Morphology of the Atlantic salmon (Salmo salar) tongue

Gill arch and raker morphology of common carp (Cyprinus carpio, Linnaeus, 1758) sampled in aquaculture system

The study aimed to investigate the morphologic aspects of common carp's gill arch and gill rakers (Cyprinus carpio, Linnaeus, 1758), an omnivore and highest-produced aquaculture species. The study used 10 common carp (395.35 ± 45.06 g) grown entirely under aquaculture conditions. The fish tissues were fixed with Glutaraldehyde (2.5%) for scanning electron microscopy and with formalin (10%) for stereomicroscopic examination. In the SEM examination, two types of taste papillae (Type II and Type III) were observed in the pharyngeal mucosa. Microridge-like structures in the epithelial layer were found to have two forms. The study findings indicate a significant decrease in gill arch lengths from cranial to caudal and a significant increase in rakers per unit area, as determined through digital calliper measurements and stereomicroscopic examinations (p < 0.05). However, there was no significant difference in measurements of gill arches and raker numbers between the bilateral symmetry of the gill arches (p > 0.05). In conclusion, it was observed that the epithelial structure on the common carp gill arch contained two types of microridge-like structures: the gill arch length decreased from cranial to caudal, and the rake density on these arches increased caudally.

The Alimentary Tract of African Bony-Tongue, Heterotis niloticus (Cuvier, 1829): Morphology Study

Simple Summary

Heterotis niloticus is a primitive freshwater teleost. It is a candidate for aquaculture in Africa with a good conversion rate and is used for evolutionary studies for its anatomical similarities with reptiles and birds. H. niloticus is also an endangered species for several reasons, including overexploitation. The purpose of the present study was to investigate, by gross anatomy and light microscope analysis, the morphological structure of the digestive system of the African bony-tongue, from the oropharyngeal cavity to the rectum, including its associated glands. A peculiar feature of this species is the presence of both bone trabeculae and well-defined cartilaginous areas in the process of ossification, in the deeper layers of the tongue. The so-called “African bony- tongue” is due to these characteristics. On both sides of the tongue, two tubular structures covered by numerous taste buds, as well as mucous cells, were found. The presence of well-defined lymphoid tissue in both pyloric ceca and rectum is described for the first time. Further investigations could aim to optimize husbandry and feeding protocols permitting, also, to understand the evolutionary process.

Abstract

A morphological study of the alimentary tract, from the oropharyngeal cavity to the rectum, including the attached glands, of African bony-tongue, Heterotis niloticus (Cuvier, 1829) was carried out by gross anatomy, and light microscope analysis. This study aimed to give a deeper knowledge of the alimentary tract morphological features of this species of commercial interest. H. niloticus is distinguished by individual morphological characteristics showing a digestive tract similar to that of reptiles and birds. Within the oropharyngeal cavity, two tubular structures with digitiform ends are arranged on both lateral sides of the triangular tongue. The oropharyngeal cavity connects the stomach by a short esophagus. This latter is adapted to mechanical trituration, and it is divided into a pars glandularis and a thick-walled pars muscularis. The gizzard flows into the anterior intestine and two blind pyloric appendages, which exhibit specific functions, including immune defense for the presence of secondary lymphoid organs. The anterior intestine continues with the middle and posterior tracts up into the rectum. According to the histological observations, all regions of the alimentary tract have common structural features, typical of hollow organs, with differences in the mucosa structure that reflects the different functions of the apparatus, from mouth to anus. Within this study, we provided the first basis for future studies on optimizing rearing conditions, feed conversion ratio, and the digestive capacity, improving the growth performance of this species, and ensuring its conservation.

Morphology of the tongue dorsal surface of turbot (Scophthalmus maximus)

This study aimed to analyze the morphology of the tongue, which varies among fish species and has not been studied in turbot (Scophthalmus maximus), using macro-anatomical, light and scanning electron microscopy (SEM). As research materials, the tongues of eight adult turbot, which were used for consumption, were examined. The roughly triangular-shaped tongue of the turbot consisted of three parts: apex, body, and root. The thickness of the tongue continued to increase from the apex to the root. Although papillae were not observed in the macroscopic examination of the tongue, microscopic examination revealed the presence of cone-like shaped papillae on the submucosa. The tongue was composed of mucosa, submucosa, and hyaline cartilage. By SEM the presence of the taste buds (Types I and III), taste pores and papillae on the dorsal surface were demonstrated. Taste buds are the first descriptions in S. maximus. Therefore our results could add new data to the fish tongue anatomy.

Morphological characteristics of the blackspot seabream (Pagellus bogaraveo) tongue: A structural and immunohistochemical study

The blackspot seabream (Pagellus bogaraveo, Brünnich, 1768) is an omnivorous, predominantly carnivorous fish. In aquaculture, it is fed with pellets rich in proteins and fat. The morphological and functional aspects of the fish tongue, the feeding modality and the tasting capacity are strictly related. Therefore, the aim of this study was to describe by scanning electron, light and confocal laser microscopy, the morphological characteristics of the tongue in this species. It showed an apex, a body and a root. There were rows of teeth on the edges of the mouth and taste pores on all the tongue dorsal surface with folds and furrows. In addition, body and root showed several fungiform-like papillae in the mucosa of the folds, covered by a weakly keratinized stratified squamous epithelium, can be observed. The papillae were innervated by S100 positive fibres. In the apex, a mesenchymal tissue with vimentin positive star-shaped stem cells was evident. The results could give a support for a wider use of the blackspot seabream as a farmed species, considering the morphological data as correlated with the potentiality of food discrimination. This provides a basis for possible applications in feeding strategies. The presence, localization and characteristics of the mesenchymal stem cells, as seen also in previous studies, could represent a further basis for future applications in clinical trials.

Anatomical, histological and immunohistochemical study of the tongue in the rainbow trout (Oncorhynchus mykiss)

The rainbow trout (Oncorhynchus mykiss Walbaum, 1792) is a fish commercially farmed all over the world. These fish are usually fed, in aquaculture, with pellets rich in proteins and fat. It is well known that there are close relationships among the adaptation of vertebrates to their environment, the capacity and the modality of feeding and the oral cavity morphology, especially the tongue one. No data are so far available about the morphology of the rainbow trout tongue, and therefore, the aim of this study was to investigate by light, scanning electron and confocal laser microscopy, the morphological characteristics of the tongue. An apex, a body and a root can be distinguished in the tongue, and the presence of teeth, taste buds and fungiform-like papillae was demonstrated. Light microscopy shows the presence of an adipose tissue pad in the deeper layer of the apex and in the most superficial layer of the root. In the deeper layer of the body, a triangular-shaped pad consisting of fusiform cells immersed in abundant extracellular matrix of the mesenchymal tissue was observed. The confocal laser microscopy shows the presence of cells with a fibroblast-like morphology positive for vimentin. In the deepest layer of the tongue root, a large area of osteo-cartilaginous tissue was observed. The results, besides the description of the morphological characteristics of the tongue, related to studies regarding the feeding, could be considered for the eventual applications of the use of mesenchymal cells, observed in adult fish, in cell therapies in different pathologies.