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Egg sacs of Liocranoides Keyserling, 1881 (Araneae: Zoropsidae) cave spiders.

Spiders are members of subterranean communities around the world. More than 1000 spider species representing ~50 families exhibit morphological adaptations to subterranean life and many more species are associated with caves to varying degrees (reviewed in Mammola & Isaia 2017). Most cave spiders are poorly known, and little is known about their reproduction, including seasonality, fecundity, and reproductive behaviors. Here we describe egg sacs and observations of spiderlings from Liocranoides Keyserling, 1881 (Araneae: Zoropsidae) spiders in caves in Tennessee. This is the first description of reproduction in this genus.

Liocranoides consists of five described species (World Spider Catalog 2018). Liocranoides unicolor Keyserling, 1881 was described first, based on specimens from Mammoth Cave, Kentucky. Platnick (1999) revised the genus and extended the range of L. unicolor into north-central Tennessee. He also described four additional species from the southern Appalachians: L. tennesseensis Platnick, 1999 (from central and eastern Tennessee), L. coylei Platnick, 1999 (southwestern Virginia, western North Carolina, and eastern Tennessee), L. archeri Platnick, 1999 (south-central Tennessee and northeastern Alabama), and L. gertschi Platnick, 1999 (northern Alabama and northwestern Georgia). However, there are multiple undescribed Liocranoides species present throughout the Appalachian region and members of this genus may exist as a species complex similar to Nesticus Thorell, 1869 (Araneae: Nesticidae) cave spiders found in Appalachia (Milne unpublished data; Hedin 1997). All five described species have been collected in caves, and two (L. unicolor and L. archeri) are known only from caves (Platnick 1999).

During a visit to Keith Cave (Franklin County, Tennessee; Tennessee Cave Survey (TCS) #FR14) on 1 June 2017, we observed nine L. archeri individuals (Fig. 1 A), as well as three egg sacs hanging from the ceiling of the upper chambers of the cave. These spherical egg sacs were ~1 cm in diameter and hung from the ceiling by a thick cord of silk ~2 cm in length. The egg sacs were covered by fragments of sediment, rock, and plant roots (Fig. 1B). Two egg sacs had mature female L. archeri in close association (within 10 cm). We collected one egg sac (Tennessee Wildlife Resources Agency permit #1605) and found 53 cleavage stage embryos inside. Although foreign materials were attached to the outside of the egg sac, no foreign material was observed inside the egg sac (Fig. 1C). During a second visit to Keith Cave on 20 June 2017, we observed one egg sac and what appeared to be the remnant of an egg sac still attached to the ceiling (Fig. 1D).

Liocranoides archeri is known from ~20 caves in south central Tennessee and adjacent northeast Alabama (Platnick 1999; Lewis 2005; Dixon & Zigler 2011; Wakefield & Zigler 2012). Liocranoides archeri has only been collected from caves and so has been considered a cave-obligate species (Niemiller & Zigler 2013). It is pale and largely uniformly colored, which may be an adaptation to cave life (Fig. 1A). It does not, however, exhibit other obvious morphological adaptations to cave life (Platnick 1999). The spiders Nesticus barri Gertsch, 1984 (Araneae: Nesticidae) (Lewis 2005) and Meta ovalis (Gertsch, 1933) (Araneae: Tetragnathidae) are also known from Keith Cave. Both have egg sacs that are quite distinct from those described here (e.g., Carver et al. 2016; egg sacs of M. ovalis are similar to those of the European M. menardi (Latreille, 1804), as described in Lepore el al. 2012).

We observed a similar egg sac in Shinbuster Crawl Cave (Rutherford County, Tennessee; TCS #RU88) on 14 July 2017. Although there was no spider in attendance, we collected immature Liocranoides from the cave and assume it was a Liocranoides egg sac. We collected and dissected the egg sac and found 26 eggs inside. The material inside the egg capsules was disorganized, suggesting these eggs failed to develop and were degenerating. Last, we observed two intact egg sacs in East Fork Cave (Dickson County, Tennessee; TCS #DI27) on 29 July 2017. One egg sac was collected and contained 42 cleavage stage embryos. A third egg sac in the cave was apparently recently hatched, with approximately 30 spiderlings on the ceiling surrounding the remnant of the egg sac. The spiderlings were nearly transparent with bodies 1-2 mm in width. We collected immature and mature L. cf. gertschi from the cave. The genitalia of the mature spiders differed slightly from the description of L. gertschi. All collected spiders have been retained by one of the authors (MAM) for further systematic study.

