe anteriorly ( Figs. 36 and 39 ); lobe includes fourth unbranched and first 4 branched rays. Anal fin of sexually mature males with bilateral hooks, (1) on each side, on last unbranched ray (iv or v), ( Fig. 39 ). Anterior (7) branched fin rays usually with bilateral hooks, 1 set for each ray. Pectoral-fin unbranched ray i in all specimens, branched rays 8-11 (10), 9.5, n = 77). Tip of pectoral extends posteriorly beyond origin of pelvic fins. Pelvic fin rays 6-7 (i, 7), n = 77. Pelvic fin with anterior (first) ray unbranched or branched (branches well separated and often posterior branch divided at tip or for its distal half ( Fig.40 ). Sexually mature, large adult males with over 220 hooks on each pelvic fin distributed as shown in Fig. 40 .

Principal caudal-fin rays 10/ 9 in all specimens, (n = 77). Modification of some rays in association with caudal pheromone pump as in Figs. 38a and b . Fin rays modified more like those in M. inequalis than any other species of Mimagoniates .

Scales cycloid, with few radii along posterior border. Terminal scales of modified caudal-fin series without exaggerated radii ( Fig. 38b ).

Lateral line incomplete, perforated scales 5-10 (8), 7.2, n = 41. Lateral series scales 40-49 (44), 44.6, n = 39. Predorsal scales 21-29 (24), 24.5, n = 42. Scale rows between dorsal-fin and anal-fin origins 13-15 (15), 14.5, n = 48. Scale rows around caudal peduncle 15-17 (16), 16.0, n = 30.

Premaxillary teeth in 2 irregular, closely packed rows ( Fig. 41 ). Determining teeth in each row impossible except in cleared and stained specimens. Thus all teeth on left premaxilla given as total. Teeth tricuspid in all large specimens, small teeth in smaller specimens sometimes bicuspid or conical. Total premaxillary teeth 7-10 (8), 8.5, n = 68. Outer and inner row premaxillary teeth somewhat compressed. Maxillary teeth 3-7 (4), 4.5, n = 75. All maxillary teeth tricuspid in large specimens ( Fig. 41 ); small specimens with posterior maxillary teeth often conical. Dentary with 4-5 (4), 4.1, large tricuspid teeth; posterior dentary teeth 4-9 (8), 6.8, with nearly always more teeth in largest specimens; anterior small dentary teeth tricuspid, posterior ones conic, n = 77 ( Fig. 41 ). Maxillary and dentary teeth shaped much like premaxillary teeth. No significant difference in tooth number found between males and females.

Vertebrae 41-43 (42), 42.4, n = 19. Dorsal limb gill rakers 5- 7 (7), 6.2, n = 19; ventral limb gill rakers 11-13 (12), 12.3, n = 58. Branchiostegal rays 4, in 1 cleared and stained specimens, with 3 rays originating on anterior ceratohyal and 1 ray from posterior ceratohyal.

Color in alcohol. See Fig. 36 for preserved color pattern of males and females. Body pale to medium brown, pale yellowish-brown ventrally, darker to much darker dorsally. Longitudinal body stripe prominent along length on body. Stripe extending from border of eye to caudal fin base and in males onto portion of caudal fin occupied by caudal organ. Comparable area on caudal fin of females also black. Remainder of caudal fin dusky due to scattered dark chromatophores, especially on fin rays. Dorsal border of first principal caudal-fin ray and ventral border of nineteenth principal caudal-fin ray usually darker than other caudal fin rays. Lateral stripe extends over all caudal gland structures. Stripe especially dark on principal rays 10, 11 and 12, less so on ray 13. Humeral spot barely distinguishable from anterior portion of horizontal body stripe, but present just posterior to posterior opercular border. Dorsal body surface very dark, nearly black, forming narrow stripe extending from supraoccipital region to base of dorsal procurrent rays of caudal fin. Second dark longitudinal body stripe extends from nape across body, continuing to base of upper dorsal-fin lobe. Stripe lies just dorsal to pale longitudinal stripe extending just dorsal to first longitudinal dark stripe. Remainder of body surface ventral to first longitudinal body stripe pale brown.

