Community structure and functional roles of meiofauna in the North Sea

Knowiedge on community structure of North Sea meiofauna has greatly increased recently. A quasisynoptic picture of meiofauna densities and copepod community structure from 171 stations of the southern North Sea, sampled in April–May 1986, has been obtained during the North Sea Benthos Survey. Latitudinal patterns in meiofauna abundance and copepod weight, abundance and diversity exist in an area between 51°30′N and 58°30′N. Using TWINSPAN-classification five major groups of copepod species can be recognized which are related to sediment type, latitude and depth. The part of the meiofauna in total benthic energy flow, their role in the benthic food web and in biogeochemical cycles is discussed based on existing literature. There are still considerable gaps in knowledge and the field is not progressing rapidly. Publication no. 599 Netherlands Institute of Ecology, Centre for Estuarine and Coastal Ecology, Yerseke, The Netherlands.     

The periodic change in adenosine 3′,5′-monophosphate concentration in sea-urchin eggs

The level of adenosine 3′,5′-monophosphate (cyclic AMP) in the eggs of the sea urchin, Anthocidaris crassispina, was found to change periodically after fertilization. The minimum and maximum levels of cyclic AMP were 1.0·10^?7 M and 1.5·10^?6 M, respectively. The activity of adenylate cyclase in a 105 000 × g precipitate reached a plateau at 20 min after fertilization and stayed constant for at least 2 h. It was also found that 1.0 mM CaCl₂ increased the activity of adenylate cyclase in the same precipitate from unfertilized eggs. In contrast, phosphodiesterase activity changed periodically and correlated with cyclic AMP levels in the eggs. Up to a concentration of 1.5·10^?6 M cyclic AMP, phosphodiesterase activity was low, but it became activated when the level of cyclic AMP rose beyond this level. These results indicate that the change in the intracellular level of cyclic AMP is regulated mainly by the change in phosphodiesterase activity.     

Properties of the foot inhibitor from hydra

Summary A substance was isolated from crude extracts of hydra that inhibits foot regeneration. This substance, the foot inhibitor, has a molecular weight of 500 daltons. It is a hydrophilic molecule, slightly basic in character and it has no peptide bonds. The pruified substance acts specifically and at concentrations lower than 10^–7 M. At this low concentration only foot and not head regeneration is inhibited. Hydra are sensitive to purified foot inhibitor between the second and eight hour after initiation of foot regeneration by cutting. In normal animals the foot inhibitor is most likely produced by nerve cells. A substance with similar biological and physico-chemical properties is found in other coelenterates.     

Les Radiolaires d'âge jurassique supérieurà crétacé supérieur dans les Radiolarites du Pinde-Olonos (Presqu'île de Koroni; Péloponnèse méridional,Grèce)

Radiolarians of several radiolarites sections of the Pindos-Olonos zone, southern Peloponnesus, lead to propose direct datations of mesozoic sediments. The acuity of such datations allow to distinguish two periods for depositionof radiolarites s.s. in the tethyan region. The first period would be Upper Jurassic and general in tethyan realm, radiolarites depositing under various latitudes (0–35°N). This would be the result of a strong ocean surface current. The second period would be Upper Cretaceous (Vraconian—Coniacian) and be geographically much more restricted (0–15°N). This could result from a weaker current. The absence of radiolaritic sedimentation is possibly the result of the destruction or insulation of the accurate basins during the obduction of ophiolites on the apulo-african realm. The inventory of Late Cretaceous radiolarian fauna, rarely done on alpine series so far, shows similar result to those obtained in Central American and California.     

Une nouvelle sous-famille,les Poulpinae, et quatre nouvelles espèces de Saitoum radiolaires mésozoiques téthysiens

Studies of skeleton elements of several jurassic species of Saitoum allow to compare them with Poulpus from Trias. The sub-family Poulpinae is introduced, caracterised by three cephalic arcs and the collar position of the cephalic structure. Among the jurassic forms, 4 species are newly described: S. corniculum, S. elegans, S. levium and S. trichylum.     

