We documented the specific richness, abundance and activity of the Mygalomorph spider community in the Natural Reserve Sierra del Tigre, Buenos Aires, Argentina. This hilly ecosystem is home for many endemic species and rich in native fauna and flora. Spider abundance was sampled monthly from May 2011 - May 2012 by hand capture and pitfall traps. The species recorded in the study area were Actinopus sp. 1 (Actinopodidae), Grammostola vachoni Schiapelli y Gerschman, 1960; Plesiopelma longisternale Schiapelli y Gerschman, 1942 and Catumiri argentinense (Mello-Leitão, 1941) (Theraphosidae). Grammostola vachoni was the dominant species in hand capture and Actinopus sp. 1 in pitfall traps. The seasonal variation, diversity, and abundance of the mygalomorph community are analyzed and discussed here. The Mygalomorphae of the Tandilia system comprises an important group of sedentary and cryptozoic spiders that seem to be dependent on habitat type and environmental factors.

En el presente trabajo se analizó la riqueza específica, abundancia y actividad de la comunidad de arañas Mygalomorphae en la Reserva Natural Sierra del Tigre, Buenos Aires, Argentina. Este ecosistema serrano alberga numerosas especies endémicas y es rico en fauna y flora nativa. La abundancia de arañas se muestreó mensualmente desde mayo de 2011 a mayo de 2012, mediante recolección manual y trampas de caída. Las especies registradas en el área de estudio fueron Actinopus sp. 1 (Actinopodidae), Grammostola vachoni Schiapelli y Gerschman, 1960; Plesiopelma longisternale Schiapelli y Gerschman, 1942 y Catumiri argentinense (Mello-Leitão, 1941) (Theraphosidae). Grammostola vachoni resultó la especie dominante en la recolección manual y Actinopus sp. 1 en trampas de caída. Se discuten y analizan la variación estacional, diversidad y abundancia de la comunidad de migalomorfas. Las Mygalomorphae del sistema de Tandilia comprenden un grupo importante de arañas sedentarias y criptozoicas que parecen depender del tipo de ambiente y factores ambientales.

When two similar species co-occur in time and space, strong mechanisms isolating them from each other are expected. Acanthoscurria suina Pocock, 1903 and Eupalaestrus weijenberghi (Thorell, 1894) are two sympatric and synchronic tarantulas that inhabit burrows in Uruguay's meadows. Here we test how and when reproductive isolation operates between these species. We exposed females of each species simultaneously to two males: either one male of each species, or two males of the same species. Males courted females of both species. Contrary to expectations, however, females of A. suina responded more effusively to heterospecific than to conspecific males, whereas females of E. weijenberghi only responded to conspecific males. Clasping (prelude of mating) was only recorded for couples of the same species. Females of A. suina at first seem to prefer the stronger body vibrations performed by heterospecific courting males than by males of their own species.

Munduruku gen. nov., é proposto para a espécie-tipo Munduruku bicoloratum sp. nov., de Juruti, e Santarém, Pará, Brasil. O principal caráter diagnóstico de Munduruku gen. nov. é a presença de uma quilha subapical lancelotada no bulbo copulatório do macho, único no grupo basal de Theraphosinae com cerdas urticantes do tipo III-IV. A espermateca da fêmea consiste em dois recipientes esferóides com pescoço em forma de funil, cada um dos quais tendo uma área esclerotizada. Em ambos os sexos, o abdômen apresenta um padrão de colorido característico, o que é incomum em adultos de terafosídeos do Novo Mundo. Tanto a quilha lanceolada do bulbo quanto o padrão de colorido do abdômen são hipotetizados como sinapomorfias do gênero.

Munduruku gen. nov. is proposed for the type species Munduruku bicoloratum sp. nov., from Juruti and Santarém, Pará, Brazil. The main diagnostic character of Munduruku gen. nov. is the presence of a subapical, lanceolate keel on the male palpal bulb, which is unique among the basal taxa of Theraphosinae with type III-IV urticating setae. The female spermathecae consist of two spheroid receptacles with funnel-shaped necks, each of which bears a sclerotized area. In both sexes, the abdomen is remarkably patterned, an uncommon feature in adults of New World theraphosids. Both the bulbus lanceolate keel and the abdominal color pattern are hypothesized as synapomorphies of the genus.

Se describe y analiza la respuesta sexual en hembras de la tarántula Grammostola vachoni en tres series de 10 experimentos cada uno bajo diferentes situaciones de encuentros entre machos y hembras: machos libres en el terrario pero sin acceso a la hembra; machos confinados dentro de un recipiente de vidrio a 30 cm de la cueva de la hembra y machos confinados en el recipiente de vidrio sobre una piedra cerrando la entrada de la cueva de la hembra. Se observaron golpes con patas y palpos y movimientos corporales de las hembras en respuesta al cortejo de los machos. Los golpes con patas y palpos podrían indicar la receptividad de las hembras y su atracción. También, este comportamiento podría orientar al macho hacia su posición. Estas hembras contestaron con golpes de patas y palpos sólo a los machos que realizaron cortejos largos junto a una búsqueda activa de la cueva de la hembra. Los movimientos corporales de la hembra, originados con patas IlI, se interpretan como un rechazo considerando que el macho dejó de cortejar e intentó escapar.

