20th International Congress of Arachnology

cracks (or pseudosegments) or, unusual for spiders, an

eversible fleshy arolium. Also, we focus on the evolution

of raptorial feet, present in both web-builder and active

hunters, which involves hyperflexion of the claws over

opposing macrosetae in several distant taxa. Finally, we

discuss the possible function of those configurations.

Keywords: morphology, anatomy, spider feet, homology,

evolution, phylogeny

Poster presentation

Comparison of zinc-based fixatives for

histochemical and histomorphometric

analysis of arachnid tissues

Damien Laudier, Karl Lewis

Laudier Histology, P.O. Box 78, New York, NY 10025, USA

dmlaud@gmail.com

Producing good histological preparations of arachnid

tissues is often quite problematic. Studies that require

high-fidelity morphological preservation for histomor-

phometric measurements, or spatial localization of

histochemical events, inconsistent or poor histologic

preparations can render samples useless for light micros-

copy analysis. The underlying causes of this variability

are not always clear-cut. However, choice of tissue fixative

is a significant factor in determining the quality outcome

of an arachnid histologic preparation. Zinc-based fixa-

tives have proven to provide exceptional morphological

preservation, retention of DNA/RNA integrity and anti-

genic properties of vertebrate tissue and some insect

tissues. However, the application of zinc-based fixatives

on arachnid tissues has been quite limited. This study

compares histological preparations of select tissue types

such as neuronal, ocular, digestive and reproductive

from several arachnid orders including: Araneae, Scor-

piones, Opiliones and Solifugae. Specimen samples were

fixed immediately post-sacrifice with various zinc-based

fixatives or with commonly used formaldehyde-based

fixatives (zinc-free). Following fixation, all tissue samples

were comparably processed, embedded and sectioned.

Staining was either tinctorial or with an antigenic

marker identifying a particular protein expression via

immunohistochemical technique. The results illustrate

that zinc-based fixatives are very effective in maintain-

ing high-quality tissue integrity for simple and complex

histological investigations of a variety of arachnid tissues.

Keywords: histology, histomorphometry, immunohisto-

chemistry, microscopy

Oral presentation

Ultrastructure in phylogeny of Araneomorpha

Pekka T. Lehtinen

Zoological Museum, 20014 University of Turku,

Turku, Finland

pekleh@utu.fi

SEM-analysis of leg cuticle of araneomorph spiders

revealed that the well known fingerprint and scaly

types represent two phylogenetic groups. It is possible to

confirm phylogenetic position of araneomorph taxa by

study of ultrastructure. Type of cuticular ultrastructure

is correlated to setal ultrastructure. Setae of groups

with fingerprint type cuticle are plumose or feathery,

while setae of groups with scaly cuticle are serrate or

simple. Fingerprint pattern is plesiomorphic in Ara-

neomorpha. Ultrastructure of basal trichobothrial plate

and tarsal organ are useful in study of phylogenetic

relationships. Fingerprint type cuticle is present in

Dysderomorpha

(including Hypochiloidea), Eresoi-

dea, RTA-clade with related Deinopoidea, Lycosoidea,

and Dionycha. Leg cuticle of Thomisidae is papular

or smooth with remnants of fingerprint type, but their

setal structure is plumose and sometimes modified

to resemble the branched type in Stiphropodidae and

Zodariidae. Scaly cuticle is present in all Araneoidea

s.lat., Archaeoidea and Palpimanoidea s.str. (but not all

Palpimanoidea sensu Platnick & Forster). Filistatidae

with different ultrastructure in all of its structures must

be excluded from Araneomorpha. Nicodamidae s. str.

and Homalonychidae with their “scaly” cuticle remain

with uncertain placing. Megadictynidae Lehtinen, 1967

is excluded from Nicodamidae. Fingerprint pattern

is best preserved in basal plates of large spines. Ara-

neomorpha has neither been evolved from any recent

group of Mygalomorpha nor from Liphistiomorpha,

but all four groups, including Filistatomorpha have

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DENVER MUSEUM OF NATURE & SCIENCE

REPORTS

No. 3, July 2, 2016

Cushing