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1. Light, Temperature, Seed Burial, and Mulch Effects on Mulberry Weed (Fatoua villosa) Seed Germination
GINA M. PENNY and JOSEPH C. NEAL
Weed Technology Volume 17; Issue 2 (April 2003) pp. 213–218
Fatoua villosa (mulberry weed) is a new and invasive weed of container nurseries and landscapes in the southeastern United States. Studies were conducted to determine the effects of light, planting depth, mulch depth, and temperature on mulberry weed seed germination and seedling emergence. Light stimulated mulberry weed seed germination, with less than 5% of seeds germinating in the dark compared with 48 to 60% germinating in the light. In all emergence studies, the highest number of seedlings emerged when seeds were placed on the soil surface, with emergence decreasing as planting or mulch depth increased. Planting depths of 1.8 cm or mulch depths of 3.7 cm reduced mulberry weed emergence by 90%. These data suggest that mulch would control mulberry weed effectively. To study the effects of temperature on germination, two seed batches collected locally in October 1998 and August 1999 were used. Maximum germination of seeds collected in 1998 occurred at 25 C, with germination decreasing at higher temperatures and no germination at lower than 15 C or over 40 C. For seeds collected in 1999, maximum germination occurred from 19 to 29 C, with germination decreasing with temperatures above 29 C or below 19 C. At temperatures of 15 and 42 C germination, percentages were 71 and 11%, respectively. Seedlings germinated at 15 C developed slowly but otherwise appeared normal. For both seed lots, seedlings were stunted and chlorotic at 38 C. That mulberry weed seed germinated over a wide range of temperatures suggests its potential to emerge throughout most of spring, summer, and autumn in the southeastern United States.
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2. Micromorphological Characterization of Ten Mulberry Cultivars (Morus spp)
Magda Biasiolo, Maria Teresa Da Canal, and Noemi Tornadore(Biology Department, Geobotany Section, Padua University, V. G. Colombo 3, 35121 Padova, Italy; E-mail: email@example.com)
Economic Botany Volume 58, Issue 4 (December 2004)
The micromorphological features of the vegetative and reproductive structures of ten mulberry cultivars grown at the Specialized Sericultural Section of the Agricultural Zoology Experimental Institute of Padua, northeastern Italy, were examined by SEM in order to determine the charactetistics that were the most valuable taxonomically. The observed specimens (leaves, flowers, seeds, and pollen grains) showed micromorphological differences regarding leaf hairiness, quantity of waxes, quality of epidermis cuticle and tepal hairiness. The effects of differing environments in altering the floral sex ratios of this basically monoecious group of plants were also investigated. However, no significant differences between the micromorphology of the seeds and the pollen grains of these selected cultivars were detected. The authors are hopeful that the information gained in this study may prove useful in the future creation of an exhaustive and final catalogue “descriptor” of cultivated varieties belonging to the genus Morus L.
Keywords: White mulberry, cultivars, SEM, leaf, flower, seed, pollen grain micromorphology
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1. Developmental Profile of Annexin IX and its Possible Role in Programmed Cell Death of the Bombyx mori Anterior Silk Gland
Yu Kaneko, Keiko Takaki, Masafumi Iwami, and Sho Sakurai
Zoological Science Volume 23, Issue 6 (June 2006) pp. 533–542
During pupal metamorphosis, the anterior silk gland (ASG) of the silkworm, Bombyx mori, undergoes programmed cell death (PCD), which is triggered by 20-hydroxyecdysone (20E). Annexin IX (ANX IX) has been identified as a 20E-inducible gene in dying ASGs, and we show here that its expression is down-regulated in tissues destined to die but not in tissues that survive pupal metamorphosis. ANX IX expression was high in the ASGs during the feeding period, when the ecdysteroid titer was low, and decreased in response to the rising ecdysteroid titer that triggered pupal metamorphosis. Before gut purge, in vitro exposure of the ASGs to 20E levels corresponding to the ecdysteroid concentration present at the time of gut purge caused a decrease in ANX IX messenger RNA levels. Expression profiles of EcR and USP, and the 20E concentration-responses of these genes, indicate the importance of the relative abundance of EcR-A and EcR-B1 isoforms in ANX IX regulation. These results suggest an involvement of ANX IX in the determination of PCD timing by delaying or suppressing the response to the increase in hemolymph ecdysteroid concentration during the prepupal period.
