Microlepidogaster dimorpha, a new species of Hypoptopomatinae (Siluriformes: Loricariidae) from the upper rio Paraná system Author Martins, Fernanda de Oliveira Author Langeani, Francisco text Neotropical Ichthyology 2011 2011-03-31 9 1 79 86 http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1679-62252011000100005&lng=en&tlng=en journal article 10.1590/S1679-62252011000100005 1982-0224
Microlepidogaster dimorpha , new species Figs. 1 , 2b , and 3
Holotype. DZSJRP 10543, 37.6 mm SL, female, Brazil , Minas Gerais , Uberaba , riacho Grotão at Fazenda Nossa Senhora da Abadia, unpaved road at BR-262, rio Grande drainage, 19º41’31”S 47º 42 ’ 57 ”W, 12 May 2007, L. G. G. Silveira & F. Langeani .
Paratypes. All from Brazil , Minas Gerais , rio Grande drainage, Uberaba. DZSJRP 5564, 11, 25.8-35.1 mm SL (10, 25.8-35.1 mm SL), road Uberaba-Almeida Campos and Nova Ponte, rio Uberaba, 19º39’40”S 47º49’23”W , 21 May 2003, J. P. Serra, F. Langeani, F. R. Carvalho & D. O. Tavares; DZSJRP 8750, 19, 2 c&s, 19.8-37.7 mm SL (14, 25.0- 37.7 mm SL), MCP 45866, 2, 26.7-30.8 mm SL, MNRJ 37848, 2, 25.5-26.8 mm SL, MZUSP 107585, 2, 27.8-30.2 mm SL, same locality of holotype, 8 Sep 2006, F. Langeani, F. R. Carvalho, C. P. Ferreira, H. F. Chaves & F. O. Martin; DZSJRP 12332, 17, 2 c&s, 20.3-34.1 mm SL (6, 29.7-37.6 mm SL), LBP 4854, 4, 29.8-32.9 mm SL, MCP 41912, 4, 28.7-34.0 mm SL, collected with holotype.
Diagnosis. Microlepidogaster dimorpha differs from M. perforatus ( Tables 3 and 4 ) and M. longicolla Calegari & Reis, 2010 by having first dorsal-fin proximal radial attached to the neural spine of seventh vertebra, with posterior portion contacting also the eighth centrum (vs. first dorsal-fin proximal radial attached to the neural spine of eighth or ninth vertebra in M. perforatus , and to the neural spine of tenth or eleventh vertebra in M. longicolla ); 29-30 vertebrae (vs. 31 in M. perforatus ; and 31-33 in M. longicolla ); 18-21 mid-dorsal plates (vs. 9-13 in M. perforatus , and 13-17 in M. longicolla ); deeper caudal peduncle (10.0-11.4% in SL vs. 7.7-8.5% in M. perforatus , and 5.4-7.3% in M. longicolla ); greater distance between dorsal-fin origin and anal-fin insertion (19.4-23.8% in SL vs. 16.4-18.8% in M. perforatus , and 14.7-16.2% in M. longicolla ); and nostril width markedly wider in males than in females (vs. approximately equivalent in size for both sexes, slightly wider in males than in females in M. perforatus , and equivalent in size for both sexes in M. longicolla ). Microlepidogaster dimorpha also differs from M. perforatus by having the iris operculum (vs. absent); median plate series complete to caudal peduncle end (vs. median plate series truncated, with last two plates of dorsal and ventral series contacting in midline); greater head depth (43.4-53.1% vs. 40.7- 42.3% in HL); greater orbital diameter (13.6-18.5% vs. 11.1- 13.5% in HL); pelvic-fin first unbranched ray longer in males than in females (vs. equivalent in size in both sexes); and supraneural without paired anterior processes (vs. processes present). Additionally, M. dimorpha can be distinguished from M. longicolla by having anterior margin of snout with a paired rostral plate (vs. snout with small plates, naked in the anterior margin); pectoral-fin axillary slit present, even in adult specimens (vs. pectoral-fin axillary slit present only in juvenile specimens); longer pectoral-fin unbranched ray (20.0-23.8% in SL vs. 13.4-16.2% in M. longicolla ).
Fig. 1. Microlepidogaster dimorpha , holotype, DZSJRP 10543, 37.6 mm SL, female, riacho Grotão at Fazenda Nossa Senhora da Abadia, Uberaba, Minas Gerais, Brazil.
Description. Morphometric and meristic data are given in Tables 1-2 . Dorsal body profile convex from tip of snout to dorsal-fin origin; descending posteriorly at dorsal-fin base; almost straight from end of dorsal-fin base to caudal-fin origin. Ventral body profile almost straight; ascending posteriorly from anus to end of anal-fin base; straight to caudal-fin origin. Greatest body depth at dorsal-fin origin. Greatest body width at opercular region, gradually tapering toward snout and caudal fin. Head profile rounded in dorsal view; rostral margins with thin plates, not deflected ventrally; anterior tip of rostrum with a median pair of plates; odontodes at anterior margin of snout small and leaf-shaped ( Fig. 2b ), some with edge slightly rounded. Odontodes equal in size
Table 1. Morphometric data for Microlepidogaster dimorpha .
Holotype (H) and 30 paratypes, 16 females, and 14 males
(DZSJRP 5564, 8750,12332; MCP 45866;MNRJ 37848; MZUSP
107585); range includes holotype. SD = Standard deviation.

