title: Pinna nobilis: A big bivalve with big haemocytes?
abstract: The fan mussel Pinna nobilis (Linnaeus, 1758) is one of the biggest bivalves worldwide. Currently, no updated information is available in the literature concerning the morpho-functional aspects of haemocytes from this bivalve species. Consequently, in this study, we characterised P. nobilis haemocytes from both a morphological and functional point of view. The mean number of haemocytes was about 5 (×10(5)) cells mL haemolymph(-1), and the cell viability was about 92-100%. Two haemocyte types were distinguished under the light microscope: granulocytes (51.6%), with evident cytoplasmic granules, and hyalinocytes (48.4%), with a few granules. The granules of the granulocytes were mainly lysosomes, as indicated by the in vivo staining with Neutral Red. Haemocytes were further distinguished in basophils (83.75%), acidophils (14.75%) and neutrophils (1.5%). After adhesion to slides and fixation, the cell diameter was approximately 10 μm for granulocytes and 7 μm for hyalinocytes. The granulocytes and hyalinocytes were both positive to the Periodic Acid-Schiff reaction for carbohydrates. Only granulocytes were able to phagocytise yeast cells. The phagocytic index (6%) increased significantly up to twofold after preincubation of yeast in cell-free haemolymph, suggesting that haemolymph has opsonising properties. In addition, haemocytes produce superoxide anion and acid and alkaline phosphatases. Summarising, this preliminary study indicates that both the granulocytes and hyalinocytes circulate in the haemolymph of P. nobilis and that they are active immunocytes.
authors.affiliation: Department of Biology, University of Padova, Via Ugo Bassi 58/B, 35131, Padova, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Matozzo
authors.affiliation: Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Ferdinando Stagno d'Alcontres, 31, 98166, S. Agata-Messina, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Pagano
authors.affiliation: Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Ferdinando Stagno d'Alcontres, 31, 98166, S. Agata-Messina, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Spinelli
authors.affiliation: Department of Biology, Electron Microscopy Laboratory, University of Padova, Via Ugo Bassi 58/B, 35131, Padova, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Caicci
authors.affiliation: Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Ferdinando Stagno d'Alcontres, 31, 98166, S. Agata-Messina, Italy. Electronic address: cfaggio@unime.it.
authors.forename: C
authors.initials: C
authors.lastname: Faggio
mesh_terms: D000818:Animals; D049872:Bivalvia / Q000166:cytology* / Q000502:physiology* / Q000648:ultrastructure; D006434:Hemocytes / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D010587:Phagocytosis
keywords: Bivalves; Haemocytes; Immune system; Pinna nobilis