Mimagoniates rheocharis Menezes & Weitzman, 1990

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 : 350-355

Mimagoniates rheocharis Menezes & Weitzman, 1990 Figs. 70-77

Species B, Weitzman et al., 1988, figs. 6, 10, 23 (phylogeny and biogeography).

Mimagoniates rheocharis Menezes & Weitzman, 1990: 399 , figs. 19-23 (type locality: Brazil, Santa Catarina, município de Praia Grande, rio Faxinalzinho at Mãe dos Homens, near Praia Grande, approximately 29°20’S 14°40’W; discussions of possible hybrid origin; phylogeny and biogeography). - Oyakawa, 1996: 480-481 (listed in type catalog). - Weitzman et al., 1996b: 196, 199, 201 (photograph; illustration of caudal fin; distribution; ecological data; relationships; courtship behavior). - Malabarba & Weitzman, 1999: 108 (distribution). - Malabarba & Weitzman, 2000: 280 (listed in discussion); - Weitzman, 2003: 226 (maximum length; distribution; remarks and references). - Machado et al., 2005: 73 (conservation status). - Menezes, 2007: 39 (listed in catalog; distribution; conservation status). - Menezes et al., 2007: 126 (photograph; distribution; systematic status; ecology; conservation). - Menezes et al., 2008: 38- 41, 43 (distribution; discussion of relationships and biogeography). - Malabarba et al., 2008: 79 (conservation status; general informations; geographic distribution; main threats; conservation strategies).

Diagnosis. Mimagoniates rheocharis may be separated from all other species of Mimagoniates by the presence of sturdy hooks on some principal caudal-fin rays. Among the species of Mimagoniates presence of hooks on some caudal-fin rays also occurs in M. microlepis and M. pulcher , but in these species they are spiny. Mimagoniates rheocharis and M. microlepis , however, have fully developed caudal-fin ray pumps ( Figs. 75 and 85 ) whereas in M. pulcher the pump is only partially developed ( Fig. 47 ).Additionally M. rheocharis differs from M. microlepis by the number of scale rows around caudal peduncle (19 to 23 vs. 15 to 18 for M. microlepis ) and scales rows between dorsal-fin and anal-fin origins (17 to 21 vs. 13 to 16 for M. microlepis ).

A few life color characters differentiate in fully mature males: the pelvic-fin rays and membranes of adult males are distally white whereas in M. microlepis the yellow and/or black pigment of the pelvic fins are continuous to edge of the fin where fin is bordered by a narrow band of white; the portion of the anal fin posterior to the anterior lobe is bordered by a broad band of deep yellow pigment, with very little to no black pigment on fin; in M. microlepis the posterior portion of the anal fin is ventrally bordered by a narrow band of black pigment, and none or very little yellow pigment.

Description. Table 11 presents morphometrics of holotype and paratypes. Except where noted, entire description refers to population sample from near Praia Grande, southern Santa Catarina. Collections treated statistically as one population sample in attempt to represent the species as a whole. Counts and ratios of measurements for other population samples taken from tributary of rio Grande given only when they differ from those from near Praia Grande.

Body compressed, relatively deep, especially near dorsal-fin origin; body deepest at vertical through anal-fin origin. Predorsal body profile relatively arched in adult males, less so in adult females and immatures which have predorsal profile gently convex to tip of snout. Body profile elevated at dorsal-fin origin. Dorsal profile of body nearly straight along dorsal-fin base to adipose fin. Body profile posterior to adipose fin somewhat concave dorsal to caudal peduncle. Dorsal-fin origin nearer to caudal-fin base than to snout tip. Ventral profile of body strongly convex in adult males from tip of lower jaw to origin of pelvic fins, less convex in females and juveniles. Abdominal profile in adult males slightly concave to anal-fin origin, straight or nearly so in females and juveniles. Body profile along anal-fin base in males slightly concave anteriorly along anterior lobe of anal fin; straight along base of remainder of fin in males and along entire anal-fin base in females and juveniles. Ventral profile of caudal peduncle convex in adult males; slightly concave or nearly straight in females and juveniles.

Lower jaw protruding slightly beyond upper jaw. Lower jaw of adult males thick and heavy compared to that of females and juveniles. Mouth angled posteroventrally. Maxilla long, extending to point ventral to a horizontal line through ventral border of eye. Maxilla extends posteriorly to point anterior to vertical through anterior border of pupil.