Character	H Minimum Maximum Mean SD
Standard length (mm)	37.6	25.0	37.7	-	-
Percents of Standard length
Predorsal length	44.8	42.3	50.0	45.3	1.5
Preanal length	57.1	53.1	62.2	58.3	1.6
Prepectoral length	25.4	23.4	29.9	26.4	1.2
Prepelvic length	36.6	33.8	42.6	37.2	1.8
Postanal length	36.9	33.0	38.5	35.7	1.4
Thoracic length	16.1	13.8	18.5	15.9	1.1
Abdominal length	21.8	19.5	23.6	21.8	1.0
Caudal-peduncle depth	10.3	10.0	11.4	10.7	0.4
Head length	30.4	29.8	37.2	32.3	1.4
Head width	22.5	21.4	24.5	22.7	0.8
Head depth	14.4	14.1	16.7	15.2	0.7
Base of dorsal-fin length	12.9	10.6	14.3	12.6	0.8
Folded dorsal-fin length	22.4	20.3	25.2	23.3	1.1
Pectoral-fin unbranched ray length	21.6	20.0	23.8	22.1	1.0
Pelvic-fin unbranched ray length	16.4	15.4	20.9	18.3	1.8
Males	-	18.3	20.9	19.9	0.8
Females	16.4	15.4	18.2	16.9	1.0
Snout-opercle length	24.9	23.8	28.8	25.7	0.9
Dorsal to anal-fin length	20.5	19.4	23.8	21.5	1.0
Percents of Head length
Head width	74.1	62.7	75.9	70.3	2.9
Head depth	47.5	43.3	53.1	47.2	2.2
Snout length	51.4	48.3	54.4	51.1	1.5
Orbital diameter	17.3	13.6	18.5	16.5	1.3
Interorbital length	44.1	38.8	44.8	42.2	1.7
Barbel length	4.5	4.0	8.1	5.5	1.0
Prenasal length	34.5	28.0	35.8	32.4	1.9
Internasal length	16.3	9.2	17.0	12.8	1.8
Nostril width	7.9	7.9	15.4	11.2	2.4
Males	-	11.5	15.4	13.5	1.2
Females	7.9	7.9	10.3	9.2	0.7
Suborbital depth	24.5	20.4	24.9	23.2	1.2

