Miniaturization in Otothyris Myers, 1927 (Loricariidae: Hypoptopomatinae)

Lizards as models to explore the ecological and neuroanatomical correlates of miniaturization

Extreme body size reductions bring about unorthodox anatomical arrangements and novel ways in which animals interact with the environment. Drawing from studies of vertebrates and invertebrates, we provide a theoretical framework for miniaturization to inform hypotheses using lizards as a study system. Through this approach, we demonstrate the repeated evolution of miniaturization across 11 families and a tendency for miniaturized species to occupy terrestrial microhabitats, possibly driven by physiological constraints. Differences in gross brain morphology between two gecko species demonstrate a proportionally larger telencephalon and smaller olfactory bulbs in the miniaturized species, though more data are needed to generalize this trend. Our study brings into light the potential contributions of miniaturized lizards to explain patterns of body size evolution and its impact on ecology and neuroanatomy. In addition, our findings reveal the need to study the natural history of miniaturized species, particularly in relation to their sensory and physiological ecology.

A new species of Parotocinclus with reduced adipose fin (Loricariidae: Hypoptopomatinae), from the rio Jacuípe basin, Bahia State, Brazil

ABSTRACT A new species of Parotocinclus, apparently endemic to the rio Jacuípe basin, Bahia State, Brazil, is described. The new species is distinguished from congeners, except P. bidentatus, P. cabessadecuia, P. dani, P. halbothi, P. muriaensis, P. pentakelis, P. seridoensis, and P. spilurus, by the presence of a reduced adipose fin. The new species differs from the aforementioned species by the absence of unicuspid accessory teeth, abdomen with broad naked areas between lateral and medial patches of plates, and snout tip completely covered by plates and odontodes. The adipose fin of the new species is restrict solely to the adipose-fin spine, lacking the adipose-fin membrane, a reduction pattern previously described to P. halbothi, a congener from rivers of the Amazonas and Marowijne basins.

Comparative gross encephalon morphology in Callichthyidae (Teleostei: Ostariophysi: Siluriformes)

ABSTRACT Callichthyidae comprises the subfamilies Callichthyinae and Corydoradinae, both of which are morphologically distinct and monophyletic. Although there is consensus regarding the monophyly of the family, the relationships of about 80% of its species, currently included in the genus Corydoras, remain poorly known. Despite the vast amount of osteological information for Teleostei, knowledge regarding the phylogenetic implications of encephalon anatomy is sparse and represents a poorly explored source of potential characters. The present study aims to describe the encephalon morphology in members of the Callichthyidae in order to propose new characters that may help address phylogenetic questions regarding this group. In addition to representatives of Callichthyidae, specimens belonging to the Nematogenyidae, Trichomycteridae, Scoloplacidae, Astroblepidae and Loricariidae were dissected for comparative purposes. Head dissection revealed information on the structure of the medulla spinalis, rhombencephalon, mesencephalon, diencephalon and telencephalon. The conditions observed on the encephalons examined suggest that representatives of Callichthyidae have great taste perception and processing, while Corydoradinae stand out for visual acuity and Callichthyinae for mechanoreception processing subunits. Our results also indicate that the encephalon has important features for systematic studies of the family bringing greater resolution to current phylogenetic hypotheses.

New species of the genus Spectracanthicus (Loricariidae, Hypostominae, Ancistrini) from the Rio Javaés (Rio Araguaia basin), with a description of gross brain morphology

A new species of Spectracanthicus is described from the Rio Javaés, Rio Araguaia basin. The new species is distinguished from its congeners (except Spectracanthicus immaculatus) by colour pattern: body dark grey to dark brown without dots or blotches (v. body colour with yellowish small dots in Spectracanthicus murinus, Spectracanthicus punctatissimus and Spectracanthicus tocantinensis and large white dots in Spectracanthicus zuanoni). It can be further distinguished from S. immaculatus by having thicker and less numerous teeth, with up to eight premaxillary and 20 dentary teeth (v. teeth thinner and more numerous with up to 22 premaxillary and 30 dentary teeth); dorsal and caudal fins without curved spines (v. dorsal and caudal fins with curved spines). Other osteological characters can also diagnose the new species from its congeners. In addition, a gross brain description and brief comments on the new species' ecological habitat are given.

P, Barros-Neto LF, Lima SMQ. Redescription of the endangered hypoptopomatine catfish Parotocinclus spilurus (Fowler, 1941) (Siluriformes: Loricariidae) from the upper rio Jaguaribe basin, northeastern Brazil

Abstract Parotocinclus spilurus (Fowler) was originally described as a species of Plecostomus based on six specimens collected in the rio Salgado, Icó Municipality, Ceará State, northeastern Brazil. Because the original description of P. spilurus is brief and uninformative, a detailed redescription of this endangered species based on the type series and on freshly collected topotypes was made. Data on osteology, intraspecific variation, sexual dimorphism and color pattern in life are presented for the first time, aiming at providing the necessary characters to differentiate the species from its congeners, as well as providing data on the distribution, habitat and conservation.

Redescription of Hisonotus notatus Eigenmann & Eigenmann, 1889 (Loricariidae: Hypoptopomatinae), the type species of the genus, and description of a new species from coastal drainages of southeastern Brazil

ABSTRACT Our analyses showed that the type series of Hisonotus notatus , type species of the genus, is mixed, composed by two different species. Based on that, we redescribe H. notatus with the designation of a lectotype, restricting the species to rio São João drainage and other small coastal drainages running to the Baía de Guanabara and to the Baía de Sepetiba in Rio de Janeiro State. We also describe a new species of Hisonotus from drainages of the rio Paraíba do Sul, Lagoa Feia, rio Macaé, and coastal rivers of Espírito Santo State, from rio Itabapoana to rio Doce basin. These two species are sister-taxa and can be distinguished by the number of plates in the mid-dorsal series.

Gross anatomy and histology of the alimentary system of Characidae (Teleostei: Ostariophysi: Characiformes) and potential phylogenetic information

A compared study of the morphology of the alimentary tract and liver of seven selected species corresponding to the main clades of the Characidae family is presented herein. Three new set of characters corresponding to 1) alimentary tract gross anatomy, 2) alimentary tract histology and 3) liver gross anatomy are evaluated as potential sources of data for future phylogenetic studies of the Characidae. Not considerable interspecific variation was observed at the histological level and therefore this source is not considered to be phylogenetically informative at the taxonomic level analyzed. In contrast, liver and alimentary tract gross anatomy presented important interspecific variation while a relatively homogenous intraspecific morphology was observed. Those characters are optimized in tree-topologies from previous phylogenetic analyses and their evolution and potential relationship with ecological traits are discussed.

Gross morphology of the brain of Pseudopimelodus bufonius (Valenciennes, 1840) (Siluriformes: Pseudopimelodidae)

The gross morphology of the brain of the pseudopimelodid Pseudopimelodus bufonius is described and compared with congeners. Observations were made on removed brains after elimination of bones from the top of the skull and severing of the cranial nerves and the spinal cord. Nine morphometric characters associated with the major subdivisions of the brain were identified, seven of which revealed significant differences among the species examined. The corpus cerebelli in all examined species of the genus is the largest structure of the brain. The behavior of the species of Pseudopimelodus is still unknown, but in other teleosts that condition is typically correlated with a higher degree of motor coordination. Relative size proportions of the tectum opticum, eminentia granularis, lobus facialis and lobus vagi, might be related to carnivory and an enhanced capacity for food selection.