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Setae morphology and the phylogeny of ground spiders (Araneae, Gnaphosidae)
1. Setae morphology and the
phylogeny of ground spiders
(Araneae, Gnaphosidae)
By Amanda Tsang
LaGuardia Community College
March 10, 2014
2. Introduction
Gnaphosids (commonly known as ground spiders) are
one of the biggest families of spiders. The group
includes 122 genera and 2,162 species (Platnik, 2013).
This study aims to provide an updated description of
the morphology of ground spider setae, integumentary
accessory organs located on the cuticle. Previous
studies have demonstrated that these structures differ
among gnaphosids and may give researchers cues for
the ground spiders classification on the generic and
subfamily level (Ovtsharenko, 1983, 1985, 1989;
Murphy, 2007).
3. Research Goals
To demonstrate morphological differences of setae in
each genera.
To provide necessary key characteristics for more
precise genera description and subfamilies delineation.
To gather data for a future cladistic analysis that will
allow us to draw a phylogenic tree of the gnaphosid
group for the first time.
4. Methods
Descriptions are based on
specimens preserved in
75% ethanol. To prepare
the specimens for
examination, the abdomen
of each specimen was
desiccated using the
critical point drying
technique, and then coated
with gold and palladium.
Specimens were then imaged using a Hitachi S-4700 Field
Emission Scanning Electron Microscope (SEM) at a 5 kv
beam voltage, and 15 mA probe current.
The Hitachi Scanning Electron Microscope
11. Gnaphosa muscorum
Flattened setae with
a longitudinal groove
in the stem. Very
short, spine-like
apophysis of uniform
size running from the
bottom to top of the
stem on each side.
12. Gnaphosa taurica
Flattened setae with
a longitudinal groove
in the stem. Very
short, spine-like
apophysis of uniform
size running from the
bottom to top of the
stem on each side.
13. Herpyllus propinqus
(2 types of setae)
1. Saber-shaped
setae, serrated on
the concave side
and flat on the
convex side.
2. Plumose setae
with two to three
brachia at the base.
14. Hypodrassodes maoricus
Squamous setae with
two pairs of brachia at
the base, and a single
spine at the top. Two
rows of scaly
outgrowths on the top
half.
22. Results
The plumose setae of Apopyllus, Drassodes, Leptodrassus, and
Nomisia all have lateral appendages covering the first half of
the stem. The number of brachia varies per genus. In
Leptodrassus and Nomisia, the brachia are almost the same
length as the stem, while in Apopyllus and Drassodes, the
brachia are shorter and vary in length along the stem.
Parasyrisca, Pterotricha and Sosticus also have plumose setae
with unpaired brachia. Parasyrisca typically has 4 to 5 brachia,
while Pterotricha has 3 to 5 short brachia and Sosticus has
approximately 7 brachia. The plumose setae of Berlandina has
approximately 11 pairs of flattened brachia covering almost
the entire stalk, while Notiodrassus only has two paired brachia
at the base.
23. Results
Anzacia has squamous setae with 3-4 brachia close to the root.
The top is serrated with one spine. Hypodrassodes also has
squamous setae, with two pairs of brachia at the base, and a
single spine at the top. Two rows of scaly outgrowths
characterize the top half. Micaria is characterized by squamous
setae with a serrated top and no brachia.
The Gnaphosa genus is characterized by a very special type of
setae which were not found among other spiders of the family.
Such a peculiar characteristic needs explanation which may be
found in the specifics of the family evolution.
Litopyllus and Herpyllus exhibited a peculiar type of saber-
shaped setae that points to their close evolutionary relation.
24. Conclusions
Our study shows that all ground spiders, with only a
few exclusions, possess setae that cover their abdomen.
There are different types of covering setae
characteristics for different gnaphosid genera and
groups of genera, which makes setae a valuable
characteristic for the ground spiders’ classification on
subfamily level and establishing of their evolutionary
relationship. Our study supports previous studies
(Ovtsharenko, 1983, 1985, 1989; Murphy, 2007) that
setae of gnaphosid spiders greatly vary in shape and
demonstrate genus specific characteristics.
25. References
Hill, D.E. 1979. The scales of salticid spiders. Zoological Journal of the Linnean Society 65: 193-218.
Lehtinen, P.T. 1967. Classification of the Cribellate spiders and some allied families, with notes on the
evolution of the suborder Araneomorpha. Ann. Zool. Fenn. 4: 199-468.
Lehtinen, P.T. 1975. The significance of hair ultrastructure in phylogenetic classification of spiders.
Journal of Ultrastructure Research 50: 362-395.
Murphy, J. 2007. Gnaphosid genera of the World. British Arachnological Society, St. Neots, Cambs. 2
volumes, The Dorset Press, Dorchester, UK.
Ovtsharenko, V.I. 1983. Spiders of the family Gnaphosidae of the European part of the USSR and
Caucasus. Zoological Institute of the Academy of Science of the USSR, Leningrad.
Ovtsharenko V.I. 1985. Cuticular microstructure of the spider family Gnaphosidae (Aranei) and its use
in the systematics. Proceedings of the Zoological Institute of the USSR Academy of Science 139: 27-35.
Ovtsharenko, V. I. 1989. Microstructures on the cuticle of the spiders of the family Gnaphosidae
(Arachnida, Aranei). Fauna and ecology of spiders and scorpions, Nauka Publishers, Moscow: 5-13.
Platnick, N.I. 2013. The world spider catalog, version 13.5, American Museum of Natural History, NY,
online at: http://research.amnh.org/entomology/spiders/catalog/index.html.
26. Acknowledgements
Thank you to Dr. Boris Zakharov who has mentored and
guided me through the entire research process.
Many thanks to Dr. Vladmir Ovtsharenko for his
suggestions and support.
Thank you to Henry Towbin and Morgan Hill at the
American Museum of Natural History Microscopy and
Imaging Facility for their technical support with the SEM.
