Mimagoniates lateralis, Weitzman & Fink, 1985

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 : 340-345

Diagnosis. Mimagoniates lateralis and M. sylvicola are the only species of the genus having a caudal fin-ray pump well developed and no hooks on caudal-fin rays ( Figs. 58 and 67 ). M. lateralis , however, has fewer lateral series scales (35 to 41 vs. 49 to 56 for M. sylvicola ), fewer horizontal scale rows from dorsal-fin origin to anal-fin origin (13 to 15 vs. 16 to 18 for M. sylvicola ), and fewer scale rows around caudal peduncle (16 to 18 vs. 19 to 20 for M. sylvicola ). Color differences between the two species are discussed in the diagnosis of M. sylvicola . Mimagoniates rheocharis and M. microlepis also with a fully developed caudal-fin ray pump in mature males, have hooks on principal caudal-fin rays ( Figs. 75 and 85 ), absent in M. lateralis and M. inequalis ; M. barberi and M. pulcher has a rudimentary caudal-fin ray pump ( Figs. 32 , 38 and 47 ).

Description. Table 9 presents morphometrics of the holotype and the population sample from Cananéia, São Paulo. The entire description refers to this population sample which includes a large series from immature to fully mature male and

Males Females and juveniles

Characters

N Range Mean SD Holotype N Range Mean SD dif.

Standard length 23 17.0-31.0 25.6 29.6 29 16.9-36.2 26.5

Depth at dorsal-fin origin 23 20.6-28.6 24.5 2.2 27.4 29 20.7-27.4 24.6 1.8 – Snout to dorsal-fin origin 23 58.8-63.5 61.6 1.1 59.5 29 59.1-65.5 61.8 1.5 – Snout to pectoral-fin origin 23 24.5-27.6 26.0 1.0 25.0 29 24.7-27.7 25.8 0.9 – Snout to pelvic-fin origin 23 41.0-45.0 43.0 1.0 42.6 29 40.2-45.3 43.6 1.2 – Snout to anal-fin origin 23 54.2-58.8 56.8 1.2 56.8 29 55.0-60.4 58.0 1.2 – Caudal peduncle depth 23 10.5-15.2 12.9 1.3 13.9 29 08.9-14.6 11.9 1.1 + Caudal peduncle length 23 08.1-10.4 09.0 0.5 09.5 29 07.9-09.9 08.7 0.5 – Pectoral-fin length 23 21.0-25.3 23.6 1.1 22.0 29 21.3-25.3 23.4 1.2 – Pelvic-fin length 23 13.7-17.8 15.5 1.3 14.2 29 12.6-15.5 14.3 0.6 + Dorsal-fin base length 23 12.0-15.0 13.3 0.8 11.8 29 11.6-14.1 12.6 0.6 – Dorsal-fin height 23 20.4-29.3 24.0 2.3 22.0 29 20.1-24.2 22.2 0.9 – Anal-fin base length 23 33.6-37.4 35.4 1.0 37.2 29 32.8-37.1 34.6 1.2 – Anal-fin lobe length 22 19.0-23.1 21.7 0.9 ---- 28 18.9-24.4 21.3 1.0 –

Eye to dorsal-fin origin 23 47.6-51.8 49.3 1.1 46.6 29 46.1-51.4 49.1 1.2 – Dorsal-fin origin to caudal-fin base 23 37.3-43.1 40.5 1.5 41.8 29 37.2-41.3 39.4 1.2 – Bony head length 23 23.8-27.3 25.2 1.0 23.6 29 23.6-27.0 25.2 1.0 – Horizontal eye diameter 23 34.2-41.6 38.2 2.3 37.7 29 35.5-41.6 38.1 1.7 – Snout length 23 20.0-25.0 22.0 1.3 24.3 29 20.0-24.3 21.4 1.1 – Least interorbital width 23 31.9-37.0 34.0 1.3 37.1 29 31.2-37.1 34.7 1.3 – Upper jaw length 23 38.4-46.0 42.9 2.0 42.9 29 38.6-47.0 42.6 2.2 –

female specimens and contains the ranges of meristic and morphometric variation in within the distributional area of Mimagoniates lateralis . Counts and ratios of measurements for other population samples taken from other areas are given only when they differ from those of Cananéia.

