Adriana E. Aquino

Postotic laterosensory canal and pterotic branch homology in catfishes

Morphology of the postotic laterosensory canal was surveyed across loricarioid and outgroup catfishes in order to resolve conflicting statements regarding homology and phylogenetic significance of intrinsic character variation. A pterotic branch is widespread among catfishes and has been identified as a synapomorphy for siluriforms, but its presence in loricarioid catfishes has been disputed. In contrast to previous statements that absence of a pterotic branch is synapomorphic for loricarioids, we confirm the presence of a pterotic branch in Nematogenys inermis and other trichomycterids, callichthyids, and loricariids. The pterotic branch is secondarily absent in scoloplacids and astroblepids. We present criteria for establishing homology of the pterotic branch and review character state optimization schemes on the currently accepted phylogeny. The postotic region of loricariids is further specialized in having an expanded swimbladder capsule that incorporates the trunk lateral line canal and has a lateral opening covered by a greatly expanded pterotic complex. The trunk lateral line enters the swimbladder capsule mesial to the pterotic lateral wall and passes anteromedially as a fleshy tube before forming the postotic canal in the pterotic, a morphology reported previously for a single loricariid representative. Variation in the relative extent and topographic position of postotic canal branches and other morphologies is diagnostic of certain loricariid taxa, suggesting a rich character complex of potential utility in phylogeny reconstruction. J. Morphol. 246:212–227, 2000.

The Temporal Region of the Cranium of Loricarioid Catfishes (Teleostei: Siluriformes): Morphological Diversity and Phylogenetic Significance

Abstract The morphology of the temporal region of the cranium of the monophyletic loricarioid catfishes was examined in representatives of the families Trichomycteridae, Callichthyidae, Scoloplacidae, Astroblepidae, and Loricariidae, and compared to non-loricarioid outgroup taxa. The results indicate the presence of derived specializations in the morphology of the pterotic bone, swimbladder capsule, lateral-line nerve, and associated structures which have not been previously recognized. Astroblepids, callichthyids, loricariids and scoloplacids differ from trichomycterids and non-loricarioid catfishes in having a reduced number of bones in the temporal region. Loricariids share with astroblepids and some trichomycterids the presence of direct contact between the trunk lateral-line canal and swimbladder capsule chamber; however, only loricariids have the lateral-line canal in direct contact with the swimbladder membrane, resulting in a laterophysic connection in addition to the otophysic connection between inner ear and swimbladder characteristic of otophysan fishes. Derived trichomycterids share with the outgroups Amphiliidae, Plotosidae and Sisoridae a cranial exit of the posterior lateral-line nerve separate from that of the vagus nerve, whereas both nerves exit the cranium via a common foramen in other loricarioids and outgroup catfishes. Callichthyids share with scoloplacids and loricariids a lateral-line nerve traversing the swimbladder capsule. Loricariids are further modified in having a compound pterotic bone that is double-layered and bears the postotic canal on the ventral layer. The dorsal layer is posteriorly expanded to enclose the lateral opening of the swimbladder capsule and an expanded capsule chamber. Based on the previously well-established scheme of interrelationships among loricarioid families, we infer that much of the variation in temporal cranial morphology over the course of loricarioid evolution has involved independent convergence toward increased functional association of primitively separate sensory structures of the octavolateralis system.

A New Species of Hisonotus (Siluriformes, Loricariidae) of the Upper Río Uruguay Basin

Abstract A new species of the hypoptopomatine genus Hisonotus (Loricariidae) is described from a small tributary of the upper río Uruguay basin near the border between Uruguay and Brazil. The new species can be distinguished from all other congeners by the following combination of characters: (1) presence of serrae along distal two thirds of posterior margin of pectoral-fin spine (versus serrae absent, posterior margin smooth); (2) odontodes along anterior margin of snout biserially arranged, dorsad and ventrad series separated by narrow odontode-free area covered by pad of soft tissue; (3) caudal peduncle short (27–34% SL, versus > 34% SL) and deep (13–15 % SL, versus < 13% SL); (4) eye large (15–19% HL, versus < 13% HL); and (5) caudal-fin pigmentation, when well defined, dark brown with a pair of whitish blotches on upper and lower lobes. The significance of the distribution of the new species is discussed relative to the degree of endemism of other fish groups in the Uruguay basin.

