Gabriel Pompozzi

Mygalomorph Spider Community of a Natural Reserve in a Hilly System in Central Argentina

Abstract The diversity, abundance, spatial distribution, and phenology of the mygalomorph spider community in the “Ernesto Tornquist” Strict Nature Reserve were analyzed in this study. Located in southwestern Buenos Aires, Argentina, the Reserve is representative of the Ventania system, which is a sigmoidal mountain belt 180 km in length. This exceptional hilly ecosystem is home for many endemic species and rich native fauna and flora. Spider abundance was sampled monthly from October 2009 to October 2010 by hand capture and pitfall traps on grassland slopes. The species recorded in the study area were: Actinopus sp.1 (Actinopodidae); Grammostola vachoni and Plesiopelma longisternale (Theraphosidae); Acanthogonatus centralis (Nemesiidae); and Mecicobothrium thorelli (Mecicobothriidae). Grammostola vachoni and Acanthogonatus centralis were the dominant species in hand capture and pitfall traps, respectively. The seasonal variation, diversity, and abundance of the mygalomorph community are analyzed and discussed here. The Mygalomorphae of the Ventania system comprises an important group of sedentary and cryptozoic spiders that seem to be highly dependent on habitat type and environmental factors.

Sexual behavior of Acanthogonatus centralis (Araneae: Mygalomorphae: Nemesiidae) from Argentina, with some notes on their burrows

Abstract Acanthogonatus centralis Goloboff 1995 is a Neotropical nemesiid distributed in hilly zones of central Argentina. The biology of the Nemesiidae is almost unknown. We describe the courtship and mating of A. centralis based on eight observed matings (three males and five females). Male courtship involved scratching and beating the ground. These behaviors have not been observed in other mygalomorph spiders and are here described for the first time. After contacting female silk, males stretched the web. Males manipulated their pedipalps and spasmodically beat their legs over the female. The mating position was typical of mygalomorph spiders. Females remained active during copulation by making body jerks and struggling. The body jerks of females could be stimulating the male to renew palpal insertion. In addition to describing this spider familys mating behavior, we also include some notes on their shelters. The tunnel-webs observed in the field had no branches, only one entrance, and a short burrow. Adult males are capable of constructing tunnel-webs, but they are quite different from those of juveniles and females, lacking the short burrow.

On the taxonomy of southern South American species of the wolf spider genus Allocosa (Araneae: Lycosidae: Allocosinae)

Three species of the genus Allocosa Banks, 1900 from southern South America are redescribed: Allocosa alticeps (Mello-Leitão, 1944), A. brasiliensis (Petrunkevitch, 1910) and A. senex (Mello-Leitão, 1945). The female of A. senex is described for the first time and the species is revalidated. A new species, A. marindia sp. nov. from southern Uruguay and southern Brazil is described. The new species is distinguished by the flattened terminal apophysis of the male bulb and the conspicuous pointed projections on the posterior margin of the female epigynum. The species inhabits in sandy estuarine and oceanic coasts with psammophile vegetation.

Aerial dispersal by Actinopus spiderlings (Araneae: Actinopodidae)

Abstract Ballooning, a form of dispersal rarely seen in mygalomorph spiders, was observed in 13 individuals of an undetermined species of Actinopus under laboratory conditions. After ascending a stick, each spiderling initiated ballooning from either the horizontal lines between sticks or from the sticks edges. They became airborne by dropping and dangling from a dragline, which then gradually lifted and lengthened to 10–15 cm in the breeze, broke at its attachment point, and served as a ballooning thread. This method of ballooning has also been observed in araneomorphs and other species of mygalomorphs, and this is probably a more primitive and shorter distance form of ballooning than that typically practiced by higher araneomorphs, which produce airborne silk lines that are pulled from the spider by air currents and are used either as spanning lines or as balloon lines that allow the spider itself to become airborne.

Sexual Behaviour of Mygalomorph Spiders: when Simplicity Becomes Complex; an Update of the Last 21 Years

Summary A generally common impression seems to be that the mygalomorphs have simple repertoires of behaviours, but many authors have concluded that this traditional portrayal of mygalomorph behaviours is misleading. An increasing number of studies of reproductive behaviour of mygalomorphs have revealed intricate and complex mechanisms of communication employed by this group. Our objective was to provide a synthetic treatment of the literature published in the last 21 years about sexual behaviour of mygalomorph spiders, in order to contribute in improving our understanding on the widespread and unique behaviours they exhibit. We provide a brief introduction to reproductive behaviour of mygalomorph spiders, and then examine some of the general patterns of courtship and mating behaviours known on some mygalomorph families.

