Mimagoniates sylvicola 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 : 345-350

Mimagoniates sylvicola Menezes & Weitzman, 1990 Figs. 63-64

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

Mimagoniates sylvicola Menezes & Weitzman, 1990: 387 , figs. 7-13 (type locality: Brazil, Bahia, município de Prado, forest stream tributary to Atlantic Ocean, near Fazenda Embaçuaba, approximately 8-9 km northwest of Cumuruxatiba, 17°05’S 39°13’W, 20 Mar 1985, N. Menezes, R. M. C. Castro; discussions of phylogeny and biogeography). - Oyakawa, 1996: 481 (listed in type catalog). - Weitzman et al., 1996a: 206 (distribution). - Malabarba & Weitzman, 1999: 84 (listed in discussion). - Weitzman, 2003: 226 (maximum length; distribution; remarks and references). - Machado et al., 2005: 73 (conservation status). - Menezes et al., 2007: 127 (photograph; distribution; systematic status; ecology; conservation status). - Menezes, 2007: 39 (listed in catalog; distribution; conservation status). - Menezes et al., 2008: 38-40 (distribution; discussion of relationships and biogeography).

Diagnosis. Mimagoniates sylvicola is morphologically most similar to M. lateralis , both species having the modified caudal-fin rays forming the caudal-fin ray pump very much alike ( Figs. 67a and 68 ) and no hooks on caudal-fin rays, characters not present in any other species of the genus. They can be distinguished by the following characters: lateral series scales 49-56 (vs. 35-41 for M. lateralis ), scale rows between dorsal-fin and anal-fin origins 16-18 (vs. 12-15 for M. lateralis ). Preserved and live colors differ between the species. Preserved males of M. sylvicola with dark lateral body stripe relatively pale and diffuse, occurring mostly at and partly dorsal to mid-lateral body region. Approximately dorsal half of opercle dark, nearly black (relatively pale in M. lateralis ). Mimagoniates lateralis with dark, relatively narrow, clearly defined lateral body stripe that lies mostly ventral to mid-lateral body region. Dark stripe continues onto ventral one-third of opercle. Males of M. sylvicola with distal one-fourth to one-fifth (less posteriorly) of anal-fin rays black (distal two-thirds to one-half black in M. lateralis ). Males of M. lateralis with distal one-fourth of most elongate anterior unbranched ray and branched portions of anterior five to six branched rays hyaline or with a thin scattering of dark chromatophores, never black as in M. sylvicola . Life color of these species quite different. Male M. sylvicola with dorsally located black lateral “stripe” obscured by silvery blue reflective color, especially anteriorly. Ventrally located black stripe of male M. lateralis deep black except at its mid-length ventral to dorsal-fin origin where partly obscured by blue to silvery pigment in some population samples. Wild caught males of M. lateralis with a yellow-orange stripe just ventral to black lateral stripe, absent in M. sylvicola , although both species often with anal-fin base yellow to orange. Mimagoniates sylvicola can be distinguished from the remaining species of the genus by the absence of hooks on principal caudal-fin rays (vs. presence of hooks in M. rheocharis and M. microlepis , Figs. 75 and 85 ) and by the presence of a well-developed caudal-fin ray pump (vs. caudal-fin ray pump rudimentary in M. inequalis , M. barberi and M. pulcher , Figs. 32 , 38 and 47 ).

Description. Table 10 presents morphometrics of holotype and paratypes. Except where noted, entire description refers to lots from near Cumuruxatiba. These collections are treated statistically as one population sample since no statistical differences were found among them. Counts for specimens from rio Camurugi are given only when they differ from those from near Cumuruxatiba.

Body compressed, moderately elongate; body deepest about midway between snout tip and dorsal-fin origin, near vertical through pelvic-fin origin. Predorsal body profile gently convex to snout tip, less so in adut females and juveniles. Body profile slightly elevated at dorsal-fin origin, straight along dorsal-fin base and nearly straight to origin of dorsal procurrent caudal-fin rays in all specimens. 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 point on abdomen about midway between pectoral- and pelvic-fin bases, less convex in adult females and immatures.Abdominal profile abruptly becomes concave and then straight to vertical through anal-fin origin. Body profile slightly convex along anal-fin base to anal-fin insertion. Ventral profile of caudal peduncle slightly convex, especially in adult males where ventral procurrent caudal fin rays enters profile. In females and juveniles this profile nearly straight.