Systematics of the Genus Hypoptopoma Günther, 1868 (Siluriformes, Loricariidae)

Abstract The systematics of Hypoptopoma Günther (1868a) is revised based on comprehensive evaluation of specimen collections and a phylogenetic analysis of the species. The genus Hypoptopoma comprises a distinctive assemblage of loricariid catfishes distributed in the lowland drainages of tropical, subtropical, and temperate latitudes of South America to the east of the Andes. Hypoptopoma is uniquely diagnosed among genera of the Loricariidae on the basis of the presence of a laterally expanded nuchal plate. Members of the genus can be further distinguished from all other loricariids, except the hypoptopomatin genus Oxyropsis, by the depressed head with eyes placed ventrolateral and visible from below. Hypoptopoma is further distinguished from all other Hypoptopomatini, including Oxyropsis, by the caudal peduncle posterior to the base of the anal fin ovoid in cross section and deeper in the dorsoventral axis. All species of Hypoptopoma, except H. spectabile, can be further distinguished among loricariids by the presence in adult stages of a column of variably enlarged and flattened odontodes positioned along the posterior margin of the trunk plates. Individuals of several Hypoptopoma species attain the largest body size for the subfamily Hypoptopomatinae, with standard length reaching 105 mm. Species of Hypoptopoma typically occur in streams of slow to moderate current and muddy to sandy bottom with marginal emergent vegetation. Based on verified specimen records, the species is distributed in the Río Amazonas basin, including the Ucayali, Madeira, and Tapajos rivers, as well as in the rivers east to the Ilha Marajo drainage (Para, Brazil), in the Tocantins and smaller coastal river drainages in northeastern Brazil (Mearim), the upper Río Orinoco basin, the Essequibo and Nickerie river basins of the Guiana Shield, and in the ríos Paraguay and lower Paraná. There are no records of Hypoptopoma in the Río Uruguay, the Atlantic coastal drainages of Uruguay and Brazil south of Rio Mearim (Maranão), the upper Paraná, and Rio São Francisco systems. Fifteen species are recognized in Hypoptopoma, seven of which are newly described herein. Phylogenetic analysis of Hypoptopoma species, based on analysis of 26 characters drawn from aspects of external morphology and internal osteology, recovered a well-supported but incompletely resolved nested set of clade relationships that suggests a widespread ancestral distribution for the group in central Amazonia, plus at least four instances of divergence of a species having a peripheral distribution from an Amazonian sister group. Relationships at the basal node were unresolved. There was insufficient evidence to resolve the relationships among H. baileyi, n. sp., of the Madeira river basin, an unresolved clade comprised of H. guianense Boesemann, 1974, of the Essequibo and Nickerie basins in Guyana and Surinam; H. psilogaster Fowler, 1915, of the upper Amazon basin in Brazil and Peru; and H. thoracatum Günther, 1868a, of the upper and middle Amazon basin; and a well-supported clade that includes all other Hypoptopoma species. The latter clade was supported by four synapomorphies and includes H. brevirostratum, n. sp., of the upper Amazon basin in Brazil and Peru, H. muzuspi, n. sp., of the Tocantins basin, and a more restricted clade supported by six character-state changes comprising the remainder of the subfamily. Two species, H. spectabile (Eigenmann, 1914) of the upland Amazon and upper Orinoco river basins of Venezuela, Colombia, Ecuador, and Peru and H. sternoptychum (Schaefer, 1996a) of the lowland reaches of the Amazon river, formerly placed in the genus Nannoptopoma Schaefer, 1996, represent a clade most closely related to a nested subset of Hypoptopoma species. These former Nannoptopoma species are reassigned to Hypoptopoma, thus rendering the former generic name a subjective junior synonym of Hypoptopoma. Hypoptopoma bianale, n. sp., of the upper Amazon River basin in Brazil and Peru represents the sister group to a largely unresolved clade comprised of H. inexspectatum (Holmberg, 1893a) of the Paraguay-Paraná basin, H. steindachneri Boulenger, 1895, of the upper Amazon basin in Brazil and Peru, H. gulare Cope, 1878, of the upper Amazon basin, H. machadoi, n. sp., of the Orinoco basin, and a clade comprised of H. elongatum, n. sp., of the lower Tapajos and lower Trombetas rivers plus H. incognitum, n. sp., of the middle Amazon basin, Tocantins, and Mearim rivers. A key to the species of Hypoptopoma is provided.

