Hemocyte morphology and phagocytic activity in the common cuttlefish (Sepia officinalis)

Abstract

Little is known about the immune system of cephalopods, in spite of their many highly derived characters within the molluscan clade, including a vertebrate-like high-pressure closed circulatory system. Further the economic importance of cephalopod fisheries, potential for aquaculture, and use as ecotoxicology models demand a thorough understanding of their immune system. In this study, we present a comprehensive characterization of hemocytes in the common cuttlefish Sepia officinalis. Cytological stainings, electron microscopy- and flow cytometry-observations highlight a single granulocyte population with various densities of eosinophilic granules and unstained vesicles. These hemocytes contain acid phosphatase-, lysozyme- and proPO system enzymes, and have high activity in bead phagocytosis assays. Interestingly, bead pre-incubation in plasma results in time-dependent aggregation perhaps resulting from hemocyanin-coating, and decrease in phagocytosis. This study provides the basis for understanding hemocyte-mediated immunity in the common cuttlefish, and essential background for future studies on cephalopod immunity.

Understanding the cephalopod immune system based on functional and molecular evidence

“…Nowadays, the number and type of cells in the haemolymph of cephalopods is under debate since current studies showed that more than one single type of cell is observed in the O. vulgaris haemolymph [57,58]. However, this statement seems not to be the same in Sepia officinalis [61].…”

“…Concerning pathogens, parasites affecting O. vulgaris have been recorded from both locations [67,68], including the coccidian Aggregata octopiana, which is recognized as the most dangerous parasite for O. vulgaris [28,69] showing a negative impact on the octopus immune system. Unlike O. vulgaris, the observations performed by light and electron microscopy in S. officinalis haemolymph showed the presence of a single cell that possess a large nucleus U-shaped and several basophilic and acidophilic granules in the cytoplasm [61]. This single cell population is supported by FC analysis, which is characterized by their large size and complexity, and is also responsible to eliminate foreign particles (see below) [61].…”

“…Unlike O. vulgaris, the observations performed by light and electron microscopy in S. officinalis haemolymph showed the presence of a single cell that possess a large nucleus U-shaped and several basophilic and acidophilic granules in the cytoplasm [61]. This single cell population is supported by FC analysis, which is characterized by their large size and complexity, and is also responsible to eliminate foreign particles (see below) [61].…”

“…Haemocytes are crucial in the cephalopod immune response [51,52,53]. Although these cells are vital to maintain the wellbeing in all different cephalopod species, the studies conducted about haemocytes are limited, and most of the observations have been performed on octopus species [45,50,54,55,56,57,58] with few descriptions available on Euprymna scolopes [59] and Sepia officinalis [46,60,61]. In one of the first studies of characterization based on morphology and immune capability of cells, Stuart [49], identified phagocytic and non-phagocytic "leucoblastic cells" in common octopus.…”

Morphological Characterization of Hemocytes and Histological Structure of the Hemopoietic Tissue \"White Body\" of the Cuttlefish \"Sepia Officinalis\" (Cephalopod:sepiidae).

“…Cephalopods are economically and medically important; they are very important in fisheries, act as host for many parasites that can be transmitted to human such as Anisakis sp. and also used as an ecotoxicology model so understanding of their immune system is very important (Hochberg, 1990;Le Pabic et al, 2014).…”