Amount Of Silk Research Articles

ВЛИЯНИЕ КОЛИЧЕСТВА КОРМА И ТЕМПЕРАТУРЫ НА ТЕХНОЛОГИЧЕСКИЕ ПОКАЗАТЕЛИ КОКОНОВ

Relevance Today, the need of the world market for fine-fiber silk threads and high-quality silk products requires the improvement of scientific research in this area, namely, a thorough study of the effects of various environmental factors on the quality and productivity of the silkworm. As you know, these factors include temperature, air humidity, movement and change of air, quantity and quality of feed, exposure to radiant energy, etc. Methods Scientists of the Department of Sericulture and Tuticulture emphasized the study of the influence of the amount of feed and temperature changes on the activity of the silk gland, and therefore, on the technological parameters of cocoons. During the study, we took mulberry silkworm caterpillars of the Ipacchi-1 x Ipacchi-2 hybrid, widely distributed in Uzbekistan, which was created by scientists of the Silk Production Research Institute. Caterpillars were fed with different amounts of food at different air temperatures. Results The results of the study showed that when feeding silkworm caterpillars with different amounts of feed and at different feeding temperatures, the technological indicators of cocoons, namely the output of raw silk, the total and continuous length of the cocoon thread, and reeling are different. In particular, at 100% feeding and optimal feeding temperature, the yield of raw silk increased by 12.2%, unwinding by 12.5-24.0%, the total length of cocoon thread by 41.4-43.2%, continuous unwinding by 43.6-45.8% and fineness of cocoon filament by 42.3-44.2%. When feeding the caterpillars with a sufficient amount of feed, the larvae develop well, the activity of the silk glands improves and a sufficient amount of silk mass accumulates. As a result, a greater amount of silk is curled in the cocoon shell, which helps to increase the technological parameters of the cocoon.

Settlement decisions by the two-spotted spider mite Tetranychus urticae

In silk-spinning arthropods, silk can be used for web building, protection, and communication. Silk is an informative material about the presence of conspecifics. It can therefore inform on habitat suitability and hence assist in habitat choice. In this context, we investigated the influence of silk on microhabitat choice by the two-spotted spider mite, Tetranychus urticae. Three factors that could potentially influence habitat choice were manipulated: the strain, number, and the stage of mites. Our study showed that these factors all influence the choice of microhabitat. The tendency of whether to settle on a silk-covered area was influenced by the origin of mites (strain effect). Adult females showed a higher tendency to settle on an area covered with the silk laid by numerous congeners (number effect). Moreover, larvae seemed to be more responsive to the presence of silk than adults (stage effect). This suggests that individuals use silk as a social cue in selecting their microhabitat and that the spatial organization and group behaviour seem to be shaped by the individuals’ response to social cues, such as the amount of silk already present.

A Captive Study on Activity-Rest, Nesting and Aggression Behavior of an Indian Ant Species, Polyrhachis lacteipennis (Smith 1858) (Hymenoptera: Formicidae: Formicinae)

In the present study, the effect of captivity on the behavioral patterns like activity-rest time budget, nesting, aggression etc. in a group of Polyrhachis lecteipennis has been documented. The ants were collected from the natural population and maintained in the laboratory keeping them either in a single formicarium or prepared formicaria interconnected with tubes to observe the behavior. About 8 types of behavioral pattern of ants were noticed. In case of necrophoresis (carrying of dead nest-mates), the space inside the formicarium was not found to be sufficient to dispose off the dead nest-mates and therefore, all the time the workers carried the dead nest-mates haphazardly possibly in search of suitable disposal area. When the worker ants with dead nest-mates were allowed to leave the formicarium, they left, disposed and came back to the formicarium. With regard to the nesting behavior, it was observed that the silk secreting property was not the only larval character, the adult workers, on the other hand, could also secrete some amount of silk. When the natural hibiscus leaf-nest dried up in the formicarium, the workers along with queens left the natural leaf-nest and make ‘tube-nest’ in the formicarium. The workers carried all the larvae and pupae to the newly forming ‘tube-nest’. It was also observed that sometimes workers took the animal food inside the ‘tube-nest’ and sometimes not. They were very aggressive towards the intruder ants but when fellow members, separated for several months were re-introduced, the residents did show almost no aggression. The maximum number (n = 10) of worker ants were observed as active during the months of May and June. Afterwards, the number gradually declined to become lowest (n = 3) in the month of January. Among the different behavior patterns studied herein, most of them were found to be innate or ‘hard-wired’, did not require the presence of stimuli like large sized natural colony, queen, egg, larvae, pupae etc. inside the formicarium.

