Morphological differences in the skin of marble trout <i>Salmo marmoratus</i> and of brown trout <i>Salmo trutta</i>

Abstract

Despite being genetically very closely related, the marble trout Salmo marmoratus and the brown trout Salmo trutta exhibit marked phenotypic differences, particularly with regard to skin pigmentation. Histological analysis of skin from the head and gill cover of differently aged individuals of the two species was carried out in order to characterize differences in skin structure. The basic structure of skin of the individuals studied corresponded with that described for other salmonids, though the head epidermis was somewhat thicker in S. marmoratus than in S. trutta, thickening with age in both species. Numerous secretory goblet cells and sporadic secretory sacciform cells were observed in the upper and middle part of the epidermis in both species. Melanophores were present in both species only in the dermis, and were bigger in S. marmoratus and present at lower average density than in S. trutta, and more or less constant across all age classes. In adult S. marmoratus with fully established marble pigmentation, light areas at low density with small (i.e. aggregated) melanophores were present, while in S. trutta melanophores were more uniformly distributed.

Comparison of pigment cell ultrastructure and organisation in the dermis of marble trout and brown trout, and first description of erythrophore ultrastructure in salmonids

“…The basic structure of skin of marble and brown trout individuals corresponds with that described for other salmonids, with melanophores present in both species only in the dermis, being bigger in marble trout but present at a lower average density than in brown trout. In adult marble trout with fully established labyrinthine pigmentation, light areas are characterised by smaller size melanophores present at lower density than in darker areas, while in brown trout melanophores are more uniformly distributed (Sivka et al 2012).…”

“…In adult marble trout with fully established labyrinthine pigmentation, light areas are characterised by smaller size melanophores present at lower density than in darker areas, while in brown trout melanophores are more uniformly distributed (Sivka et al. ).…”

“…Cx41.8M7; Watanabe & Kondo, 2012), partially in jaguar/obelix (Iwashita et al 2006). However, for the majority of these species, no morphological features of skin and pigment cell ultrastructure have to the authors' knowledge been described, except for the position of pigment cells in the skin of the aforementioned zebrafish mutant Cx41.8M7 (Watanabe M., Nishida T. & Kondo S., personal communication), and the description of basic morphological features and histochemical differences of marble and brown trout skin (Sivka et al 2012). The basic structure of skin of marble and brown trout individuals corresponds with that described for other salmonids, with melanophores present in both species only in the dermis, being bigger in marble trout but present at a lower average density than in brown trout.…”

Mucosal responses of brown‐marbled grouper Epinephelus fuscoguttatus (Forsskål, 1775) following intraperitoneal infection with Vibrio harveyi

“…Sacciform cells remained unstained with neither AB nor PAS (Figure 2e,i), indicating the absence of glycoproteins. Additionally, goblet cells showed a flocculent morphology upon staining, while sacciform cells contained a single membrane‐bound vacuole that showed homogeneous staining (Desantis et al., 2007; Fast, Sims, Burka, Mustafa, & Ross, 2002; Pickering & Fletcher, 1987; Sivka, Halacka, & Susnik Bajec, 2012; Tsutsui et al., 2018).…”

Epidermis structure in the brook trout (Salvelinus fontinalis) and its Arctic char (Salvelinus alpinus) hybrid

“…The presence of epidermal melanophores has yet to be observed in any salmonid species, even in those with expressive skin pigmentation, such as marble trout (S. marmorata; Sivka et al 2012). In some fish species melanophores are present, however, the factors dictating the presence of epidermal melanophore cells are not yet fully understood.…”