Dorsal-fin unbranched rays ii in all specimens, branched rays 8-10 (9), 8.9, n = 56; posterior ray not split to its base and counted as 1 ray. Adipose fin slender. Anal-fin unbranched iv or v, usually iv, branched rays 25-29, 26.8, n = 56; posterior ray split to its base and counted as 1 ray. Anal fin with moderately developed lobe anteriorly ( Figs. 70 , 71 and 73 ); lobe includes last unbranched ray and first 3 branched rays. Anal fin of sexually mature males with bilateral hooks, 1 on each side, on last unbranched ray ( Fig. 73 ). In most specimens anterior 7 branched fin rays with bilateral hooks, 1 set for each ray. Pectoral-fin unbranched ray i in all specimens, branched rays 10-11, 10.1, n = 56. Tip of pectoral-fin extends posteriorly beyond origin of pelvic fins. Pelvic-fin rays 8 in all specimens. Pelvic fin with first ray branched once, branches remaining close together and entire ray tapering as in congeners in which ray unbranched ( Fig. 74 ). Sexually mature, large adult males with over 400 hooks on each pelvic fin distributed as shown in Fig. 74 .

Principal caudal-fin ray count 10/ 9 in all specimens, n = 56. Fin rays modified in association with caudal pheromone pump as in Fig. 75 . Caudal-fin rays 10 and 11 with small bony hooks. Ventral borders of 4 anterior expanded ray segments of ray 11, which form anterior external wall of dorsal portion of pump chamber, with about 4 short but large hooks; 2 middle hooks often bicornate, others with single hook.

Scales cycloid, with few radii along posterior border. Terminal scale of modified caudal-fin series without exaggerated radii ( Fig. 75b ).

Lateral line incomplete, perforated scales 5-9 (7), 6.7, n = 48. Lateral series scales 41-48 (45), 44.3, n = 48. Predorsal scales = 21-24 (22), 22.3, n = 46. Scale rows between dorsal-fin and anal-fin origins 17-21 (19), 18.8, n = 55. Scale rows around caudal peduncle 19-22 (20), 19.7, n = 46.

Premaxillary teeth in 2 distinct rows ( Fig. 76 ), teeth tricuspid in all large specimens, smaller teeth sometimes bicuspid or conical in smaller specimens. Outer row teeth 5- 8 (5), 6.2, n = 55. Inner row teeth, 1-3 (3), 2.1, n = 55. Maxillary teeth 3-8 (8), 4, larger specimens usually with more teeth, n = 55. All maxillary teeth tricuspid in large specimens; small specimens with posterior teeth often conical ( Fig. 76 ). Dentary with 4 large anterior tricuspid teeth in all specimens, followed by 5-12 (12), 8.4, smaller teeth, almost always greater number of teeth in largest specimens. Anterior small teeth of posterior dentary series tricuspid, posterior ones conical, n = 54. Maxillary and dentary teeth shaped much like premaxillary teeth.

Vertebrae 37-40 (38), 38, n =107. Dorsal limb gill rakers 6-8 (7), 6.6, n = 54; ventral limb gill rakers 11-13 (12), 11.7, n = 54. Branchiostegal rays 4, in 3 cleared and stained specimens, 3 rays originating on anterior ceratohyal and 1 ray from posterior ceratohyal.

Color in alcohol. See Figs. 70 and 71 for preserved color pattern of males and females. Body pale to medium brown, pale yellowish-brown ventrally, much darker dorsally. Lateral body stripe diffuse in both sexes, especially anteriorly. Stripe extending from vertical humeral spot posteriorly to caudal fin and onto dorsal region of ventral caudal-fin lobe and small part of dorsal caudal-fin lobe. 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 vertically elongate, especially in sexually mature males. Remainder of caudal fin dusky due to presence of scattered dark chromatophores. Dorsal border of first principal and ventral border of nineteenth principal caudal-fin rays black. Middorsal body surface black, forming narrow stripe extending from supraoccipital region to base of dorsal procurrent rays of caudal fin. Remainder of dorsal body surface ventral to lateral body stripe pale brown.

Pectoral, pelvic, dorsal, and anal fins dusky with scattered dark chromatophores along fin rays and membranes. Anal fin with dark elongate stripe running length of fin. Stripe of nearly uniform width about one-fourth height of anal fin anteriorly and about one-half height posteriorly. Sexually mature males with stripe considerably darker anteriorly, especially dorsal to relatively hyaline anterior anal-fin lobe. Dorsal-fin with horizontal dark stripe in adult males and females extending from about mid-length of anterior elongate unbranched ray to posterior tips of terminal two dorsal-fin rays. Stripe usually narrow, less than one-eighth maximum height of dorsal fin. Width and intensity of stripe variable depending on sex and maturity. Preserved males sometimes with posterior portion of stripe diffuse. Adipose fin dusky with scattered dark chromatophores.

