20th International Congress of Arachnology

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60 DENVER MUSEUM OF NATURE & SCIENCE REPORTS | No. 3, July 2, 2016
Cushing
2Colección Nacional de Arácnidos (CNAN), Módulo
D, planta baja, Departamento de Zoología, Instituto
de Biología, Universidad Nacional Autónoma de
México, Ciudad Universitaria, 3er circuito interior,
Apto. Postal 70-153, CP 04510, Coyoacán, Ciudad de
México, México
Since its description in 1996, the genus Crassicrus
Reichling & West, 1996 had not been included in any
phylogenetic analysis and the relationships between
this genus and other Theraphosinae genera remain
unclear. According to a previous taxonomic revision, it
is possible that Crassicrus is phylogenetically related
to some South American genera that share some char-
acters of the morphology of the male palpal bulb of
the male, so we considered very important to perform
a systematic revision of the genus to confirm this.
With the revision of material deposited in Colección
Nacional de Arácnidos of Instituto de Biología, UNAM,
Mexico, and the American Museum of Natural History,
New York, USA, a morphological data matrix was built
consisting of 16 taxa (five of the ingroup and 11 of out-
group) and 85 characters, which 71 were binary and 14
multistate. The phylogenetic analysis was made using
the parsimony criterion and the outgroup principle to
probe the monophyly of the genus adding new species.
The analysis was conducted with equal weights and it
was performed through the method of exact searches
with implicit enumeration in the computational
program TNT. In the analysis one most parsimoni-
ous tree (L= 176, Ci= 0.55, Ri= 0.69) was obtained.
The genus Crassicrus proved to be paraphyletic, so
it was confined to include six species, the type species
C. lamanai Reichling & West, 1996, four species
previously described and also Aphonopelma stoicum
(Chamberlin, 1925). The monophyly of the genus
Crassicrus resulted supported by six synapomorphies
and high values of Jackknife (98) and Bremer (6). A
new diagnosis of C. stoicum n. comb. was elaborated.
Keywords: systematics, morphology, taxonomy, Araneae,
Mygalomorphae, Theraphosidae
Poster presentation
The physiological basis for delayed
development in social huntsman spiders:
Impacts on sociality
Marissa G. Cardillo, Linda S. Rayor
Department of Entomology, Cornell University,
Ithaca, NY 14853, USA
Are there physiological traits that facilitate social-
ity in spiders? Perhaps! Prolonged sociality with has
been found in three sparassid species within the
monophyletic clade Deleninae, Delena cancerides, D.
lapidicola, and D. melanochelis. These group-living
huntsman spiders develop differently from all other
known solitary delenine spiders–and, to our knowledge,
spiders in all other families. Like other spiders, hunts-
man spiders remain in the egg sac during their 1st
instar. After emergence followed by molting, 2nd instar
spiderlings of 26+ solitary huntsman species actively
forage. In contrast, 2nd instar spiderlings of all three
social huntsman are non-feeding and retain 1 st instar
characteristics: abundant abdominal yolk, shorter
legs, and fewer sensory hairs. Only in the 3rd instar do
the social species morphologically resemble huntsman
spiders and begin to eat. To determine the physiological
basis of these ontogenetic differences, we compared dif-
ferences in maternal investment (egg size, clutch size,
and chemical composition of yolk), standard metabolic
rates, and development time of the three social species
and five solitary species within deleninae. Our results
show that social species have larger eggs with more
yolk, spend a longer period of time as non-feeders in
1st and 2nd instars, and maintain low metabolic rates
during their non-feeding instars, all of which enable the
social spiderlings to remain non-feeding. We discuss the
implications of (1) how the timing of molting may be
precipitated by the depletion of energy and (2) devel-
opmental heterochrony on the evolution of sociality in
spiders.
Keywords: sociality, metabolism, development,
physiology