Ion Levels in the Gastrointestinal Tract Content and Plasma of Four Teleosts with Different Feeding Habits

Abstract

The teleost pseudobranch, a reduced mandibular gill arch, morphologically closely resembles a gill hemibranch. It consists of several filaments bearing numerous lamellae. The vascular system of the pseudobranch also matches that of a gill, with afferent and efferent filamental arteries and the lamellar blood space. Despite the pseudobranch's gill-like appearance, however, a gas exchange function is excluded in many teleosts by overlying opercular epithelium, effectively eliminating diffusional exchange with the external medium. The physiological function of the pseudobranch is still unknown, though its conspicuously close association with the ocular choroid rete mirabile, a structure supporting elevated oxygen partial pressures in the eye, suggests a role related to the process of oxygen secretion into the eyes of teleosts. In this paper we present new stereological data on the pseudobranch of rainbow trout (average weight: 478±114 g, x±SD, n=12). The total Cavalieri volume of the pseudobranch was 46.4 ll (97 ll kg )1 ), consisting of lamellae 49%, connective tissue 43.8%, large blood vessels 4.5%, filamental cartilage 2.3%, and central venous sinus 1.3%. Lamellae were comprised of pillar and pseudobranchial cells 81%, blood space 12.3%, and lacunar tissue 6.4%. The inner surface of the blood space in the lamellae was 12.2 cm 2 (25.5 cm 2 kg )1 ), and its volume was 2.81 ll (5.88 ll kg )1 ). The results demonstrate the pseudobranch's potential for physiological functions requiring a high surface area or surface-to-volume ratio, i.e. ion transfer, gas exchange and other regulatory processes. More detailed analysis of the function of the pseudobranch, however, has to remain subject of future morphological and physiological studies.

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“…The lamellae comprised a central blood capillary that formed a mesh work and surrounded by pseudobranchial cells. The interlamellar space was almost completely reduced and filled by a lacunar tissue as in Glossogobiusgiuris (Hamilton, 1822) (Singh et al, 1986), Atlantic cod, Gadusmorhua (Linnaeus, 1758) (Morrison, 1993), rainbow trout, Oncorhynchusmykiss (Walbaum, 1792) (Mattey et al, 1978;Waser et al, 2005), Ctenopharyngodonidella (Valenciennes, 1844) (Hamidian and Alboghobeish, 2007), Leuciscusidus (Linnaeus, 1758) (Fisher-Scherl and Hoffmann, 1986). The number of filaments increased during the fish development and varied up from 3 to 5 at the end of the experiment (Tab.…”

“…The type of pseudobranch with the free lamellae contains the chloride cells typical for the fish gills (Mattey et al, 1978;1980;Sánchez-Amaya et al, 2007;Yang et al, 2014). Whereas in covered pseudobranchs, typical for the majority of freshwater fishes, chloride cells are absent (Mattey< et al, 1978;Fisher-Scherl and Hoffmann, 1986;Kern et al, 2002;Waser et al, 2005;Hamidian and Alboghobeish, 2007). In the brackish water fishes, usually possessing the intermediate type of pseudobranchs, the chloride cells only occur on the lateral aspects of the pseudobranch (Mattey et al, 1978;King et al, 1993).…”

“…There are only a few papers devoted to pseudobranch histology (Singh et al, 1986;King et al, 1993;Waser et al, 2005;Hamidian and Alboghobeish, 2007;Yang et al, 2014 …”

In-vitro digestion models: a critical review for human and fish and a protocol for in-vitro digestion in fish

“…Electrolytes are known to affect protein solubility but have not been systematically studied for invitro digestion on fish. The electrolyte concentration in the fish gastrointestinal tract could be measured as the procedure elaborated in Becker et al [134] and recreated using inorganic salts.…”