Are Claw and Antenna lengths characteristics of Sexual Selection in Orconectues rusticus?
The Orconectes rusticus, otherwise known as the Rusty Crayfish, originated from a native range in the Ohio River and other tributaries, centuries ago. It’s introduction to other habitats is largely attributable to it’s use as fishing bait, moving the species from New Mexico to Maine in the United States and as far north as the Province of Ontario and Manitoba. Rusty crayfish in Ontario were first noted in 1963 in the Lake of the Woods, and have since then have been found in Kawartha Lakes Region, Lake Superior watershed, expanding down the Winnipeg River, into Manitoba. As a study of ...view middle of the document...
This therefore led us to the hypothesis that male and female Orconectes rusticus will differ in the secondary characteristics of claw lengths and antenna lengths. Therefore it was predicted that if sexual or natural selection is occurring, male and females would differ in secondary sexual characteristics.
In order to test our hypothesis we had to physically sample and measure the chosen characteristics of a random group of Rusty Crayfish. A total of 15 Crayfish were collected from the Otonabee River, 7 of which were female, 8 of which were male. As a lab group it was decided that the 2 features being examined and measured would be the claw length and the antenna length. Along with these two measurements the body length was also measured. Each of the crayfish varied in size and age. The lab group was split into groups and each of us had approximately 2-3 crayfish to measure. The crayfish were placed in a bucket after being in a tank. This allowed us to view any differences that were present and to see how the crayfish behaved with others. We used a ruler and measured the body lengths, each of the claws and each of the antennas. Generally, the crayfish were left in the bucket while we were measuring because if lifted the species would move too much to get an accurate measurement. Claws were measured from the tip of the claw to the bottom, widest part. The body length was measured from approximately where the species eyes are, to the end of its tail. Antenna length was measured from the top of the antenna to where it appears to be derived from its head.
Measurements of body lengths, claw lengths and antenna length of the 2 the different sexes of the Orconectes rusticus sampled are presented in Table 1. (See Appendix) As we observed the crayfish there were no interesting behavioral events that occurred. The crayfish were quite calm as we took the measurements, unless they were picked up. Body lengths typically ranged from a low, 4 cm to a high of 9.5 cm. Claw length typically ranged from 1.3 cm to 5.1 cm. Antenna length ranged from 3 cm to approximately 7.1 cm. Claw length compared to body lengths within the male and female group is presented in Graph 1. Antenna length compared to body lengths within the group of Rusty Crayfish is presented in Graph 2.
Graph 1. Claw Length compared to body length in male and female Orconectes rusticus.
Graph 2. Antenna Length compared to body length in male and females Orconectes rusticus.
It was found that male and female Orconectes rusticus differed in many different characteristics. Male Rusty Crayfish had a higher average of claw length in comparison to female. The male species had an average of 3.575 cm length and the females had an average of...