Characterization of the skin mucus in the common octopus Octopus vulgaris (Cuvier) reared paralarvae

Abstract

The Octopus vulgaris farming is impaired by the high mortality of the paralarvae during the first month of life. Several factors have been investigated in this regard, but no data exist on the body surface mucus, which represents the interface with the outside environment. This study included morphometric analysis and glycoconjugates characterization of skin mucus in reared Octopus vulgaris paralarvae during the first month of life. Four types of mucous cells were distinguished: mucous 1 (m1) and mucous 2 (m2) cells were scattered in the mantle epidermis, mucous 3 (m3) and mucous 4 (m4) in the epithelium surrounding the sucker. Except for the presence of fucosylated and neutral glycoconjugates in all mucous cells, each cell type expressed a characteristic glycopattern. m2 and m4 contained also suphate and acid non-sulphate glycans, m3 lacked sulphate glycoproteins. Lectin histochemistry showed that mantle mucous cells (m1, m2) expressed GlcNAc and lactosamine terminating glycans. m2 also contained GalNAc terminal or penultimate to sialic acid. m3 was distinguished by mannosylated glycans terminating with lactosamine and m4 by α2,6 sialoglycans. Glycoproteins terminating with lactosamine, Galβ1,3GalNAc, and α1,6-linked fucose were a common feature of paralarvae surface layer. Morphometry revealed a significant decrease of m1 and m2 abundance during the first month of life, afterwards the reared paralarvae died. Since the glycopattern did not change during the investigated period, the mantle mucous cells abundance could be related to the Octopus vulgaris paralarvae survival.

Born With Bristles: New Insights on the Kölliker’s Organs of Octopus Skin

“…The specimens were not washed with distilled water before being fixed (except O. vulgaris, see below), therefore there may be an unquantified contribution of elements from seawater in the results. The mucus layer covering the skin surface in cephalopods is also observed in octopus hatchlings (Accogli et al, 2017). It apparently covers KO and prevents or hinders their detailed observation with SEM (see Results).…”

“…In addition, the absence of KO from the oral side of arms and suckers seems also to exclude a possible role in prey detection. Querner (1927) demonstrated with the Schultze reaction that KO tufts contain chitin and, recently, Accogli et al (2017) and González-Costa et al (2020) found positive staining for lectins in the KO setae, suggesting the presence of the proteoglycan N-acetylglucosamine, which would presumably have a mainly structural role because N-acetylglucosamine is a precursor for chitin synthesis. The same authors using histochemical techniques suggested that the absence of KO staining with periodic acid-Schiff (PAS) means that no secretory function can be attributed to this organ.…”

“…As far as we know from microscopical and histochemical studies, no nervous tissue has been reported in connection with KO (Boletzky, 1973;Brocco et al, 1974;Accogli et al, 2017;González-Costa et al, 2020), excluding the suspected existence of neurons associated with the obliquely striated dermal muscle fibers of the organ. This may exclude a sensorial mechano-and/or chemoreceptor function for these organs.…”

Histochemistry as a versatile research toolkit in biological research, not only an applied discipline in pathology

“…[37][38][39][40][41][42] The biology of stem cells was extensively investigated through the labelling by specific molecular markers, during development and in the adult. [43][44][45][46] The molecular organization of cells and tissues was carefully analyzed [47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63] especially in poorly described species of mammals [55][56][57] and non-mammalian vertebrates [58][59][60][61] or in invertebrates, 62,63 while immunohistochemistry was crucial to elucidate the topographic distribution of cell lineages in different organs, [64][65][66] especially in the nervous system, [67][68][69][70][71] and during embryogenesis and the pre-or postnatal development, [72][73]…”

Potentially handicapped but otherwise functional: Malformations in prey capture tools show no impacts on octopus life

“…Octopus paralarvae feed on planktonic prey, which they capture with the aid of the suckers and arms, just before using their beaks to both wound the prey and inoculate its body with digestive enzymes and finally to suck‐up the predigested content (Villanueva & Norman, 2008). The internal pressure reduction that enables an octopus sucker to function requires the strong action of its muscles coupled with an efficient seal against the surface of the prey (Kier & Smith, 2002), helped by the mucus film that covers the sucker surface in octopus paralarvae (Accogli et al., 2017). Thus, the presence of the extranumeral beaks in the suckers could not only compromise the tridimensional structure of the musculature, but it also could disable the sealing of the sucker against the prey surface, hindering prey capture, holding, and subduing and, consequently, rendering the affected suckers inefficient.…”