Darvin Beig

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Arquivos de Zoological Sao Paulo





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The present study is a chronological accoimt of the development and differentiation of the various tissues and organs of the female stingless bee Trigona (Scaptotrigona) postica Latr. A description of its embryology based on microscopic observations of embryos reared at 28 C is presented. Whole mounts of living and fixed embryos and sectioned material representing the first 66-68 hours of the life cycle (to hatching) were analized in this investigation. The results obtained lead to the following conclusions: 1) diploid egg, somewhat concave dorsally and slightly convex ventrally, averages 1.185 mm ± 0 .024 mm in length and 0. 36 mm ± 0.05 mm in its greatest diameter just behind the anterior end; 2) the embryogenesis in this egg is very similar to that of Apis mellifera L .; 3) eggs have shown a morphological characteristic on its dorsal side associated with the polar protoplasm. It was named as “longitudal dorsal line” and till now we don’t know its function; 4) the egg periplasm is thin and totally utilized by the blastoderm cells during its differentiation; 5) the germ band or embryonic rudiment is formed at the ventral egg portion. As the embryonic rudiment elongates forcing its extremities around the egg poles, the stomodeum and proctodeum appear as ectodermal invaginations on its anterior surface and its postero-dorsal surface respectively. The serosa is the single extraembryonic membrane and arises as a peripheral extension of the dorsal blastoderm; 6) the Malpighian tubules (four) arise as two pairs of outpocketings from the blind end of the proctodeum; 7) within two hours after the anterior mesenteron rudiment begins its formation a similar group of cells, destined to form the posterior one appears behind the middle plate; 8) abdominal appendages as vestigial structures appear between 50-66 hours of development; 9) external segmentation for the most part a gradual process starts after 20 hours of development. The first transverse epidermal furrow corresponds to that dividing the II maxilla and the I thoracic. Eleven abdominal segments are present during embryonic development; 10) there is no blastokinetic movement during embryogenesis of these bees.

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