A new species of Microglanis (Siluriformes: Pseudopimelodidae) from the upper rio Tocantins basin, Goiás State, Central Brazil
Author
Shibatta, Oscar Akio
text
Neotropical Ichthyology
2014
2014-03-31
12
1
81
87
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1679-62252014000100081&lng=en&tlng=en
journal article
10.1590/S1679-62252014000100008
7ea5a23c-895c-4eb6-bb3d-9f0f019b3fd8
1982-0224
4550995
Microglanis maculatus
,
new species
Figs. 1-3
Holotype
.
INPA 41133
,
36.5 mm
SL,
Brazil
,
Goiás
, município
de Barro Alto
, upper rio
Tocantins
basin, ribeirão
Pouso Alegre
, tributary of rio
dos Patos
,
15°01’26"S
48°49’51"W
,
12 Jul 2010
,
O. A. Shibatta
,
A. Claro-García
, L.
R
.
Jarduli
&
E.
Santana da Silva.
Paratypes
.
INPA 24044
,
2
,
21.4-25.8 mm
SL,
Brazil
,
Goiás
, município
de Barro Alto
,
Igarapé Veredas
, rio
dos Patos
basin,
17 Jun 2004
,
G. M. dos Santos
.
MZUEL 5925
,
1
,
20.5 mm
SL, same data as holotype
.
Diagnosis.
Microglanis maculatus
differs from all its congeners by the presence of rounded spots in the flank. Furthermore, it differs from its congeners, except
M. robustus
, by the following combination of features: caudal fin emarginated with upper lobe slightly longer than the lower, light spot in nuchal region very small or absent.
Microglanis maculatus
differs from
M. robustus
by single hooks on anterior margin of pectoral-fin spine (
vs
. bifurcated hooks between antrorse and retrorse hooks), rays of pectoral fin I, 6 (
vs
. I, 5); anterior blotch of trunk U shaped (
vs.
inverted U shaped); broad dark stripes on dorsal and caudal fins (
vs
. thin), lower values of dorsal-fin spine length (6.9-11.1% SL
vs
. 11.3-15.4% SL), pectoral-fin spine length (12.9-17.7% SL,
vs
. 16.4-20.6% SL), and orbital diameter (11.5-12.6% SL
vs
. 14.7-16.4% SL); and higher values of mouth width (16.8-17.5% SL
vs.
11.4-13.2% SL).
Description.
Morphometric data are presented in
Table 1
. Body depressed from snout to dorsal-fin origin; posteriorly compressed. Profile slightly oblique upward from snout tip to posterior nostril, slightly convex from posterior nostril to nape, and convex from nape to dorsal-fin origin. Profile from dorsal-fin origin to end of adipose-fin base almost straight (not considering adipose fin), oblique downward. Dorsal profile straighter on small specimens (
Fig. 2
). Ventral profile from tip of lower jaw to end of anal-fin base slightly convex, almost straight. More convex in young specimens (
Fig. 2
). Head large, wider than deep. Mouth terminal, slightly prognathous. Opercular membrane large, well developed. Eye relatively small, lateral-superiorly positioned, covered by skin. Anterior nostril tubular, over lip. Maxillary barbel reaching distal opercular edge. Outer mental barbel reaching pectoralfin base. Anterior cranial fontanel not extending beyond posterior orbital border.
Dorsal fin trapezoidal; posterior border rounded; origin anterior to midpoint of standard length; not reaching adiposefin origin when adpressed; first lepidotrichium (“spinelet”) small and rigid, forming dorsal-fin locking mechanism; second ray forming spine; I, 6*(4). Adipose fin slightly elongated, posterior border angular and free. Pectoral fin triangular, not reaching pelvic-fin origin when adpressed; first ray rigid and strongly serrate on both sides (only retrorses hooks on anterior margin of pectoral fin in small specimens, and antrorses and retrorses in large specimen (
Fig. 3
), all single; I, 6*(4). Pelvic fin rounded, originating just posterior to vertical through end of dorsal-fin base, not reaching anal-fin origin when adpressed; i, 5*(4). Distal profile of anal fin rounded; anal-fin base length slightly smaller than adipose-fin base; iii, 7*(2) or iv, 5(2). Caudal fin emarginated, lobes distal profile rounded, upper lobe slightly longer than lower lobe; principal rays 7, 8*(4).
Pores of lateral-line extending just beyond vertical through posterior margin of pelvic-fin. Total gill rakers 7(1), 8(1), or 9*(2). Axillary pore absent. Six ribs; free vertebral centra 26 (total = 32 vertebrae) in
holotype
.
