Browsing by Subject "Orconectes virilis"

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    The Effect of Size Asymmetry on the Expression of Territoriality in Northern Crayfish (Orconectes virilis)
    (2011-02-01) Kindler, Mae; McCullough, Jenna
    Territoriality in female northern crayfish, Orconectes virilis, was studied through the observation of resident-intruder crayfish pair interactions based on size asymmetry. Resident-intruder pairings were chosen among 18 crayfish, with a total of 51 asymmetric interactions observed. Resident crayfish were allowed to establish themselves immediately within shelters, followed by the placement of intruder crayfish within the territory of the resident. One of three possible interactions was noted for each resident-intruder pair and shelter, including resident eviction, resident-intruder union, or resistance of intruder. It was found that resident-intruder pairs having high percent size asymmetry resulted in high eviction rates of small residents by large intruders.
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    Orconectes virilis Body Size and Shelter Preference
    (2012-04-11) Hawkinson, Anna
    Environment preference in terms of light and dark was tested on Crayfish (Orconectes virilis) from Itasca Lake in north central Minnesota. Twelve crayfish were caught from the lake and noted to be either “large” or “small”. Crayfish were individually put into one of two identical enclosures for 5 min. Every 30 sec the location of the crayfish was noted. The enclosures were divided up into four quadrants varying in covered or open and black or white sides/bottoms. Data was analyzed with graphs and chi square tests. Overall, crayfish spent a significant amount of time in the darkest covered quadrant. A significant difference was also found between the frequency of time spent in each quadrant between small and large crayfish; small crayfish remained in the darkest covered quadrant more than large crayfish.
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    Territoriality of Northern Crayfish (Orconectes virilis) in Itasca State Park
    (2011-02-01) McCullough, Jenna; Kindler, Mae
    In general, it has been shown that large crayfish will tend to win aggressive, territorial conflicts against small conspecific opponents (Figler et al. 1999). Size is not the only factor that can affect the outcomes of territorial interactions however. The “prior residency effect” suggests that the initial resident in a given area will have a dominance advantage over intruders (Peeke et al. 1995). This investigation explores the effects of territorial residency and size on the outcomes of territorial conflicts. We hypothesized that interactions between crayfish with large percent size asymmetries would result in higher eviction rates of the smaller resident by the larger intruder than interactions between crayfish with small size asymmetries. We tested this hypothesis by observing the outcomes of territorial conflicts between crayfish of various sizes in controlled environments. We found that average percent size asymmetries of interactions resulting in evictions of residents were statistically greater than the average percent size asymmetries of interactions resulting in non-evictions of residents by larger intruders. We determined that the level of percent size asymmetry with the highest likelihood of eviction ranged from 67 to 109%. These data support the proposed trend where the likelihood of successful evictions of smaller prior residents by larger intruders increases as the size differences between the two individuals increases.