Pectoral, pelvic, dorsal, and anal fins dusky with scattered dark chromatophores along fin rays and, to lesser extent, on membranes. Anal fin with dark elongate stripe running length of fin. Stripe width about one fourth height of anal fin anteriorly and about less than one-fourth of height posteriorly. Stripe narrower posteriorly than anteriorly, and of uniform width for posterior one-half of fin where it borders ventral edge of fin. Stripe darker posteriorly. In sexually mature males stripe broadens anteriorly where it is relatively pale, but covers much of surface of fin with anal-fin spines. Distal portion of anal-fin lobe relatively hyaline. Dorsal fin with horizontal dark stripe in adult males and females extending posteriorly from about mid-length of anterior elongate undivided ray to posterior tips of two terminal dorsal-fin rays. Stripe usually narrow, less than one-eighth maximum height of dorsal fin. Width and intensity of stripe somewhat variable depending on sex and maturity. Adipose fin dusky with scattered dark chromatophores.

Head dark brown around mouth and on dorsal surface of snout, between eyes, dorsum of cranium and nape. Tip of lower jaw dark brown. Portion of head posterior to infraorbitals and extending ventrally from parietal region, across dorsal opercular region pale except where first horizontal stripe extends to eye. Iris dorsal to pupil more or less silvery. Infraorbitals silvery if guanine preserved, pale yellowish brown if guanine absent. Dark brown chromatophores not dense, but scattered evenly through circumorbital area. Anterior area of opercle, all of preopercle, and branchiostegal rays silvery or pale brown, without much dark brown pigment except in area of first horizontal longitudinal stripe.

Color in life. Life colors described here taken from aquarium specimen, USNM 327586, taken from within 50 miles Asunción. Specimen in preservative shown in Fig. 36 . Sides of body pale silvery blue. Broad lateral body stripe somewhat deeper silvery blue extends immediately dorsal to silvery blue color of body sides from humeral spot to caudal peduncle termination. Back with narrow dark brown line extending from parietal region of head to just ventral to adipose fin. Lateral portion of dorsolateral portion of body brownish-yellow green color between narrow brown line and dorsomedian narrow dark brown line extending across dorsal most portion of back. Dorsal region of caudal peduncle nearly yellow. Ventral abdominal area, most of lower jaw, ventral opercular area, branchiostegal rays and their membranes silvery white. Dark pigment of head similar to that described for preserved specimens except that dorsal region of opercle appears silvery blue. Dorsal caudal-fin lobe and principal caudal-fin rays 14- 16 on ventral caudal-fin lobe bright yellow, except for black proximal half of ray 14. Black pigment continuous with black pigment surrounding structures of caudal pheromone organ. Rays 17-19 on ventral caudal-fin lobe hyaline or nearly hyaline except ray 17 which is somewhat yellow. Remainder of black pigment of caudal fin as described in preserved specimens. Anal fin with distal portion of fin rays posterior to anterior anal-fin lobe lemon yellow, forming a stripe along ventral border of fin. Distal region of anterior anal-fin lobe hyaline to white, proximally bordered by black pigment described above in preserved specimens. Basal half of anal fin hyaline with some scattered brown chromatophores and a small tint of yellow anteriorly. Posterior portion of narrow horizontal black line of anal fin pale.Approximately distal one-half of pelvic fin white, with black and yellow band proximal to this and remaining proximal portion of fin hyaline. Distal one-half of pectoral fins yellow, proximal half with black rays and yellow membranes. Dorsal fin hyaline to white distal and proximal to longitudinal black and brown longitudinal stripe.

Distribution. Known from left bank tributaries of río Paraguay and tributaries of rio Paraná, near Foz do Iguaçu, in Paraguay. See figure 3 in Menezes et al. (2008).

