Ultrastructure of the Salivary Glands of Pachycondyla(=Neoponera) villosa(Fabricius)(Formicidae: Ponerinae): Functional Changes during the Last Larval Instar

Seminal fluid production and sperm packaging in dromiid crabs (Brachyura, Podotremata)

Reproductive anatomy, including sperm storage structures and sperm transfer, is an important feature used to analyze phylogenetic relationships among taxa. We describe the male reproductive anatomy, seminal fluid production and packaging of spermatozoa in the vas deferens of primitive crabs. In all species of Dromiidae, the testes were tubular type and the vas deferens is a tube with a simple epithelium. The spermatozoa are in a central mass immersed in type I secretion, forming a large spermatic cord. In Moreiradromia antillensis and Dromia erythropus the spermatic cord is surrounded by a more complex secretion layer composed by protein granules and polysaccharides that seem to be responsible to form the sperm plaque which was absent in Hypoconcha. The sperm plaque was found in all Dromiinae species, which may result from the mating and probably act as a barrier to subsequent copulations. These patterns of elongated coenospermic spermatophore found here are unique and different from the spermatophores of all true crabs and may be considered a plesiomorphic state to spermatophoric structure in Brachyura. Our results show a novel type of spermatozoa packaging and new insights into how sperm might be transferred in Podotremata.

Recombinant Structural Proteins and Their Use in Future Materials

Recombinant proteins are polymers that offer the materials engineer absolute control over chain length and composition: key attributes required for design of advanced polymeric materials. Through this control, these polymers can be encoded to contain information that enables them to respond as the environment changes. However, despite their promise, protein-based materials are under-represented in materials science. In this chapter we investigate why this is and describe recent efforts to address this. We discuss constraints limiting rational design of structural proteins for advanced materials; advantages and disadvantages of different recombinant expression platforms; and, methods to fabricate proteins into solid-state materials. Finally, we describe the silk proteins used in our laboratory as templates for information-containing polymers.

Folding behavior of four silks of giant honey bee reflects the evolutionary conservation of aculeate silk proteins

Multiple gene duplication events in the precursor of the Aculeata (bees, ants, hornets) gave rise to four silk genes. Whilst these homologs encode proteins with similar amino acid composition and coiled coil structure, the retention of all four homologs implies they each are important. In this study we identified, produced and characterized the four silk proteins from Apis dorsata, the giant Asian honeybee. The proteins were readily purified, allowing us to investigate the folding behavior of solutions of individual proteins in comparison to mixtures of all four proteins at concentrations where they assemble into their native coiled coil structure. In contrast to solutions of any one protein type, solutions of a mixture of the four proteins formed coiled coils that were stable against dilution and detergent denaturation. The results are consistent with the formation of a heteromeric coiled coil protein complex. The mechanism of silk protein coiled coil formation and evolution is discussed in light of these results.

Programmed cell death in the larval salivary glands of Apis mellifera (Hymenoptera, Apidae)

The morphological and histochemical features of degeneration in honeybee (Apis mellifera) salivary glands were investigated in 5th instar larvae and in the pre-pupal period. The distribution and activity patterns of acid phosphatase enzyme were also analysed. As a routine,the larval salivary glands were fixed and processed for light microscopy and transmission electron microscopy.Tissue sections were subsequently stained with haematoxylin -eosin,bromophenol blue,silver,or a variant of the critical electrolyte concentration (CEC) method.Ultrathin sections were contrasted with uranyl acetate and lead citrate.Glands were processed for the histochemical and cytochemical localization of acid phosphatase,as well as biochemical assay to detect its activity pattern. Acid phosphatase activity was histochemically detected in all the salivary glands analysed.The cytochemical results showed acid phosphatase in vesicles, Golgi apparatus and lysosomes during the secretory phase and,additionally, in autophagic structures and luminal secretion during the degenerative phase. These findings were in agreement with the biochemical assay. At the end of the 5th instar, the glandular cells had a vacuolated cytoplasm and pyknotic nuclei, and epithelial cells were shed into the glandular lumen.The transition phase from the 5th instar to the pre-pupal period was characterized by intense vacuolation of the basal cytoplasm and release of parts of the cytoplasm into the lumen by apical blebbing; these blebs contained cytoplasmic RNA, rough endoplasmic reticule and, occasionally, nuclear material. In the pre-pupal phase, the glandular epithelium showed progressive degeneration so that at the end of this phase only nuclei and remnants of the cytoplasm were observed.The nuclei were pyknotic,with peripheral chromatin and blebs. The gland remained in the haemolymph and was recycled during metamorphosis. The programmed cell death in this gland represented a morphological form intermediate between apoptosis and autophagy.

Ultrastructural studies of the mandibular glands of the minima, media and soldier ants of Atta sexdens rubropilosa (Forel 1908) (Hymenoptera: Formicidae)

The mandibular glands of Hymenoptera are structures associated with the mandibles and constitute part of the salivary glands system. Histological studies in workers of Atta sexdens rubropilosa revealed that this gland contains two portions: a secretory and a storage portion or reservoir. Both portions are connected by means of canaliculi. The object of the present work was the study of the ultratructure of the mandibular glands of minima, media and soldier ant of A. s. rubropilosa by TEM techniques. The glands, in the three castes studied, possess a reservoir, constituted by a simple pavementous epithelium surrounded by the cuticular intima and the secretory portion is constituted by cells of rounded shape. The secretory cells, mainly of minima and soldier, were rich in smooth endoplasmic reticulum. The media worker and soldier presented a large number of mitochondria, of varying shape. Well-developed Golgi complexes were also present in the soldiers. The secretory cells in minima, media and soldier were provided with collecting intracellular canaliculi, which were linked to the reservoir through the extracellular portion. The cytoplasm of the canaliculi-forming cell was poor in organelles. In the individuals of the three castes of A. s. rubropilosa, the presence of lipid secretion granules suggested, beyond the other functions, also a possible pheromonal action. The different roles executed by the different insect castes are directly dependent on the glandular products and, consequently, on the secretory cellular characteristics.

Silk formation mechanisms in the larval salivary glands ofApis mellifera (Hymenoptera: Apidae)

The mechanism of silk formation in Apis mellifera salivary glands, during the 5th instar, was studied. Larval salivary glands were dissected and prepared for light and polarized light microscopy, as well as for scanning and transmission electron microscopy. The results showed that silk formation starts at the middle of the 5th instar and finishes at the end of the same instar. This process begins in the distal secretory portion of the gland, going towards the proximal secretory portion; and from the periphery to the center of the gland lumen. The silk proteins are released from the secretory cells as a homogeneous substance that polymerizes in the lumen to form compact birefringent tactoids. Secondly, the water absorption from the lumen secretion, carried out by secretory and duct cells, promotes aggregation of the tactoids that form a spiral-shape filament with a zigzag pattern. This pattern is also the results of the silk compression in the gland lumen and represents a high concentration of macromolecularly well-oriented silk proteins.