Keywords: annexin, Bombyx, 20-hydroxyecdysone, EcR, programmed cell death
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2. Release of Ecdysteroid-Phosphates from Egg Yolk Granules and Their Dephosphorylation during Early Embryonic Development in Silkworm, Bombyx mori
Ryouichi Yamada, Yumi Yamahama, and Haruyuki Sonobe
Zoological Science Volume 22, Issue 2 (February 2005) pp. 187–198
Newly laid eggs of many insect species store maternal ecdysteroids as physiologically inactive phosphoric esters. In the silkworm Bombyx mori, we previously reported the presence of a specific enzyme, called ecdysteroid-phosphate phosphatase (EPPase), which catalyzes the dephosphorylation of ecdysteroid-phosphates to increase the amount of free ecdysteroids during early embryonic development. In this study, we demonstrated that (1) EPPase is found in the cytosol of yolk cells, (2) ecdysteroid-phosphates are localized in yolk granules, being bound to the yolk protein vitellin (Vn), and (3) Vn-bound ecdysteroid-phosphates are scarcely hydrolyzed by EPPase, although free ecdysteroid-phosphates are completely hydrolyzed by EPPase. Thus, we investigated the mechanism by which ecdysteroid-phosphates dissociate from the Vn-ecdysteroid-phosphate complex, and indicated that the acidification of yolk granules causes the dissociation of ecdysteroid-phosphates from the Vn-ecdysteroid-phosphate complex and thereby ecdysteroid-phosphates are released from yolk granules into the cytosol. Indeed, the presence of vacuolar-type proton-translocating ATPase in the membrane fraction of yolk granules was also verified by Western blot analysis. Our experiments revealed that Vn functions as a reservoir of maternal ovarian ecdysteroid-phosphates as well as a nutritional source during embryonic development. This is the first report showing the biochemical mechanism by which maternal Vn-bound ecdysteroid-phosphates function during early embryonic development.
Keywords: ecdysteroids, phosphatase, V-ATPase, vitellin, embryonic development
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3. Establishment of a Sandwich ELISA System to Detect Diapause Hormone, and Developmental Profile of Hormone Levels in Egg and Subesophageal Ganglion of the Silkworm, Bombyx mori
Norio Kitagawa, Kunihiro Shiomi, Kunio Imai, Teruyuki Niimi, Toshinobu Yaginuma, and Okitsugu Yamashita
Zoological Science Volume 22, Issue 2 (February 2005) pp. 213–221
In the silkworm Bombyx mori, diapause hormone (DH) is produced in the female subesophageal ganglion (SG) and induces embryonic diapause by targeting developing ovaries. DH is processed from a precursor protein consisting of DH, pheromone biosynthesis activating neuropeptide (PBAN) and three other neuropeptides (SGNPs). Because these five neuropeptides share a common sequence, FXPRLamide, at the C-terminus, a direct and specific assay for DH itself is required in order to understand the profile of concentration changes. In this study, we produced a mouse monoclonal antibody (anti-DH[N] mAb) against the N-terminal region of DH and developed a sandwich enzyme-linked immunosorbent assay using the anti-DH[N] mAb and a rabbit polyclonal antibody against the C-terminus of DH. This procedure enabled us to specifically quantify the DH molecule at femtomolar levels (equivalent to 1/10 of SG). We then plotted DH levels in eggs and SGs during embryonic and post-embryonic development. DH was present in late-stage embryos that had been destined for the production of both diapause and nondiapause eggs. DH levels in SG gradually increased in both types during larval development and peaked at the early pupal stage. At the middle pupal stage, DH levels in SG and SG-brain complex decreased markedly in the diapause-egg producing type, thus indicating active release of DH into the hemolymph. From 5th instar larva to adult, no sexual differences in DH levels were observed in SGs or SG-brain complexes from diapause and nondiapause egg-producing types.
