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1.
J Exp Biol ; 220(Pt 11): 2108-2119, 2017 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-28373597

RESUMO

Despite their soft body and slow motion, sea cucumbers present a low predation rate, reflecting the presence of efficient defence systems. For instance, members of the family Holothuriidae rely on Cuvierian tubules for their defence. These tubules are normally stored in the posterior coelomic cavity of the animal, but when the sea cucumber is threatened by a potential predator, they are expelled through the cloacal aperture, elongate, become sticky and entangle and immobilise the predator in a matter of seconds. The mechanical properties (extensibility, tensile strength, stiffness and toughness) of quiescent (i.e. in the body cavity) and elongated (i.e. after expulsion) Cuvierian tubules were investigated in the species Holothuria forskali using traction tests. Important mechanical differences were measured between the two types of tubules, reflecting adaptability to their operating mode: to ease elongation, quiescent tubules present a low resistance to extension, while elongated tubules present a high toughness to resist tractions generated by the predator. We demonstrate that a mutable collagenous tissue (MCT) is involved in the functioning of these organs: (1) some mechanical properties of Cuvierian tubules are modified by incubation in a cell-disrupting solution; (2) the connective tissue layer encloses juxtaligamental-like cells, a cell type present in all MCTs; and (3) tensilin, a MCT stiffening protein, was localised inside these cells. Cuvierian tubules thus appear to enclose a new type of MCT which shows irreversible stiffening.


Assuntos
Colágeno/fisiologia , Tecido Conjuntivo/química , Holothuria/fisiologia , Sequência de Aminoácidos , Animais , Fenômenos Biomecânicos , Proteínas de Transporte , Colágeno/efeitos dos fármacos , Tecido Conjuntivo/ultraestrutura , Octoxinol , Resistência à Tração/fisiologia
2.
J Exp Biol ; 214(Pt 8): 1347-56, 2011 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-21430212

RESUMO

More than 100 triterpene glycosides (saponins) have been characterized in holothuroids in the past several decades. In particular, Holothuria forskali contains 26 saponins in its Cuvierian tubules and 12 in its body wall. This high diversity could be linked to a chemical defense mechanism, the most commonly accepted biological role for these secondary metabolites. We performed an integrated study of the body-wall saponins of H. forskali. The saponins are mainly localized in the epidermis and in the mesothelium of the body wall and appear to be released when the holothuroid is stressed. Among the saponins present in the epidermis, one (holothurinoside G) was detected in the seawater surrounding non-stressed holothuroids and three others (holohurinosides C and F, and desholothurin A) were secreted when the animals were stressed. In addition, two new congeners (detected at m/z 1301 and 1317) were also present in the immediate surroundings of stressed holothuroids. These new saponins do not originate from the epidermis and could come from an internal organ. Quantities of secreted saponins were very low compared with the body wall and Cuvierian tubules concentrations. At natural concentrations, saponins do not represent a threat to the health of predatory fish. The deterrent effect of saponins seems therefore to act as an aposematic signal, warning potential predators of the unpalatability of the holothuroid tissues.


Assuntos
Comportamento Animal/efeitos dos fármacos , Peixes/fisiologia , Holothuria/química , Comportamento Predatório/efeitos dos fármacos , Saponinas , Triterpenos , Animais , Holothuria/ultraestrutura , Estrutura Molecular , Saponinas/química , Saponinas/farmacologia , Água do Mar , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Triterpenos/química , Triterpenos/farmacologia
3.
PLoS One ; 5(11): e13923, 2010 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-21085713

RESUMO

BACKGROUND: Several species of sea cucumbers of the family Holothuriidae possess a particular mechanical defense system called the Cuvierian tubules (Ct). It is also a chemical defense system as triterpene glycosides (saponins) appear to be particularly concentrated in Ct. In the present study, the precise localization of saponins in the Ct of Holothuria forskali is investigated. Classical histochemical labeling using lectin was firstly performed but did not generate any conclusive results. Thus, MALDI mass spectrometry Imaging (MALDI-MSI) was directly applied and completed by statistical multivariate tests. A comparison between the tubules of relaxed and stressed animals was realized. RESULTS: These analyses allowed the detection of three groups of ions, corresponding to the isomeric saponins of the tubules. Saponins detected at m/z 1287 and 1303 were the most abundant and were apparently localized in the connective tissue of the tubules of both relaxed and stressed individuals. Saponins at m/z 1125 and 1141 were detected in lower amount and were present in tissues of relaxed animals. Finally, saponin ions at 1433, 1449, 1463 and 1479 were observed in some Ct of stressed holothuroids in the outer part of the connective tissue. The saponin group m/z 14xx seems therefore to be stress-specific and could originate from modifications of the saponins with m/z of 11xx. CONCLUSIONS: All the results taken together indicate a complex chemical defense mechanism with, for a single organ, different sets of saponins originating from different cell populations and presenting different responses to stress. The present study also reflects that MALDI-MSI is a valuable tool for chemical ecology studies in which specific chemical signalling molecules like allelochemicals or pheromones have to be tracked. This report represents one of the very first studies using these tools to provide a functional and ecological understanding of the role of natural products from marine invertebrates.


