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Lithophaga lithophaga is a rock-boring bivalve with an ability to dissolve carbonate substrata with its siphonal and pallial gland secretions. However, the molecular mechanism that enables this species to bore into calcareous rocks is not yet known. In order to identify genes potentially involved in chemical boring we performed transcriptome sequencing of pallial-gland tissue samples of L. lithophaga. Transcriptome sequencing using an Ion Torrent platform generated 60.563 million clean reads with an average read length of 96 bp. De novo assembly of clean reads produced 62,490 contigs with a mean length of 408 bp. Since the boring mechanism is attributed to calcium-binding proteins, the search focused on transcripts capable of binding this element. In all, 178 genes with calcium-binding ability were found to be expressed in the pallial gland of L. lithophaga. Annexins, calreticulin, phospholipase A 2 and V-type proton-ATPases were considered as possible candidate chemical-boring genes due to their known function and involvement in various other biological processes: e.g. ion transport, cellular catabolic process, protein folding. Transcriptome analysis of L. lithophaga revealed a set of candidate genes putatively associated with chemical boring. The selected set of genes will be studied further to verify their expression patterns and their possible involvement in the rate of chemical boring in L. lithophaga., (Copyright © 2018 Elsevier Inc. All rights reserved.)

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.