Body compressed, moderately elongate; body deepest about midway between snout tip and dorsal-fin origin near vertical through pelvic-fin origin. Predorsal body profile strongly arched in adult males, less so in adult females and immatures which have predorsal profile gently convex. Body profile elevated at dorsal-fin origin, in males, less so in females and juveniles. Dorsal profile of body nearly straight along dorsal-fin base to adipose fin in males, slightly concave in females. 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 convex in adult males from tip of lower jaw to origin of pelvic fin, less strongly 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 in region of 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 slightly convex especially 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 horizontal through ventral border of eye in all specimens. Maxilla extends posteriorly through anterior border of pupil of eye.

Dorsal-fin unbranched rays ii in all specimens, branched rays 7-8, 8 (1 spm with 7), n = 50; posterior ray not split to its base and counted as 1 ray. Anal-fin unbranched rays iv or v, usually iv, branched rays 26-30 (28), 27.6, n = 50; population sample from Paranaguá with slightly lower counts (range = 25-28, mean = 26.6); posterior ray split to its base and counted as 1 ray. Anal fin with moderately developed lobe anteriorly ( Figs. 52 , 53 , 55 and 56 ). Lobe includes fourth or fifth undivided ray and first 5-6 divided rays. Anal fin of sexually mature males with bilateral blunt hooks, 1 on each side, on last unbranched ray iv or v ( Fig. 56 ). Usually anterior 4 branched fin rays with bilateral hooks, 1 set for each ray. Pectoral-fin unbranched ray i in all specimens, branched rays 7-10, 9.3, n = 50. Posterior tip of pectoral fin extends posteriorly beyond origin of pelvic fin. Pelvic fin rays 7 in all specimens. Pelvic fin with anterior (first) ray branched in all specimens, posterior ray unbranched in most individuals ( Fig. 57 ). Sexually mature, large adult males with over 250 small to tiny hooks on each pelvic fin distributed as shown in Fig. 57 .

Principal caudal-fin ray count 10/9, n = 50. Fin rays modified in association with caudal pheromone pump as in Fig. 58 .

Scales cycloid, with few radii along posterior border. Terminal scale of modified caudal-fin series without exaggerated radii ( Fig. 58 ).

Lateral line incomplete, perforated scales 5-7 (5), 6.1, n = 33. Lateral series scales 35-41 (41), 38.8, n = 32. Population sample from Santa Catarina with higher counts (range = 38-42, mean = 41.1, n = 53. Predorsal scales 21-25 (no data for holotype) 22.3, n = 30. Population sample from Paranaguá with slightly higher counts (range = 23-26, mean = 24.1, n = 10). Scale rows between dorsal- and anal-fin origins 13-15 (15), mean = 14.4, n = 41. Scale rows around caudal peduncle 16-18 (17), 16.7, n = 28.

Premaxillary teeth in 2 distinct rows (not clear in Fig. 59 ). All teeth tricuspid in all large specimens, smaller specimens with small teeth sometimes bicuspid or conical. Outer row teeth 6-9 (7), 7.0, n = 50. Inner row teeth few, 3 2-4 (3), 2.5, n = 50. Maxillary teeth 3-9 (6), 5.5, larger specimens usually with higher number of teeth, n = 50. Population sample from Santa Catarina with slightly lower counts (range = 3-7, = 4.3, n = 53). All maxillary teeth tricuspid in large specimens; small specimens with posterior maxillary teeth often conical ( Fig. 59 ). Dentary with 4 large anterior tricuspid teeth in all specimens followed by smaller posterior teeth 5-13 (6), 8.7, number of teeth nearly almost greater in largest specimens; anterior small teeth of posterior dentary row tricuspid, posterior ones conical, n = 50 ( Fig. 59 ). Maxillary and dentary teeth shaped much like premaxillary teeth.

