Hypostomus Lacepède 1808
Hypostomus ammophilus, photo by K.S. Cummings
Hypostomus plecostomus, photo by K.S. Cummings
Hypostomus macushi, photo by J.W. Armbruster
Hypostomus roseopunctatus, Photo by K.S. Cummings
Hypostomus squalinus, photo by M.H. Sabaj
Hypostomus spinosissimus, Photo by K.S. Cummings
Plecostomus Gronovius 1754
Cochliodon Heckel 1854
Cheiridodus Eigenmann 1922
Isorineloricaria Isbrücker 1980
Aphanotorulus Isbrücker & Nijssen 1982
Squaliforma Isbrücker & Michels 2001
Watawata Isbrücker & Michels 2001
SPECIES (types examined)
Hypostomus is not diagnosed by any unique
characteristics. Characteristics considered synapomorphic for the group are:
a hatchet-shaped opercle, the anterior process of the pterotic-supracleithrum
passing halfway through the orbit, and a pointed cleithral process. In addition,
in several trees, the bulk of Hypostomus (except H. commersoni Valenciennes
and H. boulengeri [Eigenmann and Kennedy]) are supported by a pointed
transverse process of the Weberian apparatus that is fused to the pterotic-supracleithrum.
Small to large loricariids that defy a unifying description. Color pattern varies from having a white ground color and black spots, to brown and spotted, to black with red, gold, or white spots. Abdomen also varies in color from white to black and may be spotted or not. Abdomen ranges from naked to completely plated (usually with plates). Caudal fin forked with the lower lobe longer than upper. Two or three predorsal plates. Five rows of plates on caudal peduncle (except H. dlouhyi Weber which has three). Hypostomus emarginatus group, H. cordovae(Günther), and H. spiniger (Hensel) with elongated bodies with H. spinossimus most elongate with a very long, whiplike tail that is circular in cross-section in adults. Most other species have stout bodies. Lateral plates keeled or not. Cheek plates evertible to approximately a 30° angle.
SEXUAL DIMORPHISM.—In most, males develop
hypertrophied odontodes on the leading edge of the pectoral-fin spine and
the distal tip of the spine may become swollen. Additionally, in members
of the H. emarginatus clade, males develop hypertrophied odontodes
on the body during the breeding season (Armbruster & Page, 1996); these
odontodes are normally best developed on the posterolateral plates, the caudal-fin
spines, and the adipose-fin spine. In addition, H. spinosissimus develops
hypertrophied odontodes over the entire lateral and dorsal surface of the
body including the cheeks (the cheek plates are not highly evertible). Nuptial
males of H. ammophilus and H. unicolor develop elongate, unicuspid teeth (Armbruster & Page,
1996). Nuptial males of some species of the H. cochliodon group develop
wider, more widely spaced odontodes on the lateral plates (the odontodes
are not longer in nuptial males, VIEW-B).
Hypostomus is most similar to the Hemiancistrus
annectens group. Externally, Hypostomus is very difficult to separate
from the Hemiancistrus annectens group differing mainly in the lack
of highly evertible cheek plates with hypertrophied odontodes in adults (cheek
odontodes are present in H. spinosissimus, but they are present only
in nuptial males, are not highly evertible, and are accompanied by a lengthening
of nearly all of the odontodes on the body) and by usually having only one
(occasionally two) row of plates between the suprapreopercle and the exposed
opercle (vs. three, occasionally two). The only species of Hypostomus
sympatric or potentially sympatric with the Hemiancistrus annectens group
are members of the the H. cochliodon group which have wide, spoon-shaped teeth (vs. viliform teeth,
VIEW A vs B and C) and H. spinosissimus,
H. tenuicauda and H. villarsi which have a white or tan ground
color (versus dark brown) and are elongate (vs. short); thus, most Hypostomus
can be separated from the Hemiancistrus annectens group by having
a distribution east of the Andes (vs. west). Hypostomus can be distinguished
from most Pterygoplichthys by the same characters as for the Hemiancistrus
annectens group with the addition of having only 7 (vs. 9-14) dorsal-fin
rays; from all but Pseudorinelepis of the the Rhinelepis group
by having a single, medium-sized plate posterior to the pterotic-supracleithrum
(vs. many small plates); from all but Pogonopoma of the the Rhinelepis
group by usually having an adipose fin (adipose fin is also missing
in C. levis); from all the Rhinelepis group by having one unbranched
and four branched anal-fin rays (vs. one unbranched and five branched rays)
and a dorsal flap of the iris making the eye appear bilobed (vs. iris round,
without flap); and from most of the Ancistrini by a lack of highly evertible
cheek plates with hypertrophied odontodes (Spectracanthicus lacks evertible
cheek plates with hypertrophied odontodes and can be distinguished by having
the dorsal-fin membrane attached to the preadipose plate; some Pseudancistrus
lack evertible cheek plates and can be distinguished by a combination of
the presence of hypertrophied odontodes along the snout and on the cheek
and no plates on the abdomen).
Hypostomus is essentially ubiquitous across
their range. Most species are lowland, sluggish stream- and lake-dwellers
usually found associated with submerged wood; however, many species may be
found among rocks in piedmont to mountain streams with moderate to swift
flow. Members of Hypostomus may be found over substrates ranging from
mud and detritus, to gravel and cobble and boulders, to sand. Many spawn
in hollows dug into mud banks or within hollow logs (Burgess; 1989).
Throughout most of the range of loricariids except
for drainages west of the Río Atrato.
Armbruster, J.W. 1997. Phylogenetic relationships of the sucker-mouth armored catfishes (Loricariidae) with particular emphasis on the Ancistrinae, Hypostominae, and Neoplecostominae. Unpubl. Ph.D. dissertation. University of Illinois, Urbana-Champaign. 409 pp.
Armbruster, J. W. 2004. Phylogenetic relationships of the suckermouth armoured catfishes (Loricariidae) with emphasis on the Hypostominae and the Ancistrinae. Zoological Journal of the Linnean Society 141:1-80.
Armbruster, J.W. and L.M. Page. 1996. Redescription of Aphanotorulus (Teleostei: Loricariidae) with description of one new species, A. ammophilus, from the Río Orinoco basin. Copeia 1996:379-389.
Burgess, W.E., 1989. An atlas of freshwater and marine catfishes, a preliminary
survey of the Siluriformes. T.F.H. Publications, Neptune City, New Jersey.