Mimagoniates pulcher, Menezes¹ & Weitzman², 2009

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 : 335-338

Mimagoniates pulcher , new species

Figs. 45-46

Mimagoniates sp. Menezes, 2007: 38 (listed). - Menezes et al., 2008: 33, 38, 41, 43 (discussion of relationships).

Mimagoniates sp. n. Menezes et al., 2008: 39, 40 (distribution; discussion of biogeography).

Holotype. MNRJ 17814 , developing male, 35.0 mm SL, Brazil, Mato Grosso, “ Porto Velho-São Luiz de Cáceres ”, 1934, Avelar.

Paratypes. Following lot of immatures to adults collected with holotype: MNRJ 4233 , 28 , 17.8 -37.0 mm SL .

Diagnosis. Mimagoniates pulcher is apparently most similar to M. barberi and M. inequalis with respect to the modification of caudal-fin rays in association with caudal pump, but differs at once from these two species in having hooks on caudal-fin rays at least in adult male specimens (compare Fig. 47 with Figs. 32 and 38 ). Additionally, from M. barberi it is distinguished in having anal-fin rays 26-30 (31- 36 for M. barberi ) and from M. inequalis in having 43-46 lateral series scales (34-41 for M. inequalis ). Mature males of the remaining species of Mimagoniates have principal caudal-fin rays modified to form a fully developed caudal-fin ray pump ( Figs. 58 , 67 , 72 , and 80).

Description. Table 8 presents morphometrics of holotype and paratypes. The entire description refers to the single population sample available representing the types.

Body compressed, relatively elongate; body deepest at vertical line through pelvic-fin origin. Predorsal profile of body gently convex in all specimens, Body profile slightly elevated at dorsal-fin origin. Dorsal profile of body nearly straight along dorsal-fin base to adipose fin. Body profile posterior to adipose fin slightly concave dorsal to caudal peduncle. Dorsal-fin origin nearer to caudal-fin base than to snout tip. Ventral profile of body convex in developing males from tip of lower jaw to origin of pelvic fins, 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 along base 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 in developing males; slightly concave or nearly straight in females and juveniles.

Lower jaw protruding, slightly beyond upper jaw. Lower jaw of developing males and females somewhat thick and heavy compared to that of juveniles. Mouth angled posteroventrally. Maxilla long, extending to point slightly ventral to a horizontal line drawn from ventral border of eye in all specimens. Maxilla extends posteriorly to a point slightly posterior to vertical through anterior border of eye.

Dorsal-fin unbranched rays ii in all specimens, branched rays 7-8 (8), 8.0, n = 29; posterior ray not split to its base and counted as 1 ray.Anal-fin unbranched rays iv in all specimens, branched rays 26-30 (29), 28.4, n = 28; posterior ray split to its base and counted as 1 ray. Anal fin with weakly developed lobe anteriorly ( Figs. 45 , 46 and 50 ). Lobe includes last unbranched ray and first 4 branched rays. Anal fin of developing males with bilateral hooks, 1 rudimentary hook on fourth, through seventh branched rays in specimen MNRJ 4233, 37.0 mm SL ( Fig. 50 ). Pectoral-fin unbranched ray i in all specimens, branched rays range 9-11 (9), 9.8, n = 29. Posterior tip of pectoral fin extends posteriorly to origin of pelvic fins. Pelvic-fin rays 7 in all specimens ( Fig. 49 ). Sexually mature, large adult developing males with over 35 hooks on each pelvic fin distributed as shown in Fig. 49 .

Principal caudal-fin ray count 10/ 9 in all specimens, n = 29. Fin rays modified in association with caudal pheromone pump as shown in Fig. 47 . Caudal-fin rays without bony hooks in developing males, SL 25.0-35.0 mm, but with small hooks present on caudal-fin rays 9 and 10 in a larger apparently mature male, SL 37.0 mm ( Figs. 47 and 48 ).

Scales cycloid, with more radii along posterior border, including terminal scale of modified caudal-fin series than in any other Mimagoniates species ( Fig. 48 ).

Lateral line incomplete, perforated scales 7-8 (7), n = 8. Lateral series scales = 43-46 (43), 44.6, n = 8. Predorsal scales 20-22 (22), 21.1, n = 8. Scale rows between dorsal-fin and anal-fin origins 13-15 (14), 13.8, n = 4. Scale rows around caudal peduncle 16 in 4 specimens.