There are similarities between the egg sacs of Liocranoides and some other zoropsid taxa. Most notably, Tiliotus gertschi Platnick & Ubick, 2008 hangs spherical egg sacs by a cord of silk from the ceiling of caves in California (Platnick & Ubick 2008). Tengella perfuga Dahl, 1901, from Nicaraguan forests, covers its spherical egg sacs with pieces of substrate including bark, soil, and leaves (Mallis & Miller 2017). Some other zoropsid spiders, including members of Grisnoldia Dippenaar-Schoeman & Jocque, 1997 and Austrotengella Raven, 2012, encrust the egg sac with dirt and debris, but not all do (e.g., Zoropsis Simon, 1878) (Griswold 1991; Thaler & Knoflach 1998; Raven 2012).

The Liocranoides spiders and egg sacs we observed were in the twilight zone (the area to which some light penetrates) of these caves, rather than in dark zone cave habitats. The spiders were not found in webs and ran rapidly when disturbed. This suggests they are cursorial and hunt in the prevailing low light.

Over the past six years one of the authors (KSZ) participated in 241 visits to caves in Tennessee, Alabama and Georgia. The trips were distributed throughout the year, although fewer visits occurred in the winter (40/241). Across those visits these are the first observations of Liocranoides egg sacs, suggesting a brief or sporadic reproductive period for Liocranoides. Our anecdotal observations of Liocranoides egg sacs and spiderlings in June and July arc consistent with observations of reproduction in Neslicns cave spiders. Nesticus cave spiders from the southern Appalachians exhibit reproductive seasonality with a peak in June and July (Carver et al. 2016). Further observations are required to determine if Liocranoides exhibit a similar pattern of reproductive seasonality.

LITERATURE CITED

Carver, L.M., P. Perlaky. A. Crcssler & K.S. Zigler. 2016. Reproductive seasonality in Nesticus (Araneae: Neslicidae) cave spiders. PLoS ONE 11 :e0156751.

Dixon, G.B. & K.S. Zigler. 2011. Cave-obligate biodiversity on the campus of Sewanee: The University of the South, Franklin County, Tennessee. Southeastern Naturalist 10:251-266.

Griswold, C.E., 1991. A revision and phylogenetic analysis of the spider genus Machadonia Lehtinen (Araneae, Lycosoidea). Insect Systematics & Evolution 22:305-351.

Hedin, M.C. 1997. Molecular phylogenelics at the population/species interface in cave spiders of the Southern Appalachians (Araneae: Nesticidae: Nesticus). Molecular Biology and Evolution 14:309-324.

Lepore. E., A. Marchioro, M. Isaia, M.J. Buehler & N.M. Pugno. 2012. Evidence of the most stretchable egg sac silk stalk, of the European spider of the year Mela menardi. PloS ONE 7:e30500.

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Niemillcr, M.L. & K.S. Zigler. 2013. Patterns of cave biodiversity and endemism in the Appalachians and Interior Plateau of Tennessee, USA. PLoS ONE 8:e64177.

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Platnick N.I.&D. Ubick. 2008. A revision of the endemic Californian spider genus Titiotus Simon (Araneae, Tengellidae). American Museum Novitates 3608:1-33.

Raven, R.J. 2012. Revisions of Australian ground-hunting spiders. V. A new lycosoid genus from eastern Australia (Araneae: Tengellidae). Zootaxa 3305:28-52.

Thaler, K. & B. Knoflach. 1998. Zoropsis spinimana (Dufour), eine fur Osterreich neue Adventivart (Araneae, Zoropsidae). Berichte des Naturwissenschaftlich-Medizinischen Vereins in Innsbruck 85:173-185.

Wakefield, K.R. & K.S. Zigler. 2012. Obligate subterranean fauna of Carter State Natural Area, Franklin County, Tennessee. Speleobi-ology Notes 4:24-28.

World Spider Catalog. 2018. World Spider Catalog. Natural History Museum Bern, online at http://wsc.nmbe.ch version 19.0, accessed on 18 May 2018. doi: 10.24436/2

Manuscript received 11 September 2017, revised 28 June 2018.

Mary Elizabeth Yancey (1) , Nathaniel C. Mann (2) , Marc A. Milne (3) and Kirk S. Zigler (1) : (1) Department of Biology, University of the South, Sewanee, Tennessee, 37383, USA; E-mail: kzigler@sewanee.edu (2) Spencer Mountain Grotto, Spencer, Tennessee, 38585, USA; (3) Department of Biology, University of Indianapolis, Indianapolis, Indiana, 46227, USA
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Title Annotation:SHORT COMMUNICATION
Author:Yancey, Mary Elizabeth; Mann, Nathaniel C.; Milne, Marc A.; Zigler, Kirk S.
Publication:The Journal of Arachnology
Date:Sep 1, 2018
Words:1426
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