Each sample (n = 4) was performed in triplicated in the qPCR study. the dorsal epidermal cells compared with ventral skin epidermal cells. This study represents a step forward in our knowledge of the skin structure of an important farmed teleost, gilthead seabream, one of the most generally farmed fish worldwide. Furthermore, for functional characterization, experimental wounds were carried out comparing the wound healing rate between the dorsal and ventral regions of skin over the time. The results showed higher ratio of wound healing in the ventral region, whose wounds were closed after 15 days, compared to dorsal region of skin. Taking into account all together, this study represents a step forward in our knowledge of the skin structure and skin regeneration of an important farmed teleost, gilthead seabream, one of the most generally farmed fish worldwide. Introduction Gilthead seabream (L.) is one of the most widely farmed fish species, world production Triisopropylsilane increasing from 77,510 tonnes in 2002 to 158,390 tonnes in 2014 (FAO, 2016). However, due to rigorous fish farming, the most widely used method of fish production [1], fish are frequently exposed to external aggressions. Skin, as the outermost organ of the body, is usually important in this respect, since it not only functions as a physical, mechanical, biological and chemical barrier in teleosts but also confers biological and immunological protection by preventing the access of pathogens into the body [2]. Teleost skin, in sharp contrast to the skin Rabbit Polyclonal to BAIAP2L1 of mammals, is usually a non-keratinised tegument, with living cells. The outermost layer of cells forms the epidermis, which is usually of ectodermal origin and responsible for secreting the skin mucus through goblet cells [3]. The surface of the most external epithelial cells has special structures called microridges, whose functions are poorly comprehended [4]. The epidermis is usually separated from the next inner layer (dermis) by an acellular basement membrane. The dermis, which is derived from the mesoderm, is usually thicker, vascularised, and can be divided into two obvious sublayers: (i) the with vascular and neural components where scales are embedded and most of the chromatophores are located; and (ii) the which mostly consists of a dense matrix of collagen fibres [5]. Lastly, an internal layer, the hypodermis, is mainly (but not exclusively) a excess fat reservoir r composed of adipose cells that link the skin with the underlying muscle. For adaptation to the aquatic environment, fish skin is usually covered by mucus that serves to maintain homeostasis and integrity [6]. In recent years, most fish skin research has Triisopropylsilane focused on the mucus layer and gilthead seabream mucus is usually no exception in this respect. The physico-chemical parameters of skin mucus, such as viscosity, density, conductivity, pH or redox potential, have been explained [7]. The presence and large quantity of enzymes and/or immunologically active molecules, including proteases, antiproteases, esterase, phosphatase alkaline, peroxidase, lysozyme, immunoglobulin M (IgM) or bacteriostatic peptides, have also been exhibited in gilthead seabream skin mucus [8,9]. Furthermore, the proteome map of skin mucus in several teleosts [10,11], including gilthead seabream [12,13], has been characterized, as well as the proteomic profiling after dietary supplementation and/or stress [14]. However, few classical microscopic studies have been made of fish skin cells [15,16]. Few studies have taken into consideration possible differences between the epidermis from different parts of the fish body. One such paper evaluated the role of agouti-signalling protein (ASC) in the different dorsal-ventral pattern of skin pigmentation of fish [17]. At transcription level, only one study from isolated skin cells of Atlantic cod revealed changes in some immune-related (L.) (80C120 g and 15C22 cm) obtained from a local farm in Murcia (Spain) were kept in re-circulating seawater aquaria (250 L) with a flow rate of 900 L h-1 in the Marine Fish Facility at the University of Murcia and allowed to acclimatize for 2 weeks. The temperature and salinity were 22 2C and 28 , respectively. The photoperiod was of 12 h light: 12 h dark. A commercial diet (Skretting, Spain) was administered at a rate of 2% body weight day-1. Fish were anesthetized with Triisopropylsilane 100 mg l-1 MS222 prior to sampling the skin in each trial. Mucus was gently removed by a.