Álvaro Laborda

Reversed cannibalism, foraging, and surface activities of Allocosa alticeps and Allocosa brasiliensis: two wolf spiders from coastal sand dunes

Abstract Environments where prey availability is scarce or highly variable have been reported as potential settings for the occurrence of paternal investment and sex-role reversal (choosy males and competitive, courting females). Allocosa brasiliensis (Petrunkevitch 1910) and Allocosa alticeps (Mello-Leitão 1944) are two sand-dwelling wolf spiders that construct burrows along the Uruguayan coastline. Both species present a reversal in typical sex roles and size dimorphism. In the present study, we investigated foraging behavior and population density of both species by performing monthly samplings at the field during one year. Both Allocosa are general and highly opportunistic predators, varying their diet according to prey availability. The three most represented common prey belonged to Araneae, Diptera, and Hymenoptera (Formicidae). There were high levels of cannibalism in A. brasiliensis and, furthermore, males were observed frequently preying on conspecific adult females. Our discussion of the results based on hypotheses about food limitation and sex-role reversal contributes to our understanding of Allocosa species and establishes them as models for future evolutionary, behavioral, and ecological studies.

Spatial distribution, burrow depth and temperature: implications for the sexual strategies in two Allocosa wolf spiders

Allocosa brasiliensis and Allocosa alticeps are two burrowing wolf spiders that inhabit Uruguayan sandy coasts. Male efficient digging is necessary because copulation and oviposition occur inside their burrows. We examined burrow distribution, density and temperature variation according to burrow depth. Adult burrows were more frequent at the slope of sand-dunes in A. alticeps and at the base in A. brasiliensis. The base provides better digging conditions, whereas A. alticeps adults could prefer the slope to avoid intra-guild predation. Temperature buffering increased with depth, providing thermal stability in such a harsh environment as coastal dunes.

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.

New species of the spider genera Aysenia and Aysenoides from Chile and Argentina: description and phylogenetic relationships (Araneae: Anyphaenidae, Amaurobioidinae).

New spider species of the genera Aysenia Tullgren and Aysenoides Ramírez are described and their phylogenetic relationships discussed. The new species Aysenia paposo, from the coastal desert in northern Chile is sister to Aysenia araucana Ramírez. The diagnosis of Aysenia araucana is updated and new somatic variability is reported for the species. We present new records for other species of Aysenia and Aysenoides. The new species Aysenoides simoi, from temperate forests in Chile and adjacent Argentina is sister to Aysenoides nahuel. The phylogenetic analysis confirmed the monophyly of both genera. The support values of the genera are relatively high, but some internal branches show low support values. The genus Aysenia is supported by three synapomorphies, two of these from leg spination and one from the male genitalia. Aysenoides is supported by three synapomorphies from male and female genitalia.

Habitat, redescription and distribution of Latrodectus geometricus in Uruguay (Araneae: Theridiidae)

This study provides the first accurate records of Latrodectus geometricus C. L. Koch, 1841 for Uruguay and extends the known distribution of this species to the Southeastern region of South America. Data and figures of the genitalic morphology for the recognition of the species and natural history in this country are indicated. In Uruguay L. geometricus was mainly restricted to urban areas at the west of this country and it is associated with locations with high human activity.

Araneae, Deinopidae, Deinopis amica Schiapelli and Gerschman, 1957: First record for Uruguay and distribution map

This is the first record for the species Deinopis amica and for the family Deinopidae in Uruguay. The present study expands the known distribution of the species to the lower Uruguay River. Data on natural history of the species is provided.

FIRST SOUTH AMERICAN RECORDS OF HOLOCNEMUS PLUCHEI (SCOPOLI, 1763) AND SPERMOPHORA SENOCULATA (DUGÉS, 1836) (ARANEAE: PHOLCIDAE)

Holocnemus pluchei y Spermophora senoculata fueron halladas en construcciones humanas en cuatro localidades de Uruguay y una de Argentina. Estos son los primeros registros para Sudamerica de estas dos especies sinantropicas.

The orb-weaving spider genus Chrysometa in Uruguay: distribution and description of a new species (Araneae, Tetragnathidae)

The spider genus Chrysometa Simon, 1895 comprises 138 species of small (3-5 mm) Neotropical orb-weavers spiders (Nogueira et al. 2011; World Spider Catalogue 2015) mainly associated with arboreal vegetation from intermediate to low altitude forests (Levi 1986). Males of Chrysometa differ from other tetragnathids by having the palpal tibial length approximately as long as its widest point; paracymbium articulated and with several apophyses located at both ends; male cephalic region narrower than in the female and having cymbial ectobasal and ectomedian processes. Females are diagnosed by having femora without trichobothria; abdomen covered with silver guanine patches; a flat epigynum and also by their fertilization ducts originating anteriorly and crossing over the spermathecae (Levi 1986; Alvarez-Padilla & Hormiga 2011).

Description of the female of Eutichurus ibiuna Bonaldo, 1994 (Araneae: Eutichuridae) with notes on natural history and sexual behavior.

The genus Eutichurus was created by Simon (1897) on the basis of three species from Brazil and Ecuador originally placed in the family Clubionidae. Lehtinen (1967) transferred the genus to Miturgidae and created the subfamily Eutichurinae, although the limitation of this taxon was not clear. Bonaldo (1994) defined this subfamily based on the Neotropical genera Eutichurus , Radulphius Keyserling, 1891 and Ericaella Bonaldo, 1994. Ramirez (2014), based on an extensive phylogenetic analysis, elevated the rank of Eutichurinae to family, including 12 genera in the group. Ramirez (2014) indicated that the monophyly of Eutichuridae is considerably well supported, but the higher-level relationships are not totally clear and are still under discussion. The genus Eutichurus includes medium sized entelegynae ecribellate spiders distributed mostly in the Neotropics and comprising 26 valid species, from which only ten have both sexes described (World Spider Catalog 2015). One of those species is Eutichurus ibiuna Bonaldo, 1994 that was described based only on the male holotype. Recently, we examined specimens collected in Northeastern Uruguay and we found 2 females, one of which was collected with the egg sac. Some eggs were bred under laboratory conditions and we obtained six males and six females. We confirmed that the males belong to this species based on the description provided by Bonaldo (1994), and we described the female for the first time. The specimens represent the first records of the species for Uruguay, and a significant expansion of its known distribution. The new locations are situated approximately at 1200 kilometers south from the type locality.

Spider assemblages associated with different crop stages of irrigated rice agroecosystems from eastern Uruguay

Abstract The rice crop and associated ecosystems constitute a rich mosaic of habitats that preserve a rich biological diversity. Spiders are an abundant and successful group of natural predators that are considered efficient in the biocontrol of the major insect pests in agroecosystems. Spider diversity in different stages of the rice crop growth from eastern Uruguay was analysed. Field study was developed on six rice farms with rotation system with pasture, installed during intercropping stage as cover crop. Six rice crops distributed in three locations were sampled with pitfall and entomological vaccum suction machine. Sixteen families, representing six guilds, were collected. Lycosidae, Linyphiidae, Anyphaenidae and Tetragnathidae were the most abundant families (26%, 25%, 20% and 12%, respectively) and comprised more than 80% of total abundance. Other hunters (29%), sheet web weavers (25%) and ground hunters (24%) were the most abundant guilds. Species composition along different crop stages was significantly different according to the ANOSIM test. The results showed higher spider abundance and diversity along the crop and intercrop stages. This study represents the first contribution to the knowledge of spider diversity associated with rice agroecosystem in the country.