Premaxillary teeth in 2 irregular, almost undistinguishable, closely packed rows. Teeth count on left premaxilla given as total ( Fig. 51 ). Larger and smaller teeth tricuspid in all large specimens, small teeth in smaller specimens sometimes bicuspid or conical. Total premaxillary teeth 7-10 (9), 8.7, n = 29. Maxillary teeth 2-6 (5), 3.6, larger specimens usually with higher counts, n= 28. All maxillary teeth ( Fig. 51 ) tricuspid in large specimens; small specimens with posterior maxillary teeth often conical. Dentary with 4 large anterior tricuspid teeth in all specimens, smaller posterior teeth 6-10 (7), 7.2, number of teeth nearly always greater in largest specimens; anterior teeth tricuspid, posterior ones conic, n = 28. See

Males Females and juveniles

Characters

Holotype N Range Mean SD N Range Mean SD dif. Standard length 35.0 06 25.0-37.0 32.6 23 17.8-27.0 22.0

Depth at dorsal-fin origin 26.3 06 24.0-26.2 24.9 1.9 23 18.3-24.7 21.5 1.7 + Snout to dorsal-fin origin 61.7 06 59.4-64.0 61.5 1.5 23 59.8-65.7 61.8 1.5 – Snout to pectoral-fin origin 25.1 06 24.6-26.4 25.4 0.6 23 24.7-28.0 25.9 0.9 – Snout to pelvic-fin origin 44.6 06 40.6-48.0 44.2 2.3 18 40.0-48.3 44.4 2.0 – Snout to anal-fin origin 58.0 06 52.5-60.0 56.6 2.5 22 53.3-62.8 57.5 1.9 – Caudal peduncle depth 13.1 06 10.8-13.1 12.1 0.8 23 07.7-09.7 09.5 0.8 + Caudal peduncle length 08.3 06 07.2-08.7 08.2 0.5 20 06.5-08.3 07.2 0.5 +* Pectoral-fin length 20.0 06 20.0-24.4 22.0 1.4 23 20.8-24.7 22.6 1.3 – Pelvic-fin length 12.6 06 12.5-13.6 13.1 0.4 23 10.5-13.6 12.4 0.8 +* Dorsal-fin base length 13.4 06 11.6-13.4 12.5 0.7 22 10.2-13.6 12.1 1.1 – Dorsal-fin height 26.0 06 24.0-27.8 26.1 1.4 20 21.6-26.9 23.5 1.3 + Anal-fin base length 35.6 06 32.7-41.0 35.8 2.8 21 34.6-42.3 37.7 1.9 +* Anal-fin lobe length 20.0 06 16.9-21.6 19.6 1.5 21 16.8-25.5 21.6 2.1 +* Eye to dorsal-fin origin 49.1 06 48.0-52.0 49.1 1.6 23 45.8-51.6 48.1 1.5 – Dorsal-fin origin to caudal-fin base 42.3 06 40.2-42.3 41.2 0.8 23 36.2-42.0 38.8 1.4 +* Bony head length 24.3 06 23.4-26.0 24.7 0.9 22 24.0-27.3 25.4 0.7 – Horizontal eye diameter 35.3 06 34.4-38.4 36.2 1.5 22 37.0-42.5 39.1 1.5 +* Snout length 22.5 06 20.2-22.5 21.5 0.8 22 18.1-22.2 20.5 1.2 – Least interorbital width 34.1 06 34.1-36.1 35.0 0.7 22 33.3-37.0 35.2 1.2 – Upper jaw length 41.2 06 41.1-47.5 43.8 2.4 22 40.0-46.3 43.1 1.8 –

Fig. 51 . Maxillary and dentary teeth shaped much like premaxillary teeth.

