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Let [Formula: see text] be an orientation of a simple graph [Formula: see text] with [Formula: see text] vertices and [Formula: see text] edges. The skew Laplacian matrix [Formula: see text] of the digraph [Formula: see text] is defined as [Formula: see text], where [Formula: see text] is the imaginary unit, [Formula: see text] is the diagonal matrix with oriented degrees [Formula: see text] as diagonal entries and [Formula: see text] is the skew matrix of the digraph [Formula: see text]. The largest eigenvalue of the matrix [Formula: see text] is called skew Laplacian spectral radius of the digraph [Formula: see text]. In this paper, we study the skew Laplacian spectral radius of the digraph [Formula: see text]. We obtain some sharp lower and upper bounds for the skew Laplacian spectral radius of a digraph [Formula: see text], in terms of different structural parameters of the digraph and the underlying graph. We characterize the extremal digraphs attaining these bounds in some cases. Further, we end the paper with some problems for the future research in this direction.

The present study aimed to investigate the macroscopic structure of the gastrointestinal tract (GIT) of Schizothorax esocinus Heckel, 1838. The surface architecture of the buccopharynx, oesophagus and the entire intestinal tract of S. esocinus has been examined under scanning electron microscope (SEM) after fixing in 2.5% glutaraldehyde buffered with 0.1 M sodium cacodylate at pH 7.3 for 18–48 hours and post-fixation for two hours at room temperature in 1% osmium tetra oxide buffered at pH 7.3 with 0.1 M cacodylate. The mucosal surface of buccopharynx, esophagus, intestinal bulb, and intestine reveal prominent longitudinal major or primary mucosal folds which are further subdivided into the series of irregular and well-circumscribed folds called minor or secondary folds. However, in the intestinal bulb and intestine, the longitudinal major or primary folds themselves form wavy or zigzagging patterns along the mucosal surface. The fine structure of the surface epithelium further shows that the apical surfaces of the epithelial cells are ped with finger-print like microridges, arranged in various patterns and regularly spaced. The rectal mucosa, on the other hand, displays a highly irregular type of major mucosal folds. The separation can’t be seen between major mucosal folds. A thin film of mucous spread over the mucosal folds and the numerous pores through which mucous cells release their content has also been noted along the rectal mucosa. This investigation suggests the possible role of different digestive organs in relation to feeding, digestion, storage, absorption, and various other physiological processes, thereby providing a knowledge necessary to the understanding of pathological or physiological alterations in both aquaculture and natural environment.