Keywords: Diapause hormone, FXPRLamide neuropeptide family, bivoltinism, Bombyx mori, subesophageal ganglion, sandwich enzyme-linked immunosorbent assay
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4. Effects of Applaud on the Growth of Silkworm (Lepidoptera: Bombycidae)
Maria E. Vassarmidaki, Paschalis C. Harizanis, and Sergios Katsikis
Journal of Economic Entomology Volume 93, Issue 2 (April 2000) pp. 290–292
An experiment was carried out to evaluate the effect of the insecticide Applaud (buprofezin 25% WP) on the silkworm Bombyx mori (L.). This insecticide belongs to the class of insect growth regulators (IGR). The larvae were fed on leaves treated with 3 different concentrations (0.5, 1, 2 g/liter) of Applaud on the 1st d of each instar. Analysis of data with the Tukey–Kramer test at 1% significant level revealed that mortality and larval duration did not differ among the treatments. On the contrary, the larval weight, which was estimated just before mounting (procedure during which the mature larva climbing on a branch or other material to spin the cocoon), differed among the treatments. Also, cocoon weight, shell weight, and cocoon sericin and fibroin content were different among the treatments, except the shell cocoon ratio. Maximum weight was observed in the controls and minimum in the last instar treatments. Our data suggest that supplementation of Applaud through food to larvae does not affect their mortality rate. On the contrary, it affects larval growth and cocoon parameters.
Keywords: Bombyx mori, buprofezin, larval duration, larval weight, cocoon parameters
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5. Stress induction of Bm1 RNA in silkworm larvae: SINEs, an unusual class of stress genes
Richard H. Kimura, Prabhakara V. Choudary, Koni K. Stone, and Carl W. Schmid
Cell Stress & Chaperones Volume 6, Issue 3 (July 2001) pp. 263–272
This study surveys the induction of RNA polymerase III (Pol III)–directed expression of short interspersed element (SINE) transcripts by various stresses in an animal model, silkworm larvae. Sublethal heat shock and exposure to several toxic compounds increase the level of Bm1 RNA, the silkworm SINE transcript, while also transiently increasing expression of a well-characterized stress-induced transcript, Hsp70 messenger RNA (mRNA). In certain cases, the Bm1 RNA response coincides with that of Hsp70 mRNA, but more often Bm1 RNA responds later in recovery. Baculovirus infection and exposure to certain toxic compounds increase Bm1 RNA but not Hsp70 mRNA, showing that SINE induction is not necessarily coupled to transcription of this particular heat shock gene. SINEs behave as an additional class of stress-inducible genes in living animals but are unusual as stress genes because of their high copy number, genomic dispersion, and Pol III–directed transcription.
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6. The Bmdsx transgene including trimmed introns is sex-specifically spliced in tissues of the silkworm, Bombyx mori
Shunsuke Funaguma, Masataka G. Suzuki, Toshiki Tamura, and Toru Shimada
Journal of Insect Science Volume 5, Issue 17 (May 2005) pp. 1–6
Orthologue of the sex-determining gene doublesex (dsx) and known to be sex-specifically expressed in various tissues of the silkworm, Bombyx mori. Its pre-mRNA is sex-specifically spliced and encodes female-specific or male-specific polypeptides. The open reading frame of Bmdsx consists of 5 exons, of which exons 3 and 4 are female-specific and its pre-mRNA was known to undergo default processing to generate the female-type mRNA. Previous reports have shown that the mechanism of splicing of the doublesex gene is different in Drosophila melanogaster and Bombyx mori. However, intron 4 is so long that it is difficult to identify the intronic cis-element(s) required for male-specific splicing of Bmdsx pre-mRNA using Bmdsx minigenes whose introns are shortened in various manners. As a first step toward discovery of the cis-element, the Bmdsx mini gene, which consisted of exon 1 and 5 and internally shortened introns 2 to 4, was constructed, and transgenic silkworms expressing this construct were generated. Bmdsx pre-mRNA transcribed derived from transgene was sex-specifically spliced. This result shows that the mini gene contained the information necessary for the correct regulation of alternative splicing.
Keywords: alternative splicing, Bmdsx, Bombyx mori, piggyback, long intron
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7. ESTABLISHMENT AND CHARACTERIZATION OF A CONTINUOUS CELL LINE FROM PUPAL OVARIES OF JAPANESE OAK SILKWORM ANTHERAEA YAMAMAI GUERIN-MENEVILLE
SHIGEO IMANISHI, HAJIME INOUE, TAKESHI KAWARABATA, KOYU HARA, MASAKO FUNAKOSHI, CHISA YASUNAGA-AOKI, and KAZUHIKO MITSUDA
In Vitro Cellular & Developmental Biology - Animal Volume 39, Issue 1 (January 2003) pp. 1–3
Pupal ovaries of the wild oak silkworm Antheraea yamamai Guerin-Meneville were cultured in MGM-448 (Modified Grace Medium-448) medium containing 10% fetal bovine serum. After the primary culture was set up in 1988, a continuous cell line was obtained in 1991, designated as NISES-Anya-0611 (Anya-0611). The population doubling time was 54 hrs. and 19 min. at 96 passages and 88 hrs. and 29 min. at 387 passages. Spindle-shaped and spherical cells coexisted in the cell group. The cell line karyotype line was typical of lepidopteran cell lines, consisting of numerous small chromosomes. The cell line was distinguished from other lepidopteran cell lines by comparing malic enzyme, phosphoglucose isomerase, phosphoglucose mutase, and isocitric dehydrogenase isozyme patterns. The cell line was highly infected to the Antheraea yamamai nuclear polyhedrosis virus (Anya NPV). The luciferase gene of recombinant Bm NPV (BmNPVP6ETL) was able to express in the cell line, too, so that luciferase recombinant products were able to be detected in the cell body and in supernatant. The Anya NPV clone group was isolated on the cell seat using plaque purification.