and uniformly distributed, not forming rows, on head and body. Eyes small, dorsolaterally placed, not visible from ventral view. Iris operculum present. Infraorbital canal entering infraorbital series via compound pterotic. Compound pterotic roughly quadrangular in shape, without elongate posterior extension; small to median roundish perforations on posteroventral margin. Caudal peduncle slightly flattened dorsally and ventrally, somewhat rectangular in transverse section.
Abdomen partially covered by small plates, approximately same size of pupil, irregularly arranged. Body entirely covered with bone plates, except on ventral part of head, region overlying opening of swim bladder capsule, and around anus and pelvic-fin origin.
Lips roundish, papillose; lower lip larger than upper lip; larger papillae near oral opening. Maxillary barbel reduced, free from oral disk. Teeth slender, bifid; median cusp larger and rounded, lateral smaller and pointed. Premaxillary teeth 15-28 (mode = 23,24). Dentary teeth 12-25 (mode = 21). Premaxillary and dentary accessory teeth absent.
Dorsal fin ii, 6-7 (mode = 7), originating approximately at vertical through end of pelvic-fin base; its length surpassing anal-fin origin; spinelet small, somewhat rectangular, anterior and posterior margins slightly straight; locking mechanism non-functional. Anterior portion of compound supraneuralfirst dorsal-fin proximal radial contacting neural spine of 7 th vertebra; posteriorly contacting the 8 th vertebra. Pectoral fin i, 6-7 (mode = 6); originating immediately behind opercular opening and surpassing pelvic-fin origin. Cleithrum and coracoid exposed and supporting odontodes laterally, covered by skin medially. Arrector fossae partially enclosed by ventral lamina of coracoid; opening extending laterally approximately halfway towards pectoral-fin base. Pectoral axillary slit present, about 2.5 times in orbital diameter. Pelvic fin i, 5-6 (mode = 5); reaching anal-fin origin in males when depressed. Anal fin i, 4-6 (mode = 5); originating at vertical through end of dorsal-fin base. Caudal fin i, 14, i; lobes equal in size; 5-6 (mode = 5) dorsal and 4-5 (mode = 5) ventral procurrent rays.Adipose fin and azygous plates absent. Median lateral plate series 24-27 plates, complete from compound pterotic to caudal-fin base. Vertebrae 29-30 (mode = 29).
Table 2. Frequency distribution of meristic data for Microlepidogaster dimorpha . Rays and teeth counts were made for holotype (DZSJRP 10543) and for 30 paratypes (DZSJRP 5564, 8750, 12332; MCP 45866; MNRJ 37848; MZUSP 107585). Plates (counted in both sides whenever possible), procurrent rays, and vertebrae counts were made for 4 c&s paratypes (DZSJRP 8750, 12332).

Character	Frequency distribution	Range	Mode
Dorsal plates	24(3); 25(4)	24-25	25
Mid-dorsal plates	18(1); 19(3); 20(1); 21(1)	18-21	19
Median plates	24(1); 25(2); 26(1); 27(1)	24-27	25
Mid-ventral plates	17(1); 18(2); 19(3); 20(1)	17-20	19
Ventral plates	20(1); 21(1); 22(4); 23(1)	20-23	22
Premaxillary teeth	15(1); 16(1); 17(2); 18(5); 19(7); 20(4); 21(3); 22(9); 23(10); 24(10); 25(2); 26(1); 27(4); 28(1)	15-28	23-24
Dentary teeth	12(1); 14(3); 15(4); 16(7); 17(5); 18(6); 19(6); 20(5); 21(9); 22(5); 23(2); 24(2); 25(1)	12-25	21
Dorsal-fin branched rays	6(1); 7(29)	6-7	7
Pectoral-fin branched rays	6(29); 7(1)	6-7	6
Pelvic-fin branched rays	5(29); 6(1)	5-6	5
Anal-fin branched rays	4(1); 5(28); 6(1)	4-6	5
Caudal-fin branched rays	14(30)	-	14
Dorsal procurrent rays	5(2); 6(1)	5-6	5
Ventral procurrent rays	4(1); 5(2)	4-5	5
Vertebrae	29(3); 30(1)	29-30	29

Table 3. Morphometric data for Microlepidogaster perforatus (MNRJ 31886, MZUSP 10216, 10217; n = 5). SD = Standard deviation.
Table 4. Frequency distribution of meristics for Microlepidogaster perforatus . Plates (counted in both sides whenever possible), procurrent rays were made for 3 specimens, and vertebrae counts were made for 1 c&s specimen (MNRJ 31886; MZUSP 10216, 10217).