We described and analyzed the female sexual response in the tarantula Grammostola vachoni Schiapelli and Gerschman 1961 under three series of 10 experiments each with different situations for the male-female encounters: male free in terrarium but with no access to female; male confined into a glass cup at 30 cm of female burrow and; male confined into a glass cup over a heavy stone closing the female burrow. We observed leg palpal tapping and body movements of female in response to male courtship. Leg and palpal tapping could indicate a female receptive condition and her attractiveness. Also, this behavior may serve to orient male towards her location. These females responded with leg and palpal tapping only to males which present long courtships together with active searching (walking) for female location. The female body movements, originated by legs III, are interpreted here as a rejection considering that male stopped courting and tried to escape.

Hay pocos estudios detallados sobre las interacciones intraespecíficas de arañas migalomorfas. Por lo tanto, se describe el comportamiento de individuos conspecíficos de Grammostola schulzei durante interacciones nosexuales en condiciones de laboratorio. Se confrontaron y observaron pares de individuos involucrando machos adultos, hembras adultas y juveniles en condiciones de locatarios y visitantes, totalizando 115 encuentros. Cuando dos hembras adultas se enfrentaron, retrocedieron o lucharon adoptando elevaciones anteriores e intentos de mordeduras que usualmente resultaron en arañas visitantes heridas. Cuando se enfrentaron hembras con juveniles, frecuentemente se observó canibalismo sobre los juveniles. Los juveniles expuestos a otros juveniles o hembras retrocedieron o realizaron golpes con patas delanteras y tamborileos de palpos, los cuales constituyen unidades de comportamiento comunes durante el cortejo de los machos. Los machos adultos cortejaron y trabaron a algunos juveniles, mientras que los juveniles los evitaron o rechazaron el enganche. Los comportamientos observados durante las interacciones intraespecíficas podrían jugar un papel importante en la distribución espacial y podrían generar adaptaciones al territorialismo.

Intraspecific interactions of araneomorph spiders have received considerable attention, but there are few detailed studies on intraspecific interactions of mygalomorph spiders. Moreover, a thorough understanding of theraphosid biology and ecology is necessary from a conservation standpoint because natural populations may be threatened by habitat disturbances and captures for pet commerce. We described the behavior of conspecific individuals of Grammostola schulzei during non-sexual interactions, under laboratory conditions. Pairs of individuals involving adult males, adult females and juveniles were confronted and observed in resident and intruder conditions, totalizing 115 trials. When confronted two adult females, they retreated or grappled, and performed gaping display with bite attempts, usually resulted in severe injury of the intruder spiders. When confronted females with large juveniles, we frequently observed cannibalism on juveniles. Juveniles exposed to females or to other juveniles retreated or made leg tapping with forelegs and palpal drumming, which are common displays of courting adult males. Adult males courted and clasped some juveniles, but juveniles avoided or reject clasping. The behaviors observed during intraspecific interactions could play an important role determining spatial distribution and could lead to behavioral adaptations of territoriality. Rev. Biol. Trop. 59 (3): 1173-1182. Epub 2011 September 01.

Uma nova espécie de Hapalopus Ausserer, 1875 (Araneae, Theraphosidae, Theraphosinae) da Bolívia é descrita e ilustrada, baseada em machos e fêmeas.

A new species of Hapalopus Ausserer, 1875 (Araneae, Theraphosidae, Theraphosinae) from Bolivia is described and illustrated, based in males and females.

Specialized setae placed on proximal segments of appendages in tarantulas have been related to sound production (stridulation), used in defense or sexual communication. The surface structure of called stridulatory setae of Acanthoscurria suina Pocock, 1903 was studied by SEM. Three morphological types of setae were recognized and at least two of them could be involved in stridulation. Their role in sexual communication was tested by experimental removal. Our results showed no differences in the sexual success between the setaeless and control individuals. Consequently, a defensive function for stridulatory setae seems to be more likely than a sexual function.

Las setas especializadas que las tarántulas presentan en los segmentos proximales de los apéndices han sido relacionadas con la producción de sonidos (estridulación), utilizados en defensa o comunicación sexual. La estructura superficial de las setas llamadas estridulatorias en Acanthoscurria suina Pocock, 1903 fue estudiada mediante microscopía electrónica de barrido. Tres patrones morfológicos de setas fueron reconocidos y al menos dos de ellos podrían estar involucrados en la estridulación. Su rol en la comunicación sexual fue estudiado mediante remoción experimental. Los resultados no mostraron diferencias en el éxito sexual entre individuos sin setas e individuos control. Consecuentemente, parece más probable una función defensiva que sexual para dichas setas.