RESUMEN
Introduction: An excess of mucus has been observed in the water during induction of mullet spawning. Few data are available on the physiology of mullets during the induced spawning, especially data on the response of mucous-secreting cells in the gills and intestine
Aim of the work: The aims of the present studies were to evaluate the effects of stress on the mucous-secreting cells in the gills and intestine during induced spawning of Mugil cephalus [Teleostei]
Materials and methods: Quantification of possible cell hyperplasia [or depletion] and the chemical composition of the mucous cells during induction of M. cephalus spawning was carried out using histochemical techniques
Results: The majority of mucous cells were concentrated at the edge of the gill filaments. The mucous cell density in the gills was significantly increased during spawning, but it was significantly decreased during preoviposition mortality. However, the mucous cell density in the mucosal layer of the intestine was significantly decreased during spawning and at preoviposition mortality. The size of mucous cells in both the gills and the intestine was significantly decreased during spawning and at preoviposition mortality, whereas its size was significantly increased in the gills after spawning. Two types of glycoproteins [GPs] [acid and neutral] were identified in the mucous cells of the gill and intestine epithelium of M. cephalus. During induction of spawning, the amount of GPs in the mucous cells altered. The amount of each variety of the carbohydrate [intensity of reaction] differed at the different stages during spawning. In general, the secretion of acidic mucous was increased during spawning
Conclusion: The decrease in the GP contents in mucous cells of M. cephalus, as a result of their hypersecretion in response to stress early during handling and acclimation, decreased the production of mucus and reduced its protective role against desiccation of gill and intestine tissue when the ion concentration changed in water during acclimation and induced spawning. This may be considered one of the possible reasons for mortality. Therefore, caution must be exercised not only in acclimation of fish but also in minimization of exposure of fish to stress during induction of spawning