20th International Congress of Arachnology

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DENVER MUSEUM OF NATURE & SCIENCE REPORTS | No. 3, July 2, 2016
Student - poster presentation
Scorpion’s sexual behavior: a remarkable
performance of Megacormus gerstchiDiaz
Najera 1966 (Scorpiones: Euscorpiidae:
Megacormiinae)
*Laura Olguín-Pérez, Oscar Francke
Colección Nacional de Arácnidos (CNAN), Departa-
mento de Zoología, Instituto de Biología, Universidad
Nacional Autónoma de México 3er. Circuito Exterior,
Cd. Universitaria. Apartado Postal 70-153, C.P.
04510. México, D.F.
Sexual selection, as a two sex coevolution process, has
an important role in ornament and complex mating
displays, as well as in female preference for certain
phenotypes. All these processes result in individual
differential reproductive success when competing for
a mate. Historically, female choice has been neglected.
Nevertheless, its relevance related to sexual selection
force and direction, as well as the impact over male
sexual traits, is under study using several animal
systems. Some researchers have reported a particular
male scorpion behavior, known as “sexual sting”,
because it occurs during mating process. An educated
guess is that this behavior results in the releasing of
venom components, gaining some kind of sedative
effect over female and reducing the chances of being
hurt by her. We have successfully recorded eleven
mating events with captive Megacormus couples. If
female is receptive, pedipalpal grasp is allowed imme-
diately. Sexual sting is performed during promenade a
deux, with a clearly “submissive female” behavior over
a period of 50 minutes in the longest sting. Consider-
ing that venom is a costly metabolic investment, it is
of our interest to establish the costs and benefits poten-
tially involved in this behavior for both sexes in terms
of sexual conflict resolution, as well as the adaptive
value(s) of this behavior.
Keywords: scorpions, sexual behavior, sexual sting
Oral presentation
Humidity affects insect retention by spider
orb webs
Brent D. Opell, Katrina E. Buccella, Meaghan K. Godwin,
Malik X. Rivas, Mary L. Hendricks
Department of Biological Sciences, Virginia Tech,
Blacksburg, VA 24061, USA
The viscous prey capture threads of araneoid orb
spiders are smart biomaterials whose properties change
in response to their environment. As these threads are
hygroscopic, relative humidity (RH) has a significant
impact on the performance of the glycoprotein glue
core within each of a thread’s droplets. In this study
we test the hypothesis that humidity-mediated changes
in Araneus marmoreus capture threads affect the
time that actively struggling prey are retained. As
RH increased from 37% to 55% to 72%, so too did the
volume, contact area, and extensibility of a thread’s
glycoprotein cores, indicating that threads are better
equipped to retain prey at 72% RH. To assess this, we
collected capture threads from webs constructed by
14 A. marmoreus females. Thread strands from each
web were placed at equal spacing on the parallel sup-
ports of insect retention assay samplers. Samplers
were placed in 37%, 55%, and 72% RH chambers and
an anesthetized housefly was placed on three thread
strands. Each fly’s struggle and escape was captured
in a video and bouts of active escape behavior were
summed. Houseflies were retained 12 seconds longer
at 72% RH than at 37% or 55% RH. This difference is
ecologically significant because the short time after a
prey strikes a web and before a spider begins wrapping
is an insect’s best opportunity to escape from the web.
The impact of environmental humidity on an orb web’s
ability to retain prey impacts spider fitness and may
be the driving force behind inter-specific differences
in viscous thread hygroscopicity and humidity related
performance.
Keywords: biomaterial, capture thread, adhesion, prey
capture
20th International Congress of Arachnology