Color in alcohol.
Dorsal region of head, from tip of snout to nape, dark brown, ventrally continuing in suborbital and opercular region to horizontal passing through angle of mouth; intermediate region with light blotch. Ventral region
Fig. 1.
Microglanis maculatus
, holotype, INPA 41133, 36.5 mm SL, ribeirão Pouso Alegre, tributary of rio dos Patos, upper rio Tocantins basin, Barro Alto, Goiás State, Brazil.
Fig. 2.
Microglanis maculatus
, paratype, MZUEL 5925, 20.5 mm SL, ribeirão Pouso Alegre, tributary of rio dos Patos, upper rio Tocantins basin, Barro Alto, Goiás State, Brazil.
of head light with dark spots. Trunk between nape and end of dorsal fin with “U” shaped dark brown blotch. Dorsal region between end of dorsal and adipose fins with dark stripe. Second dark stripe extending along axis of body. Dark blotch at end of caudal peduncle elongated, roughly hexagonal. Lateral and ventral region of body light with several small rounded spots, several merged forming clumps. First pectoralfin ray with faint dark spot; other pectoral fin rays with series of dots in middle region. Dorsal fin bearing a broad “C”-shaped dark blotch, elongated; upper edge of dorsal fin and inner area of “C”-shaped blotch hyaline. Adipose fin with dark blotch in its middle region, edges light brown. Pelvic and anal fins hyaline, with dark spots along approximately half length of rays. Caudal-fin dark stripe approximately “3”-shaped, broad, top, and bottom edges contacting caudal-peduncle dark blotch.
Distribution.
Microglanis maculatus
is known from the rio dos Patos basin, upper rio
Tocantins
basin, in Barro Alto,
Goiás State
,
Brazil
(
Fig. 4
).
Table 1.
Morphometric data of
Microglanis maculatus
(n = 4). SD = standard deviation.
| Paratypes |
| Holotype |
Min.-Max. |
Mean±SD |
| Standard length (mm) |
36.5 |
20.5-36.5 |
- |
| Percents of standard length |
| Head length |
28.2 |
26.3-28.2 |
27.4±0.958 |
| Head depth |
10.5 |
10.3-11.3 |
10.8±0.459 |
| Interorbital width |
12.4 |
12.4-13.5 |
12.9±0.455 |
| Orbital diameter |
3.3 |
3.2-3.6 |
3.3±0.155 |
| Snout length |
11.6 |
9.6-11.6 |
10.7±0.834 |
| Mouth width |
17.0 |
16.8-17.5 |
17.1±0.305 |
| Maxillary barbel length |
26.6 |
19.0-30.4 |
24.5±5.001 |
| Pelvic fin length |
17.4 |
17.4-20.0 |
18.5±1.252 |
| Dorsal-fin spine length |
10.2 |
6.9-11.1 |
9.8±1.961 |
| Pectoral-fin spine length |
14.2 |
12.9-17.7 |
15±2.009 |
| Posterior cleithral process length |
10.2 |
9.6-10.6 |
10.1±0.432 |
| Predorsal length |
36.6 |
35.8-38.3 |
36.8±1.063 |
| Prepelvic length |
50.3 |
47.2-50.5 |
48.8±1.826 |
| Preanal length |
70.6 |
67.2-70.6 |
69.1±1.490 |
| Caudal peduncle depth |
11.6 |
11.6-15.7 |
13.2±1.821 |
| Caudal peduncle length |
17.0 |
15.2-18.2 |
16.7±1.276 |
| Body width |
26.6 |
25.2-27.2 |
26.3±0.854 |
| Body depth at dorsal fin |
17.6 |
17.6-20.5 |
19.6±1.390 |
| Dorsal-fin base length |
13.3 |
12.1-13.3 |
12.8±0.515 |
| Adipose-fin base length |
28.7 |
21.0-28.7 |
24.4±3.351 |
| Anal-fin base length |
13.7 |
13.5-14.9 |
14.0±0.633 |
| Percents of head length |
| Interorbital width |
43.8 |
43.8-49.6 |
47.2±2.436 |
| Orbital diameter |
11.5 |
11.5-12.6 |
12.1±0.439 |
| Snout length |
41.1 |
34.2-41.7 |
39.1±3.420 |
| Mouth width |
60.3 |
60.3-66.5 |
62.7±2.719 |
| Maxillary barbel length |
94.2 |
70.9-115.4 |
89.7±19.67 |
| Head depth |
37.0 |
37.1-43.0 |
39.4±2.527 |
Habitat.