Revision of Oxyropsis Eigenmann and Eigenmann, 1889(Siluriformes, Loricariidae)

Abstract The armored catfish genus Oxyropsis is diagnosed as a monophyletic assemblage of three species of the family Loricariidae on the basis of presence of a single row of enlarged odontodes along the trunk midline lying adjacent, and immediately dorsal to, the lateral line canal. Oxyropsis is here resurrected from synonymy with Hypoptopoma Günther (1868) and three species, distributed in the middle and upper Amazon, Negro, and Orinoco basins of South America, are diagnosed and redescribed. The type species, Oxyropsis wrightiana Eigenmann and Eigenmann (1889), occurs in the upper Amazon and lower Ucayali River basins and is diagnosed among congeners by the presence of seven ultimate median series trunk plates, which are progressively smaller and narrower than the immediately preceding plates, and by pectoral spine serrae either extremely reduced in size (height less than one-sixth of the spine width) or absent. Oxyropsis carinata (Steindachner, 1879) occurs in the middle and upper Amazon River basin and is diagnosed by the presence of three or four ultimate plates of the median series distinctly narrower than preceding plates, pectoral spine serrae well developed both in size (tooth height approximately one-fifth of the spine width) and extent along the spine shaft and by greater numbers of teeth. Oxyropsis acutirostra Ribeiro (1951) occurs in the Negro and upper Orinoco basins and is diagnosed by the presence of a truncated median plate series, plates not extending to the caudal fin base and fewer teeth. Its holotype is presumed lost. Among Oxyropsis species, caudal peduncle depression covaries with standard length and degree of median plate series reduction. This observation, coupled with intrinsic differences in the association of related features among loricariids, further supports the hypothesis that trunk depression and caudal peduncle elongation have coevolved multiple times within the Loricariidae.

Depicting the tree of life in museums: guiding principles from psychological research

The Tree of Life is revolutionizing our understanding of life on Earth, and, accordingly, evolutionary trees are increasingly important parts of exhibits on biodiversity and evolution. The authors argue that in using these trees to effectively communicate evolutionary principles, museums need to take into account research results from cognitive, developmental, and educational psychology while maintaining a focus on visitor engagement and enjoyment. Six guiding principles for depicting evolutionary trees in museum exhibits distilled from this research literature were used to evaluate five current or recent museum trees. One of the trees was then redesigned in light of the research while preserving the exhibits original learning goals. By attending both to traditional factors that influence museum exhibit design and to psychological research on how people understand diagrams in general and Tree of Life graphics in particular, museums can play a key role in fostering 21st century scientific literacy.

Oxyropsis ephippia , a New Hypoptopomatine Catfish (Siluriformes: Loricariidae) from Guyana

Oxyropsis ephippia, a new species of loricariid catfish in the subfamily Hypoptopomatinae, is described from the Essequibo and Branco basins, Guyana. Based on the presence of a keel-like row of relatively enlarged odontodes on trunk median plates immediately above the lateral line canal, the new species is assigned to the genus Oxyropsis Eigenmann & Eigenmann 1889. It can be distinguished from its congeners by having the keel-like row on each median plate dominated by a single odontode (one closest to the posterior margin of the plate) conspicuously larger than preceding ones, and by having the sides of the trunk below the median series (approximately between median plates 7 to 12) shielded only by plates of the midventral series, with the exclusion of plates from the ventral series. The report of O. ephippia from the Essequibo is the first record of the genus in a river system that drains the north-central portion of the Guiana Shield into the Atlantic Ocean.