20th International Congress of Arachnology

DENVER MUSEUM OF NATURE & SCIENCE

REPORTS

No. 3, July 2, 2016

International Congress of Arachnology

to soil contaminated with heavy metals would affect the

survival and foraging behavior of the wolf spider

Pardosa

milvina.

Our experiment decoupled environmental

exposure and dietary uptake. In a full factorial design we

housed animals on contaminated or uncontaminated soil

and fed them collembolans that had been reared on each

soil type. Exposure to contaminated soils reduced survival

especially for males. Both soil type and prey type affected

prey consumption, but effects varied over time and between

sexes. This study indicates a complex interaction between

environmental and dietary contamination on behavioral

responses for the wolf spider

P. milvina

and underscores

the need for more studies of the manner in which anthro-

pogenic factors influence natural food webs.

Keywords: behavioral ecology, heavy metals, toxicity,

Collembola

Student - oral presentation

Kinematic consequences in locomotor per-

formance after autotomy in

Prionostemma

harvestmen

*Ignacio Escalante, Marc A. Badger, Damian O. Elias

University of California, Berkeley, 130 Mulford Hall.

Berkeley, CA 94720 USA

iescalante@berkeley.edu

Animals face predictable challenges throughout their life-

times. For instance, predation attempts are ubiquitous, and

likely drive the evolution of adaptations to avoid predators.

Some animals voluntarily release legs (autotomy) during

predation attempts. While autotomy may secure immedi-

ate survival, animals can face long term consequences of

limb loss, particularly in locomotor performance. Given

this, strategies to compensate for damage are expected, for

example making biomechanical adjustments in a running

gait. We studied this in harvestmen (Opiliones) because

autotomy is frequent and regeneration does not occur.

We examined an undescribed species of

Prionostemma

(Sclerosomatidae) in the Costa Rican rainforest to test

the hypothesis that compensation after losing legs occurs

with changes in biomechanical kinematics of running

over time. By controlling the time since autotomy and the

number, type and asymmetry of legs lost, we quantified

changes in locomotor performance while running on a

horizontal track over time using high speed video. We

found an immediate decrease in the kinematics of running

(velocity, acceleration, sinuosity of the trajectory, and

stride length), as well as an increase in duty factor after

autotomy. However, harvestmen did not recover initial

performance after a 14-day period. Interestingly, one third

of autotomized individuals performed different types of

gaits (“pronking”, “bobbing”, or running), which seldom

occurred in intact individuals. Our findings suggest that,

along with kinematic, autotomy might impose prevail-

ing challenges in the energetic balance and survival of

harvestmen. Compensation seems not to be occurring at

least in their general pattern of locomotion. Overall, this

project outlines the potentially non-reversible locomotor

consequences in harvestmen imposed by environmental

damage. Future work could focus on behavioral plasticity

or shifts in habitat use that harvestmen might use to alle-

viate the exposure to predators.

Keywords: autotomy, biomechanics, daddy long-legs

harvestmen, running

Student - Poster presentation

Sensory shifts following autotomy in the

golden orb-weaver spiders (

Nephila clavipes

)

Ignacio Escalante

, Virginia Settepani

, David R. Nelsen

Department of Environmental Sciences, Policy, and

Management. University of California - Berkeley, 130

Mulford Hall. Berkeley, CA 94720, USA;

Department

of Biological Sciences, Aarhus University Ny Mukeg-

ade 114-116 Building 1535, Office 216. 8000 Aarhus

C, Denmark;

PO Box 370, Department of Biology

and Allied health, Southern Adventist University, Col-

legedale TN 37315 USA

dnelsen@southern.edu

Arachnids possess many of their sensory organs on their

appendages. However, the voluntary release of an append-

age (“autotomy”) is a frequently used anti-predator

strategy. Consequently, loss of an appendage could result

in reduced locomotion, sensory abilities, especially

relevant for prey (or predator) detection, location, and

capture ability. Any reduction in prey capture or predator