Head dark brown around mouth and on dorsal surface of snout, between eyes, dorsal portion of cranium and nape. Tip of lower jaw dark brown. Head dark brown posterior to infraorbitals and from parietal region ventrally, across dorsal opercular region. Dark area continues ventrally across posterior region of opercle to just reach interopercle; looks similar in form to humeral spot. Iris dorsal to pupil dark brown, most of remainder of iris silvery. Infraorbitals silvery if guanine preserved, pale yellowish brown if guanine absent. Dark brown chromatophores scattered evenly through circumorbital area. Anterior area of opercle, all of preopercle, and branchiostegal rays silvery or pale brown, without much dark brown pigment.

Color in life. Life colors described here taken from slide of an adult male 41.8 mm SL (MZUSP 40281) from site located immediately north of city of Osório, Rio Grande do Sul. Sides of body pale silvery blue. Broad lateral body stripe somewhat deeper silvery blue from humeral spot to caudal peduncle termination. Just dorsal to silvery blue color of body sides, back with narrow dark brown line extending from parietal region of head to just ventral to adipose fin. Lateral portion of dorsal portion of body between narrow brown line and dorsomedian narrow dark brown line extending across dorsal most portion of back, brownish-yellow green color. 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 of ventral caudal-fin lobe hyaline or nearly hyaline except in ray 17 somewhat yellow. Remainder of black pigment of caudal fin as described above for preserved specimens. Anal fin with distal portion of fin rays posterior to anterior anal-fin lobe lemon yellow, forming stripe along ventral border of fin. Distal region of anterior anal-fin lobe hyaline to white, proximally bordered by black pigment described above for preserved specimens. Black pigment mixed with yellow. Basal half of anal fin hyaline with some scattered brown chromatophores and small amount 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 it 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.

Sexual dimorphism. Females lack caudal pheromone pump organ and pelvic- and anal-fin hooks described above for males. Live color of females is unknown but likely more subdued than that of sexually mature males. Table 11 indicates that of the morphometric characters showing significant differences between sexes only those related to caudal peduncle depth and pelvic-fin length are statistically different using regression analysis. See discussion in the “sexual dimorphism” section for this species in Menezes & Weitzman (1990: 412-415).

Distribution. Mimagoniates rheocharis occurs in small coastal streams and rivers from Santa Catarina to northern Rio Grande do Sul, Brazil. See figure 3 in Menezes et al. (2008).

Ecology. In addition to the scarce information available in the ecological notes in Menezes & Weitzman (1990: 421-422), recent data from Malabarba et al. (2008) indicates that Mimagoniates rheocharis lives in small streams with moderate flowing and shallow clear waters, with rocks and less abundant fallen leaves, sand or mud. Specimens are usually found in small numbers in still waters near the banks where the water current is slower, under the shadow of marginal vegetation. Few specimens can also be found in micro-habitats among rocks and macrophytes, especially when larger portions of still water are occupied by Mimagoniates microlepis . The species seems to be very sensitive to change in water quality especially with respect to dissolved oxygen and pH. Feeds mainly on a variety of terrestrial insects that fall from surrounding trees and are preyed upon on the water surface. Small amounts of aquatic insects and micro-crustaceans are also eaten. Like other members of the Glandulocaudinae , M. rheocharis is forest-dependent and survives only in streams where the marginal vegetation is preserved.

Remarks. Menezes & Weitzman (1990: 414-416) discussed statistical comparisons of meristic and morphometric data between M. rheocharis and M. microlepis . These are not repeated here. Although some overlap was found in many characters, significant differences were found in most of the features compared. Similar comparisons and results were made with Mimagoniates inequalis in the same publication.

Menezes & Weitzman (1990: 416-421) discussed the possible hybrid origins of M. rheocharis from M. inequalis and M. microlepis through introgression, concluding that although such an origin might be possible, the data then available allowed sister species status between M. rheocharis and M. microlepis . In view of the phylogenetic analysis undertaken herein, however, that tentative conclusion will have to be reevaluated.

Material examined. Holotype. MZUSP 40278 , adult male, 47.3 mm SL, Brazil, Santa Catarina, município de Praia Grande, rio Faxinalzinho at Mãe dos Homens, near Praia Grande, approximately 29°20’S 14°40’W . Paratypes. Collected with holotype: MCP 13616 ,