Cytological changes and DNA and protein synthesis in parthenogenetically activated sea urchin eggs

Summary The present study deals with cytological observations, DNA and protein synthesis in artificially activated sea urchin eggs. The eggs were activated by means of Loeb's double treatment with butyric acid and hypertonic sea water. Most of the eggs ofHemicentrotus pulcherrimus divided when the chromosomes duplicated after formation of the first monaster and other eggs divided at a later cell cycle. In the eggs ofTemnopleurus toreumaticus, however, haploid division at the first cell cycle was observed predominantly.Activated eggs that were treated for 25 min with hypertonic sea water showed a marked uptake of³H-thymidine during the two periods of 30–40 min and 90–100 min after the double treatment. These periodic changes in the³H-thymidine uptake paralleled morphological changes within the nucleus. However, these periods of increased uptake were not observed in the eggs treated with hypertonic sea water for 60 min. During exposure to hypertonic sea water, the³H-thymidine-uptake by eggs activated with butyric acid decreased gradually. When the uptake of¹⁴C-valine by eggs was measured, a very low level was seen in unfertilized eggs. The level of uptake increased strikingly when the eggs were activated with butyric acid but was suppressed by the hypertonic treatment. However, removal of the eggs to sea water allowed the uptake to return to the former high level. This pattern suggests that the hypertonic treatment has an inhibitory effect on the synthesis of protein (or enzymes) which obstruct cleavage induction.     

Commitment to vegetalized development in sea urchin embryos

Summary Strongylocentrotus purpuratus embryos were reared in 0.025 M LiCl, which causes commitment to vegetalized development within 5 h after treatment begun at fertilization. Treated and control embryos were labelled with³⁵S-methionine for 3 h intervals from 2–14 h, solubilized, and subjected to 2-dimensional polyacrylamide gel electrophoresis. Comparison of autoradiographs of the gels, in which over 400 proteins can be detected, indicate that while LiCl treatment causes a short delay in the initiation or cessation of synthesis of a few proteins, no qualitative or major quantitative differences can be detected between control and treated embryos. Normal gastrulae and vegetalized exogastrulae labelled 38 h after fertilization have several differences in patterns of protein synthesis. We conclude that the early determinative events involved in vegetalization are not reflected in detectable differences in the pattern of protein synthesis.     

The form and function of cnidarian spirocysts

Summary The electron-dense capsule tip (apical cap) of sea anemone and coral spirocysts is of a different structure than the capsule wall. The capsule wall is composed of a double layer of fiber-like materials which cross each other at roughly right angles. The innermost layer is characterized by numerous serrations, the tips of which project into the lumen of the capsule. Within each serration, a band of finely cross-striated material encircles the capsule at right angles to its longitudinal axis. The membrane lining the lumen of the capsule appears to be continuous with the wall of the undischarged thread. The outer capsule wall layer consists of closely spaced microfilaments (cnidofilaments) which are oriented in the longitudinal axis of the capsule. The cnidofilaments appear to merge with the apical cap material. Contrary to some previous reports in the literature, it has been found that spirocysts normally discharge by eversion, as do nematocysts. The relationship of the capsule wall sub-structure to the spirocyst discharge process is discussed.Thanks are due Dr. Cadet Hand for the use of the facilities of the Bodega Marine Laboratory of the University of California and B. Miller, F. Doroshow, C. Bigger, G. Chapman and E. Chang for expert technical assistance. The use of the facilities of the Electron Microscope Laboratory and Electronics Research Laboratory of the University of California at Berkeley and the Eelectron Microscope Laboratory of the Florida State University is gratefully acknowledged. Part of this work was made possible by NSF Grant GB-40547 to the senior author     

THE CYST-THECA RELATIONSHIP IN CALCIODINELLUM OPEROSUM EMEND. (PERIDINIALES, DINOPHYCEAE) AND A NEW APPROACH FOR THE STUDY OF CALCAREOUS CYSTS

The paratabulate calcareous cyst of Calciodinellum operosum Deflandre was recorded in a sediment trap sample collected in the Bay of Naples (Tyrrhenian Sea, Italy). The germination of this resting stage produced a phototrophic vegetative cell that had the typical plate pattern of a Scrippsiella species. The cyst morphotypes, observed in a clonal culture of this species, ranged from cysts with well-developed paratabulation to cysts in which the paratabulation was barely visible, to cysts covered by irregularly shaped crystals. The analysis of thin sections of the calcareous cysts using the polarized light microscope equipped with crossed nicols and a gypsum plate showed that the optical orientation of the calcite crystals was tangential in all the morphotypes examined. We suggest that the crystallographic method we describe might provide insights for calcareous cyst taxonomy and phylogeny .     

Acremonoside,a phenolic glucoside from the sea fan-derived fungus Acremonium polychromum PSU-F125

A new phenolic glucoside, acremonoside (1), along with two known compounds, F-11334 A₂ and 2,2-dimethyl-2H-chromen-6-ol, were isolated from the sea fan-derived fungus Acremonium polychromum PSU-F125. The structure of 1 was elucidated by spectroscopic techniques, acid hydrolysis and X-ray crystallographic analysis. The isolated compounds were tested for antibacterial, antimalarial, antimycobacterial and cytotoxic activities.