Project Proposal

Project Proposal

Morgan Tupper & Jason Charbonneau 10/8/19

BIO 334 Animal Behavior Research Proposal

Mentor: Dr. Karen Cangialosi

Changes in Territorial Organization of Lasiodora cristata (Aranaea) Given Changes in Environmental Stimuli

  1. Introduction
  2. Background and Significance

The immense and wide ranging diversity of Arthropods contributes to the Phylums deep rooted speciation in all habitable corners of the world.  This species richness and variance pertains to over one-million known organisms [10]. Though arachnids comprise a relatively small amount of Phylum Arthropoda (i.e. about 60,000 species), they are arguably some of the most advanced and derived predators of their segment of the animal kingdom.  Arachnids are categorized under joint legged invertebrates [1]. Araneae is the order that pertains to spiders. With over 50,000 described species and more being discovered and documented [9].  

Due to the complexity of observed and researchable behaviors of spiders, they are model organisms for behavioral experiments.  Of the wide range and variation of behaviors exhibited by araneae there is included, predation, intraspecific interactions, multimodal mating exhibitions and an array of hunting strategies.  Spiders have remarkable sensory systems. Some of the more derived groups of spiders such as genus Phidippus (jumping spiders) have developed highly advanced sensory modalities.  This includes chemoreception, biodetection assays, lyriform sound detection orgams, eyes of various visual detection functions (UV light detection, polarization), hair covered appendages capable of mechanodetection, etc. [7].  

Family Theraphosidae (Tarantulas), despite being well known, has been inadequately researched to date.  Theraphosids, despite their physical size and diverse biological range worldwide, are lesser derived forms of Aranea.  Early fossil finds indicate that ancient spider species originating circa the Carboniferous period (~330-380 M years ago) lacked spinnerets, were likely cursorial hunters and physically dominant and immense.  This is reminiscent of the species that are still observable today. None utilize web spinage for the acquisition of prey and all exhibit cursorial behavior when hunting. Changes in the environment, predators and evolutionary pressures acted as a driver to smaller size and diversification.  These modifications may have helped them to hide and escape natural predators, also of large magnitude when compared to the organisms of the current age [2].  

Theraphosids are categorized under infraorder Mygalomorphae.  Mygalomorphae deviate from Araneomorphs (true spiders) predominantly due to their chelicerae structure.  The chelicerae are large relative to other species. The chelicerae are suspended via the maxilla over the labium, with defining, inferior pointing fangs.  Such structure correlates to downward strikes of the fangs, in contrast to Araneomorphs lateral-medial pincer movement [11]. Supplemental distinguishing features are seen in full bodies covered in hair and thickened pads of scopulae on inferior side of tarsi.  

Save instances of predatory and mating behaviors, it is generally accepted that Tarantulas live sedentary lifestyles.  Most if not all species burrow and are only active nocturnally. When not in burrows a Tarantula will hide essentially anywhere they can fit and conceal their bodies.  An exception to this is males during the mating season, whom may readily be found moving about in broad daylight [15].  

Due to their representative nature of the ecosystems and communities they comprise, we believe it important to investigate the potential effects of environmental changes on the passive nature of these organisms.  How will they choose a substrate and is there a greater affinity given a specific set of circumstances? We take into account the multitude of independent variables possible that may affect Theraphosid behavior; habitat fragmentation, habitat limitation, resulting in more clustered groupings of reclusive individuals, changes in temperature, humidity, available substrate, hiding spots, etc.  Responses to such drivers vary accordingly. Aggressiveness assays have been established in a previous study and will also be employed in a more general context [4]. Materials and methods section will detail the selected independent and dependent variables utilized and measured during the experiment.

  1. Specimen Selection

13 subfamilies exist under Theraphosidae.  Theraphosa typically only encompass the populations of tarantulas found in Central America upwards to the southernmost reaches of the Continental United States.  Though other families exist in Africa, Australia and South East Asia, there is presented a plethora of minor-moderate alterations to the populations in these regions.  ‘New World’ Tarantulas are most relevant to current American Arachnological studies. This is due to the projected evolution of spiders, with the earliest of protospider fossils being discovered in modern day Gilboa New York, USA. 380 million years ago, this portion of the above sea-level continental plate was likely South-west Baltica, long after the initial splits of Pangea [13].  It is unclear whether this connection indicates lesser or greater derivation of Theraphosids that still fulfill niches in the Western hemisphere.

