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DENVER MUSEUM OF NATURE & SCIENCE
REPORTS
|
No. 3, July 2, 2016
Student - oral presentation
Net-casting neuroanatomy: Sensory struc-
ture modifications match central nervous
system investment in the net-casting spider,
Deinopis
spinosa
*Jay A. Stafstrom
1
, Eileen A. Hebets
1
, Peter Michalik
2
1
School of Biological Sciences, University of Nebraska
- Lincoln, USA;
2
Institute of Zoology and Museum,
University of Greifswald, Germany
jstaf@huskers.unl.eduIn attempt to better understand the link between
brain and behavior, it’s common practice to compare
differences in brain size across animals differing in
behavior. Here, we investigate the relative investment
of visual processing centers and sensory integra-
tion centers in a species of spider that undergoes a
dramatic behavioral and morphological shift upon
maturity.
Deinopis spinosa
are nocturnal, net-casting
spiders that possess massive secondary eyes used in
their unique form of active foraging. Once mature,
males cease foraging and their eye size decreases,
inferring a decrease of reliance on vision, a sense
extremely important within the juvenile stages of life.
We tested the hypothesis that external sensory struc-
ture investment (i.e., eye diameter) predicts internal
sensory processing investment (i.e., visual processing
centers). Using micro-computed X-ray technology, we
calculated the volume of various processing centers
in penultimate and mature male and female spiders,
inferring investment from relative volume of focal
brain regions. As expected, mature males invested
relatively less than penultimate males in visual only-
processing centers (ON1 and ON2), while females
do not show this trend. We also find a significant
relative increase in arcuate body volume in mature
males, another trend not seen in female
D. spinosa
.
This brain region, previously described as a sensory
integration center, may be responsible for processing
information related to mate searching in mature male
spiders, likely chemical in nature.
Keywords: neuroethology, neuroanatomy, visual process-
ing, nocturnal predator, net-casting spider, Deinopidae
Student - poster presentation
Nocturnal no more: Body condition pre-
dicts diurnal foraging in the net-casting
spider,
Deinopis subrufa
Jay Stafstrom
1
, Mariella Herberstein
2
, Eileen Hebets
1
1
School of Biological Sciences, University of Nebraska,
Lincoln, USA;
2
Department of Biological Sciences,
Macquarie University, Australia
jstaf@huskers.unl.eduThe time of day at which an animal is most active
directly affects many aspects of its ecology and behav-
ior. For example, nocturnal animals must forage under
dim light conditions. Many nocturnal animals seem to
have overcome this constraint by increasing the sen-
sitivity of their eyes, commonly by increasing eye size.
With the largest eyes of any spider, net-casting spiders
from the genus
Deinopis
are well-suited for visually-
guided, nocturnal behavior. Past
Deinopis
research
has illustrated the importance of vision in nocturnal
foraging, the day-time inactivity/diurnal cryptic
behavior of multiple
Deinopis
species, and an intense
retinal shedding every morning and re-synthesis every
night. Taken together, these studies have led many
to believe
Deinopis
spiders to be strictly nocturnal,
while also being functionally blind during the day-
light hours. Recent field and laboratory observations
dispute the long held belief of
Deinopis
being strictly
nocturnal. Here, we first document diurnal foraging
behavior of
Deinopis subrufa
and empirically test
the effects of light environment and body condition
on the likelihood to forage during the day. We show
that between 10–20% of
D. subrufa
remain foraging
during daylight hours in their natural habitat. We also
show that diurnal foraging activity is not dependent on
light levels experienced in laboratory condition, but is
predicted, in part, by body condition. Our study high-
lights the importance of careful field observations and
empirical testing when labeling an animal’s potential
activity pattern.
Keywords: activity patterns, nocturnal, diurnal, net-
casting spiders
20
th
International Congress of Arachnology