Keywords: insect, wild silkworm, primary culture, karyotype, isozyme patterns, nuclear polyhedrosis virus
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8. Effects of Wolbachia in the uzifly, Exorista sorbillans, a parasitoid of the silkworm, Bombyx mori
H.P. Puttaraju and B.M. Prakash
Journal of Insect Science Volume 5, Issue 30 (November 2005) pp. 1–7
The uzifly, Exorista sorbillans (Diptera: Tachinidae), a parasitoid of the silkworm, Bombyx mori L. (Lepidoptera: Bombycidae), harbours Wolbachia (Rickettsia) endosymbionts. Administration of 0.05 mg/ml oxytetracycline to the adult uziflies removed Wolbachia endosymbionts and resulted in different reproductive disorders, such as i) reduction in fecundity of uninfected females, ii) cytoplasmic incompatibility in crosses between infected males and uninfected females, iii) sterility in the crosses between both males and females from uninfected populations, and iv) sex-ratio distortion in uninfected females irrespective of the presence of Wolbachia in males. However, tetracycline treatment did not have much effect on longevity of the uzifly. These results suggest that the interaction of Wolbachia with its uzifly host is one of mutual symbiosis as it controls the reproductive physiology of its hosts.
Keywords: fecundity, cytoplasmic incompatibility, sterility, sex ratio, tetracycline
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9. Apoptosis and Adhesion of Hemocytes During Molting Stage of Silkworm, Bombyx mori
Toshio Okazaki, Noriyuki Okudaira, Kikuo Iwabuchi, Hajime Fugo, and Tatsuo Nagai
Zoological Science Volume 23, Issue 3 (March 2006) pp. 299–304
To clarify the regulatory mechanism of the rapid changes in the hemocyte density in the silkworm, Bombyx mori, during ecdysis, we evaluated the relationship between the hemocyte density and the incidence of apoptosis during this stage. We also evaluated the role of the sugar chains on the adhesion of hemocytes by analyzing the effects on the hemocyte density of the injection of enzymes that cut sugar chains and monosaccharides into the body cavity.
The hemocyte density was increased in the molting stage and spinning, and then decreased after the ecdysis. During spinning, the diameter of the granulocytes markedly increased, in which fatty granules in the cytoplasm increased, becoming foamy. They were identified to be apoptotic hemocytes using the Hoechst staining and the Comet assay. The decrease in the hemocyte density during spinning was mainly caused by the apoptosis of granulocytes. Next, we focused on the fluctuation of hemocyte density during the molting stage. Examination of the changes in the hemocyte density induced by injecting glycoside hydrolases, neuraminidase, sialic acid, or monosaccharides into the body cavity during the fourth molt stage and the third day in fifth instar larva demonstrated that the alteration of hemocyte density was regulated by the attachment and detachment of hemocytes via a selectin ligand, sugar chains. As with the injection of glycoside hydrolase, neuraminidase, sialic acid and fucose raised the hemocyte detachment, and it was assumed that the selectin ligands include the sialyl Lewis x like sugar chains, the same as mammalian lymphocytes.
