• Applied Microscopy
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• v.19 no.1
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• pp.49-58
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• 1989

Ultrastructure of the excretory duct of the small ampullate gland in the orb web spider, Nephila clavata L. Koch are studied with light and electron microscopes. The small ampullate glands, located near the midline portion of the abdominal cavity, are connected with the spigots(large spinning tubes) on the middle spinnerets and composed of three parts which are the excretory duct, the storage sac and the convoluted tail. The excretory duct of this gland is enclosed by a thin layer of the outer connective tissues. By the morphology of the apical cuticles and internal textures of the epithelial cells, the duct is subdivided into two regions which are proximal duct region near the sac and distal duct region near the spinnerets. At the distal region of the ducts, the subcuticle which had the function of water removal form the progenetive silk material is well developed, whereas at the proximal region this cuticle disappeared and instead of these, endocuticle is developed. Moreover the epithelium of the distal duct region is composed of columnar epithelial cells, but at the proximal region the epithelium is changed to squamous or cuboidal forms. In the cytoplasm of the epithelial cells, rough endoplasmic reticula, Golgi comlexes and large secretory vesicles related to the production of the cuticular materials are well developed. And between the adjacent epithelial cells, specialized septate junction and desmosomes are formed along the plasma membrane.

• Applied Microscopy
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• v.50
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• pp.9.1-9.8
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• 2020

The fine structural characteristics of cardiac muscle cells and its myofibril organization in the orb web spider N. clavata were examined by transmission electron microscopy. Although myofibril striations are not remarkable as those of skeletal muscles, muscle fibers contain multiple myofibrils, abundant mitochondria, extensive sarcoplasmic reticulum and transverse tubules (T-tubules). Myofibrils are divided into distinct sarcomeres defined by Z-lines with average length of 2.0 ㎛, but the distinction between the A-band and the I-bands is not clear due to uniform striations over the length of the sarcomeres. Dyadic junction which consisted of a single T-tubule paired with a terminal cisterna of the sarcoplasmic reticulum is found mainly at the A-I level of sarcomere. Each cell is arranged to form multiple connections with neighboring cells through the intercalated discs. These specialized junctions include three types of intercellular junctions: gap junctions, fascia adherens and desmosomes for heart function. Our transmission electron microscopy (TEM) observations clearly show that spider's cardiac muscle contraction is controlled by neurogenic rather than myogenic mechanism since each cardiac muscle fiber is innervated by a branch of motor neuron through neuromuscular junctions.

• Proceedings of the Zoological Society Korea Conference
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• 2000.04a
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• pp.69.2-69
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• 2000

No Abstract, See Full Text

• Proceedings of the Zoological Society Korea Conference
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• 1997.04a
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• pp.67.2-67
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• 1997

• Proceedings of the Korean Society of Applied Entomolohy Conference
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• 2002.11a
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• pp.102-102
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• 2002

• Korean journal of applied entomology
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• v.48 no.1
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• pp.109-115
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• 2009

The thermal stability and mechanical properties of Nephila clavata and Bassaniana decorata spider silks were measured and compared with those of aramid and polyester fibers. The thermal stability of the spider silk was lower than those of the commercial aramid and polyester fibers. However, the mechanical properties of the spider silk were far superior to that of the polyester fiber. The effect of the water content of the spider silk on its thermal stability and mechanical property was examined by conducting the silk to heat treatment at $100^{\circ}C$ under vacuum for various times. The results indicated that spider silk subjected to heat treatment for 1.5 hr had excellent thermal stability and mechanical property.

• The Korean Journal of Zoology
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• v.33 no.3
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• pp.354-364
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• 1990

The ultrastructure and silk formational process of the flagelliform glands, one of the capture thread producing organs in the orb web spider (Nephila clavata L. Koch), have been studied with electron microscope. A pair of flagelliform glands consist of three distinct regions: excretory duct, storage sac and convoluted tail. This gland is connected to the large spinning tube (spigot) of the posterior spinnerets with two pairs of aggregate glands, and showed a characteristic spigot structure called "triad". The excretory duct consists of three long segments surrounded by the same sheath of connective tissue. The distal duct near the spinning tube bears the electron lucent subcuticles which have the functions of water removal and orientation of the silk fiber, whereas the proximal duct near the sac contains the cuticule precursor transported through the intercellular space. Cytoplasms of the sac and tail regions have well developed rough endoplasmic reticulum and contain the round secretory granules commonly, but the electron densities and internal textures of the granules do not coincided. Adjacent epithelial cells are connected with the specialized septate junctions, and secretory granules accumulated at the apical pole are released to the lumen by the apocrine secretion.secretion.

• Proceedings of the Zoological Society Korea Conference
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• 2003.08a
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• pp.130.1-130
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• 2003

No Abstract, See Full Text

• Applied Microscopy
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• v.18 no.2
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• pp.77-90
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• 1988

The ultrastructure of the excretory duct of the large ampullate gland in the orb web spider, Nephila clavain L. Koch are studied with light and electron microscopes. The excretory ducts of the large ampullate glands connected with the large spinning tubes(spigots) on the anterior spinnerets are basically composed of three superposed types of the layers which are inner cuticles, monolayered epithelial cells and peripheral connective cells. According to the morphological characteristics of the cuticles and internal textures of the epithelial cells, the long excretory ducts are subdivided into three(distal, middle and proximal) portions. Especially, at the distal portion of the ducts near the spinning tubes, the electron lucent subcuticles which had the functions of water removal and orientation of silk fibers are well distributed, whereas at the middle and proximal portions these layers disappeared and instead of these, endocuticles are developed. The endocuticle contains two types of bands, which are electron dense and electron lucent. And along the length of the cuticular stem in the excretory duct, these two alternating bands are twisted spirally. In the cytoplasm of the columnar epithelial cells of the distal portion, rough endoplasmic reticula and Golgj complexes, related to the production of the cuticular materials are well developed. Between the adjacent epithelial cells, specialized septate junctions and desmosomes are formed along the plasma membranes. At the proximal portion of the duct, densely accumulated secretory materials appeared, and these are released to the inner canal by the apocrine secretion.

• The Korean Journal of Zoology
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• v.32 no.3
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• pp.211-220
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• 1989

The fine structure of the aggregate glands-one of the capture thread producing organs-in the orb web spider, Nephila clavata L.Koch, is studied with light and electron microscopes. Gluey capture threads or sticky spirals of the orb web are originated from the silks of two flagelliform glands and four aggregate glands which are connected to the posterior spinnerets, and the arrangement fo their spigots(large spinning tubes) shows a charaterstic form called "triad". The aggregate galnd is composed of large and multilobed secretory portion and thick excretory duct surrounded by large irregular nodules. The excretory duct of the aggregate galnds basically consists of three superposed types of cells which are inner columnar epithelium, nodule-forming cells and outer connestives. The cuticles of the proximal duct near the secretory portion are composed of endocuticle and exocuticle, whereas ghe distal duct near the spinning tubes has a electron lucent subcuticle which had the functions of water removal and orientation of silk fibers. In the cytoplasmic process of the large and irregular nodule-forming cells surrounded by invaginations of the plasma membranes, numerous mitochondria and glycogen particles are contained. The maturational level of the nodule cells is perceived from the appearence of these cell inclusions. The secretory portion of the glands which porduce the secretory silk material shows two layers of the cells which are simple cuboidal epithelium and several connective layers. In the cytoplasm of the glandular epithelial cell, rough endoplasmic reticulums are well developed, and two types of secretory granules are observed. Between the adjacent epithelial cells, specialized septate junctions are formed along the plasma membranes.membranes.