[Ultrastructural aspects of Carcinus maenas L. hemocytes (Crustacea, Decapoda), parasitized by Sacculina carcini Thompson (Crustacea, Cirripeda) : reactive activity, collagen genesis]

The collagen embedding Sacculina roots is synthesized by hemocytes of Carcinus maenas and is described. Hemocytes engaged in the secretion of collagen as a reaction against a parasite constitute a defensive mechanism still largely unknown within Crustacea.

[Particles resembling virus associated with the Y organ of the crab Carcinus maenas (Crustacea, Decapoda)]

Virus-like particles have been observed in the Y organ of the shore Crab., Carcinus maenas. These particles are ovoïd in form and enveloped. Their morphogeneses occur by budding from the plasmic membrane. Their relationship to viruses of Crustacea is discussed.

On the fine structure of the regressing ecdysial glands of carcinus maenas L. (Crustacea Decapoda) parasitized by Sacculina carcini Thompson

The ecdysial glands (Y organs) of the crab Carcinus maenas regress in the presence of an external parasite, Sacculina carcini. This regression is more or less severe and may lead to complete autolysis. Three gradual stages in this involutionary process are described. In stage I, the gland cells are nearly normal. Nuclei and cytoplasmic organelles remain unchanged, but large vacuoles begin to appear. Stage II corresponds to more or less drastic nuclear pyknosis and cytoplasmic alterations. Myelin figures are large and numerous. Lysosomes and autophagic vacuoles with phosphatase activity are abundant. However, the general cellular architecture remains preserved. Stage III corresponds to irreversible cytolysis; nuclear envelopes and plasma membranes have disappeared. What remains is an accumulation of cellular debris becoming engulfed by circulating hemocytes. Not all of the gland cells of any given Y organ show the same degree of regression; degeneration is asynchronous. Structures seemingly corresponding to absorptive roots of the parasite are seen. Their lumen is coated with microvilli. The putative direct and indirect influences of the rhizocephalan parasite on its host are discussed. Our results on regressing Y organs of parasitized crabs are compared with those on regressing ecdysial glands of insects.

[Ultrastructure of the blood cells present in the Y organ of Carcinus maenas L. (Crustacea, Decapoda)]

Ultrastructural characters of the hemocytes in the Y organ of Carcinus maenas lead us to assimilate these cells to the "granulocytes". In the degenerating glands, these hemocytes evolve towards a peculiar physiological state: they show a phagocytic activity which confers on them macrophagic properties.

[Vesicles of the smooth endoplasmic reticulum in the Y organ of Carcinus maenas L. (Crustacea, Decapoda)]

The smooth endoplasmic reticulum in the Y organ cells consists of vesicular and tubular elements containing a slightly electron dense substance. The contents of these vesicles are released either at the gland surface or within the intercellular spaces. These processes which are concomitant with the hormonal activity preparatory to the molting, may represent the release of crustecdysone or of one of its precursors.