Drafts

    Spider webs are extremely thin, the largest silk fibers being only 5-10 μm. Some can be as thin as only 50 nm, making spider webs very difficult to measure. We found a publication that explains the use of light microscopy to accurately and precisely measure the width of spider webs. Webs are extremely strong, comparable to steel and also super flexible. However, because of the microscopic size, the different principles of silk have not been greatly investigated. In this review they used a polarized light microscope to illuminate the spider webs and images were taken that were then used for comparisons and measurements.

Georges bank is a region of ocean just south of the Gulf of Maine and East of cape cod Massachusetts. This region is only 45 meters deep, allowing sunlight to reach the bottom making it very nutrient reach. Furthermore, the gulf stream and Labrador current intersect here, bringing their own nutrients and “mixing it up.” The cold water makes it perfect for the Atlantic cod and a variety of other fish species. Due to this large productivity, Georges Banks has been an important economic fishing zone. Unfortunately overfishing over the last hundreds of years has decreased the biomass of this area by nearly 90%. 66% of this decline has occurred in the last 50 years alone. Unfortunately this does not seem to be changing, despite attempts of (admittedly insufficient) regulation. Recent fears of global warming seem to be effecting the gulf of Maine significantly. Unfortunately the fish here are adjusted to live in the cold waters, and as water temperature rises it will only get harder for them to survive here. Not only is the loss of fish species tragic on its own, but we as humans rely on this area for food and money.

To determine the relationship between spider weight and spider web thickness, 3 different species of spiders of different sizes will be collected from various sites around campus. We will collect 2 spiders in each species. The spiders will be weighed on analytical scales and will be sorted based on weight. They will then be placed in separate containers  and will be allowed to spin out spider silk.The spiders will be left in their containers to make a web for 5 days. We will feed them 1 fruit fly each day. We will remove the web with tweezers and place onto a microscope slide. The silk will be fixed onto microscope slides using distilled water as a buffer. The silk will be observed under a microscope at 40x magnification and be characterized based on size, using a stage micrometer, and web type. The webs will be sorted based on type, and then subgroups will be made based on size. The data will be analyzed based on the spider species and then the web size will be compared to spider weight to determine if any correlation exists.

We want to contrast two different periods of starvation (3-days vs. 7-days) and see the impact on spiders’ eating habits (feeding rate, feeding interval) and movement. We also want to observe the combined impact of various environmental stressors and starvation (heat and cold) on spiders’ morphology and behavior. Since a study on long-term starvation revealed that there was difference in the behavior of wolf male and wolf female spiders after food deprivation ( ), we want to observe any difference in behavior due to short-term food deprivation. We also want to observe the impact of competition on predatory behavior after food-deprivation.

    We hypothesize that there would be no difference in morphology after a short starvation period, since metabolism is adjusted and resources are reallocated over a long time (Wilson, 2014). However, we expect there to be significant behavioral change between the not-starved spider and the 7-day-starved spider in terms of feeding speed and feeding amount. We expect the environmental stressors to negatively impact web-building abilities and feeding for all groups of spiders. And, we expect female wolf spiders to feed in a more uniform pattern compared to their male counterparts (reference ). We also expect there to be more aggression present (in the competitive group) between the 7-day starved spiders compared to both the 3-day starved spiders and not-starved spiders.

These studies of long-term starvation also reveal two fundamental facts about spider metabolism. During starvation period, resources will be reallocated from reproductive potential and growth to maintenance and survival to ensure that reproduction can take place when conditions improve (Wilson, 2014; ). Spiders do not adjust metabolism to maintain a constant body weight, rather their lipid is stored efficiently and prepare them for long periods of food deprivation (Jensen et al., 2010).

    Although the effect of long-term starvation has been widely studied on spider morphology, behavior and movement, research is scarce about the impact of short-term food deprivation. This scenario is a much more likely one in the real world, especially for house spiders whose insect supply is limited. Due to our regular interaction with these kinds of spider much of our surrounding environment is shaped by their predatory behaviors. In this proposal, we aim to look into the impacts of short-term starvation on the morphology, behavior and movement of common spiders in Amherst: wolf spiders and cellar spiders.

The feeding behavior of any species can tell us a lot about its metabolism, movement patterns, predatory instincts, and overall ecological impact on its surrounding biomass. Most species of spiders (order: Araneae) are predators, who feed on insects and small invertebrates through the synthesis of sticky webs. Their feeding pattern is mainly influenced by the size and shape of the prey and whether the spider has enough strength to overpower it: preys are supposed to be smaller than the spider’s body but larger than its head. Web-weaver spiders can also survive a long time without food due to spending minimal energy (reference.)

