-A subclass of pheromones is necromones, which contain oleic acid as a primary component. -Some pheromones trigger aggregation between organisms, others can trigger separation. -Necromones trigger necrophoric (organisms remove their dead) or necrophobic (organisms avoid their dead) behavior. -Arthropods use pheromones, this includes sowbugs and cockroaches. Chemical signals are picked up by antennae. II. Hypothesis:
When given a choice between two identical shelters, sowbugs will display necrophobic behavior by aggregating in the shelter that does not contain oleic acid. III. Biological Rationale:
-C.D. Rollo study showed that cockroaches display necrophobic behavior around oleic acid (dead conspecifics). -Semi-social behavior and necrophobic activity are linked, while social behavior and necrophoric activity are linked. -Cockroaches and Sowbugs are both arthropods, and they both display semi-social behavior. -Evidence shows necromones being old method of risk avoidance (420 Ma). All arthropods shared common ancestor at some point.
I - Introduction:
Some arthropods use a class of chemicals called pheromones for intraspecific communication (2.1). A subclass of these pheromones is called necromones (2.3), which signal the death or injury of conspecifics (2.4). Studies have shown that the primary component of some necromones is oleic acid, a type of unsaturated fatty acid (2.4). Organisms can react in two different ways to these chemical signals: Social species, which need to live in colonies in order to survive, undergo necophoric behavior, where organisms actively remove their dead from the nest or colony. Semi-social species, which can operate both individually and in a group, undergo necrophobic behavior, where the organisms actively avoid their dead, injured, or anything excreting oleic acid (2.4). These avoidance and removal responses are adaptive in the sense that when the organism senses the acid, it signals that there may be danger; disease or a predator, which should be avoided. By avoiding areas containing oleic acid, or removing the dangerous individual, the organisms are effectively avoiding a potentially hazardous situation. One species, cockroaches, exhibit necrophobic behavior, and are also semi-social (2.4). The experimentally tested species, sowbugs, are also semi-social organisms, and use pheromones for intraspecific communication (1.3). This raises the question “do sowbugs exhibit necrophobic behavior?” Therefore, we hypothesized that when given a choice between two identical shelters, sowbugs will display necrophobic behavior by aggregating in the shelter that does not contain oleic acid. A null hypothesis would state that when given a choice between two identical shelters, sowbugs will not exhibit a preference between aggregating in a shelter that contains oleic acid and one that does not.
We think this hypothesis is rational due to several factors. An experiment by C.D. Rollo investigating cockroaches showed that 100% of cockroaches displayed necrophobic behavior when exposed to dead conspecifics (2.4). Evidence also shows that semi-social behavior and necrophobia are linked, as displayed by the cockroaches. Sowbugs, as mentioned earlier, are also semi-social because of individual feeding and group aggregation. It would then be expected that they would also exhibit necrophobic behavior. Evidence also shows that necromones are a very old risk avoidance mechanism (2.4), if sowbugs display necrophobic behavior, it would show that necrophobia as an adaptive trait developed before crustacea diverged into its own subphylum.
-Dependent Variables: How many sowbugs are found in each shelter after 20 minutes. -Independent Variables: One shelter contains oleic acid and one does not. B.
All the constant variables concern the shelters, surrounding environment, and sowbugs. These should not interfere with the independent and...