Influence of light,DMSO and glycerol on the hatchability ofThamnocephalus platyurus Packard cysts

Effects of two light intensities and different concentration of dimethyl sulfoxide (DMSO) and glycerol on hydrated cyst hatching inThamnocephalus platyurus were studied. A maximum of 65±6% hatching was recorded within seven days at 2500 lux continuous light regime. Hatching was at a minimum during the first two days, peaked between the third and fourth days, decreased thereafter. Hatching success was a function of duration of light exposure. Eight percent of cysts hatched in the dark, while cysts exposed to 24h light and subsequently incubated in the dark showed 27±2% hatching. Hatchability was significantly increased (23%) in 0.0375% DMSO and 0.0125% glycerol. Concentration above 0.05% DMSO and 0.025% glycerol had no or a negative influence on hatching. Since low concentrations of DMSO were non-toxic, apolar compounds like Ca²⁺ ionophore can be dissolved in DMSO to study the role of Calcium in cyst hatching.     

Historical biogeography and morphological differentiation ofStreptocephalus torvicornis (Waga) since the Würm III-glaciation

We argue that the Würm III glaciation eradicated possible European populations ofS. torvicornis, and that today, a reconquest of Europe takes place on two fronts.A western wave has reached the Pyrenees, an eastern one now occupies most of eastern and northern Europe. The western route probably started in the Maghreb, the eastern one in the Levant and the Ponto-Caspian. Animals in the west had to move north by crossing, at right angles, a series of east-west oriented river valleys and progressed slowly; animals in the east could move up river valleys extending north-east, and moved quickly. Italy was not occupied, becauseS.torvicornis is a warm stenotherm, and by the time the climate had warmed sufficiently for it to reach the southern shore of the mediterranean (ca 6000 BP), the gap with Italy was probably too large for a crossing. Cold-loving species (of the generaBranchipus, Chirocephalus) conversely, and could freely flow across the Central Mediterranean at low sea-levels (ca 12000 BP), and now occur in Italy (and the rest of Europe) as well as in Northern Africa.A prediction of our hypothesis is that the pioneer populations in Spain and Central Europe should have been isolated longest. Thisis tested and confirmed by their comparative morphology, and two subspecies,S. t. torvicornis andS. t. bucheti are reinstated.A gap across the Nile Valley where onlyS. rubricaudatus seems to occur, deserves further study.     

Culturing the fairy shrimp Streptocephalus dichotomus Baird using livestock waste – a reclamation study

The present study describes a defined culturetechnique for the fairy shrimp, Streptocephalusdichotomus. It emphasizes reclamation of low-cost organiclive-stock waste(cow-dung), lime powder, and urea. These compounds wereused to enrich algal and diatom populations in themedium. These algae and diatoms were fed to filter feedingfairy shrimps to yield anostracanbiomass. A production of 262 ± 6 animals l^–1was obtained in an experimental tank compared to 36 ± 4animals l^–1 in the controls. Interestingly,the total number of clutches in experimentalfemales (12 ± 2), relative to the control (7 ± 1),increased too.     

Thyrotropin stimulation of the phosphorylation of serine in the N-terminal of thyroid H1 histones.

The analysis of thyroid nuclear proteins by polyacrylamide gel electrophoresis has demonstrated that thyrotropin and dibutyryl adenosine 3':5'-monophosphate stimulate specifically the phosphorylation of H1 histones in an intact cell system. This effect does not require new protein synthesis and implicates the phosphorylation of secrine residue(s) situated in the N-terminal part of H1 histones.     

On the continental Copepod fauna of Morocco

A series of samples, collected in different parts of Morocco, contained 26 species and one subspecies of Copepoda. Ten among these are new to the fauna of Morocco and one is new to Science. Two species (Eucyclops hadjebensis Kiefer and Mixodiaptomus laciniatus atlantis Kiefer) are endemic to Morocco; Afrocyclops gibsoni Brady and Thermocyclops schuurmanae Kiefer are Ethiopan species. The former reaches its limit of Northern extent East of the Atlas mountains; the latter is a pluvial relict. The remaining species have either a cosmopolitan, circummediterranean or North-African distribution, with the exception of Cyclops abyssorum mauretaniae which is a southern element of the Eurasiatic genus Cyclops. Its taxonomical status is reviewed in some detail. Thermocyclops infrequens Kiefer is synonymized with T. schuurmanae Kiefer. It is concluded that the largest gaps in our knowledge of the Copepoda of Morocco are now in the group of the Harpacticoida.Contribution no. 14 of the biological expedition of the University of Gent (Belgium) to Morocco, July–August 1971     

Cyst hatching in Anostraca accelerated by retinoic acid,amplified by Calcium Ionophore A23187, and inhibited by Calcium-channel blockers

Cyst hatching, under standardized conditions, of the Anostracan species Thamnocephalus platyurus and Streptocephalus dichotomus was significantly accelerated but not increased by applying the morphogen retinoic acid (RA). Cyst hatching was enhanced but not accelerated by artificially increasing the inflow of Ca²⁺ to the embryonic cells, using Calcium Ionophore A 23 187. Cyst hatching was accelerated and amplified, to a level in excess of the summed effects of each treatment, by a combined application of RA and ionophore. It was inhibited almost quantitatively by the Calcium-channel blockers Nifedipin and Verapamil. The significance of these findings is discussed.     

The vitelline envelope,chorion, and micropyle of Fundulus heteroclitus eggs

The architecture and transformation of the vitelline envelope of the developing oocyte into the chorion of the mature egg of Fundulus heteroclitus have been examined by scanning and transmission electron microscopy. The mature vitelline envelope is structurally complex and consists of about nine strata. The envelope is penetrated by pore canals that contain microvilli arising from the oocyte and macrovilli from follicle cells. During the envelope's transformation into the chorion, the pore canals are lost and the envelope becomes more fibrous and compact and its stratified nature less apparent. The micropyle, of pore, through which the sperm gains access to the enclosed egg is located at the bottom of a small funnel-shaped depression in the envelope. Internally, the micropyle opens on the apex of a cone-like elevation of the chorion. During the development of the envelope, structured chorionic fibrils, the components of which are presumed to be synthesized by the follicle cells, become attached to its surface. These chorionic fibrils are though to aid in the attachment of the egg to the substratum and perhaps to help prevent water loss during low tides when the egg may be exposed.     

Numerical simulation of a stroke: computational problems and methodology

We discuss the difficulties of the numerical simulation of a stroke, and we describe the numerical methods which we have developed and used to obtain some realistic results. Nowadays, the computations are performed in two-dimensional slices of a brain, but the strategies to obtain full three-dimensional simulations are explored. This paper is written so as to be understandable by non-mathematicians.