Studying Posterior Eye

Function in Rabida Rabidosa

Courtney Dunn, Debbie Huynh, Kerry Harrington, Nancy Huynh

Introduction

Question: Do wolf spiders use their posterior eyes to catch their prey at night?

H0: There will be no difference in prey catching ability between normal, partially, and completely blind spiders.H1: If the posterior eyes are used for night vision, then the spiders should have significantly reduced ability to capture prey in the dark with posterior eyes painted.

There has been extensive work done on jumping spiders and the functions of the different sets of eyes, and how they are used to hunt in varying light conditions.

In jumping spiders, the posterior eyes are used for prey detection in low-light conditions and the anterior eyes are used in brighter conditions (Blest, et al)

Significance

Experimental methods

1. Collect spiders

2. Fast for at least 1 day

Methods

3. Cool spiders thoroughly.

4. Paint eyes:a. posterior eyes only

b. all eyesc. back

5. Acclimations:

a. Allow spider to warm up for 15 min.

b. Allow cricket to acclimate in container for 15 min.

Methods

6. Add spiders to cricket container7. Allow 15 min. for trial in total darkness8. Repeat for all treatments.

Result Expected value= (Row total x column total) / grand totalX2= [(19-7.67) 2 /7.67] + [(1-7.67) 2 /7.67] + [(3-7.67) 2 /7.67]X2= 25.38α= 5.99 [for d.f=2]

Yes No Row totals

Normal vision 19 1 20

Expected 7.67 12.33

Partially Blind 1 19 20

Expected 7.67 12.33

Totally Blind 3 17 20

Expected 7.67 12.33

Column total 23 37 60 Grand total

DiscussionThe blinding of the posterior eyes has significant effect on wolf spiders' ability to capture prey.

The fact that partially blinded spiders captured fewer crickets than totally blinded spiders was surprising, but I think it was a chance occurrence that could be ruled out by performing more trials.

However, the function of the posterior eyes could be further tested by blinding the anterior eyes and testing for prey- capture ability in darkness.

Conclusion

Accept H1 - blinded eyes reduced their ability to catch prey in the dark