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| Fig. 4. Lateral views of life specimens of: a, Hypostomus formosae, MACN Ict 9722, 82.8 mm SL; Argentina: Formosa
Province: Bañado La Estrella; b, H. boulengeri, MACN Ict 9723, 57.8 mm SL; Argentina: Paraguay River:
Formosa City, right side, reverse.
(Photographs by Yamila P. Cardoso). pfeil-verlag.de
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Hypostomus formosae, new species, is described from the Paraguay River Basin and H. boulengeri is redescribed. Morphological and molecular analyses show that these two species belong to the ‘H. plecostomus species group’. Hypostomus formosae can be distinguished from H. boulengeri by having the tip of the snout completely covered with small plates (vs. naked snout tip) and fewer premaxillary and dentary teeth (13-28 vs. 16-32, and 10-25 vs. 15-31, respectively). The molecular phylogenetic analysis indicates that the sister species of H. formosae is H. plecostomus from the Amazon and the Guyanas, highlighting past inter-basin ichthyofauna exchanges.
Hypostomus formosae, new species
Diagnosis. Hypostomus formosae is distinguished
from the species of the Hypostomus cochliodon
group by having bicuspid teeth (vs. spoon-shaped
unicuspid teeth). The color pattern of H. formosae
(dark roundish dots on a lighter background)
differentiates this species from species that have
dorsum dark grey with numerous creamy dots.
Hypostomus formosae is distinguished from the
rest of its congeners by the combination of high
values for abdominal length (19.1-30.3 % SL),
pectoral-fin spine length (30.4-35.5 % SL), head depth (54-90.5 % HL), caudal-peduncle depth
(9.7-12.5 % SL), cleithral width (31.1-39.3 % SL)
and dorsal-fin spine length (26.8-40.5 % SL), and
low values for caudal-peduncle length (28.5-
34.8 % SL), inter-dorsal length (12.0-20.1 % SL),
median plate series (25-26), number of plates
between dorsal and adipose fin (6-8), number of
plates between anal and caudal fin (11-14). Also,
H. formosae can be distinguished from H. piratatu
by the shape of teeth (short vs. long crown) and
from H. boulengeri by having the tip of the snout
completely covered with small plates (vs. naked
snout tip) (Fig. 3) and fewer premaxillary and
dentary teeth (13-28 vs. 16-32, and 10-25 vs.
15-31, respectively).
Distribution. Hypostomus formosae is known
from the Paraguay River Basin in Argentina and
Paraguay.
Ecological notes. Habitat description based on
collecting localities of MACN Ict 9720, 9721, 9722
and CFA IC-11972. The specimens were obtained
recently at three sites in the Paraguay River
Basin: La Estrella, Saladillo Stream and Riacho
Porteño, Argentina. The bottom of these streams
was mainly composed of sandstone boulders
with patches of sand and pebbles. Hypostomus
formosae was found in well oxygenated waters
(5.9-6.6 mg·l
-1
) with moderate current. Water
turbidity was 51.1-98.1 N.T.U., conductivity
67-660 µS· cm-1
, and the pH 6.4-7.3. We do not
have habitat information for the others specimens.
Etymology. The species is named after the Formosa
Province, Argentina. A noun in genitive.
Hypostomus boulengeri
(Eigenmann & Kennedy, 1903)
(Fig. 5)
Plecostomus boulengeri Eigenmann & Kennedy,
1903.
Plecostomus guacari (non La Cepède, 1803): Regan,
1904.
Plecostomus plecostomus (non Linnaeus, 1758):
Eigenmann et al., 1907.
Diagnosis. Hypostomus boulengeri is distinguished from species of the Hypostomus cochliodon species group by having bicuspid teeth (vs. unicuspid spoon-shaped teeth). The color pattern of H. boulengeri (dark roundish dots on a lighter background) differenciates this species from species that have dorsum dark grey/brown covered by numerous rounded creamy dots. Hypostomus boulengeri is distinguished from the rest of its congeners, with the exception of H. piratatu and H. formosae, by the combination of high values for mandibulary ramus length (9-16 % HL), orbital diameter (13-20 % HL), upper caudal-fin ray length (24.9-42.8 % SL) and lower values for caudal-fin ray length (26.1-46.4 % SL), and by having 25-26 plates in the median plates series. Hypostomus boulengeri can be distinguished from H. piratatu by the shape of teeth (short vs. long crown) and from H. formosae by having the snout tip with a naked zone (vs. completely covered with minute plates) (Fig. 3) and more premaxillar and dentary teeth (16-33 vs. 13-28 and 15-33 vs. 10-25, respectively).
Distribution. Hypostomus boulengeri is known
from the Paraguay River Basin in Argentina,
Brazil and Paraguay.
Ecological notes. Based on the collecting locality
of sample MACN Ict 9723. These specimens
were found in the margin of the large Paraguay
River. The bottom of the river is made of sand and
pebbles. The surface of the water was covered by
vegetation. The specimens were found in well oxygenated
waters (4.97 mg·l
-1
) with slow current.
Water turbidity was 193 N.T.U. Conductivity was
163.3 µS· cm-1
. The pH was 6.9. We do not have
ecological information for the others specimens.
Yamila P. Cardoso, Florencia Brancolini, Ariel Paracampo, Marta Lizarralde, Raphael Covain and Juan I. Montoya-Burgos. 2016. Hypostomus formosae, A New Catfish Species from the Paraguay River Basin with Redescription of H. boulengeri (Siluriformes: Loricariidae). Ichthyol. Explor. Freshwaters. 27(1); 9-23. http://www.pfeil-verlag.de/04biol/pdf/ief27_1_02.pdf