Ecology. Field notes taken by R. M. Bailey and J. N. Taylor indicate that specimens collected in southern Paraguay ( UMMZ 205417 , UMMZ 205418 and UMMZ 205420 ) were found in small tributaries (arroyos), rivers (ríos) and pools. Two specimens ( UMMZ 205415 ) were collected from a brown colored stream, visibility of about 0.3 m, surrounded by partly wooded ravine. The current at the collecting site was 0.3-0.5 m /second. Other two specimens ( UMMZ 205418 ) were caught from green clear waters, visibility of 10 m, located also in a partly wooded ravine .

Sexual dimorphism. Females lack the caudal pheromone pump organ, anal-fin and pelvic-fin hooks of males. Table 7 indicates that some morphometric characters differ significantly between males and females. Regression statistics, however, indicated that only those related to pelvic-fin length, dorsal-fin height and caudal peduncle depth are statistically significant. Figures 42 to 44 indicate that males reach longer lengths than the females. Figure 42 graphically indicates that males and females of M. barberi show significant sexual dimorphism in pelvic-fin length, but in males growth of pelvic fin is continuous following the model of a regression line (r² = 0.903) whereas in females the pelvic fin grows at a different rate not following the linear regression model (r² = 0.06). Figure 43 provides graphic evidence that there is a slight divergence in dorsal-fin height between males and females as they become sexually mature and increase in length. Figure 44 also indicates a divergence in caudal peduncle depth beginning around 20.0 mmSL.

Material examined. Lectotype. BMNH 1907.10.22:5, adult male, 33.1 mm SL, Paraguay, (arroyo Yâca [= Yhaca, also Yaca], near Estación Caballero; arroyo Yhaca is at 25°39’S 56°53’W and Caballero is at 25°40’S 56°49’W . Paralectotypes. Collected with lectotype: BMNH 1907.10.22 : 6-8, young adult female, 2 adult males, 23.7-29.5 mm; BMNH 1990.10.9 : 1, young male, SL 25.8 mm SL ( Note : this specimen found in original type series but not catalogued until 1990); USNM 179827 , young-adult, 2 females, 24.2-29.7 mm SL. Non-types. All collected in Paraguay unless otherwise noted. UMMZ 205420 , 2 adult males, 5 young-adult females, 23.6-34.5 mm SL, c&s 1 adult male 35.6 mm, San Pedro, río Aguaray-mi at bridge on dirt highway 2.1 km N of junction with easterly road to Captain Bado, about 23°33’S 56°34’W; UMMZ 205417 , 1 juvenile, 2 females, 17.6-25.4 mm SL, Canendiyu, small arroyo tributary to arroyo Curuguaty , about 5.3 km by dirt road NNW of Curuguaty , 24°23’S 55°42’W; UMMZ 205418 , 1 juvenile, 1 adult female, San Pedro / Canendiyu, río Corrientes and adjacent pool, about 32.4 km W of turnoff to Curuguaty , 24°19’S 55°59’W; UMMZ 205415 , 1 adult female, 1 adult male, 30.3 32.6 mm SL, Canendiyu, río Jejui, tributary to río Jejui Guazu about 41 km N of Curuguaty and 2 km S of Ygatimi, about 24°09’S 55° 37’W; USNM 86296 , 1 juvenile, SL approx. 19.0 mm, “probably Paraguay; USNM 327586 , 1 adult male, 32.7 mm SL aquarium specimen collected “within 50 miles of Asuncion ”; MHNG 2241.78 , 9 juveniles-adults, 21.5-25.4 mm SL, San Pedro Province (southern Paraguay) , without further locality data; MHNG 2477.61 , 26 young-adults, 13.3-28.0 mm SL, Caaguazú, 15 km north east of Carapo (= Carayao), arroyo Hondo, approximately 25°01’S 056°32’W. MHNG 2481.90 , 27 young-adults, 12.2-31.0 mm SL, Caaguazú, río Guyraugua (= Guyraunguá), approximately 25°15’S 56°02’W; MHNG 2481.91 , 3 juveniles, 17.5-20.4 mm SL, Alto Parana, río Acaray , (this river extends approximately between 25°32’S 54°36’W and 24°58’S 55°20’W), C. Dlouhy, 16 Oct. 1986 .