The effects of predation risk on female silk deposition and male response to predator-cued conspecifics in the wolf spider, Pardosa milvina (Araneae: Lycosidae)

Female Pardosa milvina (Hentz 1844) wolf spiders advertise sexual receptivity toward males via silk draglines, and male P. milvina exhibit conspicuous courtship behavior when encountering silk from females. Previous studies suggest that female P. milvina may benefit by limiting silk advertisements and excreta deposition when encountering silk from the predator, H. helluo, and male P. milvina may exhibit corresponding reductions in courtship when encountering silk from conspecific females previously exposed to H. helluo silk. We tested these predictions by comparing the amount of silk and excreta deposited by unmated female P. milvina exposed or not exposed to predator cues (silk and excreta) from H. helluo. We also measured and compared male P. milvina courtship latency and intensity in the presence of silk from females previously exposed or not exposed to predator silk from H. helluo. Contrary to predictions, we found a significant increase in excreta, dragline, and attachment disk deposition after females were exposed to H. helluo cues. Male P. milvina courtship latency did not vary among treatments despite increases in female silk deposition, but males significantly decreased courtship intensity when exposed to silk from females under predation risk. Vertical climbing to escape the predator cues may cause an increase in female silk deposition.

Recovery of spiders from the effects of parasitic wasps: implications for fine-tuned mechanisms of manipulation

The larva of the ichneumonid wasp Polysphincta gutfreundi induces its host, the orb-weaving spider Allocyclosa bifurca , to build a highly modified, physically stable orb web, to which the larva then attaches its pupal cocoon, and to add an otherwise unusual linear silk stabilimentum to this web that may camouflage the cocoon. The effects of the larva are apparently due to a chemical product or products that it introduces into the spider. Behavioural modification is gradual, and various behavioural effects arise in a consistent order. If the wasp larva is experimentally removed just before it kills the spider, the spider's behaviour recovers gradually in the reverse order. In addition, a greater delay in removing the larva leads to more pronounced and enduring behavioural changes, so the larval effects may depend on a cumulative or dose-dependent process. Changes in numbers and lengths of radii and numbers of sticky spiral loops could result from correlated larval effects on the reduction in the amount of silk in the spider's sticky spiral silk glands (or a signal thereof), but several other types of behavioural change are probably under separate controls; multiple larval products may be involved. The larvae may affect higher levels of behavioural decisions by spiders that determine overall web ‘design’, rather than lower levels, such as control of particular behaviour patterns, as may be affected by related wasps. The larva's effects are fine-tuned to details of the host's natural history.

Does the Giant Wood Spider Nephila pilipes Respond to Prey Variation by Altering Web or Silk Properties?

AbstractRecent studies demonstrated that orb‐weaving spiders may alter web architectures, the amount of silk in webs, or the protein composition of silks in response to variation in amount or type of prey. In this study, we conducted food manipulations to examine three mechanisms by which orb‐weaving spiders may adjust the performance of webs to variation in prey by altering the architectures of webs, making structural changes to the diameters of silk threads, and manipulating the material properties or amino acid composition of silk fibers. We fed Nephila pilipes two different types of prey, crickets or flies, and then compared orb structure and the chemical and physical properties of major ampullate (MA) silk between groups. Prey type did not affect orb structures in N. pilipes, except for mesh size. However, MA silk diameter and the stiffness of orbs constructed by spiders fed crickets were significantly greater than for the fly group. MA fibers forcibly silked from N. pilipes fed crickets was significantly thicker, but less stiff, than silk from spiders fed flies. Spiders in the cricket treatment also produced MA silk with slightly, but statistically significantly, more serine than silk from spiders in the fly treatment. Percentages of other major amino acids (proline, glycine, and glutamine) did not differ between treatments. This study demonstrated that orb‐weaving spiders can simultaneously alter some structural and material properties of MA silk, as well as the physical characteristics of webs, in response to different types of prey.