Keywords: Bombyx mori, hemocyte, apoptosis, adhesion, sialyl Lewis x
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10. Immunocytochemical Identification of Neuroactive Substances in the Antennal Lobe of the Male Silkworm Moth Bombyx mori
Masaaki Iwano and Ryohei Kanzaki
Zoological Science Volume 22, Issue 2 (February 2005) pp. 199–211
As a first step towards understanding the functional role of neuroactive substances in the first olfactory center of the male silkworm moth Bombyx mori, we carried out an immunocytochemical identification of antennal lobe neurons. Antibodies against γ-aminobutyric acid (GABA), FMRFamide, serotonin, tyramine and histamine were applied to detect their existence in the antennal lobe. In the present immunocytochemical study, we clarified four antenno-cerebral tracts from their origin and projection pathways to the protocerebrum, and revealed the following immunoreactive cellular organization in the antennal lobe. 1) Local interneurons with cell bodies in the lateral cell cluster showed GABA, FMRFamide and tyramine immunoreactivity. 2) Projection neurons passing through the middle antenno-cerebral tract with cell bodies in the lateral cell cluster showed GABA and FMRFamide immunoreactivity. Projection neurons passing through the outer antenno-cerebral tract with cell bodies in the lateral cell cluster showed FMRFamide immunoreactivity. 3) Centrifugal neurons passing through the inner antenno-cerebral tract b with cell bodies located outside the antennal lobe showed serotonin and tyramine immunoreactivity. Our results revealed basic distribution patterns of neuroactive substances in the antennal lobe and indicated that each projection pathway from the antennal lobe to the protocerebrum contains specific combination of neuro-active substances.
Keywords: neuroactive substances, immunocytochemical, antennal lobe, projection pathway, silkworm moth
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11. Gene Expression Profiling in the Silkworm, Bombyx mori, During Early Embryonic Development
Sun-Mee Hong, Si-Kab Nho, Nam-Soon Kim, Jin-Sung Lee, and Seok-Woo Kang
Zoological Science Volume 23, Issue 6 (June 2006) pp. 517–528
We prepared a cDNA library for a microarray from eggs of the silkworm, Bombyx mori, at the germ-band formation (24 hours after fertilization) stage. Using a microarray constructed with 2,445 ESTs, we screened gene expression profiles during germ-band formation at six specific time points in the early embryonic stages (from the unfertilized egg to the formation of abdominal leg appendages), and determined 241 of these cDNAs to represent genes that were expressed differentially during the germ-band formation stage. These differentially expressed genes grouped into two clusters. In the early and late clusters, 203 and 38 genes were upregulated, respectively. In the upregulated clusters, we isolated several genes that were associated with development and cell communication, including egalitarian, RAD23b, innexin 2, and senescence-associated protein. Northern blot hybridization revealed that the expression patterns of 14 genes had changed in each of the stages. In this study, we assessed changes in the levels of gene expression in relation to the germ-band formation stages in whole Bombyx embryos.
Keywords: silkworm, Bombyx mori, cDNA microarray, embryogenesis, development, cell communication
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12. A Rapid Increase in cAMP in Response to 20-Hydroxyecdysone in the Anterior Silk Glands of the Silkworm, Bombyx mori
Mohamed Elmogy, Jun Terashima, Masatoshi Iga, Masafumi Iwami, and Sho Sakurai
Zoological Science Volume 23, Issue 8 (August 2006) pp. 715–719
In the anterior silk glands (ASGs) of the silkworm, Bombyx mori, intracellular cAMP increases transiently to a very high level shortly after the hemolymph ecdysteroid peak in the prepupal period. In cultured ASGs obtained on the day of gut-purge, cAMP levels were increased by 20-hydroxy-ecdysone (20E), and this increase was enhanced by an inhibitor of phosphodiesterase, but was not affected by α-amanitin, indicating the 20E action may not be mediated via gene expression. The increase in cAMP occurred within 30 seconds of exposure to a physiological concentration of 20E (1 μM), and also by ponasterone A. Our findings indicate a nongenomic action of ecdysteroids in insects, which may be an additional mechanism by which this steroid hormone induces acute responses in tissues and cells.
