20th International Congress of Arachnology

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DENVER MUSEUM OF NATURE & SCIENCE REPORTS | No. 3, July 2, 2016
spider Larinioides cornutus. L.cornutus individuals
were collected from sites in northeast TN. After a 7-day
entrainment period, spider cephalothoraxes were dis-
sected and haemolymph was collected at 4 different time
points over a 24-hour cycle. We measured gene transcrip-
tion levels and neurohormone levels in haemolymph and
cephalothoraxes using RNA-sequencing and HPLC-ED,
respectively. Levels of catecholamine neurohormones did
change over the 24-hour period however, the patterns
found were not uniform. Like brain-reward pathways
in many other taxa, dopamine levels did rise during
foraging periods (nighttime) of L. cornutus. In addition,
patterns in gene expression further supported the fluctu-
ating patterns of catecholamines.
Keywords: circadian rhythms, neurochemistry,
transcriptomics
Oral presentation
Three dimensional analysis of the arachnid
locomotory system - topics and problems
Christian S.Wirkner, Jens Runge
Universität Rostock, Allgemeine und Spezielle Zoologie,
Institut für Biowissenschaften, Universitätsplatz 2,
18055 Rostock, Germany
The arachnid locomotory apparatus has formed the
focus of zoological research for many decades. However,
the 3D revolution opens up fascinating new possibilities
for visualizing highly complex animal features and
therefore makes a re-investigation of the locomotory
system and all its substructures necessary. Here we
present the concepts behind a recently started project
in which the cuticular, muscular and nervous elements
of all four pairs of walking legs will be described three
dimensionally for representatives of all major arachnid
lineages. In addition, the complete prosomata, i.e., the
extrinsic locomotory musculature and all other skeletal
musculature will be studied in order to account for the
structural basis of leg movement and the generation
of the hydraulic pressure responsible for leg extension
in a number of arachnid taxa. As well as presenting
major components of the locomotory system, we discuss
theoretical problems which occurred during the initial
investigations.
Poster presentation
Role of elongated chelicerae in male-male
contest and female mate-choice in the spider
genus Myrmarachne(Araneae: Salticidae)
B. H. Wong, Mindy J. M. Tuan, Daiqin Li
Department of Biological Sciences, National University
of Singapore, 14 Science Drive 4, 117543, Singapore
Exaggerated male structures, which are sexually dimor-
phic, have evolved in many animals, and often serve a role
in sexual selection, that is, either male-male competition
or female mate-choice or both. Such exaggerated struc-
tures also exist in ant-mimicking jumping spiders from the
genus Myrmarachne in the form of elongated chelicerae.
This study focused on the species Myrmarachne maxil-
losa as the model for investigating the role of elongated
chelicerae in sexual selection, effect of which is suggested
by the variance of chelicera size within males and between
the sexes of the species. Males are randomly pitted against
each other to examine the effect of chelicera length in
male-male competition; males and females are randomly
paired in simultaneous-choice trials to examine the effect
of chelicera length in female mate-choice. Our results
showed that males with longer chelicerae won the major-
ity of the fights, and females preferred males with longer
chelicerae that courted longer. We concluded that chelicera
length can be used as a reference for success in male-male
competition as well as preference in female mate-choice.
Keywords: ant-like jumping spider, Myrmarachne,
male-male contest, female mate-choice, ornament,
armament, sexual behavior
Oral presentation
Repeated evolution of power-amplified
predatory strikes in trap-jaw spiders
(Araneae, Mecysmaucheniidae)
Hannah M. Wood1, Dilworth Y. Parkinson2 , Charles E.
Griswold3 , Rosemary G. Gillespie4, Damian O. Elias4
1Department of Entomology, National Museum of
20th International Congress of Arachnology