When considering some of the first observations made of modern Tarantulas, some of the most prevalent revolve around their territoriality and associated assays.  Territoriality may be a trait exhibited in a wide array of behaviors. Individual organization: perhaps residing in the burrow, exposed, defensively poised or other could be indicative of organism stress, individual propensity towards defensiveness/aggressiveness and general environmental health.  Spiders comprise a group of keystone species in many environments; their regulation of smaller organisms, pests and fuel to higher consumer tiers is pivotal to the health of ecological communities. The indirect effect of their presence influences a large portion of their community and sustained life of their ecosystem.  

With climate change as an ever imposing presence on world ecology and ecosystem health, it is important to address how variation in temperature and humidity might drive tarantula specimens.  This past year, the Amazon rainforest was devastated by the worst forest fires in recorded history. There was seen an 80% increase in the number of forest fires in the Amazon from 2018 to 2019 [6].  A study by the European Geosciences Union indicated that areas that were targeted for deforestation for repurposing the land for crops was on average 1.05o C higher once altered [13].  We may therefore reasonably conclude a potential impact to spider species found in the Amazon, given the environmental disasters.

Lasiodora cristata, the Brazilian Red and White Tarantula was chosen for organism of study.  They are known to be partially aggressive and nervous during interactions. Like most Tarantula species, Lasiodora cristata burrows during most of the daylight hours.  Recommended substrate for these creatures in captivity is peat moss.  Additional measures to better replicate natural environment and reduce organism stress and acclimation time are detailed in the materials and methods.  Optimal active temperature and humidity are suggested between 24-27oC and 75-80 % humidity.  Though these organisms are thought to be well tolerant to variation in these conditions, we raise the question if there are consequences for relatively fast change in acclimated environment on individuals of this species.  We focus this study on L. cristata in order to gain knowledge on overall ecological health, biology and behavioral patterns of this reclusive species.  

  1. Objectives and Hypothesis 

The question we propose given the literature, is how will temperature variation affect substrate affinity.  The main objective of this research is to observe the change in territorial organization of tarantulas when presented with this environmental stimuli. Specifically we want to determine if tarantulas change their nesting sites, hiding spots, burrowing behavior or exhibit more aggressive territorial behaviors when their acclimated habitat temperature is changed.

We propose the following hypothesis:

Ha: Changes in temperature will influence substrate choice for burrowing of tarantulas

  1. Predictions

Changes in temperature will influence substrate choice for burrowing of tarantulas.  If we increase the temperature of the terrariums that holds the specimens, there will be a change is substrate choice from the soil to the peat moss. If the temperature is decreased to room temperature, we predict the specimens are also likely to be more sporadic, less sessile and exhibit greater stress when at high temperatures for unnatural periods of time.  We go on to speculate that substrate choice will be less consistent at varied temperatures, as is discussed in materials and methods under subsection temperature (I).  

2. Materials and Methods

L. cristata was ordered from Michigan Arachnid, a professional breeder, recommended by Tarantula specialist Dr. Cara Shillington at the University of Michigan.  The team has been informed from this source that the specimens are infants, ¼-½ “ in size.

Previous studies provide evidence that suggests Theraphosids prefer malleable substrates that still support structurally sound burrows.  A 2007 study in the Journal of Natural History found that surveyed specimens in the wild prefered clay-infused soil when contrasted to soil laden with roots or sand [8].  Given other suggestions for keeping L. cristata, substrate choices for the specimen are specified to 3-5 inches of peat moss, thick, pliable soil and tree bark or a hollow branch [5].  

  1. Housing and Feeding

Recommendations from the breeder to best preserve and feed the specimens is to keep the specimens in the viles they are delivered in.  They are to be kept in the Keene State College Putnam Science Center greenhouse as it is the warmest most humid location that will best resemble the natural environment of L. Cristata.  