The specimens from the ribeirão Pouso Alegre were collected at the mouth of a creek amid the adventitious roots of riparian trees that stand out from the banks. Attempts were made to collect in the region above this point, where the bed was rocky, but no specimen was captured. The ribeirão Pouso Alegre presents riparian vegetation in good condition, bedrock, with sand, clay litter, logs and branches at the mouth (
Fig. 5
), dissolved oxygen
7.8 mg
/L, pH 7.65, conductivity 85ì S/cm, water temperature 22.5° C, mean depth 6.5±
0.93 cm
, mean width 4.1±
0.66 m
, mean speed water 0.12±
0.02 m
/s. Other nine species of fish were collected in the same location and are listed in Claro-García & Shibatta (2013).
Fig. 3.
Dorsal view of left pectoral-fin spine of (a) holotype (INPA 41133, 36.5 mm SL) and (b) paratype (MZUEL 5925, 20.5 mm SL) of
Microglanis maculatus
, from ribeirão Pouso Alegre, tributary of rio dos Patos, upper rio Tocantins basin, BarroAlto, Goiás State, Brazil. Scale bar = 1 mm.
Fig. 4.
Type locality of
Microglanis maculatus
(red circle), ribeirão Pouso Alegre, tributary of rio dos Patos, upper rio Tocantins basin, Barro Alto, Goiás State, Brazil.
Etymology.
The specific epithet
maculatus
means spotted, an adjective from the Latin
macula
, in reference to the dark brown spots on the trunk.
Multivariate morphometrics analysis.
The first principal component retained 76.5% of the variance of morphometric
variables, and all eigenvalues showed positive signs, which allows to interpret it as the representative of size (larger specimens to the right of graph). The second component retained 7.8% of the variance and on this axis there was discrimination between species (
Fig. 6
).
Microglanis maculatus
differed from
M. robustus
in this analysis by higher values of anal-fin base length, interorbital width and eye diameter (positive highest values), and smaller values of pectoral fin spine length, dorsal fin spine length and adipose fin base length (negative highest values;
Table 2
). The discriminatory nature of some characters coincided with its proportions with SL or HL (
Table 1
).
Discussion.
The color pattern of
M. maculatus
was the first character to draw attention to a new species, and this study evidenced its uniqueness among congeners. Coloration pattern in
Microglanis
is quite variable and complex, resulting in a large number of configurations among the species of the genus. Even so, it is possible to observe in the literature that the color pattern proved to be useful for species identification. For example, among the species of the Araguaia-Tocantins basin,
M. robustus
has a dark and thin stripe at the base of the caudal-fin rays, at middle of caudal fin and at middle of dorsal fin (Ruiz & Shibatta, 2010), and
M. xylographicus
has dark brown body with light streaks on the flanks (Ruiz & Shibatta, 2011).
Microglanis oliveirai
is the only species that does not have a unique distinctive mark (Ruiz & Shibatta, 2011), although this condition helps to distinguish it from the other species of the basin.
Fig. 5.
Ribeirão Pouso Alegre, tributary of rio dos Patos, Barro Alto, Goiás State, type locality of
Microglanis maculatus
.
Specimens collected just in the mouth of stream (brightest area).
The shape of hooks on the anterior margin of the pectoralfin spine have been used as well to distinguish
Microglanis
species (
e
.
g
., in
M. zonatus
all hooks on anterior margin are retrorse; Eigenmann & Allen, 1942). This character however, should be used with caution in
M
.
maculatus
due to ontogenetic variation on the hook morphology. Small specimens of
M. maculatus
may present only retrorse hooks while large specimens have antrorse and retrorse hooks. The analysis of hook morphology on the anterior margin of the pectoral spine on large and small specimens of
M. maculatus
, evidenced that all hooks are retrorse until the ninth hook (counting from the base of spine), and beyond the ninth hook, antrorse hooks become more numerous. The single hooks, as present in
M. maculatus
, is a very common character in
Microglanis
, but forked hooks is not related to the ontogenetic development, and it seems to be characteristic of
M. robustus
.
Table 2.
