20th International Congress of Arachnology

DENVER MUSEUM OF NATURE & SCIENCE

REPORTS

No. 3, July 2, 2016

Cushing

scrape their pedipalps across the female’s genitalia and

inflate hematodochae without embolus insertion at

certain periods during mating. These types of behaviors

have been previously classified as “flubs”. Here we describe

a functional purpose of these behaviors: removing sticky

masses of rival sperm that have been partially or entirely

drilled out of the female but remain stuck to her ventral

surface or to the conductor itself. In summary,

T. elongata

males bias paternity in their favor by removing internal

amorphous mating plugs composed of rival male sperm.

Keywords: Sexual selection, sperm competition

Oral presentation

An Aristotelian view on trapdoor spiders

Arthur Decae

M. Smallegangehof 25, 4331WC Middelburg, The

Netherlands.

halldec@planet.nl

Within the order Araneae, Mygolomorphae are gener-

ally considered a ‘lesser’ branch of the (spider) tree of

life. In comparison with their putative sister clade the

Araneomorphae, Mygalomorphae are less diverse, less

common, less derived, less complex, less visible and cer-

tainly less well-known. Recent work however shows that

Mygalomorphae are much more common and diverse

than previously perceived. Most of the new knowledge on

mygalomorph spiders is morphologically or molecularly

based and obtained from the studies of collected and pre-

served specimens. Knowledge of the living mygalomorph

spiders is very limited. This is particularly true for the

numerous fossorial mygalomorphs that may loosely be

indicated as trapdoor spiders. Trapdoor spiders appear to

show a remarkable evolutionary conservatism expressed

in their habits and general anatomy. Molecular work has

shown that trapdoor spiders not only appear to be ancient,

but actually are ancient in the sense that species ages have

been estimated to exceed 30 million years. Such times for

species survival indicate that trapdoor spiders make perfect

models for studies of morphological stasis that will con-

tribute to the ongoing debate concerning tempo and mode

in evolution. The long term survival of species furthermore

suggests a high level of adaptation that questions the

supposedly ‘lesser’ degree of morphological and behavioral

specialization in trapdoor spiders. To appreciate the func-

tional specializations in trapdoor spider morphology and

behavior (and to correct some common misconceptions)

the Aristotelian question ‘what for?’ is asked to provide the

necessary background knowledge for hypothesis building

and further research. This Aristotelian question will be

discussed with respect to the functional morphology of the

chelicerae and pedicel in burrow construction and of the

appendages in prey handling and locomotion.

Keywords: functional morphology, evolutionary stasis

Student - poster presentation

Leg autotomy in the fishing spider

Dolomedes

triton

and its effect on antipredator and

locomotor behavior

Alexander E. DeMarco

, Carl N. Keiser

, Thomas C.

Jones

, Jonathan N. Pruitt

1,3

Department of Biological Sciences, East Tennessee

State University, PO Box 70300 Johnson City, TN

37614, USA;

University of Pittsburgh, Department

of Biological Sciences, 204 Clapp Hall, 4249 Fifth

Avenue, Pittsburgh, PA 15260, USA;

Department of

Ecology, Evolution, and Marine Biology, University of

California, Santa Barbara, CA 93106

demarcoa@goldmail.etsu.edu

Phenotypic plasticity, the ability of an organism to alter

its phenotype in the face of different stressors, is a phe-

nomenon that is widespread throughout nature. Plasticity

in behavioral syndromes (animal personalities), a topic

that is steadily increasing in interest within animal

behavior, falls under this umbrella and can have sig-

nificant implications for an organism in terms of overall

fitness. The six-spotted fishing spider,

Dolomedes triton

(Araneae, Pisauridae) is an intriguing model for study-

ing antipredator behavior (boldness) across different

contexts, due to predation pressures from both terrestrial

and aquatic sources. Like most spiders,

D. triton

is able

to autotomize a limb in order to escape from a preda-

tor or remove itself from another situation that could

cause significant harm or death. This project aims to

test the hypotheses that when an individual

D. triton