Care is taken to keep the relative environments created within each separate terrarium consistent, that they may be used as replicates.  A realistic and manageable figure established by the research team is 4 spider specimens. The housing is kept at a constant temperature which will be dictated by the temperature of the greenhouse they will be subsequently kept in. Theraphosidae are being fed via wingless drosophila and will be fed frequently (3-4 times weekly, >3 flies) as the specimens received are in a juvenile state. Adult tarantulas only need to be fed about once weekly  [10].  

  1. Temperature

The thermal tolerance limit of many arthropods may help them choose suitable burrowing sites. Researchers have found that most species of Theraphosidae prefer to live in an environment at around 30 degrees celsius [3]. All Theraphosidae belong to a category known as poikilotherm, or organisms that either don’t control their body temperature, or control their body temperature through behavioral means. This characteristic gives Theraphosidae the built-in ability to survive across a range of body temperatures. They barely notice the temperature change until it approaches extremes, somewhere below 16 degrees C and above 38 degrees C. Theraphosidae begin to lose all bodily functions near freezing temperatures and somewhere around 43 degrees C [12].

It has been found that there is a strong correlation between the placement of burrows in a Theraphosidae’s niche, and the temperature of the environment. Theraphosidae burrows are randomly distributed with regard to one another, but the borrows were in very specific locations. The location of these burrows were often found in locations with very low fluctuating temperatures and high humidity. This directly relates to reduced desiccation and lower metabolic rates. Other studies have shown that these conditions can affect growth rates, food consumption, adult longevity and egg production. Also, the construction of burrows requires high energy requirements which leads to long periods of residency, making initial site selection important [16].

Theraphosidae build burrows in locations with high morning temperatures. This allows the spiders to raise their metabolic rate before daily activities. In contrast, low midday and evening temperatures allow Theraphosidae to maintain those metabolic rates and reduce mortality risks associated with high environmental temperatures. This specific location of burrows does affect the rate at which Theraphosidae find prey, but the low metabolic rate reduces the need for high feeding rates [16].

The major exception for temperature, burrow habitation relating to thermoregulation, is the behavior of males during mating season.  

  1. Burrows

Distribution of burrows within an aggregation is known to be random. Burrows can be found in both fossorial substrates and the trunks of decaying trees. Trunks provide Theraphosidae with an easy food source in the form of termites and other invertebrates.  Theraphosidae appear to prefer burrowing sites composed of just bare soil as opposed to sites with leaf litter. It has also been found that Theraphosidae prefer to dig their burrows in sites containing sandy loam where there is partial protection from the sun. The first third of the burrows are typically lined with silk and is used for prey detection and support for the burrow walls. The shape of the burrow is specific to the individual and has been found to vary greatly. 

We define the burrows exhibited by the specimens by the parameters above.  Amount of burrows, if there are more than one, are to be recorded. During periods of active observation it is to be noted if the specimen is inside the burrow and how long they remain there for each period of continuous observation.

  1. Experimental Design

Theraphosidae do not require a large amount of space. Burrowing or terrestrial spiders require a space roughly three times the leg span, and about double the leg span wide. On the bottom, a substrate is present at least two to four inches deep to provide space to burrow. These substrates will be distributed as evenly as possible inside of a one-gallon terrarium.  Each terrarium is coupled with a petri dish filled with a water supply for the organism. This is the source of hydration as well as a supplementation for humidity. terrariums are also to be misted down no less than twice a week for the duration of organism habitation. Recommended levels of humidity are reported at 75-80%, which is consistent with rainforest ecology.

In order to test whether environmental temperature makes a significant difference in the type of substrate that the tarantula decides to make its burrow we will begin with a one-gallon tank separated into three different areas. Each area will be identical in every aspect except for the substrate at the bottom of the tank. The tank will be separated into three distinct sections. Each section will contain a specific substrate. The substrates that we will be working with are peat moss, soil and decaying wood. 

A researcher will manually transplant the specimen from the housing vile into the previously prepared terrarium.  The team actively observed the specimen for no less than 10 minutes. After it appears that the tarantula has dug a burrow and chosen a substrate, it is removed from the tank, the substrate will be changed to new bedding, and the tarantula will be placed back into the vile at greenhouse conditions.  This will be performed with each individual at regular greenhouse conditions each day for one week. The weekend will be allotted for a decompression period. This process will be repeated for the hot conditions, however the terrariums will be treated for one-hour with a heat lamp prior to specimen deposit.  The temperature of the terrarium will be recorded and is intended to be ~38o C, replicating a drastic heating of the Amazon during the wild fires.

