The distribution and characterization of heterochromatin in a series of cultivars, parents, new amphiploids and progeny of hexaploid triticale were comparatively studied using C-banding and morphometric analysis. A high level of intervarietal polymorphism was detected for the banding pattern. The chromosome pairs 4A and 1R presented the most constant pattern of heterochromatin distribution among 31 triticale lines studied. A total of 126 bands have been catalogued, from which 28, 59, and 39 belong, respectively, to the A, B and R genomes. The ratio of polymorphic bands per genome was 23/28, 36/59, and 30/39. The chromosomes displayed heterochromatin modifications consistent in both presence–absence and relative length of their content per genome, when passed from the parents to the amphiploids. Variations in the heterochromatin were also observed among sister plants coming from crosses between wheat and triticale. The heterochromatin content showed gradual tendencies either to increase or decrease in each genome during successive self-cross generations after that cross. The existence of a systematic process of variation of heterochromatin content in triticale is assumed, and the nature of this phenomenon is discussed.Key words: triticale, tetraploid wheat, rye, C-banding, heterochromatin.

Genetic variability in 20 natural populations of the species Elytrigia repens (L.) Nevski and Elytrigia pungens (Pers.) Tutin collected at different geographical places in Spain has been analysed using eight isozyme systems. Analysis of the isoenzymatic patterns indicates inter-and intrapopulational variability in all of the isozyme systems except LAP. The data of intrapopulational variability level, calculated in each population, did not show significant differences in either species. The factorial analysis of correspondence showed a specific distribution of the populations into two groups, based on a series of discriminatory isoenzymatic bands that belonged to different systems and whose relative importance is discussed. The dendrogram obtained with the UPGMA method established a specific distribution for the populational subgroups within each species grouping, and showed a lower level of interpopulational variability in E. repens than in E. pungens. Our results suggest a significant relationship between isozyme variability and several geographical variables (latitude, longitude and altitude).

Meiosis in four primary hexaploid triticale lines, in their component two tetraploid wheat and two rye parents, and in the hybrids obtained by crossing within each ploidic level was studied using Giemsa banding. The individual chromosomes were identified and their meiotic behaviour at first metaphase was analyzed in each line. In each new triticale line, the level of pairing for wheat chromosomes was moderately reduced and for rye chromosomes was very significantly reduced, in comparison with that of the wheat and rye parents used to synthesize it. The pairing intensity observed suggests the presence of a strong negative intergenomic interaction between the rye and wheat genomes in triticale, irrespective of whether the rye is in a homozygous or heterozygous genotypic condition. The homozygosity or heterozygosity in the wheat constituent does not appear to effect the behaviour of the rye chromosomes in triticale.Key words: triticale, meiosis, C-banding, heterosis.

Thermoregulatory behavior of red sea urchin Strongylocentrotus franciscanus and purple sea urchin S. purpuratus was determined in a horizontal thermal gradient. The preferred temperature select by the red sea urchin was 17.5 ± 0.3 ºC during the diurnal cycle and 16.8 ± 0.4 ºC for the night. The purple sea urchin preferred temperature during daytime of 18.8 ± 0.2 ºC and night was 17.4 ± 0.3 ºC. For both species of sea urchin preferendum between day and night cycles were different (P < 0.05), the purple sea urchin preferred higher temperatures that red urchin, suggesting that S. purpuratus use thermoregulatory behavior as a mechanism of environmental segregation to avoid competition for space and food with red sea urchin.

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