Lower jaw protruding beyond upper jaw. Lower jaw of males thick and heavy compared to that of females. Mouth angled posteroventrally. Maxilla extending posteriorly to point

Males Females and juveniles

Characters

Holotype N Range Mean SD N Range Mean SD dif.

Standard length 30.2 44 17.0-30.2 22.1 45 14.5-26.6 19.4

Depth at dorsal-fin origin 29.1 44 21.5-29.3 25.7 2.2 44 20.6-27.2 23.9 1.6 + Snout to dorsal-fin origin 61.6 44 57.0-63.8 60.0 1.3 44 57.2-62.2 60.1 1.2 – Snout to pectoral-fin origin 28.1 44 24.7-29.0 26.6 1.1 44 24.3-27.4 25.9 0.7 – Snout to pelvic-fin origin 43.4 44 39.7-45.9 43.3 1.3 44 40.0-46.8 43.2 1.5 – Snout to anal-fin origin 55.6 44 55.0-59.5 57.2 1.2 44 54.3-60.9 56.9 1.5 – Caudal peduncle depth 13.2 44 08.7-14.2 11.6 1.4 44 8.5-11.6 10.0 0.7 + Caudal peduncle length 12.3 44 10.1-13.8 12.1 0.8 44 10.1-13.8 12.0 0.9 – Pectoral-fin length 23.2 44 20.6-24.7 22.6 0.9 44 20.2-24.5 22.5 1.1 – Pelvic-fin length 14.9 44 11.7-16.0 13.9 1.1 44 11.1-14.2 12.7 0.8 + Dorsal-fin base length 14.2 44 11.9-16.5 14.0 0.9 44 11.8-15.1 13.6 0.1 – Dorsal-fin height 19.2 44 15.9-21.9 18.5 1.3 41 14.4-20.6 17.5 1.4 – Anal-fin base length 33.4 44 29.5-34.5 32.6 1.1 44 30.4-35.2 32.6 1.1 – Anal-fin lobe length 19.2 44 17.9-22.5 20.3 1.0 43 17.2-22.5 20.1 1.1 –

Eye to dorsal-fin origin 46.4 44 43.6-48.4 46.3 1.1 44 42.8-51.0 46.2 1.3 – Dorsal-fin origin to caudal-fin base 43.7 44 39.4-45.6 42.3 1.4 44 39.8-46.9 42.2 1.4 – Bony head length 27.8 44 24.7-28.5 26.6 0.9 44 24.7-27.9 26.0 0.6 – Horizontal eye diameter 35.7 44 35.0-44.1 39.3 2.2 45 39.0-44.4 41.6 1.3 – Snout length 22.6 44 21.0-26.0 23.4 1.2 45 21.6-26.1 23.9 1.2 – Least interorbital width 33.3 44 32.1-37.5 34.7 1.3 45 32.0-37.0 35.0 1.3 – Upper jaw length 45.2 44 41.3-48.2 45.7 1.7 45 42.1-47.8 45.3 1.5 –

anterior of vertical through anterior border of pupil.

Dorsal-fin unbranched rays ii in all specimens, branched rays 8-9, (8), 8.0 (3 specimens with 9), n = 90; of 6 specimens from rio Camurugi (not included in n = 90) 2 with 8 and 4 with 7 branched rays; posterior ray not split to its base and counted as 1 ray. Adipose fin slender. Anal-fin unbranched rays iv in all specimens, branched rays 23-26 (25), 24.8, n = 90; posterior ray split to its base and counted as 1 ray. Anal fin with moderately developed lobe; anterior portion including last unbranched ray and first 5-6 branched rays.Anal fin of sexually mature males with bilateral blunt hooks on anterior 6 branched fin rays, 1 set of hooks for each ray ( Fig. 65 ). Pectoral-fin unbranched rays i in all specimens, branched rays 9-11 (10), 9.7, n = 90; all 6 specimens from rio Camurugi with 10 branched rays. Posterior tips of longest pectoral-fin rays extend posteriorly beyond origin of pelvic fin; of about equal length in both sexes. Pelvic-fin rays 7 (7 in all specimens except 1 with 8, n = 90, [count 8 for pelvic-fin rays of M. sylvicola in Menezes & Weitzman (1990: 391) is error]. Pelvic fin with anterior most ray branched in all specimens ( Fig. 66 ). Adult males with total of over 100 small to tiny hooks present on rays of pelvic fin, distributed as shown in Fig. 66 . Each ray bears 9 to over 40 hooks, depending on the maturity of the specimen and/or the fin ray.

