Sphaeroma Serratum Research Articles

Influence des glandes antennaires sur la regulation ionique, la teneur en eau et eventuellement la mue de Sphaeroma serratum (Crustacea, Isopoda, Flabellifera)

1. 1. In Sphaeroma serratum, the removal of the antennary glands causes a small change in the regulation of the hemolymph sodium concentration, inducing hypocalcemia and a rise in water content. 2. 2. The marked changes of calcemia and water content, which normally follow ecdysterone injection, are reduced in Sphaeroma which lack the antennary glands. 3. 3. The possible role of the antennary glands in parts of the proecdysial and ecdysial processes is discussed.

Cycle biologique de l'isopode Jaera hopeana dans les milieux marins et lagunaires du Nord-Est de la Tunisie

A comparative study shows that invasion of some salt-water lakes by Jaera hopeana Costa, 1853, a commensal species of Sphaeroma serratum, has not induced any notable modifications in its life cycle. This life cycle has been defined by following mensual evolution in the composition of field populations. Reproduction occurs throughout the year, but is more intense during some periods; growth is continuous in immature individuals, but ceases in summer in males and females. The life span is about 6 to 10 months; the species has, therefore, a short generation time.

Ecdysterone, premue et exuviation chez Sphaeroma serratum (fabricius, 1787) (crustacea, isopoda, flabellifera)

Injecting ecdysterone makes pubescent males of Sphaeroma serratum enter proecdysis; they reach the D 2 stage about 11 to 13 days later; however they remain then blocked at this stage, without leaving their old cuticle, before dying between the Days 10 and 20. The haemolymph of these animals correlatively undergoes variations, similar to those of a normal premolt: raising of calcemia and osmotic pressure, light lowering of the water content; between the stages D2 and D,E an important and sudden lowering of calcemia and osmotic pressure can be observed. At the same time on the contrary, the water content raises only slightly, for the old cuticle sets limits to the increasing volume of the Spherom. After injecting ecdysterone to nonpubescent animals, these leave their cuticle, and their water content raises as much as during a normal exuviation. The exuviation factor (Graf, 1972a and b, C. R. Acad. Sci. 274, 1731—1734; 275, 2045–2048) produced by the Y organs ( Blanchet, 1974, C. R. Acad. Sci. 278, 509–512) would therefore perhaps control only cuticle leaving.

Variations saisonnieres des capacites ionoregulatrices de Sphaeroma Serratum (Fabricius, 1787) (Crustacea, Isopoda, Flabellifera)

1. 1. Haemolymph sodium concentration of Sphaeroma serratum varies throughout the year. 2. 2. Its ionoregulatory abilities undergo an annual cycle: they are important in the winter and weak in the summer. 3. 3. Ionoregulation increases with low and mean temperatures (8–15°C). 4. 4. Senescence which appears at the end of the biological cycle of S. serratum lowers its ionoregulatory abilities.

Free amino acids of hemolymph during pubertal molting and senescence in Spaeroma serratum (Isopoda, Flabellifera

In Sphaeroma serratum, the amino-acidemia is high (about 120 mg/100 ml) during the intermolt stages. The relative proportions of the different free amino acids show only slight differences in young males and senescent ones. At the time of the puberty molt, the total amino-acids concentration (including taurine) of the hemolymph increases sharply during premolt (up to 267 mg/100 ml), falls after ecdysis (down to 97 mg/100 ml and then rises up to the level of the intermolt stage. These variations are due not only to concentration or dilution of the whole hemolymph constituents, but also to specific modifications of the concentration of some of the free amino-acids with respect to the others. These variations of the amino-acidemia, mainly those of serine, proline, glycine, alanine and of the amine taurine, could play a definite role in increasing the osmotic pressure of the hemolymph during premolt, as a preparation to ecdysis.

Properties of the (Na +-K +)-ATPase from pleopods of Sphaeroma serratum (Fabricius)

1. 1. The conditions for optimal activity of Sphaeroma serratum pleopods (Na +-K +-ATPase (pH; temperature; Na +,K +,Mg 2+, ATP concentrations) and for ouabain inhibition were studied. 2. 2. A maximal activation of enzyme was found for an exceptionally high ratio of 6 mM Mg 2+ per 3 mM ATP. 3. 3. The Na +-activation showed two maxima at 30 and 100–120 mM, both being K + dependent. 4. 4. The hypothesis of two different (Na −-K +)-ATPases is proposed and a Na + and K + transport model is suggested.

An idealized model of dissolved sulfate distribution in Recent sediments : Berner Robert A., 1964. Geochim. cosmochim. Acta. 28 (9): 1497–1503

The cuticle of the cornea in Crustacea is an interesting example of a composite material compromising between two distinct functions. As part of the dioptric apparatus of the ommatidia within the complex eye it forms transparent micro-lenses that should as well maintain the mechanical stability of the head capsule. We analyzed the ultrastructure and composition of the isopod cornea cuticle of the terrestrial species Ligia oceanica and the marine Sphaeroma serratum. We used a variety of tissue preparation methods, electron microscopic techniques as well as electron microprobe analysis and Raman spectroscopic imaging. The results reveal various structural adaptations that likely increase light transmission. These are an increase in the thickness of the epicuticle, a reduction of the thickness of the outer layer of calcite, a spatial restriction of pore canals to interommatidial regions, and, for S. serratum only, an increase in calcite crystal size. In both species protein–chitin fibrils within the proximal exocuticle form a peculiar reticular structure that does not occur within the cuticle of the head capsule. In L. oceanica differential mineralization results in a spherically shaped interface between mineralized and unmineralized endocuticle, likely an adaptation to increase the refractive power of the cornea maintaining the mechanical stability of the cuticle between the ommatidia. The results show that the habitat and differences in the general structure of the animal’s cuticle affect the way in which the cornea is adapted to its optical function.

Jaera hopeana, an intertidal isopod new to the British fauna

A long-established population of Jaera hopeana living ectocommensally upon Sphaeroma serratum is described from Wembury. This is a new record for the British fauna and is the northernmost record of a species which is found predominantly in the Mediterranean and Black Sea.

Sur Un Phénotype Nouveau, Marmoratum, De L'Espèce Sphaeroma Serratum (Fabricius), Des Cotes Occidentales D'Afrique

A new phenotype, marmoratum, of the Isopod Sphaeroma serratum (F.), occurring on the coasts of W. Africa, is described. This phenotype, near to the previously described phenotype ornatum, is determined by an autosomal gene, dominant to the gene albicans, epistatic with the gene discretum, and perhaps an allelomorph of the gene ornatum.