Copulatory behavior of Microstigmatidae (Araneae: Mygalomorphae): a study with Xenonemesia platensis from Argentina

Abstract Microstigmatidae are small ground-dwelling and free-living spiders. The present study reports on the copulatory behavior of Xenonemesia platensis Goloboff 1989, constituting the first report on sexual behavior of the Microstigmatidae. Our findings in X. platensis did not show evidence of pheromones associated with silk. The courtship behavioral units of males was comprised of quivers by legs I and II, brusque movements of the palps, and leg tapping with legs II. During mating, a novel courtship behavior by males was observed that consisted of tapping and scraping with legs II on the female legs. The present study not only gives a description of mating behavior in Microstigmatidae for the first time, but also reports strong evidence of nongenital copulatory courtship activity in mygalomorph spiders.

On Puan, a New Genus of Goblin Spiders from Argentina (Araneae, Dysderoidea, Oonopidae)

ABSTRACT A new genus of Oonopidae, Puan, is described from Argentina. The genus exhibits several features also found in orsolobids, including a well-sclerotized sperm duct and an H-shaped eye pattern. Puan resembles the oonopid genus Unicorn Platnick and Brescovit but differs in male palpal morphology. In addition, males lack the clypeal horn characteristic of Unicorn. Two new species, P. chechehet and P. nair, are described from the southwestern mountains of Buenos Aires province. Complex copulatory bulbs are the principal characteristic of these species and could be a synapomorphy for the genus.

Another migid in the wall: natural history of the endemic and rare spider Calathotarsus simoni (Mygalomorphae: Migidae) from a hill slope in central Argentina

A population of Calathotarsus simoni Schiapelli and Gerschman (1975) was discovered on a hillside in the Ventania system, Argentina. Our objectives were to quantify burrow density, record burrow morphology and door characteristics and describe the micro-habitat. We counted 57 burrows and report a density of 0.01 burrows/m2. Aggregation indices suggest that burrows are aggregated under some area plots but more evenly distributed on others. The trapdoor is thick and rigid with bevelled edges connected to the entrance rim by a narrow articulated hinge. Two egg sacs from females were obtained and data on eggs and spiderlings are presented. We registered six burrows of an undetermined species of Actinopus. While a few specimens of Actinopus sp. were found inhabiting this hillside, the highest proportion of burrows belonged to C. simoni. Spider diversity on the hillside shows the predominance of Linyphiidae, Nemesiidae and Gnaphosidae. One juvenile of C. simoni was captured using pitfall traps.

Triple interaction network among flowers, flower visitors and crab spiders in a grassland ecosystem

This study presents the first description of a tri-trophic interaction network with crab spiders as predators. Monthly observations of flowering entomophilous plant species were recorded between December 2009 and March 2010 and their flower visitors and predators (crab spiders) were caught, with or without prey. Moreover, flower visitors of different orders were caught to evaluate the amount of pollen transported. In order to analyze changes in the plant species and crab spiders, we evaluated the interaction networks in which we had removed different orders of prey (Hymenoptera, Diptera and Lepidoptera) from the original network. Our results indicate that crab spiders select their preys within the community. Furthermore, the Hymenoptera carried higher pollen loads and were the less frequent prey. When the Diptera preys were removed from the initial interaction network, network changes mainly affected the species richness of crab spiders. Decrease in density of Diptera could increase plant resources useful for flower visitors carrying great pollen loads and could promote pollination. Crab spider prey might be restricted to only the more vulnerable flower visitors (e.g. smaller dimensions, without sting or with delicate cuticula) which consume resources and are inefficient as pollen carriers. The selected predation could not negatively affect the fitness of plants.

The genus Grammostola Simon 1892 (Araneae: Theraphosidae): a new species from western Argentina, new synonymy and distributional data

Grammostola diminuta sp. nov. (Araneae: Theraphosidae) is described from northwestern Argentina; Grammostola vachoni Schiapelli and Gerschman 1961 is considered a senior synonym of Grammostola fossor syn. nov. Schmidt 2001 on the basis of material examined from the collection of the Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (MACN-Ar). The geographic distribution of G. vachoni is extended on the basis of new records. Additionally, we present new diagnoses and new distributional data for Grammostola chalcothrix Chamberlin 1917, Grammostola inermis Mello-Leitão, 1941 and Grammostola pulchripes (Simon 1891). http://www.zoobank.org/urn:lsid:zoobank.org:act:D9D0702F-1317-420B-BBFF-890104A66998