• Applied Microscopy
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• v.28 no.4
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• pp.503-512
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• 1998

Fine structure of the cutaneous pigments in the black widow spider, Latrodectus mactans are studied with light and electron microscopes. The cutaneous pigments are only observed in epidermal layer just beneath the cuticle. These pigments are compactly distributed around the spinnerets which located at caudal area of the abdomen. According to the fine structural characteristics of the pigment granules, two main types of guanine pigment granules-carotenoid vesicles and reflecting platelets - are observed in the cytoplasm of the epidermal cells. Morphological features of these pigment granules are characterized as the electron dense carotenoid vesicles and the electron lucent reflecting platelets. Marginal electron density of the carotenoid vesicle is different from that of internal region, whereas the reflecting platelets have laminated crystalline granules. Typiral structures of these pigment granules are very similar to those of invertebrate's chromatophores, especially erythrophores and iridophores. Moreover differentiation of these pigment granules are also originated from the small vesicles of Golgi complexes similarly to those of cutaneous chromatophores.

• Animal cells and systems
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• v.6 no.4
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• pp.327-333
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• 2002

Among the silk glands in the black widow spider Latrodectus mactans, the ampullate one is the most predominant gland in both sexes, and is com-posed of three functional parts - excretory duct, storage ampulla and convoluted tail regions. This experiment was performed using mechanical pulling stimulation with electric motor equipment to reveal a correlation between silk usage and silk producing system in this poisonous spider. The mature secretory products in glandular epithelium are closely packed and appear as electron-opaque spherical vesicles. A part of the vesicles with fine fibrillar paracrystalline texture seems to store some proteins which will function at the time of final assembly into fibrils. Most of the secretory silk products which originated from the rough endoplasmic reticula of the glandular epithelial cells are grown by fusion with surrounding small vesi-cles. However, the Golgi complex does not seem to play an important role in this process of secretion. According to progressive maturation of secre-tory silk product, these granules are progressively filled with a fine fibrillar material, and thus appear much more electron-dense than those of earlier states. When the secretory product is extruded from the glandular cavity, the epithelium is rapidly changed to a thinner layer of tall columnar cells with less definitive cell membranes. After extruding there ave a few secre-tory droplets within these cells, thus causing this region to stain much lighter.

• Entomological Research
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• v.48 no.5
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• pp.429-438
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• 2018

Fine structural characteristics of the cardiac muscle and its sarcomere organization in the black widow spider, Latrodectus mactans were examined using transmission electron microscopy. The arrangement of cardiac muscle fibers was quite similar to that of skeletal muscle fibers, but they branched off at the ends and formed multiple connections with adjacent cells. Each cell contained multiple myofibrils and an extensive dyadic sarcotubular system consisting of sarcoplasmic reticulum and T-tubules. Thin and thick myofilaments were highly organized in regular repetitive arrays and formed contractile sarcomeres. Each repeating band unit of the sarcomere had three apparent striations, but the H-zone and M-lines were not prominent. Myofilaments were arranged into distinct sarcomeres defined by adjacent Z-lines with relatively short lengths of $2.0{\mu}m$ to $3.3{\mu}m$. Cross sections of the A-band showed hexagon-like arrangement of thick filaments, but the orbit of thin filaments around each thick filament was different from that seen in other vertebrates. Although each thick filament was surrounded by 12 thin filaments, the filament ratio of thin and thick myofilaments varied from 3:1 to 5:1 because thin filaments were shared by adjacent thick filaments.

• Applied Microscopy
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• v.50
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• pp.20.1-20.9
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• 2020

Arthropods have an open circulatory system with a simple tubular heart, so it has been estimated that the contractile pumping structure of the cardiac muscle will be less efficient than that of vertebrates. Nevertheless, certain arthropods are known to have far superior properties and characteristics than vertebrates, so we investigated the fine structural features of intercalated discs and cardiac junctions of cardiac muscle cells in the black widow spider Latrodectus mactans. Characteristically, the spider cardiac muscle has typical striated features and represents a functional syncytium that supports multiple connections to adjacent cells by intercalated discs. Histologically, the boundary lamina of each sarcolemma connects to the basement membrane to form an elastic sheath, and the extracellular matrix allows the cells to be anchored to other tissues. Since the intercalated disc is also part of sarcolemma, it contains gap junctions for depolarization and desmosomes that keep the fibers together during cardiac muscle contraction. Furthermore, fascia adherens and macula adherens (desmosomes) were also identified as cell junctions in both sarcolemma and intercalated discs. To enable the coordinated heartbeat of the cardiac muscle, the muscle fibers have neuronal innervations by multiple axons from the motor ganglion.

• Applied Microscopy
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• v.26 no.1
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• pp.17-31
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• 1996

The venomous apparatus of the black widow spider, Latrodectus mactans, is composed of chelicera and paired venom glands in the cephalothorax. Each glands is surrounded by a thin adventitia and striated muscular bundles resting on a basal membrane. Along the musculature neuromuscular synaptic contacts are formed by a motor axon and the muscle fibers. The secretory epithelium, which made up of simple and long columnar cells with extensive finger-like processes, creates a simple acinar gland. The secretory surfac is increased by a sort of fringes extended from the basal membrane into the gland lumen, and the luminal surface of the epithelium is marked by the presence of closely spaced microvilli. The venoms of the black widow spider are produced from two types of secretory granules within the epithelial cells. During the secretory phase, these granules are transformed into droplets and suffering a condensation. Finally the secretory products are released by the apocrine secretion. After the gland is emptied, the basal epithelial cells present a high proliferative process and regenerate the columnar epithlial cells.

• Proceedings of the Zoological Society Korea Conference
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• 2003.08a
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• pp.156.3-156
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• 2003

No Abstract, See Full Text

• Animal cells and systems
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• v.2 no.1
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• pp.145-152
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• 1998

The spinning apparatus and production of secretory silk from silk gland of the black widow spider, Latrodectus mactans were studied with scanning and transmission electron microscopes. The silk glands were located in seven groups on the spinnerets including each pair of major and minor ampullate, 3 pairs of tubuliform, 1 pair of flagelliform, 2 pairs of aggregate, about 50 pairs of pyriform and over 250 pairs of aciniform glands, respect- ively. Each group of silk gland feeds silk into one of the three spinneret pairs. Secretory silk is synthesized from rough endoplasmic reticulum (rER) of glandular epithelial cells. The secretory silk is transported from toe rER into the secretory vacuoles which are grown up by fusion with the surrounding small vesicles including the secretory silk. The secretory vacuoles, which show a gradual increase in electron density with the process of maturity, are formed without involvement of the Golgi complex, suggesting that they do not play an important role in the processing of the secretory silk. The secretory silk products are released by the mechanism of apocrine secretion, losing part of their cytoplasm. Moreover, another type of silk precursor, possibly protein, appears as granular material, and is also discharged to the luminal cavity.