Morphometric data loadings, eigenvalues and percentages relating to the first (PC1) and second (sheared PC2) eigenvectors of Principal Components obtained from the analysis of combined samples of
Microglanis maculatus
(n = 4) and
M. robustus
(n= 9).
| PC1 |
Sheared PC2 |
| Standard length |
0.239280 |
-0.038350 |
| Head length |
0.278703 |
-0.103961 |
| Head depth |
0.171251 |
-0.112866 |
| Interorbital width |
0.242410 |
-0.242650 |
| Orbital diameter |
0.209448 |
-0.213312 |
| Snout length |
0.313553 |
-0.113407 |
| Mouth width |
0.205055 |
-0.014658 |
| Maxillary barbel length |
0.200505 |
-0.024377 |
| Dorsal-fin spine length |
0.084876 |
0.489930 |
| Pectoral-fin spine length |
0.056110 |
0.519076 |
| Predorsal length |
0.220810 |
0.002021 |
| Prepelvic length |
0.231539 |
0.028533 |
| Pelvic to anal length |
0.249099 |
0.016903 |
| Caudal peduncle depth |
0.219993 |
-0.081367 |
| Body width |
0.220662 |
0.017422 |
| Body depth at dorsal fin |
0.140803 |
0.097062 |
| Dorsal-fin base length |
0.294262 |
-0.188299 |
| Adipose-fin base length |
0.323613 |
0.326230 |
| Anal-fin base length |
0.263716 |
-0.420258 |
| Eigenvalue |
0,111 1 |
0,011 |
| Percents of total variance |
76.5% |
7.83% |
Fig. 6.
Principal component analysis (PC1
vs
. sheared PC2) of combined samples of
Microglanis maculatus
(black diamonds; n = 4) and
M. robustus
(light squares; n = 9).
Noteworthy is the restricted geographic distribution of
M. maculatus
. Some
Microglanis
species apparently has a wide geographic distribution (
e.g.
,
M. cottoides
in coastal rivers of Southern and South
Brazil
; Menezes
et al.
, 2007), which may indicate large dispersal ability of these species. However, despite the sampling efforts in different locations of the upper rio
Tocantins
basin,
M. maculatus
was found only in the rio dos Patos basin, in Barro Alto. The species was not found in another 20 sampling points on different streams of the rio dos Patos and rio
Maranhão
basins (Claro- García & Shibatta, 2013), and neither on the ichthyological survey conducted in the Serra da Mesa (
Bartolette
et al
., 2012
), slightly on North of the
type
locality. The small number of specimens collected and the apparent restricted distribution of
M. maculatus
in the rio dos Patos basin, indicate that this species is rare.
Comparative material.
Microglanis carlae
:
Paraguay
.
MHNHP 3667
,
holotype
,
34.1 mm
SL,
rio Salado
, río
Paraguay
basin,
26°39’S
58°05’W
;
MZUSP 98255
,
paratypes
, 5,
23.4-29.1 mm
SL.
Microglanis cibelae
:
Brazil
.
Rio Grande do Sul
.
MCP
19822
,
paratypes
, 3,
34.9-48.7 mm
SL, arroio do
Ouro
, tributary of
rio Maquiné
,
29º34’00"S
50º16’00"W
;
MCP
21190
,
9
,
24.6-42.4 mm
SL,
Osório
,
rio Tramandaí
basin,
29º57’57"S
50º13’45"W
.
Microglanis cottoides
:
Brazil
.
Rio Grande do Sul
.
MCP
10826
,
5
,
38.2-49.5 mm
SL,
rio Sanga
das
Águas Frias
, rio
Uruguai
basin;
MCP
17706
,
4
,
25.1-45.3mm
SL, arroio
Quarizinho
, tributary of
rio Buricá
, rio
Uruguai
basin,
27º47’00’’S
54º 14’00"W
.
Microglanis eurystoma
:
Brazil
.
Santa Catarina
.
MCP
13405
,
holotype
,
77.6 mm
SL, rio
Uruguai
,
27º18’00"S
52º20’00"W
.
Brazil
.
Rio Grande do Sul
;
MCP
12698
,
10 paratypes
,
26.3-41.1 mm
SL, arroio do
Passo Alto
, rio
Uruguai
basin,
28º11’00"S
55º16’00"W
.
Microglanis garavelloi
:
Brazil
.
Paraná
,
MZUSP 88006
,
holotype
,
31.7 mm
SL, ribeirão
Taquari
, upper rio
Paraná
basin
;
MZUSP 1732
,
paratypes
, 2,
23.7-30.8 mm
SL, ribeirão
Taquari
,
23º12’24"S
50º56’50"W
;
MCP 1678
,
4 paratypes
(3c&s),
24.6-27.9 mm
SL, ribeirão
Taquari.
Microglanis iheringi
:
Venezuela
.
Aragua
.
USNM 121985
,
1 paratype
,
31.3 mm
SL,
río Turmero
,
Portuguesa
.
CAS
64403
,
3
,
27.4
-41.0 mm SL,
río Orinoco.
