Reproductive ecology of the freshwater red alga Batrachospermum delicatulum (Batrachospermales, Rhodophyta) in three tropical streams

Batrachospermum delicatulum specimens from three stream segments were analyzed from a tropical region in south-eastern Brazil (20°18′- 20°49′S, 49°13′-49°46′W). Physical and chemical parameters and the spatial placement of thalli were investigated along with the reproductive characteristics of the gametophytic phase. Sequence data of the cox 2-3 spacer region was also utilized to evaluate genetic variation in individuals within and among stream segments. Gametophyte occurred under relatively diverse environmental conditions, whereas thalli abundance was weakly or not correlated to environmental variables within the stream segments. All specimens examined were dioecious. The ratio of male/female plants was relatively low (0.5 to 1.3) and male plants tended to occur as clumps (two or three plants together). High reproductive success was observed, as indicated by the occurrence of 100% fertilized (carposporophytic) female plants. This is similar to previous reports for this and other dioecious species, which is remarkable considering the relatively low proportion of male/female plants. Results support the two hypotheses to explain the high reproductive success in dioecious species. The occurrence of male plants in clumps was evidence for a strict spatial relationship (i.e. male plants located in upstream position of female plants in order to release spermatia, which would be carried by eddies through female plants). In contrast, the occurrence of male and female plants adjacent to each other allowed outcrossing among neighboring plants with intermingled male and female branches, which seemed more applicable to some situations (low turbulence habitats). The cox 2-3 spacer region from the 18 individuals sequenced was 376 bp and the DNA sequence was identical with no base pair substitutions. Likewise, a previous study of another Batrachospermum species showed that the same haplotypes were present in all stream segments from the same drainage basin, even though the stream segments were a considerable distance apart. Short distance dispersal either by small birds or waterway connectivity might explain these findings.

Foucault's heraclitism and the concept of history

Deleuze states that Foucault would have created a new relationship between men and history, a relationship other than that established by the philosophers of history. In order to specify the steps Foucault took to accomplish this invention, I shall support, according to Deleuze, Foucault s Heraclitism as the basis for a genuine Foucaultian concept of history. After outlining the risks taken by Foucault s concept of history, I observe this concept at work through the three periods that perform his thought: Archeology, Genealogy and Aesthetics of Existence. The main characters that embody his concept of history through these periods are: a) the discontinuous profile of history; b) the denaturalization of would-be unhistorical objects; c) the historical dimension of body; d) the eddies of subjectivation in history. We shall focus our inspection on the turn made along Foucault s work when he takes into a new account the theme of subjectivity, mostly in the last two volumes of the History of Sexuality. Thus, our attention turns to the subjectivity defined as a process, in order to investigate individual identity as the result of history.