Figures

Fig 43. Mimagoniates barberi, dorsal-fin length as function of SL by sex.

Fig. 36. Mimagoniates barberi, male above, UMMZ 205420, 35.6 mm SL, female below, SL 26.8 mm, Paraguay, San Pedro, rio Aguarai-mi, tributary to rio Paraguay, paratypes.

Fig. 32. Mimagoniates inequalis, adult male, MCP 9892, 37.0 mm SL; osteology of caudal skeleton and caudal-fin squamation (lower left inset) lateral view, left side. Cartilage represented by crosshatching.

Fig. 38. Mimagoniates barberi, adult male, UMMZ 205420, 35.6 mm SL; osteology of central basal region of caudal skeleton, principal caudal-fin rays 6-15, lateral views, left side, anterior is at left. Principal ray 12 indicated by arrow. (a) Illustrates glandular groove between rays 11 and 12. (b) Illustrates relationship of modified dorsal caudal-fin lobe squamation to glandular groove. Modified scales together their epidermis form movable flap just lateral to surface of rays and groove that bear most of glandular tissue. Modified from Menezes & Weitzman (1990).

Fig. 58. Mimagoniates lateralis, adult male, USNM 236088, 31.6 mm SL; caudal skeleton, lateral view, left side, anterior at left. Inset at lower left illustrates modified dorsal lobe caudal-fin squamation in relation to osteological structures of caudal organ. Modified from Weitzman et al. (1988).

Fig. 67. Mimagoniates sylvicola, adult male, USNM 300364, 32.5 mm SL; osteology of central basal region of caudal-fin skeleton, principal fin rays 6-15, lateral view, left side, anterior at left. Principal caudal-fin ray 12 indicated by arrow. (a) Illustrates area of fully developed caudal organ. (b) Illustrates relationship of modified dorsal-fin squamation to pump chamber skeleton. Modified from Menezes & Weitzman (1990).

Fig. 75. Mimagoniates rheocharis, adult male, USNM 279879, paratype, 45.4 mm SL; osteology of central basal region of caudal-fin skeleton, principal fin rays 6-15, lateral view, left side, anterior at left. Principal caudal-fin ray 12 indicated by arrow. (a) Illustrates area of fully developed caudal organ. (b) Illustrates relationship of modified dorsal-fin squamation to pump chamber skeleton.Modified from Menezes & Weitzman (1990).

Fig. 47. Mimagoniates pulcher, developing male, MNRJ 4233, 34.2 mm SL; osteology of principal caudal rays 7-15, lateral view, left side, anterior at right.

Fig. 37. Mimagoniates barberi, male, USNM 327586, 32.7 mm SL; central region of caudal-fin base and fin showing beaded tissue indicated by arrow, especially along borders of rays 11 and 12, the rays that border groove of primitive caudal pump. Modified from Menezes & Weitzman (1990).

Fig. 39. Mimagoniates barberi, adult male, UMMZ 205420, 32.7 mm SL; anterior 13 anal-fin rays, lateral view, left side.

Fig. 40. Mimagoniates barberi, adult male, UMMZ 205420, 32.7 mm SL; pelvic-fin rays, ventral view, left side.

Fig. 41. Mimagoniates barberi, adult male, UMMZ 205420, 35.9 mm SL; jawsand dentition,lateral view, right side, anterior at left.

Fig. 42. Mimagoniates barberi, pelvic-fin length as function of SL by sex.

Fig. 44. Mimagoniates barberi, caudal peduncle depth as function of SL by sex.