Substrate Preference of Native Elimia Snails
Snails fill several niches in a habitat (Turner,et. al. 2009). Snails impact their environment as consumers (Evans-White, et. al. 2005), prey items (Dalesman, et. al. 2010) and can be environmental pests as well (Karatayev, Alexander Y., et. al. 2009). By understanding the substrate preferences of native Elimia sp. snails, one can better understand the distribution of these snails within their habitat and aid in monitoring and controlling populations.
The objective of this study was to determine the preferred substrate of native Elimia sp. snails. Pseudo-habitats were created in 10 gallon aquaria and snails were allowed to move among two types of substrates within any one aquarium. Observations were periodically made over the course of two months in which individual snails and their locations were observed.
I randomly sampled a 1km section of the White river that passes through Morrow’s Meadows Park in Yorktown, IN. I sampled quadrats from the bridge on Riverside Rd. to the fork where Buck Creek joins the river. Water depth and number of individual snails were collected to evaluate the average snail per volume of water existing at this location. Individuals were also collected at this time.
Three aquaria were set-up in the Teaching and Research greenhouse, in a moderately lit area. Each aquarium was divided into two substrate types. Tank one was half gravel and half sand, tank two was half gravel and half was left bare and tank three was half sand and half left bare (Fig. 1-3). Fifteen wild-collected Elimia sp. snails were put into each aquarium containing a water depth of 15 cm. Each tank also contained an airstone which was placed in the divide line between substrates. Snail locations were observed and recorded over the course of two months. Thirty one observations were made during this time on varying days at a myriad of times in the day to avoid recording behavior that may happen at a particular time of day (e.g. if locations were light dependent).
The mean number of snails for gravel substrate was 8.922 individuals, the mean for sand was 5.234 and the mean number of snails in areas with no substrate was 3.238 with a standard deviation of 2.868 (Table 1). A chi-square test was performed and it was found that the snails frequent gravel substrate the most, followed by sand and a bare bottom respectively (p-value 0.00). Table 2 shows the number of individuals for each observation. This table also shows substrate preference over time. Although snails consistently frequent gravel, the frequency for gravel and sand increase as colder months approach (Table 2).
Conclusion and Discussion
The data shows that native Elimia sp. snails frequent gravel substrates more often than sand, and frequent sand substrate more that a bare bottom aquarium (no substrate). There could be several reasons for this behavior. Algae growth may be more abundant on gravel due to rougher surfaces and more surface area than sand or gravel. Snails may frequent gravel more because there is more food availability. Another reason the snails may display such behaviors is due to the approach or presence of cold weather and shorter days.
Although the temperature in the greenhouse is set at 70 degrees Fahrenheit (+/- 1 degree), the temperatures can range from 55 degrees to 105 degrees Fahrenheit before alarming staff. It would be valuable to conduct further observations over seasons while monitoring temperatures and amount of daylight to evaluate whether affinity for a certain substrate varies depending on temperatures or light availability. For instance snails may frequent gravel/sandy substrates more during cold months/shorter days in preparation for the winter or snails may frequent areas with no substrate more during warm temperatures/longer days. Although the general frequencies would be expected to be similar, this type of research would give further insight as to why snails frequent one substrate more than others.
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