Hypostomini

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

TAXA LIST


  • With the inclusion of Aphanotorulus, Cochliodon, Isorineloricaria, Squaliforma, and Watawata, Hypostomus is, with 138 currently valid species, by far the largest genus of loricariids. The genus was monophyletic in all analyses, but the phylogenies have provided no good methods of splitting the genus up further. Certainly Cochliodon and Watawata are synonyms of Hypostomus, and Aphanotorulus, Squaliforma, and Isorineloricaria form a monophyletic group. At most, it might be necessary to recognize a separate genus for Aphanotorulus, Isorineloricaria and Squaliforma together, but there is currently no good evidence to support this and certainly no evidence at all to recognize any other taxa. The information below is based on Armbruster (1997).


    GENUS SYNONYMY

    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)



  • DIAGNOSIS

    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.



    DESCRIPTION

    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).



    COMPARISONS

    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).



    ECOLOGY

    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).



    DISTRIBUTION

    Throughout most of the range of loricariids except for drainages west of the Río Atrato.



    LITERATURE CITED

    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. 784 pp.



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