Mariana de S. Carvalho

Cytotoxic Plakortides from the Brazilian Marine Sponge Plakortis angulospiculatus.

Three new plakortides, 7,8-dihydroplakortide E (1), 2, and 10, along with known natural products 3, 4, spongosoritin A (5), 6-8, and plakortide P (9), were isolated from Brazilian specimens of Plakortis angulospiculatus. Compounds 2, 3, 5, and 7-9 displayed cytotoxic activities with IC50 values ranging from 0.2 to 10 μM. Compounds that contained a dihydrofuran ring were generally less active and displayed time dependence in their activity. The activities of compounds 2 and 7-9, carboxylic acids bearing a common six-membered endoperoxide, were higher overall than for compounds 3 and 5. The modes underlying the cytotoxic actions of plakortides 2, 3, 5, 7, and 9 were further investigated using HCT-116 cells. While dihydrofurans 3 and 5 induce a G0/G1 arrest, six-membered peroxides 2, 7, and 9 delivered a G2/M arrest and an accumulation of mitotic figures, indicating a distinctly different antimitotic response. Confocal analysis indicated that microtubules were not altered after treatment with 2, 7, or 9, therein suggesting that the mitotic arrest may be unrelated to cytoskeletal targets. Overall, we find that two related classes of natural products obtained from the same extract offer cytostatic activity, yet they do so through discrete pathways.

Comments on brazilian Halichondria Fleming (Halichondriidae, Halichondrida, Demospongiae), with the description of four new species from the São Sebastião Channel and its environs (Tropical Southwestern Atlantic)

Over 70 species of Halichondria Fleming, 1828 are known world-wide, but only five from the Brazilian Coast. Brazilian records have their status re-evaluated here, and four new species are described for the Sao Sebastiao Channel area, in the Tropical Southwestern Atlantic, viz. H. cebimarensis sp. n., H. sulfurea sp. n., H. migottea sp. n. and H. tenebrica sp. n.

Phakellia sur sp. nov. (Demospongiae, Halichondrida, Axinellidae) from the lower slope off Cape Horn (South America), with a revision of the genus

Abstract Phakellia sur sp. nov. is described from the lower slope off Cape Horn (South America). The species differs from other Phakellia by the possession of straight strongyles as a category of megascleres. A revision of literature records of Phakellia is also provided.

Two new species of Aaptos (Demospongiae, Hadromerida) from Brazil (western Atlantic).

Twenty-one species of Aaptos Gray, 1867 are known world-wide, of which only three were reported from Brazil. Two new species of this genus are here described from the Brazilian coast (Potiguar Basin, Northeastern Brazil): A. hajdui sp. nov. and A. potiguarensis sp. nov. Both possess only one category of strongyloxeas and one of styles, although both with wide size variation, suggesting that the diagnosis of the genus should be revised. Previous Brazilian records of A. aaptos have their status re-evaluated here, and only three species of the genus can be considered valid in Brazil: A. glutinans, A. hajdui sp. nov. and A. potiguarensis sp. nov.

Two new species of Halichondrida (Demospongiae) and the first record of Phycopsis and Ciocalapata for Brazil

Two new species of the genera Phycopsis and Ciocalapata are described from the shallow waters off the Brazilian coast. This is the first record of Phycopsis in South Atlantic, with Phycopsis styloxeata sp. nov. being the only species of the genus that presents three categories of spicules: two of styles and one of oxeas. Ciocalapata, here represented by Ciocalapata minuspiculifera sp. nov., displays smaller oxeas and styles when compared to its congeneric C. amorphosa (Ridley & Dendy, 1886). The definition of this genus was modified and its geographical and bathymetric distributions now extend from the coast of Argentina to the northeastern coast of Brazil (state of Bahia) and from deep (1.097 m) to shallow (14-20 m) waters, respectively.