Keywords: ecdysone, cAMP, silk gland, programmed cell death, Bombyx mori
* Corresponding author. Phone: +81-76-264-6250; Fax : +81-76-264-6255; E-mail: firstname.lastname@example.org
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13. Brain-Derived Neurotrophic Factor Promotes Neurite Growth and Survival of Antennal Lobe Neurons in Brain from the Silk Moth, Bombyx mori in vitro
Jin Hee Kim, Dong Kyung Sung, Chan Woo Park, Hun Hee Park, Cheolin Park, Soung-Hoo Jeon, Pil Don Kang, O-Yu Kwon, and Bong Hee Lee
Zoological Science Volume 22, Issue 3 (March 2005) pp. 333–342
This study was conducted to investigate effects of brain-derived neurotrophic factor on the neurite growth and the survival rate of antennal lobe neurons in vitro, and secretion of brain-derived neurotrophic factor-like neuropeptide from brain into hemolymph in the silk moth, Bombyx mori. In primary culture of antennal lobe neurons with brain-derived neurotrophic factor, it promoted both a neurite extension of putative antennal lobe projection neurons and an outgrowth of branches from principal neurites of putative antennal interneurons with significance (p<0.05). name="cor1">* Corresponding author. Phone: +82-2-3290-3156; Fax: +82-2-3290-3623; E-mail: email@example.com
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C. Non mulberry sericulture
1. Impact of Pollen Grains from Bt Transgenic Corn on the Growth and Development of Chinese Tussah Silkworm, Antheraea pernyi (Lepidoptera: Saturniidae)
Wendong Li, Kongming Wu, Xiaoqi Wang, Guirong Wang, and Yuyuan Guo
Environmental Entomology Volume 34, Issue 4 (August 2005) pp. 922–928
The tussah silkworm, Antheraea pernyi (Lepidoptera: Saturniidae), is an important natural resource for the silk industry and has been cultured using wild host plants for >2,000 yr in China. To clarify whether there is any risk from pollen of Cry1Ab-containing corn varieties on this insect, the frequency of pollen dispersal and deposition of corn pollen near cornfields and impact on the development of tussah silkworm larvae were studied separately in the field and laboratory. The field survey showed that the pollen density was the highest inside the cornfield with a value of 1,000 grains/cm2. The pollen deposition rapidly declined with distance from the edge of the cornfield as expected in most cases. No significant differences were observed in the amounts of pollen deposited on glass slides positioned at different heights from the ground at each distance. In the laboratory bioassays, there were no significant differences in the larval mortality and weight of Chinese tussah silkworm between treatment with pollen grains from a transgenic corn line and a nontransgenic corn control at a density of 1,000 pollen grains/cm2. Also no significant negative impact was found for efficiency of conversion of digested food (ECD), efficiency of conversion of ingested food (ECI), and efficiency of approximate digestion of food (AD) at the level of 1,000 pollen grains/cm2. The results of this study suggest that the impact on the Chinese tussah silkworm of Bt corn pollen from the hybrid to be commercialized in China is negligible in the natural environment.
Keywords: pollen grains, Bt transgenic corn, Chinese tussah silkworm, environmental impact
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1. Modeling Of The Stress-Strain Behavior Of Egg Sac Silk Of The Spider Araneus Diadematus
Els Van Nimmen, Kris Gellynck, Tom Gheysens, Lieva Van Langenhove, and Johan Mertens
Journal of Arachnology Volume 33, Issue 2 (August 2005) pp. 629–639
Spider silk has attracted the attention of many scientists because of its desirable physical properties. Most of this attention has been devoted to dragline silk, a thread that has high tensile strength, high strain and ultra-low weight. To help understand structure-property relationships in spider silks, the tensile behavior of egg sac (cylindrical gland) silk of Araneus diadematus Clerck 1757 was compared with dragline (major ampullate gland) and silkworm silks. In addition, stress-strain curves of egg sac silk were simulated by a spring-dashpot model, specifically a Standard Linear Solid (SLS) model. The SLS model consists of a spring in series with a dashpot and in parallel with another spring, resulting in three unknown parameters. The average stress-strain curve of fibers from five different egg sacs could be accurately described by the model. Closer examination of the individual stress-strain curves revealed that in each egg sac two populations of fibers could be distinguished based on the parameters of the SLS model. The stress-strain curves of the two populations clearly differed in their behavior beyond the yield point and were probably derived from two different layers within the egg sac. This indicates that silks in the two layers of A. diadematus egg sacs probably have different tensile behavior.
Keywords: Spider silk, tensile behavior, cocoon, cylindrical gland, tubuliform gland, Araneidae
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2. Physical properties of Hydropsyche siltalai (Trichoptera) net silk
Sarah A. BrownA, Graeme D. RuxtonA, and Stuart HumphriesB
Journal of the North American Benthological Society ;Volume 23, Issue 4 (December 2004)
Suspension-feeding trichopterans spin a fine-silk capture net that is used to remove suspended matter from the water. The efficiency of these nets has previously been studied by considering the geometry of the web structure but the material from which the nets is constructed has received little attention. We report measurements of the tensile strength and extensibility of net silk from Hydropsyche siltalai. These measurements place caddisfly silk as one of the weakest natural silks so far reported, with a mean tensile strength of 221 ± 22 megaNewtons (MN)/m2. We also show that H. siltalai silk can more than double in length before catastrophic breakage, and that the silk is at least 2 orders of magnitude stronger than the maximum force estimated to act upon it in situ. Possible reasons for this disparity include constraints of evolutionary history and safety margins to prevent net failure or performance reduction.
