Interaction of equatorial waves through resonance with the diurnal cycle of tropical heating

In this work, a new theoretical mechanism is presented in which equatorial Rossby and inertio-gravity wave modes may interact with each other through resonance with the diurnal cycle of tropical deep convection. We have adopted the two-layer incompressible equatorial primitive equations forced by a parametric heating that roughly represents deep convection activity in the tropical atmosphere. The heat source was parametrized in the simplest way according to the hypothesis that it is proportional to the lower-troposphere moisture convergence, with the background moisture state function mimicking the structure of the ITCZ. In this context, we have investigated the possibility of resonant interaction between equatorially trapped Rossby and inertio-gravity modes through the diurnal cycle of the background moisture state function. The reduced dynamics of a single resonant duo shows that when this diurnal variation is considered, a Rossby wave mode can undergo significant amplitude modulations when interacting with an inertio-gravity wave mode, which is not possible in the context of the resonant triad non-linear interaction. Therefore, the results suggest that the diurnal variation of the ITCZ can be a possible dynamical mechanism that leads the Rossby waves to be significantly affected by high frequency modes.

Reproductive cycle of Ophionereis reticulata (Ophiuroidea, Echinodermata) on the southeast coast of Brazil

The reproductive cycle of Ophionereis reticulata, a common sediment-rocky shore-interface ophiuroid, was examined monthly from January 2002 to January 2003 at Praia Grande beach (Sao Sesbatiao, state of Sao Paulo, Brazil). Mature individuals were found from January 2002 to April 2002 and from November 2002 to January 2003. Spawning was regcorded from January 2002 to March 2002 and from November 2002 to January 2003. Mature sperm is still present in April which could be involved in the fertilization of the last oocytes spawned in March and April. November and December marked the final point in the maturation process, with a high concentration of yolk and lipid nutrients in the oocytes. Ophionereis reticulata showed, for the period analyzed, a single spawning period, during spring and summer.

Trypanosome Prereplication Machinery Contains a Single Functional Orc1/Cdc6 Protein, Which Is Typical of Archaea

In unicellular eukaryotes, such as Saccharomyces cerevisiae, and in multicellular organisms, the replication origin is recognized by the heterohexamer origin recognition complex (ORC) containing six proteins, Orc1 to Orc6, while in members of the domain Archaea, the replication origin is recognized by just one protein, Orc1/Cdc6; the sequence of Orc1/Cdc6 is highly related to those of Orc1 and Cdc6. Similar to Archaea, trypanosomatid genomes contain only one gene encoding a protein named Orc1. Since trypanosome Orc1 is also homologous to Cdc6, in this study we named the Orc1 protein from trypanosomes Orc1/Cdc6. Here we show that the recombinant Orc1/Cdc6 from Trypanosoma cruzi (TcOrc1/Cdc6) and from Trypanosoma brucei (TbOrc1/Cdc6) present ATPase activity, typical of prereplication machinery components. Also, TcOrc1/Cdc6 and TbOrc1/Cdc6 replaced yeast Cdc6 but not Orc1 in a phenotypic complementation assay. The induction of Orc1/Cdc6 silencing by RNA interference in T. brucei resulted in enucleated cells, strongly suggesting the involvement of Orc1/Cdc6 in DNA replication. Orc1/Cdc6 is expressed during the entire cell cycle in the nuclei of trypanosomes, remaining associated with chromatin in all stages of the cell cycle. These results allowed us to conclude that Orc1/Cdc6 is indeed a member of the trypanosome prereplication machinery and point out that trypanosomes carry a prereplication machinery that is less complex than other eukaryotes and closer to archaea.