Comparative ultrastructure of the mandibular gland in Scaptotrigona postica ( Hymenoptera, Apidae, Meliponini) Workers and males

Differences in the ultrastructure and function of the mandibular glands in developing workers and maturemales of the meliponine stingless bee Scaptotrigona postica suggest that there are age-dependent variationsin the contents of the secretion and glandular functions. In this work, we used transmission (TEM) andscanning (SEM) electron microscopy to examine the mandibular glands of S. postica workers of differentages and compared them with those of mature males. The gland anatomy did not vary between workers andmales. However, the ultrastructure of the gland cells changed according to the worker’s age, task, and sex.The mandibular gland cells in workers and males had a well developed smooth endoplasmic reticulum andpleomorphic mitochondria, indicating that the cells were involved in lipid synthesis. However, the secretionvaried in morphology and electrondensity between workers and males, which suggested differences in itscontents and, possibly, in glandular functions.

Morphological, chemical and developmental aspects of the Dufour gland in some eusocial bees (Hymenoptera, Apidae): a review

Morphological, chemical and developmental aspects of the Dufour gland in some eusocial bees (Hymenoptera, Apidae): a review. The present revision focused on the more recent data about the Dufour gland in some eusocial bees, taking in account general aspects of its morphology, secretion chemical nature, bio-synthetic pathway and development. Many functions have been attributed to this gland in eusocial bees, but none are convincing. With the new data about this gland, not only the secretion chemical pathway of the Dufour gland may be reasonable understood, as its function in some eusocial bees, especially Apis mellifera Linné, 1758, which has been extensively studied in the last years.

Aspectos morfológicos, químicos e do desenvolvimento da glândula de Dufour em algumas abelhas eussociais (Hymenoptera, Apidae): revisão. Esta revisão aborda os mais recentes dados sobre a glândula de Dufour em algumas abelhas eussociais, considerando aspectos gerais da sua morfologia, do seu desenvolvimento, da natureza química da sua secreção, assim como sua via bio-sintética. Muitas funções têm-se atribuído à glândula de Dufour nas abelhas eussociais, mas nenhuma suficientemente convincente. Os novos dados a respeito dessa glândula permitem não só conhecer razoavelmente bem a via bio-sintética como a função da secreção da glândula de Dufour em algumas abelhas eussociais, especialmente em Apis mellifera Linné, 1758, a qual tem sido extensivamente estudada nos últimos anos.

Programmed cell death during ovarian differentiation in queens of Apis mellifera Linné, 1758 (Hymenoptera, Apini)

In this study, we examined various aspects of ovarian development in adult honey bees queens (Apis mellifera). Caged honey bee queens showed an initial programmed germ cell differentiation that was independent of any external or environmental stimulus. In young queens, division of the stem germ cells resulted in cysts of clone cells (cystocytes) that were connected through intercellular bridges and appeared as rosettes. The cystocytes started differentiate shortly before the queens reached sexual maturity (about 5 days old). The oocyte subsequently appeared as a large, stained cell connected to parallel, double rows of smaller cells, or nurse cells. If the queens did not mate, germ cell differentiation was “switched off”, and development of the ovary was interrupted in an intermediate developmental stage, without follicular cell organization. Therefore, in such queens, there were no pevitellogenic follicles. This finding could explain why wvirgin queens rarely lay eggs and why after fecundation they require several days to start laying. The absence of previtellogenic follicles may also indicate that some stimulus is required for continuation of the vitellogenesis and ovary development.

Late Gametogenesis in Leptodactylus labyrinthicus (Amphibia, Anura, Leptodactylidae) and Some Ecological Considerations

Histological aspects of late gametogenesis in Leptodactylus labyrinthicus and of unfertilized oocytes collectes from clutches in the field were studied by light microscopy. Specimens were collected durin the reproductive period to determine why only 10 por cento of the oocytes deposited in foam nests are fertilized. Sections of ovaries and oocytes were stained with hematoxylin and eosin, mercury bromophenol blue and toluidine blue. During the reproductive phase, the ovaries were completely developed and consisted of a sack-shaped, multilobular structure, with each lobe containing many oocytes in advanced developmental stages. Atretic oocytes were also seen in the ovaries during the reproductive phase. Oocyte development in the ovaries was considered synchronous, although few oocytes were seen in the early developmental stages. There were differences in the morphology or stainning of oocytes in the ovary and of unfertilezed oocytes. Testicular development was synchronic with that of the ovary, with the testes also being fully developed during the reproductive period. Each seminiferous tubule had many cysts containing all of the phases of spermatogenesis, specially spermatids with different levels of nuclear condensation. Free spermatozoa were also observed in the lumen of the seminiferous tubule. The significant proportion of unfertilized oocytes present in many clutches may indicate that males produced an insuffucient number of spermarzoa to fertilize all of the oocytes or that females deposited additional oocytes subsequent to spawning. These unfertilized oocytes are ingested by larvae and may represent a reproductive strategy for increasing tadpole survival.

Occurrence, morphology and ultrastructure of the Dufour gland in Melipona bicolor Lepeletier (Hymenoptera, Meliponini)

The occurrence, morphology and ultrastructure of the Dufour gland in Melipona bicolor Lepeletier, 1836 are presented. The Dufour gland is not present in workers. In virgin queens the gland cells show characteristics of low activity, which are described in the text. In physogastric queens the gland epithelium is higher and the cells more active than in virgin queens, showing numerous basal plasmic membrane invaginations impregnated by an electrondense material, increased apical invaginations and accumulation of substances that will be released to the gland lumen in the subcuticular space. Therefore, the data show that the Dufour gland is more developed in physogastric than in virgin queens, indicating a possible involvement of the Dufour gland in the reproduction of this species.