Supplementary material (DOI: 10.1098/rspb. 2017.0363)
Adhesion enhancement of cribellate capture threads by epicuticular waxes of the insect prey sheds new light on spider web evolution Raya A. Bott1, Werner Baumgartner2, Peter Bräunig1, Florian Menzel3 and Anna-Christin Joel1*
1: RWTH Aachen University, Institute of Biology II, Worringerweg 3, Aachen, Germany 2: JKU Linz, Institute of Biomedical Mechatronics, Altenberger Straße 69, 4040, Austria 3: University of Mainz, Institute of Zoology, Johannes-von-Müller-Weg 6, Mainz, Germany
Corresponding author (*): Anna-Christin Joel RWTH Aachen University, Institute of Biology II Worringerweg 3, 52074 Aachen, Germany +49 241 8024838
[email protected]
1
Figure S1: Setup for removing the elytron (as prey surrogate) from a capture thread. Threads were picked up with two parallel metal wires (distance: 0.7 mm) and one elytron of C. maculatus was adhered at the margin of each thread. After allowing the propagation of the matrix to seize half of the thread’s length, an additional wire was included, separating the elytra from the rest of the thread (depicted here). Every second thread was cut between elytron and the additional wire to eliminate continuous contact (compare left and right panel). The other threads served as a control.
2
Figure S2: Adhering capture threads of different cribellate species on elytra of C. maculatus shows a “fusion” of nanofibres (*). Some regions still show single nanofibres (+). SEM images.
3
Figure S3: Characterization of a new adhesive mechanism. A) Transmission electron microscopic analysis showed the existence of single nanofibres in “fused” areas (*). However, nanofibres are embedded in a fluid matrix with low vapour pressure. B, C) The propagation of the fluid matrix in cribellate capture threads depends on the ambient temperature (B) and the concentration of the epicuticular waxes (C). Data are presented as mean ± SD with n = 3 (B: 80°C), n = 4 (C: 25% and 50%), n = 5 (C: 6.25% and 12.5%), n = 6 (B: 4°C and 22°C; C: 100%), n = 7 (B: 40°C) and n = 8 (B: 50°C).
4
Table S1: Overview of tested insects. Insects were brought into contact with the cribellate capture thread of U. plumipes. Using the SEM, we controlled whether “fusing” nanofibers could be observed at the contact point. *: only wing tested. Reaction Orthoptera:
Gryllidae:
Acheta domestica (house cricket)
Hemiptera:
Pentatomidae:
Eurydema oleraceum (rape bug)
Yes No
Peribalus strictus (vernal shield bug)
Coleoptera:
Pyrrhocoridae:
Pyrrhocoris apterus (firebug)
Yes
Cercopidae:
Cercopis vulnerata (black-and-red froghopper)
No
Chrysomelidae: Callosobruchus maculatus (cowpea weevil)
Yes
Donacia marginata (a leaf beetle) Elateridae:
Hemicrepidius niger (a click beetle)
Yes
Ampedus sanguineus (a click beetle) Carabidae:
Harpalus distinguendus (a ground beetle)
Yes
Cantharidae:
Cantharis fusca (a soldier beetle)
No
Coccinellidae:
Harmonia axyridis (Asian ladybeetle) Psyllobora vigintiduopunctata (22-spot ladybird)
Lepidoptera: Geometridae:
Yes
Xanthorhoe fluctuata* (garden carpet) No Colostygia pectinataria* (green carpet)
Diptera:
Sarcophagidae: Sarcophaga sp.* (flesh fly)
Yes
Calliphoridae:
Lucilia sp. (green bottle fly)
No
Drosophilidae:
Drosophila melanogaster (fruit fly)
Yes
Syrphidae:
Xanthogramma citrofasciatum (a hoverfly)
No Total: 11 of 19
5
Table S2: Hydrocarbon composition of cribellate capture threads from Uloborus plumipes before and after contact with Callosobruchus maculatus elytra, and C. maculatus cuticular hydrocarbons. Previous to any treatment, no hydrocarbons were present on the threads. However, after contact with C. maculatus elytra, the threads contained hydrocarbons similar to the cuticular hydrocarbon profile of C. maculatus. ‘+’: present, and accounting for at least 1% of the overall hydrocarbons. ‘t’: traces present with a relative abundance below 1% of the overall hydrocarbons. ‘–‘: not detectable. Substance
Retention index
Cribellate capture Cribellate thread after contact capture thread with C. maculatus
C. maculatus cuticular hydrocarbons
n-C25
25.00
–
t
t
3-MeC25
25.73
–
t
t
n-C26
26.00
–
t
t
4-MeC26
26.57
–
t
–
3-MeC26
26.72
–
t
–
n-C27
27.00
–
+
+
9-MeC27
27.37
–
+
t
7-MeC27
27.41
–
t
–
5-MeC27
27.51
–
+
t
9,13-;9,17-DiMeC27
27.65
–
t
t
3-MeC27
27.75
–
+
+
5,9-DiMeC27
27.82
–
t
t
n-C28
28.00
–
t
+
3,7-DiMeC27
28.10
–
+
t
9-;10-;11-MeC28
28.34
–
+
t
6-MeC28
28.45
–
t
–
4-MeC28
28.59
–
t
t
9,13-DiMeC28
28.63
–
t
t
7,11-DiMeC28
28.70
–
t
–
3-MeC28
28.75
–
t
t
n-C29
29.11
–
+
+
9-;11-;13-;15-MeC29
29.35
–
+
+
7-MeC29
29.43
–
t
t
5-MeC29
29.52
–
t
t
9,13-DiMeC29
29.64
–
+
+
7,11-DiMeC29
29.73
–
+
t
3-MeC29
29.78
–
+
+
5,9-;5,11-DiMeC29
29.83
–
t
t
7,11,15-TriMeC29
29.93
–
t
–
n-C30
30.00
–
–
t
3,7-;3,9-;3,11-;3,13-; 3,15-DiMeC27
30.07
–
+
t
3,7,11-TriMeC29; 12MeC30
30.33
–
+
t
6
8,12-;9,13-DiMeC30
30.60
–
+
t
3-MeC30
30.74
–
–
t
n-C31
31.00
–
t
+
11-;13-MeC31
31.30
–
+
t
9,13-DiMeC31
31.62
–
+
t
7,11-DiMeC31
31.69
–
t
t
3-MeC31
31.74
–
–
t
7,11,15-TriMeC31
31.92
–
t
–
n-C32
32.00
–
–
t
5,9,13-TriMeC31
32.05
–
t
–
unknown
32.31
–
t
–
unknown
32.58
–
t
–
n-C33
33.00
–
–
t
13-MeC33
33.30
–
t
t
11,15-DiMeC33
33.56
–
+
t
unknown
33.60
–
–
t
7
Movie S1: Fluid matrix consisting of cuticular waxes propagates from the prey (here: elytra of C. maculatus) through the cribellate capture thread (here: U. plumipes). Sped up 8 times.
Movie S2: Single puffs of the capture thread of U. plumipes peel off the elytra of C. maculatus. Sped up 2.4 times.
8