    Due to their unique metabolism and ability to survive without food for extended periods of time, the effect of long-term starvation has been widely studied in spiders. And, the results indicate that starvation still affects various spiders’ morphology, feeding behavior and movement patterns without causing prompt death. Southwestern longlegs spider, Physocyclus mexicanus, exhibit smaller body size, reduced weight, and smaller testis size under severe dietary restrictions (Wilson, 2014). Running crab spider, Philodromus rufus, feed at a higher rate after being starved (Haines and Sisojevic , 2012). The wolf spider, Pardosa agrestis, is more susceptible to cannibalistic tendencies when hungry (Samu et al., 1999). Food-limited wolf spider, Tigrosa helluo, show more locomotive activity than their satiated counterparts (Walker et al., 1999). And, spiders of various species show distinct aeronautic dispersal and ballooning movements after starvation (Mestre and Bonte, 2012; Weyman and Sunderland, 1994).

The feeding pattern of spiders reveal a lot about their metabolism, locomotive behavior, predatory instincts, and ecological impact on surrounding biomass. Long-term starvation affects all of these variables to different extent in different species. However, it is not well-understood how short-term starvation may affect spiders’ feeding behavior and movement. In this proposal, we aim to assess the impact of short-term starvation on feeding behavior and movement of cellar spiders and wolf spiders, under various environmental stressors and in presence of competition. Spiders (n=3) will be placed in individual clear containers and starved for either a 3-day or 7-day period, and their behavior will be contrasted with their satiated counterparts. To understand the combined effect of environmental stressors and food deprivation, some cellar spiders will be placed in cold (18 C) or hot (30 C) environments. The difference in feeding pattern between male and female wolf spiders after short-term starvation will be recorded. And, to assess the impact of competition after starvation, multiple cellar spiders will receive a limited amount of food. All data should be collected in a qualitative manner, outside of feeding rate and mortality of spiders ,and will be analyzed in comparison to the control group of not-starved spiders. Understanding the impact of short-term starvation on spiders’ predatory and locomotive behavior will broaden our knowledge of their metabolic activities and will help us better utilize them for pest control.

By generating a Lokta-Volterra model and analyzing the results of this competition, the outcome of the competition between C. maculate (Species 1) and E. Civile (Species 2) can be determined as reaching stable equilibrium. This outcome will be most likely to occur based on the data points present in the model which in turn generates isocline 1, isocline 2, and four separate arrow sets in the respective zones that all point to a central, stable equilibrium point. In Zone 1, below both of the isoclines, the populations of both competing species will increase. In Zone 2, which is found above Species 2 (E. Civile) isocline and below Species 1 (C. maculate) isocline, the population size of Species 1 will increase and the population size of Species 2 will decrease. In Zone 3, which is found above both species isoclines the population of both Species 1 and Species 2 will decrease. In Zone 4, which is found above Species 1 isocline and below Species 2 isocline the population size of Species 1 will decrease and the population size of Species 2 will increase.

By generating a Lokta-Volterra model and analyzing the results of this competition, the outcome of the competition between C. maculate (Species 1) and E. Civile (Species 2) can be determined as reaching stable equilibrium. This outcome will be most likely to occur based on the data points present in the model which in turn generates isocline 1, isocline 2, and four separate arrow sets in the respective zones that all point to a central, stable equilibrium point. In Zone 1, below both of the isoclines, the populations of both competing species will increase. In Zone 2, which is found above Species 2 (E. Civile) isocline and below Species 1 (C. maculate) isocline, the population size of Species 1 will increase and the population size of Species 2 will decrease. In Zone 3, which is found above both species isoclines the population of both Species 1 and Species 2 will decrease.

By generating a Lokta-Volterra model and analyzing the results of this competition, the outcome of the competition between C. maculate (Species 1) and E. Civile (Species 2) can be determined as reaching stable equilibrium. This outcome will be most likely to occur based on the data points present in the model which in turn generates isocline 1, isocline 2, and four separate arrow sets in the respective zones that all point to a central, stable equilibrium point. In Zone 1, below both of the isoclines, the populations of both competing species will increase. In Zone 2, which is found above Species 2 (E. Civile) isocline and below Species 1 (C. maculate) isocline, the population size of Species 1 will increase and the population size of Species 2 will decrease. In Zone 3, which is found above both species isoclines the population of both Species 1 and Species 2 will decrease.