Enzymatic degradation behavior of porous silk fibroin sheets

We investigated the degradation behavior of porous silk fibroin sheets by in vitro enzymatic experiments with α-chymotrypsin, collagenase IA, and protease XIV. With 1.0 U/ml protease XIV, 70% of a silk fibroin sheet was degraded within 15 days at 37°C. When the fibroin sheet was exposed to collagenase IA, the amount of Silk II crystalline structure in the sheets decreased slightly, and a small amount of Silk I crystalline structure was formed. When protease XIV was used, almost all Silk II disappeared, but the crystallinity increased overall because the amount of Silk I increased. During digestion with protease XIV, the pore size of the fibroin sheets increased with increasing degradation time, until the sheets finally collapsed and became totally shapeless. The average molecular weight of the products after degradation with the three enzymes followed the order protease XIV < collagenase IA < α-chymotrypsin. More than 50% of the products resulting from degradation with protease XIV were free amino acids.

Web-building behaviour in the orb-weaving spider Zygiella x-notata: influence of experience

Zygiella x-notata is an orb-weaving spider that often renews its trap daily. Web building has associated costs and benefits, and building successive webs may have consequences for lifetime reproductive success. In the laboratory, we tested the ability of Z.x-notata to modify its building behaviour in response to various stages in predation (prey detection, capture and ingestion) experienced with a previous web. We determined which stages provided information for the spiders. Spiders that detected, captured and ingested prey and then rebuilt their web used less silk and made a smaller capture area than in the previous web. There was no effect of prey detection alone on the next web. Capture without feeding gave the same results as capture followed by feeding. The spiders that ate prey without detection and capture (feeding by hand) had the same energetic gains as spiders that caught prey but delayed building a new web. The spiders thus showed plasticity in web-building behaviour and in the amount of silk used (energetic investment) in the short term (from one web to the next). Changes in body condition may therefore influence web construction. Moreover, information gained during prey capture appeared to influence the size and structure of the next web. This ability should enable spiders to adapt their web building to maximize their fitness.

Reduced aggressive behavior: A benefit of silk-spinning in the parsnip webworm, Depressaria pastinacella (Lepidoptera: Oecophoridae)

The parsnip webworm, Depressaria pastinacella, spins a silken web within the umbels of its host plant, the wild parsnip Pastinaca sativa, and aggressively defends this web against conspecifics. We first established experimentally that the number of aggressive interactions between caterpillars with their webs removed was significantly higher than for webworms with intact webs. In order to determine whether web-spinning acts to divide food resources and reduce aggressive interactions, we measured relative weight gain and total silk production of parsnip webworms isolated from one another, grouped together with webbing undisturbed, and grouped together with webbing removed daily. Parsnip webworms isolated from one another and therefore unable to engage in aggressive interactions attained the highest pupal weights and spun the smallest amount of silk; caterpillars with webs removed daily and therefore with frequent aggressive interactions until territories were reestablished had the lowest pupal weights and spun the greatest quantity of silk. Our findings indicate that, for the parsnip webworm, constructing a silken web reduces aggressive encounters among conspecifics.

The effects of temperature on the web‐building behaviour of the common house spider, Achaearanea tepidariorum

1. Because spiders are ectothermic animals, the temperature regime of the microhabitat in which an individual finds itself may affect important performance traits of that individual. The present study examined the effects of temperature on attributes of webs spun by Achaearanea tepidariorum (C. L. Koch), as well as testing temperature preference in this species. The effects of temperature on the amount of silk per web produced by Achaearanea tepidariorum and the prey‐capture efficiency of webs produced at different temperatures were determined by using webs constructed at 5, 10, 15, 20, 25 and 30°C. The temperature preferences of A. tepidariorum within a thermal gradient were also determined. 2. Web mass was related to temperature, exhibiting a quadratic relation with a maximum web mass occurring at approximately 20°C. 3. Number of strands per cm3 of webs varied directly with web mass; webs with greater strand densities were more efficient at capturing flies. 4. The number of spiders observed in each temperature range in the thermal gradient indicated a non‐uniform distribution, with the spiders avoiding temperatures in the highest range (27·3±2·0°C). 5. These data suggest an optimal temperature for web construction at which webs produced are more efficient at capturing prey. The data also suggest that this species may avoid sites that do not provide an adequate thermal environment.