Vertebrae 37-40 (38), 38.4, n = 28. Dorsal limb gillrakers 6- 7 (6), 6.03, n = 28; ventral limb gill rakers 11-13 (12), 11.8, n = 28. Branchiostegal rays 3, in 1 cleared and stained specimen, 3 rays originating on anterior ceratohyal and 1 ray from posterior ceratohyal.

pattern of males and females. Body pale brown, slightly lighter ventrally. Scattered dark chromatophores all over body, more heavily concentrated laterally and extending onto middle caudal-fin rays, indicating what could have been diffuse stripe, more evident in males than in females. Dark line slightly above midbody from about vertical crossing pelvic-fin origin Color in alcohol. Description based on specimens kept in alcohol since 1939 so that it likely reflects only vestiges of original coloration. See Figs. 45 and 46 for preserved color to caudal peduncle.

Pectoral, pelvic, dorsal, and anal fins with scattered dark chromatophores along fin rays and membranes. Anal fin with dark, elongate stripe running length of fin; stripe wider and more conspicuous anteriorly in both sexes. Dorsal-fin with diffuse horizontal dark stripe in developing males and females extending posteriorly from about mid-length of anterior elongate undivided ray to posterior tips of two terminal dorsal-fin rays. Adipose fin dusky with scattered dark chromatophores.

Head brown overall with scattered dark chromatophores, those on infraorbitals below eye and opercular bones slightly darker than those along midbody. Iris silvery. Circumorbitals pale yellowish brown.

Sexual dimorphism. Fully mature males and females are not represented in available sample. The largest developing male (37.0 mm SL) has a caudal pheromone organ and anal and pelvic-fin hooks ( Figs. 47 to 50) but the largest developing female (26.3 mm SL) lacks the caudal organ and fin hooks of males. Table 7 indicates that body depth, caudal peduncle depth and dorsal-fin height might be sexually dimorphic and tend to be greater in males than in females.

Distribution. The only available sample of Mimagoniates pulcher originated from an uncertain locality in the upper rio Paraguai in Mato Grosso, Brazil (see notes on the type locality). See fig. 3 in Menezes et al. (2008).

Etymology. The name pulcher is from the Latin meaning beautiful and refers to the usual blue color of the species of Mimagoniates when alive.

Notes on type locality. The type locality for M. pulcher is vague and one of us (Menezes) was unable to locate this species on two collecting trips to the area around Cáceres (= São Luiz de Cáceres in 1934) in 1991 and 1992. At first we assumed that “Porto Velho-São Luiz de Cáceres” implied that this lot was collected somewhere between Cáceres, Mato Grosso State and Porto Velho, Rondônia State, a straight line distance of a little over 600 km. Examination of an American Geographical Society of New York map: Cuyabá for 1930, revealed another Porto Velho, this time in Mato Grosso on the upper part of the rio Arinos, a tributary of the rio Juruena into the rio Tapajós of the Amazon basin. The map shows this Porto Velho as a head water stopping point for river traffic with a trail leading south to Cuiabá and then to Cáceres. A collecting trip to this area and southward yielded no specimens of Mimagoniates . The area is now partly under soy bean culture and no typically black waters were found. Alteration of the habitat may have changed the nature of the streams of the area. Mimagoniates pulcher , if it was originally found in this region, may be extinct.

Remarks. The structure of the caudal organ of Mimagoniates pulcher is more similar to that of M. barberi than to any other species of Mimagoniates (compare Fig. 47 to Fig. 38 ). Since Fig. 47 is based on a developing male it might be possible that in mature males the caudal organ is more developed and attains a modified structure.

Figures

Fig. 45. Mimagoniates pulcher, male, MNRJ 17814, SL 35.0 mm SL, Brazil, Mato Grosso, “Porto Velho-São Luís de Cáceres”, holotype.

Fig. 46. Mimagoniates pulcher, female, MNRJ 4233, SL 26.3 mm SL, Brazil, Mato Grosso, “Porto Velho-São Luís de Cáceres”, paratype.

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. 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. 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. 50. Mimagoniates pulcher, developingmale, MNRJ 4233, 37.0 mm SL; anterior 13 anal-fin rays, lateral view, left side.

Fig. 49. Mimagoniates pulcher, developing male, MNRJ 4233, 37.0 mm SL; pelvic-fin rays, ventral view, left side.

Fig. 48. Mimagoniates pulcher, male, MNRJ 4233, 43.2 mm SL; caudal-fin squamation of dorsal and ventral portions of caudalfin lobe.

Fig. 51. Mimagoniates pulcher, developing male, MNRJ 4233, 34.2 mm SL; jaws and dentition, lateral view, right side, anterior at left.