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This study describes the morphology and histochemistry of the digestive tube of the herbivorous fish Rhytiodus microlepis, which is commonly found in the Amazonian floodplain lakes, Brazil. Thirty‐eight fish were used in this study. The digestive tube was measured and dissected for anatomical description, and stained with (i) haematoxylin and eosin, for histological analyses; (ii) periodic acid–Schiff, for detected neutral mucins; and (iii) Alcian Blue (AB) pH 1.0 and 2.5 for acid and sulphated acid mucins. The oesophagus, with its secretory cells and taste buds, is adapted for lubrication of vegetable matter, resistance to friction and reception of stimuli. The stomach is U‐shaped and rich in gastric glands, particularly in cardiac and fundic regions, which are adapted to receive large amounts of food, and promotes the digestion. The intestine comprises more than 70% of the digestive tube. All portions of the intestine, except the rectum, have the same pattern of mucosal folds, and the goblet cells reacted positively to all histochemical methods (PAS, AB 1.0 and 2.5), while rodlet cells reacted only to periodic acid–Schiff (PAS) staining. Neutral mucins and sulphated acid mucins predominated in the anterior portion of the intestine and a high concentration of carboxylated acid mucosubstances were present in the other portions. The rectum showed a strong reaction to all histochemical methods. The muscular layer of the intestine consists of three layers, which showed features presumably related to the rigid nature of the food. A simple squamous epithelium constitutes the serous layer over the entire length of the tube. [ABSTRACT FROM AUTHOR]

The reptilian tongue has morphological and functional variations according to the feeding mechanisms and habitat of the species. This study aimed to understand the morphofunctional characteristics of the tongue of the lizard Salvator merianae, through anatomical, histological and scanning electron microscopy analyses. This study involves five adult animals, which were collected in the municipality of Viçosa, Minas Gerais, from Brasil. The tongue of S. merianae was protractile and bifid, important to drive molecules from the environment to the vomeronasal organ and thus identify odors and locate prey, besides being strongly muscular and with keratinized and pigmented stratified epithelium for protection. Mucous secretion was present as an important tool for lubrication and protection in view of the protrability of the tongue and the great presence of bacteria. Morphological specialization of the S. merianae tongue reflect its direct participation in food assimilation, with squamiform papillae for the mechanical function of maintaining prey in the oral cavity and contributing to swallowing. Taste buds were not found, which excludes the tongue participation in the taste, although it has olfactory sensory function in association with the vomeronasal organ. [ABSTRACT FROM AUTHOR]

A new rheophilic species of the genus Rineloricaria is described for the Amazon basin in Colombia. Rineloricaria cachivera n. sp. differs from its congeners by having anterior to the first predorsal plate, an inconspicuous saddle-like mark; the presence of dark, diffuse blotches, present as unified dark colouration along most of the dorsal portion of the head, without bands or spots on the head; a long snout that occupies more than half the head length (HL), between 58.0% and 66.3% HL; a naked portion on the cleithral area from the border of lower lip reaching the origin of pectoral fin; and by having five series of lateral plates in longitudinal rows below the dorsal fin. The new species is morphologically similar to Rineloricaria daraha; however, it can be distinguished by the presence of six branched pectoral fin rays (vs. seven) and the lower lip surface with short thick papillae (vs. long finger papillae). An identification key to the Rineloricaria species of the Amazon River basin in Colombia is provided. The new species is herein categorized as Least Concern, following the IUCN criteria., (© 2023 The Authors. Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of Fisheries Society of the British Isles.)

A new species of Hypostomus with spoon-shaped teeth is described from the Rio Cupari basin, a right margin affluent of the lower Rio Tapajós, Pará State, Brazil. The new species inhabits rocky bottom areas in the main channel of Rio Cupari and its tributaries. The new species can be distinguished from all its congeners, except from the Hypostomus cochliodon group, by having six to eight spoon-shaped teeth, dentaries angled at less than 80° and the absence of a notch between the hyomandibular and the metapterygoid. The new species is distinguished from all species of the H. cochliodon group by its unique colour pattern, containing dark vermiculations on head and anterior portion of the trunk, and by the absence of medial buccal papillae., (© 2020 The Fisheries Society of the British Isles.)