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In sensory cells of the organ of Bellonci, phaosomes originatefrom cisternae of rough endoplasmic reticulum which become flattened and parallel to each other. They are compared to phaosomes of photoreceptor cells in Copepoda and to myeloïd bodies of interstitial cells of epiphysis and of retinal pigment epithelium of different vertebrates.
Removal of optic lobes does not seem to have an important effect on moulting. On the contrary, the removal of protocerebron and optic lobes from C4 males Spheroms prevents them from beginning a premoult; if the operation is performed during the D0 or D1 stages, the Spheroms advance up to D2 but do not moult. The implantation of protocerebron and of optic lobes into brainless Spheroms remaining in C4 seems to restore premoult only with difficulty. In Sphaeroma serratum, the protocerebron would therefore exert a control upon both the beginning of premoult and the ecdysis.
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The zymograms of the digestive caeca and the intestine in seven species of Isopods are established. The glucidasic activities predominate. A relative proteasic poverty is noted as well as the absence of lipases however, the esterases exist. The enzymatic pattern of the gut suggests its participation in the alimentary digestion. The enzymes distribution allows us to establish relations with the food preference of the animals. Some particularities (trypsin, alpha and beta glucosidase) favour a comparison of the marine species with the supralittoral species on one hand and with terrestrial species on the other. This fact does not exclude however the systematic interest of the zymograms.
After having completed their puberty (terminal) molt, males of Sphaeroma serratum, Sphaeroma hookeri and Cymodoce truncata present a degeneration of their Y organs. The degenerative process lasts 1 to 1,5 months in reared animals: it results in a reducing length of Y organs, while nucleus become less numerous and cellular fragments appear. On the contrary, in females of these species, Y organs seem to remain up to death. These facts are perhaps a general characteristic of the family Sphaeromatidae.
The three species A. patersoni, P. mediterranea, L. wollastoni, were found to show a marked response to pressure changes, swimming upwards with increased pressure and downwards with decreased pressure. Endogenous rhythm of activity tended to disappear in specimens maintained under constant pressure conditions equivalent to 20 meters depth. But circadian exogenous rhythm is more clearly determined with Pontellids submitted both to constant pressure (2 bar) and diurnal changes in light intensity than with Pontellids kept under normal pressure. Perception of little changes in hydrostatic pressure is perhaps used by hyponeustonic species to help in depth regulation.
The utilization of marine amphipods Podocerus fulanus and Corophium acherusicum, and the marine isopod Paracerceis sculpta in heavy metal toxicity tests (Cd and Cu) demonstrated on the one hand, the value of these animals as tests subjects when exposed to various polluting agents and, on the other hand their tolerance to heavy metals in acute toxicity tests.
Thirty-three male length-frequency samples are analysed first by a multivariate procedure. The evolutionary cycles are pointed out by the interpretation of the first two components. The simulation model is built up on the basis of factorial analysis. The assessment of age classes parameters (mean, standard deviation, percentage) is then carried out by the simulation of data. Their configuration with respect to the two components points out the proximity of the observed and generated samples and shows the value of the statistical model.
Orchestia gammarellus females and males were X-irradiated with doses of 2,300-40,000 R. The LD 50/20 is 2,300 R. No egg-laying was observed in any irradiated females. Radiosensitivity of embryos was higher than that of the female parent.
In males of Sphaeroma serratum, ecdysterone is titrated, using gas chromatography, during the puberty molt. Its quantity is weak, except during D0 and D1.
The molting hormone content is low during stages C, D0, D1' a-b; it rises up in D 1' c and attains a maximum in D 2. An important decrease of the hormone titer is observed at ecdysis. This titer is slightly lower at stage A and increases again at stage B. Only ecdysterone is detected at stages B and D 2.
The haemolymph of oostegite males of Ligia oceanica and of iM intersexes of Armadillidium vulgare gives a hyperproteinemy owing to stocking of fractions representing vitellogenic proteins of extraovarian source. The only intersexes with ovary or ovariotestis present a vitellin proteic fraction.
Certain ecological aspects of Ergasilus centrarchidarum on largemouth and spotted bass from Lake Fort Smith, Arkansas, were studied during July 1970 through June 1971. There were no significant differences in E. centrarchidarum intensities between host sexes. E. centrarchidarum tended to increase in abundance with the age of the hosts through the first 3 years, then declined in older hosts. Maximum abundance and egg production occurred during the summer months. Optimum temperatures for abundance and egg production ranged from 24 to 29 C. There was no evidence of antagonism among E. centrarchidarum and other concomitant species of gill parasites.
A total of 2,568 specimens of 3 species of ostracod, namely Herpetocypris sp., Ilyocypris sp., and Cypria reptans Brohnstein, 1928, was collected between November 1994 and April 1995 from the Ceresina Canal, a tributary of the River Brenta (northern Italy), and examined for larval helminths. Larvae of Neoechinorhynchus rutili Müller, 1780 were found in the hemocoel of C. reptans. The prevalence of infection ranged from 8.57 to 14.51%. Most larvae were in the cystacanth stage (a new geographical record for this cystacanth). Not more than 3 larvae were encountered in a single host. Among 48 aquatic alder fly larvae of Sialis lutaria collected over 6 mo, together with the crustacean, no infected larvae were encountered. Specimens of Gasterosteus aculeatus (Pisces: Gasterosteiformis) collected with the arthropods from the same site were found to be parasitized with adult N. rutili. Fish stomach content analysis showed ostracods to be a major food item of three-spined sticklebacks in the study area during much of the year.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.