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- Coordinated regulation of chromatophore differentiation and melanogenesis during the ontogeny of skin pigmentation of Solea senegalensis (Kaup, 1858)Publication . Darias, Maria J.; Andree, Karl B.; Boglino, Anais; Fernandez, Ignacio; Estevez, Alicia; Gisbert, EnricAbnormal pigmentation of Senegalese sole has been described as one problem facing the full exploitation of its commercial production. To improve our understanding of flatfish pigmentation of this commercially important species we have evaluated eleven genes related to two different processes of pigmentation: melanophore differentiation, and melanin production. The temporal distribution of gene expression peaks corresponds well with changes in pigmentation patterns and the intensity of skin melanization. Several gene ratios were also examined to put in perspective possible genetic markers for the different stages of normal pigmentation development. Further, the phenotypic changes that occur during morphogenesis correspond well with the main transitions in gene expression that occur. Given the dramatic phenotypic alterations which flatfish undergo, including the asymmetric coloration that occurs between the ocular and the blind side, and the synchrony of the two processes of morphogenesis and pigmentation ontogenesis, these species constitute an interesting model for the study of pigmentation. In this study we present a first approximation towards explaining the genetic mechanisms for regulating pigmentation ontogeny in Senegalese sole, Solea senegalensis.
- Vitamin A affects flatfish development in a thyroid hormone signaling and metamorphic stage dependent mannerPublication . Fernandez, Ignacio; Ortiz-Delgado, Juan B.; Darias, Maria J.; Hontoria, Francisco; Andree, Karl B.; Manchado, Manuel; Sarasquete, Carmen; Gisbert, EnricVitamin A (VA) and retinoid derivatives are known morphogens controlling vertebrate development. Despite the research effort conducted during the last decade, the precise mechanism of how VA induces post-natal bone changes, and particularly those operating through crosstalk with the thyroid hormones (THs) remain to be fully understood. Since effects and mechanisms seem to be dose and time-dependent, flatfish are an interesting study model as they undergo a characteristic process of metamorphosis driven by THs that can be followed by external appearance. Here, we studied the effects of VA imbalance that might determine Senegalese sole (Solea senegalensis) skeletogenetic phenotype through development of thyroid follicles, THs homeostasis and signaling when a dietary VA excess was specifically provided during pre-, pro-or post-metamorphic stages using enriched rotifers and Artemia as carriers. The increased VA content in enriched live prey was associated to a higher VA content in fish at all developmental stages. Dietary VA content clearly affected thyroid follicle development, T3 and T4 immunoreactive staining, skeletogenesis and mineralization in a dose and time-dependent fashion. Gene expression analysis showed that VA levels modified the mRNA abundance of VA- and TH-specific nuclear receptors at specific developmental stages. Present results provide new and key knowledge to better understand how VA and TH pathways interact at tissue, cellular and nuclear level at different developmental periods in Senegalese sole, unveiling how dietary modulation might determine juvenile phenotype and physiology.
- Normal and histopathological organization of the opercular bone and vertebrae in gilthead sea bream Sparus aurataPublication . Ortiz-Delgado, Juan B.; Fernández Monzón, Ignacio Valentín; Sarasquete, Carmen; Gisbert, EnricThis study provides a comprehensive description of the tissue organization of non-deformed and deformed opercula and vertebrae from gilthead sea bream Sparus aurata juveniles by means of histological, histochemical and immunohistochemical approaches. Two types of opercular anomalies are described: the folding of the opercle and subopercle into the gill chamber, starting at the upper corner of the branchial cleft and extending down to its lower third; and the partial lack of the operculum (opercle, subopercle, interopercle and preopercle underdeveloped) with a regression of the loose edge extending down to its lower third. Histological observations revealed a rare type of bone remodelling process in the opercular structure, which consisted of the coalescence of contacting bone tissues (presumably from the preopercle and opercle), resulting in skeletal tissue with a trabecular aspect filled by a single-cell epithelium of cubic osteoblastic-like cells. Differences in collagen fiber thickness and its 3-dimensional arrangement between normal and deformed opercula were also found. Lordotic vertebrae were characterized by the formation of fibrous cartilage in the haemal and/or neural sides, indicating that a metaplastic shift occurred during the process of lordosis. Another major histomorphological change found in lordotic vertebrae was the complete loss of notochordal sheath integrity. Histological alterations were coupled with an imbalance of cell death and cell proliferation processes in lordotic vertebrae as well as that of bone formation/resorption, and extracellular matrix deposition activity differences which might have resulted from the remodelling process occurring in lordotic vertebrae. Altogether, these results provide an increase in our basic knowledge of bone disorders that contribute to our understanding of the mechanisms by which these skeletal anomalies appear in this fish species and which hamper its production efficiency.