Vertebrae 37-42 (37), 39.3, n = 68. Dorsal limb gill rakers 6- 7 (6), 6.2, n = 50; ventral limb gill rakers 11-13 (12), 11.8, n = 50. Branchiostegal rays 4 in 4 cleared and stained specimens, 3 rays originating on anterior ceratohyal and 1 ray from posterior ceratohyal.

Color in alcohol. See Figs. 52 , 53 and 55 for preserved color pattern of males and females. Body pale to medium brown, pale yellowish-brown ventrally, much darker dorsally. Humeral spot barely distinguishable from anterior portion of horizontal body stripe. Dark lateral body stripe clearly defined in both sexes, below midbody, narrower anteriorly from ventral border of eye to about vertical through tip of pectoral fin, wider from this point to caudal-fin base and extending onto part of caudal fin occupied by caudal organ in males and onto an equivalent area on caudal fin of females. Lateral stripe extends over all caudal gland structures, including those derived from dorsal caudal-fin lobe such as modified caudal squamation. Stripe especially dark on principal ray 10, and basal portions of rays 11, 12, and 13; less so in females. Remainder of caudal fin dusky due to scattered dark chromatophores. Dorsal border of first and ventral border of nineteenth principal caudal-fin rays black. Distal part of posterior most lower procurrent rays black. Another dark stripe dorsal to lateral stripe and separated from it by a pale area extending from dorsal border of eye to about vertical through origin of dorsal fin. This dorsal stripe narrower anteriorly, wider and darker posteriorly. Dorsal most body surface dark, forming narrow stripe extending from supraoccipital region to base of dorsal procurrent rays of caudal fin. 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 width about two-thirds height of anal fin anteriorly and little more than one-half height posteriorly. Stripe narrower posteriorly, but of uniform width for posterior one-half of fin where it borders ventral edge of fin, broadens anteriorly in sexually mature males, especially dorsal to distally relatively hyaline anterior anal-fin lobe. 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 terminal two dorsal-fin rays. Stripe usually narrow, less than one-eighth maximum height of dorsal fin. Width and density of stripe variable depending on sex and sexual maturity. 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. Region of head posterior to infraorbitals and extending ventrally from parietal region, across dorsal opercular region pale except where horizontal dark stripe extends to eye. Iris dorsal to pupil dark brown. Infraorbitals silvery if guanine present, pale yellowish brown if guanine absent. Dark brown chromatophores scattered evenly across 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 most inferior horizontal stripe.

Color in life. Life colors described here taken from color slides of fishes in aquarium. Sides of body pale silvery blue. Lateral stripe deep black anteriorly and obscured by blue to silvery pigment especially above anal-fin base. Dorsal part of body posterior to black stripe extending to below dorsal-fin origin brownish orange color. Longitudinal area between dorsal and lateral black stripes slivery white obscured by blue to silver pigment. Ventral opercular area, branchiostegal rays and membranes, and abdominal area silvery white. Lower jaw dark except for its median part with silvery blue color. Dorsal region of opercle brownish orange. Dorsal, caudal and anal fins with scattered orange red chromatophores. Dark colors of these fins as in preserved specimens. Basal portion of anal fin hyaline with some scattered orange brown chromatophores. Distal region of anterior anal-fin lobe hyaline. Males photographed just after capture with anal fin base yellow orange. Pelvic fins hyaline with scattered dark chromatophores. Pectoral fins hyaline other than for some yellow and dark chromatophores. Dorsal fin hyaline distal to longitudinal black and brown stripe, with orange brown chromatophores proximal to stripe.

Sexual dimorphism. Females lack a caudal pheromone pump organ and pelvic-fin and anal-fin hooks described above for males. Life colors of females are more subdued than that of mature males.