Character	Minimum Maximum		Mean	SD
Standard length (mm)	29.93	32.76	-	-
Percents of Standard length
Predorsal length	45.5	47.8	46.7	1.0
Preanal length	54.8	58.4	57.2	1.4
Prepectoral length	25.5	27.5	26.5	0.8
Prepelvic length	35.2	36.6	35.9	0.6
Postanal length	35.5	39.5	37.1	1.6
Thoracic length	13.6	15.5	14.4	0.8
Abdominal length	19.3	23.2	20.8	1.6
Caudal-peduncle depth	7.7	8.5	8.1	0.3
Head lenght	33.2	34.7	34.1	0.6
Head width	21.0	23.2	22.4	0.9
Head depth	13.9	14.4	14.2	0.2
Base of dorsal-fin length	11.2	12.6	11.6	0.5
Folded dorsal-fin length	21.0	22.8	22.1	0.7
Pectoral-fin unbranched ray length	19.5	20.7	20.1	0.4
Pelvic-fin unbranched ray length	15.0	19.1	16.6	1.7
Snout-opercle length	24.1	26.5	25.7	0.9
Dorsal to anal-fin length	16.7	18.8	17.5	0.8
Percents of Head length
Head width	60.6	68.0	65.6	3.0
Head depth	40.7	42.3	41.6	0.7
Snout length	47.5	51.9	49.2	1.9
Orbital diameter	11.1	13.5	12.6	1.0
Interorbital length	36.7	41.2	39.3	1.9
Barbel length	6.0	8.7	7.1	1.1
Prenasal length	32.2	35.3	33.6	1.4
Internasal length	10.0	12.7	11.6	1.0
Nostril width	11.2	12.4	11.9	0.62
Suborbital depth	20.4	21.7	21.0	0.5

Character	Frequency distribution	Range Mode
Dorsal plates	25(1); 26(4); 27(1)	25-27	26
Mid-dorsal plates	9(1); 10(2); 11(1); 12(1); 13(1)	9-13	10
Median plates	21(2); 23(2); 25(2)	21-25 21/23/25
Mid-ventral plates	19(3); 20(3)	19-20	19/20
Ventral plates	20(2), 21(2); 22(2)	20-22 20/21/22
Premaxillary teeth	16(4); 17(4); 18(1); 19(1)	16-19	16/17
Dentary teeth 11(1); 12(2); 13(4); 14(1); 15(2) 11-15			13
Dorsal-fin branched rays	7(5)	-	7
Pectoral-fin branched rays	5(1); 6(4)	5-6	6
Pelvic-fin branched rays	5(5)	-	5
Anal-fin branched rays	5(5)	-	5
Caudal-fin branched rays	14 (5)	-	14
Dorsal procurrent rays	4(1); 5(2)	4-5	5
Ventral procurrent rays	4(3)	-	4
Vertebrae	31	-	31

Color in alcohol. Most specimens with a dark brown color along the dorsal portion of head and dorsal midline of body. Four dorsal dark saddles, not extending laterally, inconspicuous in adults. Longitudinal clear stripe from dorsal portion of snout to nostril. Lateroventral portion of head unpigmented. Lateral portion of body brown; an inconspicuous dark longitudinal stripe at median plate series, extending from compound pterotic to vertical through end of depressed dorsal fin. Ventral surface of body light brown. Dorsal, anal, pectoral, and pelvic-fins membrane hyaline; all rays with transverse dark bands. Caudal fin mostly dark brown, except for hyaline portions at lobe tips, middle-rays extremities, and a circular area in the middle of each lobe.
Sexual dimorphism. Males with a conspicuous urogenital papillae immediately posterior to anus (vs. absent in females); expanded flap of skin on dorsal surface of the first pelvic-fin ray and branched rays, less developed in the latter (vs. absent in females); pelvic fin reaching anal-fin origin, its first unbranched ray 18.3-20.9% in SL (vs. pelvic fin not reaching anal-fin origin, its first unbranched ray 15.4-18.2% in SL in females); males, usually with fewer teeth than females, probably related with their smaller size; males with wider nostril width (11.5-15.4% of HL vs. 7.9-10.3% in females), with an anterior single row of 4 to 6 small odontodes associated with skin of the anterior portion of anterior nostril (vs. absent in females; Fig. 3 ).
Distribution. The species is known from rio Uberaba and riacho Grotão, both tributaries of the rio Grande, upper rio Paraná system, Minas Gerais, Brazil ( Fig. 4 ).
Etymology. Epithet dimorpha from the Greek di, two, double, and morphe, form, in allusion to the accentuated sexual dimorphism presented by the species. A feminine adjective.