3. Data Analysis

  1. Sample Data Sheet

                 Cool                                     Greenhouse Conditions       Hot

IndividualPeat mossSoilWoodPeat MossSoilWoodPeat MossSoilWood
1








2








3








4








The tarantulas preference of substrate at each temperature will be marked accordingly. 

  1. Statistical Analysis

Because the data being collected is non-numerical, we will be using a Chi-square goodness-of-fit test. We will be counting how many times the individuals chose a certain substrate at a particular temperature. In this case, we will be looking at if our variables are associated. After data is collected, we will construct a table of observed frequencies. After, the expected frequencies will be calculated using the formula: 

(Column Total x Row Total) / Grand Total

After the expected values are calculated, the chi-square value must be solved for. This will be done using the formula:

x^2 = Sum ( (O E)^2 / E)

The test statistics are then compared to the critical value: if it is bigger, we reject the null hypothesis.

BehaviorColdRoom TempWarmRow Totals
Peat Moss



Soil



Decaying Wood



Column Total



3. References

  1. About arachnids, Amreican Arachnological Society, 2019
  2. BioExpedition Publishing, Spider evolution, 354 NW, 46 ST. Miami, FL.33166, 2019
  3. Canals, Mauricio, et al. “Adaptation of the Spiders to the Environment: the Case of Some Chilean Species.” Frontiers in Physiology, Frontiers Media S.A., 11 Aug. 2015
  4. Charbonneau, Jason A. 2019. Effects of Hunger on Lycosa carolinensis (Araneae) Intraspecies-Communal Behavior, Keene State Department of Biology, Mentor: Dr. Karen Cangialosi
  5. Fouskaris, J., & Somma, F. (2002).  Brazilian Red and White Tarantula. Petbugs caresheets
  6. Kessler, R. (2019, August 22). The Amazon Is Burning. Retrieved from https://www.ecohealthalliance.org/
  7. Long, Skye M., “Spider Brain Morphology & Behavior” (2016). Doctoral Dissertations. 707
  8. Machkour-M’Rabet, Salima & Henaut, Yann & Sepúlveda, Alejandra & Rojo, Roberto & Calmé, Sophie & Geissen, Violette. (2007). Soil preference and burrow structure of an endangered tarantula, Brachypelma vagans (Mygalomorphae: Theraphosidae). Journal of Natural History. 41. 1025-1033. 10.1080/00222930701384547.
  9. Myers, P. (2001). Arachnida, Animal Diversity Web, University of Michigan. 
  10.  McLeod, Lianne. “What Do Tarantulas Eat, Why Do They Molt, and Can You Hold Them?” The Spruce Pets, The Spruce Pets, 30 Sept. 2019, www.thesprucepets.com/pet-tarantulas-1237346.
  11. Peachey, Donna & Gordon, The Biocam Museum of Life Series.  Kelowna, B.C. Canada VIY 7N8 Box 417 PBC, 1999
  12. Gallon, R. C. 2019. The Natural History of Tarantula Spiders, British Tarantula Society
  13. Sabajo, C. R., le Maire, G., June, T., Meijide, A., Roupsard, O., and Knohl, A.: Expansion of oil palm and other cash crops causes an increase of the land surface temperature in the Jambi province in Indonesia, Biogeosciences, 14, 4619–4635, https://doi.org/10.5194/bg-14-4619-2017, 2017.
  14. “TEMPERATURE.” MYTHS: TEMPERATURE, people.ucalgary.ca/~schultz/Temperature.html.
  15. The Upper Devonian World 380–350 million years ago, 2019. The Map Archive, Unit 6 Springfield Commercial Centre, Bagley Lane, Pudsey West Yorkshire LS28 5LY
  16. Western Exterminator Company, 2019. Rentokil Initial plc. Riverbank Meadows Business Park, Blackwater Camberley, Surrey GU17 9AB
  17. Yáñez, Martha, and Graham Floater. “Spatial Distribution and Habitat Preference of the Endangered Tarantula, Brachypelma Klaasi (Araneae: Theraphosidae) in Mexico.” SpringerLink, Kluwer Academic Publishers


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