Principal caudal-fin ray count 10/ 9 in all specimens, n = 90. Fin rays modified in association with caudal pheromone pump as in Figs. 67 and 68 . Fig. 68 illustrates a relatively immature pump, while fig. 67 shows a presumably mature pump in which pump chamber has well-developed water entrances and exit.

Scales cycloid, almost deciduous, with few radii along posterior border; smallest scales often nearly without or without radii. Terminal scale of modified caudal series with exaggerated radii appearing as incisions of posterior scale borders ( Figs. 67 b and 68 b ).

Lateral line incomplete, perforated scales 6-8 (8), 7, n = 34; 2 specimens from rio Camurugi with 9 perforated scales. Lateral series scales 49-56 (53), 52.7, n = 34. Predorsal scales 24-28 (25), 25.9, n = 39. Scale rows between dorsal- and anal-fin origin 16-18 (17) 16.7, n = 64. Scale rows around caudal peduncle 19-20 (20), 19.7, n = 21; 1 specimen from rio Camurugi with 22 scale rows around caudal peduncle.

Premaxillary teeth in 2 distinct rows although this not apparent in Fig. 69 . Larger teeth tricuspid, smaller teeth tricuspid or bicuspid, smallest ones unicuspid. Outer row teeth 3-7 (6), 5.4, n = 90. Inner row teeth 3-7 (3), 3.0, n = 90. Maxillary teeth 5-10 (6), 6.8, larger specimens usually with highest counts, n = 90; two specimens from rio Camurugi with 11 maxillary teeth. Maxillary teeth show increase in number with increasing SL from mean of 5.9 in 9 specimens of 15.5 to 16.5 mm SL to mean of 7.6 in 14 specimens of 25.0 to 30.5 mm SL.Anterior 4- 5 maxillary teeth tricuspid and larger than remaining teeth one-fifth height of fin. Stripe borders distal ends of fin rays posteriorly; anterior portion of dark stripe separated from distal ends of first five or six fin rays by relatively hyaline area on anterior lobe of fin. Dorsal fin with horizontal dark stripe extending posteriorly from about mid-length of anterior elongate unbranched ray to posterior tips of two terminal dorsal-fin rays. 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. Iris dorsal to pupil dark brown to black, most of remainder of iris silvery with some dark brown or black areas ventrally. Infraorbitals pale brown or silvery with evenly scattered dark chromatophores. Ventral area of opercle, preopercle and posterior region of branchiostegal rays silvery, without much dark brown pigment.

with 1 or 2 cusps ( Fig. 69 ). Dentary with 4 large anterior tricuspid teeth in all specimens, n = 90; smaller posterior dentary series unicuspid except tricuspid anterior most tooth, 6-12 (10), 8.9, n = 90 ( Fig. 69 ). One specimen from rio Camurugi with 13 dentary teeth. Maxillary and dentary teeth shaped much like premaxillary teeth.

Vertebrae 39-41 (40), 39.9, n = 88. Dorsal limb gill-rakers 6- 7 (6), 6.0, n = 90, two specimens from rio Camurugi with 5 dorsal limb gill-rakers; ventral limb gill-rakers 11-13 (12), 11.7, n = 90. Branchiostegal rays 4 in 3 cleared and stained specimens, 3 rays originating from anterior ceratohyal and 1 ray from posterior ceratohyal.

Color in alcohol. See Figs. 63 and 64 for preserved color pattern in males and females. Body pale to medium brown, almost white ventrally, darkest dorsally. Lateral body stripe pale, diffuse, best developed in males. Stripe extending from darker opercular spot on dorsal half of opercle posteriorly to dark, spot-like region on caudal peduncle. Immediately posterior to spot caudal gland region covered by black pigment forming triangular-shaped area with its posterior apex and continuous onto ray 11 and to certain extent ray 12. Remainder of caudal fin dusky due to scattering of dark chromatophores, especially along ventral border of 19 th principal caudal ray. Dorsal body surface dark dusky, especially in area of predorsal scales.

Pectoral, pelvic, dorsal, and anal fins dusky from scattered dark chromatophores along fin rays. Pelvic fins considerably darker than pectoral fins.Anal fin with a dark, elongate stripe running length of fin. Width of stripe about one-fourth to Color in life. Life color patterns taken from color slides and color notes made while collecting specimens from clear and black waters near Cumuruxatiba. Sides of body silvery deep blue with dorsal region dark brown and abdominal area silvery white. All fins translucent, lemon yellow with dark brown pigment described above under preserved color description appearing brown to black. Females with similar color pattern but blue, yellow, and dark pigment patterns much paler. Caudal-fin rays 13 and 14 considerably darkened with black pigment in life. Some male specimens display considerable but rather diffuse lateral dark brown stripe below lateral mid-region of body. Specimens from rio do Sul, Cumuruxatiba area (USNM 276547), gold silvery in color and without blue coloration. Some with black pigment considerably reduced, absent, or covered in patches by guanine, especially on lateral surface of body sides.