Among the morphometric characters having significant differences between males and females ( Table 9), only caudal peduncle depth and pelvic-fin length are significantly different using regression statistics. Fig. 62 provides graphic evidence of a slight divergence in caudal peduncle depth between males and females. Fig. 61 clearly demonstrates a difference in pelvic-fin length as a function of standard length between males and females as they become sexually mature and increase in length.

Distribution. Mimagoniates lateralis is restricted to small blackwater streams, rivers and ponds in the coastal area between Santos, São Paulo and Santa Catarina, Brazil. See figure 3 in Menezes et al. (2008)

Ecology. Field data indicate that Mimagoniates lateralis is entirely confined to acid black waters ( Fig. 60 ). MZUSP 53275 (75 specimens) and USNM 326250 (66 specimens) were collected from a black water stream near Cananéia , São Paulo, running in a disturbed stretch of Mata Atlântica. The stream was on the average 1.7 m wide and 0.4 deep and the fishes occurred in both sunlight or shaded areas over sandy-rocky bottoms covered with filamentous algae and dead leaves .

Remarks. Myers, in Eigenmann & Myers (1929: 492) examined the type of Mimagoniates lateralis AMNH 4072, and identified it as a female M. microlepis . Schultz (1959: 11) did not examine the type but nevertheless identified the species as M. inequalis and confused specimens of both these species and M. microlepis as M. microlepis . See also discussions under M. microlepis and M. inequalis . The fine photograph of M. lateralis published in Axelrod (1959: 12) was identified as M. microlepis therein, as M. barberi in Harald Schultz (1959: 47), as M. inequalis in L. P. Schultz (1959: 8) and as M. tenuis by Géry (1977: 357). L. P. Schultz (1959: 11), again without examining the type specimen, identified M. tenuis actually a male of M. lateralis , as a specimen of M. microlepis .

The specimens of M. lateralis, USNM 94117, that were used by Rachow (1928: 15) and Myers in Eigenmann & Myers (1929: 493), to identify species Mimagoniates species imported into Europe and North America from eastern Brazil. Myers, in Eigenmann & Myers (1929: 493), lists the total lengths of these specimens as 47-53 mm. The longest total length we could find was 43.2 mm. We are unable to explain the disparity, but is no doubt that Myers (1929) sent these specimens to J. R. Norman for comparison with specimens of M. barberi as indicated by the accompanying note by Myers (1929) that states that the specimens were found identical to the types of M. barberi by Norman (see also Myers, in Eigenmann & Myers 1929: 493). This information was relayed to Rachow and constituted the source of misidentification of M. lateralis by aquarists for many years. This lot also has two labels in it by L. P. Schultz. The first notes that L.P. Schultz compared these specimens with his types of M. barberi (USNM 179827) and found them “not identical”. We agree with L.P. Schultz but the other note in L.P. Schultz’s handwriting labels these specimens as “ Mimagoniates inequalis ”, a misidentification.