Keywords: Hydropsyche siltalai, tensile strength, extensibility, breaking strain, stress
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3. Spider Dragline Silk: Correlated And Mosaic Evolution In High-Performance Biological Materials
Brook O. Swanson, Todd A. Blackledge, Adam P. Summers, and Cheryl Y. Hayashi
Evolution Volume 60, Issue 12 (December 2006) pp. 2539–2551
The evolution of biological materials is a critical, yet poorly understood, component in the generation of biodiversity. For example, the diversification of spiders is correlated with evolutionary changes in the way they use silk, and the material properties of these fibers, such as strength, toughness, extensibility, and stiffness, have profound effects on ecological function. Here, we examine the evolution of the material properties of dragline silk across a phylogenetically diverse sample of species in the Araneomorphae (true spiders). The silks we studied are generally stronger than other biological materials and tougher than most biological or man-made fibers, but their material properties are highly variable; for example, strength and toughness vary more than fourfold among the 21 species we investigated. Furthermore, associations between different properties are complex. Some traits, such as strength and extensibility, seem to evolve independently and show no evidence of correlation or trade-off across species, even though trade-offs between these properties are observed within species. Material properties retain different levels of phylogenetic signal, suggesting that traits such as extensibility and toughness may be subject to different types or intensities of selection in several spider lineages. The picture that emerges is complex, with a mosaic pattern of trait evolution producing a diverse set of materials across spider species. These results show that the properties of biological materials are the target of selection, and that these changes can produce evolutionarily and ecologically important diversity.
Keywords: Biomaterials, biomechanics, independent contrasts, major ampullate silk, phylogenetic signal, tensile test, web
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4. Spider Silk Proteins – Mechanical Property and Gene Sequence
Anna Rising, Helena Nimmervoll, Stefan Grip, Armando Fernandez-Arias, Erica Storckenfeldt, David P Knight, Fritz Vollrath, and Wilhelm Engström
Zoological Science Volume 22, Issue 3 (March 2005) pp. 273–281
Spiders spin up to seven different types of silk and each type possesses different mechanical properties. The reports on base sequences of spider silk protein genes have gained importance as the mechanical properties of silk fibers have been revealed. This review aims to link recent molecular data, often translated into amino acid sequences and predicted three dimensional structural motifs, to known mechanical properties.
Keywords: spider silk, MaSp1, MaSp2, structure, function
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5. The Combing of Cribellar Silk by the Prithine Misionella Mendensis, with Notes on Other Filistatid Spiders (Araneae: Filistatidae)
LARA LOPARDO and MARTÍN J. RAMÍREZ
American Museum Novitates Volume 3563, Issue 1 (May 2007) pp. 1–14
We present the first observations of the combing and attaching behavior in the subfamily Prithinae (Filistatidae), taken from Misionella mendensis. We compare its web architecture with that of other prithines (Pritha nana and Pikelinia sp. from Chile) and filistatines (Kukulcania hibernalis and Filistata insidiatrix). The combing behavior of M. mendensis corresponds to the stereotyped type I combing behavior, as is known for other filistatids. However, M. mendensis attaches the cribellar segments in a unique way, splitting the cribellar segment longitudinally and pushing each half to the substrate, attaching the silk with the tarsi of both legs IV simultaneously. These stereotyped movements result in web units of a very characteristic structure. We report the same split attachment behavior in the prithine Pikelinia tambilloi. We scored these observations into a previous dataset for filistatid relationships. Because of the missing observations on attachment behavior in the North American basal genus Filistatinella, the sister group of all other prithines, the evolution of split cribellar strands is a potential synapomorphic characteristic for the Prithinae, or at least the subgroup excluding its basal taxon.Link to full article (you may need subscription): http://www.bioone.org/perlserv/?request=get-pdf&doi=10.1206%2F0003-0082%282007%29529%5B1%3ATCOCSB%5D2.0.CO%3B2