Microglanis leptostriatus
:
Brazil
.
Minas Gerais
.
MZUSP 47456
,
2 paratypes
,
28.4-28.7 mm
SL,
rio Verde
,
rio São Francisco
basin
;
MZUEL 3733
,
6 paratypes
,
19.3-27.4 mm
SL,
rio Cruz
,
rio São Francisco
basin.
Microglanis malabarbai
:
Brazil
.
Rio Grande do Sul
.
MCP
37252
,
1
,
47.7 mm
SL, arroio
Alexandrino
rio Ijuí
basin,
28º10’25"S
54º48’05"W
;
MCP
37187
,
1
,
50.1 mm
SL, arroio
das Pedras
rio Ijuí
basin,
28º12’07"S
54º04’30"W
.
Microglanis nigripinnis
:
Brazil
.
Rio de Janeiro
.
MZUSP 80223
,
1
,
47.2 mm
SL, tributary of
rio São João
,
Eastern
basin
;
MZUSP 80229
,
2
,
38.3-43.5 mm
SL, tributary of
rio São João.
Microglanis parahybae
:
Brazil
.
Rio de Janeiro
.
MNRJ 15989
,
5
,
30.3-34.2 mm
SL,
rio Dois Rios
, rio
Paraíba
do
Sul
basin
;
MNRJ 16047
,
5
,
28.6-38.9 mm
SL,
rio Muriaé
, rio
Paraíba
do
Sul
basin.
Microglanis pataxo
:
Brazil
.
Bahia
.
MZUSP 54516
,
10
,
24.9-31.4 mm
SL,
rio Mucuri
,
East
coast basin.
Microglanis pellopterygius
:
Ecuador
.
Napo
.
ANSP 130437
,
holotype
,
68.1 mm
SL,
rio Aguarico
,
00
o
06’N
76
o
51’W
;
MEPN 88.4
-
12
,
2
,
22.4-23.1 mm
SL, tributary of the
río Aguarico.
Microglanis poecilus
:
Guiana
.
Kurupukari.
ROM
60738
,
1
,
22.5 mm
SL, unknown stream of río
Essequibo
,
4
o
46’20"S
58
o
45’W
;
ROM
62390
,
1
,
17.1 mm
SL,
Shimiri Stream
,
Yawiri
, río
Essequibo
basin,
4
o
42’13"S
58
o
42’43"W
;
ROM
62391
,
1
,
17.1 mm
SL, río
Essequibo
,
4
o
48’22"S
58
o
46’14"W
.
Brazil
.
Amazonas.
INPA 28575
,
3
,
18.6-20.6 mm
SL,
rio Aripuanã
,
rio Madeira
basin
.
Brazil
.
Roraima
.
INPA 28576
,
3
,
19.8-20.4 mm
SL, igarapé
Ano Bom
,
rio Branco
basin
;
INPA 8052
,
3
,
24.8-26.2 mm
SL, igarapé
Maracá
,
rio Branco
basin,
Pará.
INPA 6828
,
3
,
19.2-25.8 mm
SL,
rio Jamanxin
,
rio Tapajós
basin,
5
o
27’11"S
55
o
52’40"W
.
Microglanis robustus
:
Brazil
.
Pará.
INPA 8053
,
holotype
,
20.3 mm
SL, lower rio
Tocantins
,
rio Tocantins-Araguaia
basin
;
INPA 32885
,
11 paratypes
(2 c&s),
18.4-23.3 mm
SL, same data as holotype
;
INPA 7943
,
2 paratypes
, 20.0-
22.2 mm
SL
;
INPA 7957
,
3 paratypes
,
19.2-21.7 mm
SL,
Jatobal
, lower rio
Tocantins
.
Microglanis secundus
:
Suriname
.
Brokopondo
.
MHNG 2621.038
,
6
,
18.9-27.1 mm
SL,
rio Mindrineti
.
Brazil
.
Pará.
INPA 5730
,
7
,
18.5-31.1 mm
SL,
rio Trombetas
,
rio Amazonas
basin
;
INPA 7950
,
3
(2 c&s),
24.4-28.1 mm
SL
rio Trombetas
,
rio Amazonas
basin.
Microglanis variegatus
:
Ecuador
.
Vinces.
USNM 083653
,
1 paratype
,
29.1 mm
SL, pools in forests near
Vinces.
Los rios
.
MHNG 298.033
,
2
,
25.2-27.7 mm
SL,
río Palengue
;
MHNG 1232.11
,
2
,
23.6-26.2 mm
SL,
Hazienda Clementina
.