Material examined. Holotype. AMNH 4072 , adult female, 29.6

mm SL, no locality data. Types of Coelurichthys tenuis . AMNH 4087 (holotype), adult male, 30.0 mm SL, no locality data ; AMNH 4088 (catalogued as a cotype but not called a type in Nichols, 1913:152), adult male, 29.7 mm SL, no locality data. Non-types. All collected in Brazil . USNM 254266 , 1 young adult male, 2 adult females, 23.4-25.4 mm SL, São Paulo, “small blackwater stream south of Santos ” ; CAS 36634 , spms 90, young to adults, 8.7-31.6 mm SL, São Paulo, “second stream east of Fazenda São Luis, near Santos ” ; USNM 257200 , 4 young to adult males, 27.3-31.4 mm SL, 3 young to adult females, 24.3-25.7 mm SL, São Paulo, Itanhaém ; MZUSP 53274 , spms 8 males, 27.5-34.7 mm SL, 1 female, SL 27.0 mm, adults ; USNM 326250 , 66 , young to adults, 12.1-36.2 mm SL, São Paulo, small blackwater stream where crosses road SP 193, about 11 km from center of town of Cananéia ; USNM 326784 , 66 , young to adults, 11.2-31.3 mm SL ; MZUSP 53275 , 75 young to adults, SL 12.0-31.0 mm ; USNM 226468 , 2 adults, male and female 31.0- 32.6 mm SL, field color photograph and black and white of preserved specimens, Paraná, road between Matinhos and Paranaguá at km 11, roadside ditch, blackwater ; USNM 257202 , 10 adults, 22.3-32.0 mm SL ; USNM 94117 , 16 adults, 23.5-32.5 mm SL, Paraná, Paranaguá (Note: According to a note these are aquarium specimens received from Arthur Rachow for identification. See discussion of M. lateralis below) ; USNM 236564 , adult male, c&s, 31.4 mm SL, removed from USNM 94117 ; MNRJ 6397 , 42 young to adults, 12.8-36.9 mm SL, Paraná, Paranaguá, “estrada do mar” (= road eastward along the estuary of Baía de Paranaguá toward the Atlantic Ocean , see Myers, 1952: 131 and upper fig. p. 132) at km 9.5, Rio Vila , 25°33’S 24°25’W ; MZUSP 20495 , 20 young to adults, 17.5-27.5 mm SL, Paraná, small blackwater stream 5 km of Guaratuba , 25°55’S 48°37’W ; USNM 236081 , 1 female, 1 male, 26.5-27.5 mm SL, c&s ; USNM 236088 , 1 male, 1 female, 31.3-31.6 mm SL, c&s ; USNM 254259 , 21 immatures to adults, 18.7-31.8 mm SL ; USNM 254267 , 3 adult males, 30.1-37.6 mm SL , USNM 254265 , 7 young to adults, 16.9-29.2 mm SL , USNM 254268 , 1 male, 1 female, 29.8-29.9 mm SL ; USNM 257201 , 5 , immature to adults, 20.6-36.0 mm SL ; USNM 257113 , 18 immatures to adults, 20.4-29.5 mm SL , USNM 254258 , 20 juveniles to adults, 19.2-33.0 mm SL, Santa Catarina, rio Vermelho, Barra do Sul in Ilha de São Francisco, about 35 km from Joinville , 26°14’S 48°35’W ; USNM 177703 , 6 , young adults to adults, 24.3-31.8 mm SL, “Rio Grande do Sul, Porto Alegre” (Note: This last locality, as reported, is undoubtedly wrong. These aquarium specimens were probably imported from Porto Alegre but not captured there) .

Figures

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. 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. 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. 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. 52. Mimagoniates lateralis, young adults female above, male below. USNM 226468, 31.0 and 32.6 mm SL respectively, Paraná State, road between Paranaguá and Matinhos, at km 11.

Fig. 53. Mimagoniates lateralis, live adult male, USNM 254268, 29.9 mm SL, Brazil, Paraná State, unnamed blackwater stream emptying into Atlantic Ocean about 5 km S of Guaratuba.

Fig. 55. Mimagoniates lateralis, live adult female, USNM 254268, 29.8 mm SL, Santa Catarina State, rio Vermelho, Barra do Sul in Ilha de São Francisco, about 35 km from Joinville.

Fig. 56. Mimagoniates lateralis, adult male, USNM 236088, 31.6mm SL; anterior 9 anal-fin rays of adult male, lateral view, left side.

Fig. 57. Mimagoniates lateralis, adult male, USNM 236088, 31.6 mm SL; pelvic-fin rays, ventral view, left side.

Fig. 59. Mimagoniates lateralis, adult male, USNM 236088, 31.6 mm SL; jaws and dentition, lateral view, right side, anterior at left.

Fig. 62. Mimagoniates lateralis. Caudal peduncle depth as function of SL by sex.

Fig. 60. Habitat of Mimagoniates lateralis, blackwater stream, rio Vermelho, in Barra dos Sul, Ilha de São Francisco, Santa Catarina State, Brazil.