The Basal Inhibition in Hydra may be Mediated by a Diffusing Substance

The decay, following basal disk removal, of the disk-mediatedinhibition of disk formation in hydra is as slow as would beexpected, were the inhibition mediated by a diffusing substance. When a hydra's size is changed, either by adding or by removingmass, the inhibition intensity changes in the manner expectedif the vehicle of the inhibition is a substance diffusing fromthe disk and destroyed by all the cells of the body.     

Isozyme variability and differentiation between Rhodnius prolixus, R.robustus and R.pictipes, vectors of Chagas disease in Venezuela

Enzyme polymorphism in triatomine bugs of the genus Rhodnius (Hemiptera: Reduviidae), vectors of Chagas disease, is analysed using both starch and polyacrylamide gel electrophoresis. Out of forty-five enzymes assayed, the electromorphs of seventeen of them: AO, CA, DIA, ES, ES-A, FH, GPD, G6PD, GPI, MDH, ME, 6PGD, PGM, ACON, ACPH, LAP and SOD, involving twenty-two putative structural loci, were scorable. These gene-enzyme systems were therefore selected for routine characterization of R.prolixus Stal adults from different strains. The first thirteen enzymes, involving sixteen structural loci, were also analysed in first instar nymphs of the three species, R.prolixus, R.robustus Larrousse and R.pictipes Stal. Allelic frequencies were calculated for three R.prolixus strains: three to five loci appeared to be polymorphic. The proportion of polymorphic loci (22%) and the average heterozygosity (0.06) indicated low genetic variability, with significant differences between the strains at individual loci. Rhodnius prolixus and R.robustus were found to have identical isozymic patterns. R.pictipes was genetically well differentiated, with twelve diagnostic loci.     

ON THE TUBE ULTRASTRUCTURE AND ORIGIN OF CALCIFICATION IN SABELLIDS (ANNELIDA, POLYCHAETA)

Abstract:  Tube ultrastructure of Jurassic and Cretaceous Glomerula is very similar to that of Recent Calcisabella , supporting the synonymy of these genera and the early Mesozoic origin of calcification in sabellids. Tube structure of serpulids differs from that of Glomerula ; calcareous tubes probably evolved convergently within Sabellida. The tube wall in Recent Glomerula piloseta is composed of subparallel lamellae of aragonitic, irregular spherulitic prisms in the inner layer, and spherulites in the outer layer. Calcified lamellae are separated by organic films of different thickness. The structure of the internal tube layer in Glomerula piloseta , and the structure of entire wall in fossil Glomerula , are similar to the tube structure of Dodecaceria (Polychaeta, Cirratulidae). The irregular spherulitic prisms of Glomerula are similar to those found in the external layer of Hydroides dianthus and the internal layer of Spiraserpula caribensis .