Assessment of the Scales of Gilthead Seabream (Sparus aurata L.) by Image Analysis and Atomic Force Microscopy

Francisco Casado,Santiago Casado,Diana Ceballos-Francisco,María Esteban

doi:10.3390/fishes3010009

Abstract

Understanding the protective role of fish skin is critical to improving the development of aquaculture, since skin is the main surface that separates the animal from its always hazardous environment. Many techniques have been used for its study, but certain structural characteristics of fish skin still remain not clearly understood. That is the case with scales, which have always been attributed a mere protective role, but which are proving to have more functions than it was traditionally thought. To acquire a deeper knowledge, scales from six different regions of gilthead seabream (Sparus aurata L.) were studied and measured by image analysis. Results prove that scales from the base of the dorsal fin are larger than those in other parts of the fish body while scales from the peduncle are the smallest of the skin. Furthermore, a technique relatively new in this field, known as atomic force microscopy (AFM), was used to obtain representations of the ultrastructure of the scales and measure certain features such as the circuli and the lines in the basal layer. The data obtained allowed us to compare the height of circuli among the different scales, showing that they were higher in scales from the dorsum and the operculum. The present results introduce a nanostructural model of the scales of gilthead seabream that might serve as a useful guideline for future studies.

Highlights

With the development of modern aquaculture, further understanding of fish skin is proving critical to managing fish health in intensive farming facilities [1], since the high density of fish inside the cages or tanks implies frequent aggression, which usually leads to problems in the skin [2]
The measurement of scales with light microscopy revealed that scales were larger in the middle
Discussion part of the body, with the scales from the base of the dorsal fin larger than those from the ventral measurement of scales with light microscopy revealed This were larger in the middle side, while the smallest were found in the peduncle

Summary

Introduction

With the development of modern aquaculture, further understanding of fish skin is proving critical to managing fish health in intensive farming facilities [1], since the high density of fish inside the cages or tanks implies frequent aggression, which usually leads to problems in the skin [2]. To keep skin damage to a minimum, and maintain the health of the animals, it is vital to improve our knowledge of the structure of the organ and the mechanisms involved in its protection. Scales are a type of hard plates which developed over evolution in many bony fishes to provide protection against external hazards, without compromising the necessary range of movements of the animals [5,6]. They play a crucial role in maintaining the structure of the upper layers of skin [7]. The most common type of scales in teleost fish is elasmoid scales, which derive phylogenetically from the ganoid scales of species like sturgeons [9,10]

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Conclusion