The segregation of progenitor somatic cells from those of the primordial germ cells during early cleavage divisions occurs in certain copepods exhibiting the phenomenon of chromatin diminution during early embryogenesis. These species provide an interesting alternative to the usual reproductive strategy of other species of freshwater cyclopoid copepods. Levels of DNA for the soma and germ cells of Mesocyclops longisetus have been determined for individual nuclei by using Feulgen-DNA cytophotometry to monitor changes of DNA amounts during gametogenesis and early cleavage stages of embryogenesis. Germ cell nuclei of both female and male adults contain marked elevations of DNA, far in excess of expected 4C DNA level for their replication prior to meiosis. The elevated amounts of DNA in these germ cells are equivalent to the elevated DNA content found during the gonomeric divisions observed in embryos. Following the gonomeric divisions there is roughly a 40% loss of germ cell heterochromatin during the chromatin diminution stages of embryogenesis. The role of this excised DNA remains unclear.

Made available in DSpace on 2015-04-17T14:55:25Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1509338 bytes, checksum: e0a2529155ec99b45b55b847965af181 (MD5) Previous issue date: 2012-07-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Cyclopoid copepods have been used as biological agents in successful programs to control mosquito larvae, but the impacts of this predation on adult mosquito populations are still poorly understood. The present study compared the sex ratios and body sizes (measure as wing length) of Aedes albopictus mosquitoes emerging from recipients containing the copepod predator Mesocyclops ogunnus with control situations without this predator. We found that copepod predation significantly biased mosquito sex ratios towards females, and that both the males and females emerging from copepod-containing recipients were significantly larger than control insects. The ecological and epidemiological consequences of the changes induced by copepod predation on mosquito populations are discussed. / Copépodos ciclopóides têm sido utilizados como agentes de controle biológicos em programas de controle de larvas de mosquito, mas os impactos dessa predação sobre as populações de mosquitos adultos ainda são pouco compreendidos. O presente estudo comparou as razões sexuais e o tamanho do corpo de mosquitos Aedes albopictus (com base no comprimento da asa) que emergiram de recipientes contendo o copépodo predador Mesocyclops ogunnus com aqueles que emergiram de recipientes controles. Com base nos resultados obtidos constatou-se que a predação de copépodos alterou significativamente a razão sexual de mosquitos favorecendo fêmeas. Machos e fêmeas que emergiram de recipientes contendo copépodo foram significativamente maiores em comparação aqueles que emergiram do controle. As alterações induzidas pela predação de copépodos em populações de mosquitos apresentam importâncias ecológicas e epidemiológicas, visto serem as fêmeas de mosquitos do gênero Aedes os principais vetores do dengue .

Chromatin diminution is defined as the elimination of DNA during the differentiation of early embryonic cells into pre-somatic cells. While it was first observed in the nematode Parascaris equorum, it also been identified in other parasitic nematodes, hagfish and copepods. In the copepod Mesocyclops edax, up to 90% of genomic DNA is eliminated during chromatin diminution. It was previously shown that the eliminated DNA contained highly repetitive heterochromatic sequences. Here, we digested pre- and post-diminution DNA with BamHI and produced small libraries of clones from each. Analyses revealed no decrease in low copy numbered sequences, such as transposable elements. Rather, both libraries are found to be surprisingly similar in all aspects analysed. Further comparison also demonstrated similarity of our libraries with the DNA sequences eliminated from Cyclops kolensis. Consequently, we suggest that M. edax eliminates portions of euchromatic DNA, in addition to the previously characterized satellite sequences.

Chromatin diminution is defined as the elimination of DNA during the differentiation of early embryonic cells into pre-somatic cells. While it was first observed in the nematode Parascaris equorum, it also been identified in other parasitic nematodes, hagfish and copepods. In the copepod Mesocyclops edax, up to 90% of genomic DNA is eliminated during chromatin diminution. It was previously shown that the eliminated DNA contained highly repetitive heterochromatic sequences. Here, we digested pre- and post-diminution DNA with BamHI and produced small libraries of clones from each. Analyses revealed no decrease in low copy numbered sequences, such as transposable elements. Rather, both libraries are found to be surprisingly similar in all aspects analysed. Further comparison also demonstrated similarity of our libraries with the DNA sequences eliminated from Cyclops kolensis. Consequently, we suggest that M. edax eliminates portions of euchromatic DNA, in addition to the previously characterized satellite sequences.

Chromatin diminution is defined as the elimination of DNA during the differentiation of early embryonic cells into pre-somatic cells. While it was first observed in the nematode Parascaris equorum, it also been identified in other parasitic nematodes, hagfish and copepods. In the copepod Mesocyclops edax, up to 90% of genomic DNA is eliminated during chromatin diminution. It was previously shown that the eliminated DNA contained highly repetitive heterochromatic sequences. Here, we digested pre- and post-diminution DNA with BamHI and produced small libraries of clones from each. Analyses revealed no decrease in low copy numbered sequences, such as transposable elements. Rather, both libraries are found to be surprisingly similar in all aspects analysed. Further comparison also demonstrated similarity of our libraries with the DNA sequences eliminated from Cyclops kolensis. Consequently, we suggest that M. edax eliminates portions of euchromatic DNA, in addition to the previously characterized satellite sequences.