20th International Congress of Arachnology

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92 DENVER MUSEUM OF NATURE & SCIENCE REPORTS | No. 3, July 2, 2016
Cushing
spiders. Cryptic speciation and genomic divergence levels
were explored in an integrative framework, using existing
genomic resources and newly sequenced AE markers.
Keywords: next-generation sequencing, anchored
enrichment, species delimitation, population genomics
Oral presentation
Visual scanning by the principal eyes of
freely moving jumping spiders
Cole Gilbert1 , Madeleine Q. Perkins1, Daniel B. Zurek2
1Department of Entomology, Cornell University,
Ithaca, NY, USA; 2Department of Biological Sciences,
University of Pittsburg, Pittsburg, PA, USA
The lenses of arthropod eyes are fixed to the exoskeleton.
Thus, to change their direction of gaze to view objects
of interest with the high acuity region of the retina, the
animal must re-orient its eye stalk, head, or entire body.
The principal eyes (AM) of jumping spiders (Salticidae)
perform high acuity inspection and spectral analysis of
objects. Unlike the condition in spiders of almost all other
families, salticid AM retinas are attached to three pairs of
muscles that can move the retina horizontally, vertically,
and torsionally to change the gaze direction through the
fixed lens. We have filmed (60fps) and quantified these
retinal movements in the horizontal plane as transparent
spiders (Thiodina sp.) walked freely in a blank arena,
tracked a small (4.5o) horizontally moving (24o/s), high
contrast target with retinal and body movements, and
inspected a scaffolding to select an escape route from the
arena. Retinal scanning movements occur independently
or synchronously in the two eyes. Retinal movements may
occur while the spider walks, but occur more frequently
when stopped. The angular range of gaze movement is
greater in the ipsilateral direction than into the contra-
lateral visual field. Consequently, when a moving target
approaches in the spider’s peripheral visual field, the ipsi-
lateral retina begins tracking the target first. As it passes
into the contralateral field of view the other retina begins
to follow the target more closely. When this retina reaches
the end of its movement range, a body turn may occur.
Keywords: vision, predatory behavior, lab experiment
Poster presentation
Spatial cognition in jumping spiders:
Assessment of path length to prey and
vantage point
Cole Gilbert, Madeleine Q. Perkins
Department of Entomology, Cornell University,
Ithaca, NY, 14853, USA
Jumping spiders (Salticidae) of several species,
including Portia spp. (Spartaeinae) and Phidippus
spp. (Dendryphantinae), have been demonstrated to
be able to plan routes to prey that they cannot jump
directly on or walk straight toward. Salticid visual
acuity is very good and such situations must often
occur in nature as the spiders forage among shrub-
bery, recognize acceptable prey and then calculate a
route through the vegetation to reduce the separation
and bring the spider to a vantage point from which
it can jump on to its prey. In laboratory experiments
with spiders of several species in the genus Phidippus,
we examined two aspects of the potential spatial cog-
nitive planning that a jumping spider might employ
when approaching prey. We used a binary choice
protocol to test whether spiders prefer to take the
shorter versus longer path to prey when both lead to
prey. We tested a range of path disparities from 15%,
which was a linear difference of 3.4cm, to 75%, which
was a linear difference of 16.7cm. At smaller dispari-
ties spiders did not significantly choose the shorter or
longer path, but as disparities increased the probabil-
ity of a spider choosing the shorter path increased. In
a second experiment, we offered the spiders a choice of
two equidistant paths both leading to the prey, but one
terminated above the prey and the other terminated at
a similar separation below the prey. The majority of
spiders chose the elevated path that would allow them
to jump down on the prey.
Keywords: vision, predatory behavior, route planning,
lab experiment