immatures to adults 3, 24.3-40.8 mm SL; USNM 279878 , adults 3, 33.3-47.8 mm SL. Following 3 lots of immature to adult paratypes: Santa Catarina, município de Nova Veneza, rio Jordão at Jordão Alto , approximately 28°36’S 49°28’W , MCP 13617 , immatures to adults 83, 21.9-39.0 mm SL ; MZUSP 40279 , immatures to adults 81, 22.4- 42.8 mm SL ; USNM 279879 , immatures to adults 89, 22.8-49.0 mm SL. Following lots collected in Santa Catarina, município de Praia Grande, tributary of rio Grande approximately 29°20’S 49°40’W : MZUSP 40280 , immatures to adults 29, 13.5-38.4 mm SL ; USNM 306339 , immatures to adults 18, 17.0-40.0 mm SL. Following lots collected in Rio Grande do Sul, município de Osório : MZUSP 40281 , adult male, 41.8 mm SL, arroio das Pedras , approximately 29°52’S 50°19’W ; MCP 13613 , young adults 7, 27.5-31.3 mm SL, arroio Água Parada, tributary to rio Maquiné, in Maquiné , approximately 29°40’S 50°11’W ; MCP 10806 , adult male, 39.5 mm SL, município de Torres, tributary of rio Três Forquilhas, Chapéu , approximately 29°19’S 49°44’W . Non-types. Following lots collected from Santa Catarina, município de Praia Grande, arroio Facão, tributary of rio Grande at Mãe dos Homens, 29º13’59”S 50º03’09”W : USNM 326749 , immatures to adults 33, SL 30.8-39.8 mm ; MCP 21710 immatures 34, 25.8-32.0 mm ; MZUSP 53276 , immatures to adults 34, SL 24.5-33.5 mm. Following lots, collected from Santa Catarina, município de Praia Grande, rio Canoas, 8 km from Praia Grande in direction of Mãe dos Homens, 29º14’S 50º01’W : USNM 326752 , immatures to adult 3, 28.5-42.4 mm SL ; MZUSP 53277 , immatures 3, 25.7-30.5 mm SL. Following lot, collected from Santa Catarina, município de Praia Grande, rio Canoas, about 13 km upstream of Praia Grande , USNM 326751 , immature 1, 27.3 mm SL. Following lots all collected from Rio Grande do Sul, município de Três Cachoeiras, rio das Pacas near Morro Azul (discharges into lagoa Jacaré of the rio Mampituba system), approximately 29º24’S 49º57’W , USNM 326750 , immature 1, 23.8 mm SL; município de Torres, rio dos Mengue between towns of Morro Azul and Rua Nova, a tributary to lagoa Jacaré of the rio Mampituba system, approximately 29º17’S 49º55’W , MCP 21711 , immature 3, 24.4-27.0 mm SL; Terra de Areia, rio Padre at Itati , a tributary of rio Três Forquilhas , approximately 29º28’S 50º03’W , USNM 326753 immatures-adults 4, 27.7-31.3 mm SL .

Figures

Fig. 70. Mimagoniates rheocharis,adult male, MZUSP 40278, holotype, 47.3 mm SL, Brazil, Santa Catarina State,rio Faxinalzinho at Mãe dos Homens, near Praia Grande. Modified from Menezes & Weitzman (1990).

Fig. 71. Mimagoniates rheocharis, female,USNM 306339, paratype, 34.3 mm SL, Brazil, Santa Catarina State, tributary of Rio Grande. Modified from Menezes & Weitzman (1990).

Fig. 72. Mimagoniates rheocharis, adult male, USNM 279879, 49.0 mm SL; central basal region of caudal-fin and adjacent caudal peduncle, lateral view, left side, anterior at left.Arrow at left indicates anterior intake region of pumpchamber; middle arrow indicates region of lateral slit with ray half of principal caudal ray 11 just dorsal to arrow tip; arrow at right points to opening of posterior exhaust vent of pump chamber. Modified from Menezes &Weitzman (1990).

Fig. 73. Mimagoniates rheocharis, adult male, USNM 279879, paratype, 45.4 mm SL; anterior 13 anal-fin rays of adult male, lateralview,leftside.Modified fromMenezes&Weitzman(1990).

Fig. 74. Mimagoniates rheocharis, adult male, USNM 279879, paratype, 45.4 mm SL; pelvic finof adult male, ventral view,left side, anteriorat left.ModifiedfromMenezes &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. 76. Mimagoniates rheocharis, adult male, USNM 279879, paratype, 45.4 mm SL; jaws and dentition of adult male, lateral view, right side, anterior at left. Modified from Menezes & Weitzman (1990).

Fig. 77. Mimagoniates microlepis, young adults male below, female above, USNM 254261, 61.2.0 mm and 43.0 mm SL, respectively, Brazil, São Paulo State, rio Silva on road between Ubatuba and Taubaté.

Fig. 85. Mimagoniates microlepis, adult male, USNM 236089, 45.3 mm SL; osteology of caudal skeleton and caudal-fin squamation (lower left), lateral view, left side. Principal caudal ray 12 indicated. Relationship of modified dorsal lobe caudal-fin squamation to caudal gland shown in inset at lower left. Distal regions of ventral and posterior scales and their epidermis form flap partly covering intake openings of pump chamber. Modified from Menezes et al. (1988).

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.