Sexual dimorphism. Females lack caudal pheromone pump organ, anal-fin and pelvic-fin hooks of males and display more subdued live body coloration as noted above. Table 10 indicates significant differences in body depth, caudal peduncle depth, and pelvic-fin length between males and females. The regression analyses and the discussion of these sexually dimorphic differences are presented in the “sexual dimorphism section” for this species in Menezes & Weitzman (1990: 394-396).

Distribution. Mimagoniates sylvicola is known from small streams in southern Bahia, Brazil. See figure 3 in Menezes et al. (2008).

Ecology. Ecological notes for this species are presented in Menezes & Weitzman (1990: 398-399). However, since the time the specimens of M. sylvicola were collected, the environment where they live was severely altered. The tall forest protecting creeks and rivulets and providing shade for the cocoa plantations in southern Bahia was mostly removed and the trees used in wood production after the drastic decrease in the price of cocoa. As a consequence the species is now at risk of becoming extinct since it is restricted to those particular types of habitats. Further information is available in Menezes & Lima (2008).

Material examined. Holotype. MZUSP 36612 , adult male, 30.2 mm SL, Brazil, Bahia, município de Prado, forest stream tributary to Atlantic Ocean, near Fazenda Embaçuaba, approximately 8-9 km northwest of Cumuruxatiba , 17°05’S 39°13’W . Paratypes. Collected with holotype: MZUSP 28817 , juveniles to adults 42, 15.1-30.2 mm SL ; USNM 276557 , juveniles to adults 42, 14.7-33.5 mm SL, 1 male SL 29.3 mm and 1 female 26.6 mm SL, c&s. Following paratypes all collected 20 Mar 1985 by N. Menezes et al. unless otherwise noted : MZUSP 28815 , 77 , 11.0- 27.4 mm SL ; USNM 276547 , juveniles to young adults 77, 14.4-27.4 mm SL, Brazil, Bahia, município de Prado, first stream (locally called rio do Sul) south of rio Caí , on road between Cumuruxatiba and Itamaraju, 17°00’S 39°12’W . MZUSP 28816 , 28 , 12.7-25.1 mm SL; 6, juveniles to adults, 13.2-24.0 mm SL, Brazil, Bahia, município de Prado, small stream NW of Cumuruxatiba , about 17°01’S 39°12’W . USNM 300633 , juveniles to adults 5, 22.3-31.3 mm SL and USNM 300634 , 1 , c&s, 31.8 mm SL, Brazil, Bahia, município de Porto Seguro, riacho Ronca Água, tributary to right margin of rio Camurugi, tributary to rio João de Tiba drainage, approximately 16°20’S 39°07’W , 19 Feb 1986, I. Rosa and party. Non-types. USNM 276556 , juveniles 25, 13.9-24.8 mm SL, same data as MZUSP 28816 above .

Figures

Fig. 63. Mimagoniates sylvicola, young adult male, MZUSP 36612, holotype, 30.2 mm SL, Brazil, Bahia, município de Prado, unnamed forest rivulet near Fazenda Embaçuaba, 8-9 km NW of Cumuruxatiba. Modified from Menezes & Weitzman (1990).

Fig. 64. Mimagoniates sylvicola, adult female, MZUSP 93873, Brazil, Bahia, município of Canavieiras, stream between Ouricana and Santa Luzia.

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. 68. Mimagoniates sylvicola, adult but still developing male, USNM 276557, 29.3 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 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. 65. Mimagoniates sylvicola, adult male, USNM 300634, 32.5 mm SL; anterior 11 anal-fin rays, lateral view, left side. Modified from Menezes & Weitzman (1990).

Fig. 66. Mimagoniates sylvicola, adult male, USNM 276557, 29.3 mm SL; pelvic-fin rays of adult male, ventral view, left side, anterior at left. Modified from Menezes & Weitzman (1990).

Fig. 69. Mimagoniates sylvicola, adult male, USNM 276557, 29.3 mm SL; jaws and dentition of adultmale, lateral view, right side,anteriorat left.ModifiedfromMenezes &Weitzman(1990).