Coscinoderma sporadense sp.n. from the Aegean Sea with comments on Coscinoderma confragosum (Porifera, Dictyoceratida)

Coscinoderma sporadense sp.n. is described from shallow waters in the North Aegean. This is the first record of a Coscinoderma species from the Mediterranean. The new species is compared to the deep water East Atlantic Coscinoderma confragosum Poléjaeff, 1884, and clear differences between them are established. The status of the genus Coscinoderma is discussed.     

Crassophyllum thessalonicae sp.n. (Octocorallia, Pennatulacea), from the Aegean Sea

A new pennatulacean species, Crassophyllum thessalonicae sp.n. is described from the Mediterranean (North Aegean Sea). This is the first record of a Crassophyllum Tixier-Duri vault, 1961 species from the Mediterranean Sea. The differences between the new species and C. cristatum Tixier-Durivault, 1961, the other known species of the genus, are discussed, and the genus Crassophyllum is critically compared with the other two related genera Pteroeides Herklots, 1858 and Sarcoptilus Gray, 1848.     

Allozyme variation and genetic inter-relationships between seven flatfish species (Pleuronectiformes)

A total of 11 enzymes coded by 14 loci were assayed for each of 17 populations (from the north east Atlantic and Mediterranean) of seven flatfish species, including representatives of three of the four European families of the order Pleuronectiformes. Diagnostic alleles were observed for each species and there were fixed differences between the species at many loci. Thus all species were genetically distinct, although there were some common alleles. H_obs was higher than the average of a range of fish species and was also higher than that of vertebrate species as a whole. It seems that flatfish as a group may show higher levels of genetic variation than other fish. Values of genetic identity for all pairwise comparisons fell comfortably within the ranges expected. The data support the grouping of plaice and flounder into a single genus, Pleuronectes , but it is concluded that the retention of the dab in a separate genus, Limanda , is justified. A high level of genetic divergence was found between Dover and thickback soles. Genetic divergence data support the hypothesis that Pleuronectes flesus luscus in the Aegean Sea is a distinct subspecies of Pleuronectes flesus (flounder). The data show a clear separation of the Mediterranean Dover sole population from those in the Atlantic. Low genetic divergence was observed between the Aegean Sea and Atlantic brill populations. It is speculated that about 5 Mya the families Pleuronectidae and later Soleidae evolved from the ancestral Scophthalmidae.     

Non-Coordinate Genetic Alterations in the Expression of Catalase and other Glyoxysomal Enzymes during Maize Development

In the scutellum of maize during post-germinative development,the primary form of catalase expressed is the product of theCat2 structural gene, CAT-2. The developmental time-course ofCAT-2 protein follows a rapid increase with a peak at approximately4–5 d alter germination and a subsequent decline. An inbredstrain of maize, A337, has been found to exhibit a similar generalizedprofile with the significant exception that the level of CAT-2protein present in the scutellum is far above that in the ‘typical’maize lines exemplified by W64A. Our data suggest that the higherlevels of CAT-2 exhibited in A337 are due to increased synthesisand accumulation of more CAT-2 protein, and not merely to enzymeactivation. A comparison of A337 and W64A showed that the twolines are similar with respect to number of glyoxysomes andwith the exception of catalase, other microbody associated enzymesexhibit similar activity levels and developmental profiles.Thus, the results presented suggest that the catalasc developmentalprogramme characteristic of line A337 is not due to a concurrentincrease and subsequent decline in the number of glyoxysomesformed in the scutellum during this developmental period butis instead due to a greater level of CAT-2 protein. The datafurther support our earlier findings that the genes coding forglyoxysomal enzymes in maize are non-coordinately regulated. Key words: Gene regulation, glyoxysomes, catalase, glyoxysomal enzymes     

Regulation of Glyoxysomal Enzyme Expression in Maize

The activity levels of three glyoxysomal enzymes (catalase, isocitric lyase, and malate synthase) were measured in the scutellum following germination of the inbred lines W64A, R6-67, and A16. In W64A, as in most maize lines examined, germination was accompanied by a rapid and synchronous increase in the activities of all three enzymes, and reached a peak at about day 4 and declined thereafter. In R6-67, catalase activity continues to increase past day 4 and reaches its highest activity level on later days. In A16, catalase activity is very low due to the lack of expression of the Cat2 gene. Despite these significant differences in catalase expression, the levels of the other two glyoxysomal enzymes did not differ in these inbred lines. Artificial inhibition of catalase in W64A by exogenous application of 10^–4 M aminotriazole did not inhibit germination, nor did it alter the levels of the other two glyoxysomal enzymes. Similarly, application of 10^–4 M itaconate to W64A seeds inhibited the appearance of isocitric lyase, but did not inhibit germination or alter the levels of malate synthase or catalase. Comparative cell fractionation and immunological studies were conducted with W64A and A16 and their microbodies were observed under the electron microscope. Cell fractionation studies were also conducted with W64A seeds germinated in the presence of aminotriazole or itaconate. Thus, our results suggest that the expression of these three glyoxysomal enzymes is not regulated coordinately in the maize scutellum.