Miguel Simó

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.

Characterisation of burrow architecture under natural conditions in the sand-dwelling wolf spider Allocosa brasiliensis

Abstract Allocosa brasiliensis (Petrunkevitch, 1910) is a wolf spider that constructs silk-lined burrows along the coastal sand dunes of Argentina, Brazil and Uruguay. This species shows a reversal in typical sex roles and sexual size dimorphism expected for spiders. Females are the smaller and mobile sex, which initiates courtship at the male burrow entrance. Mating occurs in the male burrow, and when it ends, the male leaves and the female stays inside. Females prefer to mate with those males showing longest burrows, so burrow dimensions would be under strong sexual selection pressures. Previous studies in the laboratory indicated that male burrows are longer than those of virgin females, which were described as simple silk capsules. Preliminary observations suggested that juvenile burrows presented differences from those of adults; however, detailed observations of A. brasilienisis burrow characteristics at the field were lacking. The aim of this study was to characterise the burrows of adults and juveniles of A. brasiliensis under natural conditions. We recorded the dimensions of burrows inhabited by males, females and juveniles (n = 30 for each category) and created beeswax moulds that reflected burrow shape. Juveniles inhabited tubular burrows with two branches and two openings; on the contrary, adults were found in tubular burrows with a single entry. Males and females inhabited burrows of similar length and width, but those of juveniles were shorter and narrower. We discuss the results and their possible functional explanations according to the selective pressures expected for each developmental stage and sex.

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.

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.

Allocosa brasiliensis (Araneae, Lycosidae) as a Bioindicator of Coastal Sand Dunes in Uruguay

Summary Predators such as spiders are particularly vulnerable to habitat fragmentation and are considered good bio-indicators of nature conservation or habitat degradation. As occurs all around the globe, the Uruguayan coastal sand dunes have been drastically diminished and fragmented, and seriously affected by human modifications such as urbanization, tourism, and introduction of exotic species. The objectives of the present study were to identify the indicator species of two adjacent areas of the sandy coastline of Uruguay (Marindia, Canelones) and, specifically, to confirm whether Allocosa brasiliensis can be considered a biological indicator of the open dunes with scarce psammophile vegetation in this locality. We used the IndVal method which quantifies the indicator value of each species. Allocosa brasiliensis had the highest indicator value for open dunes fixed with psammophilic native vegetation, reflecting its greatest specificity and fidelity to this environment.

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.

Nocturnal Surface Activity and Behavioural Responses to Floods in Allocosa senex (Araneae: Lycosidae)

Abstract Allocosa senex is distributed along the sandy coasts of Argentina, Brazil and Uruguay. Individuals are nocturnal and build burrows in the sand, where they stay during the day and in the Southern Hemisphere winter. Most studies of this species have been carried out in estuarine or oceanic beaches. A. senex faces an important environmental stress because its habitat, particularly in coastal lagoons, is affected by periodic floods. The behavioural responses of individuals of this species under those conditions are unknown. Our objective was to estimate the abundance, density, and cursorial dispersal of A. senex in two beaches of a coastal lagoon in Rocha, Uruguay. Additionally, we tested A. senex behavioural responses to floods under laboratory conditions. The results showed that the abundance and dispersal ability of A. senex individuals are higher at sites with greater availability of suitable habitat. Females were the most mobile sex and showed the highest recapture frequencies. A. senex individuals survived artificial floods and displayed swimming and diving behaviours. These results suggest a high degree of adaptation of this wolf spider to inhabit coastal environments and cope with its extreme variations.

On the taxonomy of Latonigena auricomis (Araneae, Gnaphosidae), with notes of geographical distribution and natural history

The male of Latonigena auricomis Simon, 1893 is described for the first time and the female is redescribed. New records are provided for Argentina, Brazil and Uruguay. Notes on the natural history and a potential distribution model of the species are presented in the Neotropical Region.