Assuntos
Holothuria/metabolismo , Invertebrados/metabolismo , Saponinas/análise , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz/métodos , Animais , Holothuria/anatomia & histologia , Imuno-Histoquímica , Invertebrados/anatomia & histologia , Lectinas/análise , Lectinas/metabolismo , Biologia Marinha , Estrutura Molecular , Análise de Componente Principal , Saponinas/química , Saponinas/metabolismo , Água do Mar , Estresse Fisiológico
4.
Mar Drugs ; 8(1): 173-89, 2010 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-20161976

RESUMO

To avoid predation, holothuroids produce feeding-deterrent molecules in their body wall and viscera, the so-called saponins. Five tropical sea cucumber species of the family Holothuriidae were investigated in order to study their saponin content in two different organs, the body wall and the Cuvierian tubules. Mass spectrometry techniques (MALDI- and ESI-MS) were used to detect and analyze saponins. The smallest number of saponins was observed in Holothuria atra, which contained a total of four congeners, followed by Holothuria leucospilota, Pearsonothuria graeffei and Actinopyga echinites with six, eight and ten congeners, respectively. Bohadschia subrubra revealed the highest saponin diversity (19 congeners). Saponin mixtures also varied between the two body compartments within a given animal. A semi-quantitative approach completed these results and showed that a high diversity of saponins is not particularly correlated to a high saponin concentration. Although the complexity of the saponin mixtures described makes the elucidation of their respective biological roles difficult, the comparisons between species and between body compartments give some clues about how these molecules may act as predator repellents.


Assuntos
Toxinas Marinhas/análise , Toxinas Marinhas/química , Saponinas/análise , Saponinas/química , Pepinos-do-Mar/química , Animais , Cromatografia Líquida de Alta Pressão , Hemolíticos/análise , Hemolíticos/química , Oceano Índico , Isomerismo , Estrutura Molecular , Especificidade de Órgãos , Pepinos-do-Mar/anatomia & histologia , Especificidade da Espécie , Espectrometria de Massas por Ionização por Electrospray , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Ésteres do Ácido Sulfúrico/análise , Ésteres do Ácido Sulfúrico/química , Espectrometria de Massas em Tandem , Triterpenos/análise , Triterpenos/química
5.
Comp Biochem Physiol B Biochem Mol Biol ; 152(2): 124-34, 2009 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19036349

RESUMO

Sea cucumbers contain triterpene glycosides called saponins. We investigated the complex saponin mixture extracted from the common Mediterranean species Holothuria forskali. Two different body components were analyzed separately: the body wall (which protects the animal and is moreover the most important organ in terms of surface and weight) and the Cuvierian tubules (a defensive organ that can be expelled on predators in response to an attack). MALDI/MS and MALDI/MS/MS were used to detect saponins and describe their molecular structures. As isomers have been found in the Cuvierian tubules, LC/MS and LC/MS/MS were performed to identify each saponin separately. Twelve saponins have been detected in the body wall and 26 in the Cuvierian tubules. All the saponins from the body wall are also present in the Cuvierian tubules but the latter also contain 14 specific saponins. The presence of isomeric saponins complicated structure elucidation for the whole set but 16 saponins have been described tentatively. Among these, 3 had already been reported in the literature as holothurinosides A and C, and desholothurin A. Molecular structures have been proposed for the 13 others which, in the present work, have been provisionally named holothurinosides E, F, G, H, I, A(1), C(1), E(1), F(1), G(1), H(1) and I(1) and desholothurin A(1). The diversity and organ specificity of the saponins described here are much higher than what had been reported to date in any sea cucumber species.


Assuntos
Especificidade de Órgãos , Saponinas/química , Pepinos-do-Mar/química , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Animais , Cátions , Cromatografia Líquida , Saponinas/isolamento & purificação , Extratos de Tecidos
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