20th International Congress of Arachnology

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DENVER MUSEUM OF NATURE & SCIENCE REPORTS | No. 3, July 2, 2016
Oral presentation
Why are they social?
Leticia Avilés
Department of Zoology and Biodiversity Research
Centre, University of British Columbia, Vancouver, BC
V6T 1Z4, Canada
All spider species that exhibit cooperative web build-
ing, prey capture, feeding, and brood care, build dense
tri-dimensional webs. We argue that it is the interaction
between such webs with particular environmental factors
that explains where species with different levels of social-
ity occur. Reviewing research carried out in the genus
Anelosimus, we show that large social colonies can only
form in areas where an abundance of large insects allows
the spiders to overcome a scaling challenge of their tri-
dimensional webs. The absence of subsocial or solitary
Anelosimus in the lowland rainforest, on the other hand,
may be due to the presence in this environment of strong
rains and high rates of predation, which we demonstrate
to be important for web quality and colony survival with
a transplant experiment. Thus, somewhat surprisingly, it
appears that the primary driver of sociality in spiders in
this genus may be colonizing environments where solitary
living may not be possible, with accessing large insects
being a necessary, but secondary benefit of group living.
Keywords: social spiders, groups living, prey capture,
scaling
Oral presentation
Transcriptomics identifies gene repertoires
underlying functional differentiation of
cob-weaving spider silk glands
Nadia A. Ayoub1, Thomas H. Clarke1,2, Jessica E. Garb3,
Robert Haney3, Cheryl Y. Hayashi 3
1Washington and Lee University, Department of Biology,
204 West Washington Street, Lexington, VA 24450, USA;
2University of California, Riverside, Department of
Biology, Riverside, CA, USA; 3University of Massachu-
setts, Lowell, Department of Biology, Lowell, MA, USA
Spiders (Araneae) owe their ecological success as keystone
predators in large part to their usage of silk. Orb-web and
cobweb weaving spiders possess seven morphologically
distinct gland types, each synthesizing a task-specific fiber
or glue. The spectacular properties of these proteinaceous
spider silks, including draglines with tensile strength
rivaling steel and capture spiral filaments that can extend
threefold, make them prime targets for the development of
biomimetic materials through recombinant technology.
Spider silk synthesis also is a model system to study the
evolution of tissue-specific gene expression and the role
of gene duplication in functional novelty. For instance,
the spidroin gene family encodes structural constituents
of fibers and diversification of spidroin family members is
associated with new fiber functions. Using deep sequenc-
ing of mRNA, we profiled transcript abundance in each of
the seven silk gland types, along with three non-silk gland
tissues, for three cobweb weaving species. We identified the
transcripts in each species that are significantly more abun-
dant in particular silk glands than non-silk gland tissues.
Gene expression patterns were consistent among all three
species, likely reflecting coordinated functions of subsets of
glands. Evolutionary analyses based on expression levels of
homologous transcripts and phylogenetic reconstruction of
individual gene families demonstrated broad conservation
of expression patterns and suggested that when changes in
expression pattern do occur, they do not have to be coupled
to gene duplication. Our study is a landmark in understand-
ing spider silk gland specialization, and more generally, the
evolution of tissue-specific transcriptomes.
Keywords: spider silk, genetics, molecular evolution,
tissue-specific expression
Student - Oral presentation
Complicate or simplify sex? The evolution
of genitalia in Gnaphosidae spiders
Guilherme H.F. Azevedo1,2, Charles E. Griswold3,
Adalberto J. Santos1
1Departamento de Zoologia, Instituto de Ciências Biológi-
cas, Universidade Federal de Minas Gerais. Av. Antônio
Carlos, 6627, 31270-901, Belo Horizonte, MG, Brasil;
2Pós-graduação em Zoologia, Universidade Federal de
20th International Congress of Arachnology