title: The reaction of the sponge Chondrosia reniformis to mechanical stimulation is mediated by the outer epithelium and the release of stiffening factor(s).
abstract: Although sponges are still often considered to be simple, inactive animals, both larvae and adults of different species show clear coordination phenomena triggered by extrinsic and intrinsic stimuli. Chondrosia reniformis, a common Mediterranean demosponge, lacks both endogenous siliceous spicules and reinforcing spongin fibers and has a very conspicuous collagenous mesohyl. Although this species can stiffen its body in response to mechanical stimulation when handled, almost no quantitative data are available in the literature on this phenomenon. The present work was intended to quantify the dynamic response to mechanical stimulation both of intact animals and isolated tissue samples in order to evaluate: (i) the magnitude of stiffening; (ii) the relationship between the amount of stimulation and the magnitude of the stiffening response; (iii) the ability of the whole body to react to localized stimulation; (iv) the possible occurrence of a conduction mechanism and the role of the exopinacoderm (outer epithelium). Data on mesohyl tensility obtained with mechanical tests confirmed the difference between stimulated and non-stimulated isolated tissue samples, showing a significant relationship between ectosome stiffness and the amount of mechanical stimulation. Our experiments revealed a significant difference in tensility between undisturbed and maximally stiffened sponges and evidence of signal transmission that requires a continuous exopinacoderm. We also provide further evidence for the presence of a chemical factor that alters the interaction between collagen fibrils, thereby changing the mechanical properties of the mesohyl.
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy. Electronic address: dario.fassini@gmail.com.
authors.forename: Dario
authors.initials: D
authors.lastname: Fassini
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Parma
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Lembo
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy.
authors.forename: M Daniela
authors.initials: MD
authors.lastname: Candia Carnevali
authors.affiliation: Department of Biological and Biomedical Sciences, Glasgow Caledonian University, G4 0BA Glasgow, United Kingdom.
authors.forename: Iain C
authors.initials: IC
authors.lastname: Wilkie
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Bonasoro
mesh_terms: D000818:Animals; D055252:Cell-Derived Microparticles / Q000502:physiology; D003094:Collagen / Q000378:metabolism; D004848:Epithelium / Q000502:physiology; D010812:Physical Stimulation; D011161:Porifera / Q000502:physiology*; D015398:Signal Transduction; D013718:Tensile Strength
chemical_list: D003094:Collagen
keywords: Collagen; Mesohyl mechanical properties; Pinacoderm; Signal transmission; Stiffening factor