Histological, histochemical and ultrastructural analysis reveals functional division of the oesophagogastric segment in freshwater tubenose goby Proterorhinus semilunaris Heckel, 1837

Katarzyna Wołczuk,Dariusz Płąchocki,Tomasz Kakareko,Julita Nowakowska

doi:10.1007/s00435-014-0250-7

Katarzyna Wołczuk, Dariusz Płąchocki + Show 2 more

Open Access

https://doi.org/10.1007/s00435-014-0250-7

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Abstract

Histological and histochemical features of the oesophagogastric segment of the alimentary canal as well as ultrastructure of gastric gland cells of freshwater tubenose goby Proterorhinus semilunaris were examined. The studies revealed that despite the lack of anatomical distinction, the oesophagogastric segment is histologically divided into the oesophagus, oesogaster and stomach, which provides evidence for the functional compartmentation of this organ. The oesophagus was characterised by the presence of numerous goblet cells secreting mainly a mixture of neutral and acid mucopolysaccharides. In the stomach, the apical zone of the surface epithelial cells contained neutral mucopolysaccharides. Numerous proliferating cells were scattered throughout the surface epithelium. In the lamina propria of the stomach, a well-developed layer of gastric glands was observed. The glands were of the alveolar type and occupied nearly the entire length of the stomach except the pyloric region. The gastric gland cells were varied into light and dark; however, their ultrastructure was identical. All cells had numerous mitochondria and a well-developed tubulovesicular system typical for the oxynticopeptic cells, but pepsinogen granules were not present in the cytoplasm of these cells. These findings contribute new evidence to literature reports that not all gobiid fish are stomachless. Moreover, they suggest higher adaptation of the species to utilise protein-rich food compared to stomachless fish, and its ability to adjust the alimentary canal quickly to changing diet. How this may facilitate establishment of P. semilunaris in invaded environments remains an open question.

Highlights

Gobiidae is one of the largest families of the acanthomorph fish including over 1,950 species inhabiting marine, brackish, as well as fresh waters of the moderate and tropical zones (Nelson 2006; Thacker 2011; Thacker and Roje 2011)
This finding changes the view on the stomachless nature of the alimentary canal of Gobiidae, but most of all, it uncovers hidden peculiarities of P. semilunaris alimentary canal, showing higher adaptation of the species to utilise protein-rich food compared to stomachless fish, and suggesting its potential to adjust the alimentary canal quickly to changing diet, which may facilitate establishment of the species in dynamic, nutritionally variable environments
The study clearly shows the functional differentiation of the oesophagogastric segment of P. semilunaris despite the fact that the fish does not have an anatomically separate stomach

Summary

Introduction

Gobiidae is one of the largest families of the acanthomorph fish including over 1,950 species inhabiting marine, brackish, as well as fresh waters of the moderate and tropical zones (Nelson 2006; Thacker 2011; Thacker and Roje 2011). Varied food preferences as well as environmental conditions in which the Gobiidae live contributed to the development of a number of adaptation features in the structure of their digestive system (Geevarghese 1983; Kobegenova and Dzhumaliev 1991). These fish have one feature in common though: they lack a well-developed stomach (Geevarghese 1983; Kobegenova and Dzhumaliev 1991). Not all researchers share this opinion (Geevarghese 1983; Hur et al 2005; Wu et al 2010), there is still lack of clear

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