No abstract

To emerge from the egg case, Argiope aurantia spiderlings must penetrate a tightly woven outer cover composed primarily of large-diameter cylindrical gland fibers and small-diameter fibers, likely of aciniform gland origin. They accomplish this using enzymatic digestion and mastication to form a communal hole in the outer cover. The involvement of proteolytic enzymes in this process was demonstrated by zymography of spiderling homogenates and washes made from the edges of holes. The specific source(s) of the proteases is unknown, but histological examination of spiderling sections indicates that the digestive tract, venom glands, and gnathocoxal glands are all functioning at the time of emergence from the egg case. Observations on edges of holes indicate that spiderlings are able to solubilize the small-diameter fibers completely, but cylindrical gland fibers only partially. In the outer cover, cylindrical fibers are composed of numerous fibrils embedded within a matrix. Spiderlings appear to be unable to solubilize the fibrils, but digestion of the matrix allows the spiderlings to push the fibrils aside to create the opening.

No abstract

As web spiders usually hang with their head downward, geometrical differences in body position could affect the organization of their central nervous system (CNS). Nevertheless, most of our knowledge of spider's CNS is dependent on what has been revealed from wandering spiders. To fill the gap, we describe here the fine structural organization of the ganglionic neurons and nerves in the geometric orb web spider Nephila clavata. Nerve cells in the supraesophageal ganglion in N. clavata are packed in the frontal, dorsal and lateral regions, but the nerve cells of the subesophageal mass are only restricted to the ventral and ventrolateral regions. High resolution transmission electron microscopy (TEM) reveals the fine structural details of the neuroglial cells and the neuronal cells which have a conspicuous Golgi apparatus, rough ER, free ribosomes and well‐developed mitochondria. Comparing fine structural characteristics of the CNS ganglia with those of wandering spiders in most respects, it has been revealed that the geometrical difference may affects to the arrangement of receptors in the central body known as an important association center for web building behavior. In particular, remarkable differences can be detected in the protocerebral area by the extraordinary development of the central body including absence of the globuli and associated mushroom bodies.

Synthesis of protein by the major ampullate silk glands in the barn spider, Araneus cavaticus was stimulated by depleting the storage of silk protein in the ampulla by mechanically pulling fiber from the spigot. After this treatment, fine structural changes of the glandular epithelium during silk production were examined using light and transmission electron microscopes. In the process of rapid production, major secretory silk was synthesized at the tail region via rER of glandular epithelial cells, and was transported into the ampulla region. The mature secretory product in glandular epithelium appears almost spherical vacuoles which were grown up by fusion with the surrounding small vesicles including the secretory silk. Unlike to a typical process of the secretion, the ampullate silk of tail region seems to bypass either concentrating or packaging steps by the Golgi apparatus. However there's no doubt that the Golgi apparatus also play an important role in the secretory process of the ampulla region. After mechanical pulling stimulation, both epithelia of ampulla and tail regions appeared as a thinner layer of columnar cells with less definitive cell membrane. There are few secretory droplets within these cells, thus causing this region to stain much lighter. It is obvious that the cell loses part of its cytoplasm in this process, and disorganization of the secretory product occurs when it is extruded from the cells by a apocrine release.

No abstract

Fluorescein and horseradish peroxidase-labeled monoclonal antibodies were used to localize the predominant toxic peptide CSTX-1 in the venom gland of the spider Cupiennius salei. There was no polarity of CSTX-1 expression in repleted glands, whereas the glands of previously milked spiders showed a decreasing immunofluorescent response from the distal to the proximal portion. Detailed investigation revealed a new structure in the venom-secreting epithelium, which is postulated to be an evolutionary adaptation to increasing gland volume. CSTX-1 was found to be synthesized and stored as a fully active toxin within complex units, composed of long interdigitating cells running perpendicular to the muscular sheath and extending into the central lumen of the gland. These venom-producing units were found in all sectors of the gland, including the transitional region between the main gland and the venom duct. The venom is liberated from the venom-producing units into the glandular lumen following the contraction of the surrounding muscle layer. Free nuclei or other cellular fragments, which would have provided evidence for a holocrine secretion process, were not found in the glandular lumen or in the crude venom obtained by electrical stimulation. The fine regulation of the spider's venom injection process is postulated to be the function of the bulbous ampulla, situated in the anterior third of the venom duct.

The microstructural characteristics of the capture thread production from silk glands in the orb web spiders were analyzed using scanning and transmission electron microscopes. Sticky and gluey capture threads of the web are originated from the silks of two flagelliform glands and four aggregate glands. They supply precursors of the secretory silks to a pair of characteristic “triad” spinning units on the posterior spinnerets. The aggregate gland is composed of large and multi‐lobed secretory region and thick excretory duct surrounded by large irregular nodules. The excretory duct of this gland basically consists of three superposed types of cells which are inner columnar epithelium, nodule forming cells and outer connectives. The nodules contain numerous mitochondria and glycogen particles within their cytoplasm and they are surrounded by the same sheath of thin connective tissues. Secretory region of the aggregate gland which produce water‐soluble components of the capture thread comprises discrete secretory vesicles and extensive rough endoplasmic reticulum. Characteristically, secretory droplets are formed without involvement of the Golgi complexes, suggesting that they do not play an important role in the processing of the capture threads. However the electron densities and internal textures of the granules are observed with diverse according to their maturation level. Finally, the secretory products are released by the mechanism of apocrine secretion losing part of their cytoplasm during this process.