Ferretti, N. E. & F. Pérez-Miles. 2011. Intraspecific non-sexual interactions of Grammostola schulzei (Araneae: Theraphosidae) under laboratory conditions. Revista de Biología Tropical (International Journal of Tropical Biology and Conservation) 59 (3): 1173–1182.
Abstract. 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.
Megjegyzés: a Grammostola schulzei (Schmidt, 1994) fajt a közelmúltban szinonimizálták a G. vachoni Schiapelli & Gerschman, 1961 fajjal [Ferretti et al. (2011)].
Dor, A., S. Calmé & Y. Hénaut. 2011. Predatory interactions between Centruroides scorpions and the tarantula Brachypelma vagans. Journal of Arachnology 39 (1) :201–204. DOI: 10.1636/St08-84.1
Abstract. In the Yucatan Peninsula, the tarantula Brachypelma vagans Ausserer 1875 is commonly associated with human settlements, as are the scorpions Centruroides gracilis Latreille 1804 and C. ochraceus Pocock 1898. Nonetheless, scorpions are virtually absent from villages showing a high density of tarantulas. Predatory interactions between these predators could explain the lack of local overlap. To test this hypothesis, we observed the behavioral interactions between B. vagans and C. gracilis or C. ochraceus in experimentally controlled conditions, and we compared these interactions to interactions between the tarantula and two prey species: cricket and cockroach. For observations, a pre-adult tarantula was placed in an experimental arena in which we introduced either a scorpion or an insect. In all, 115 trials were performed. We recorded time elapsed and behavioral responses: avoidance, attack, escape, capture, and attack success. Tarantulas preyed on all prey with the same attack success (63.8% ± 0.8%), but they attacked and captured cockroaches quicker and more often than the other prey (87% vs. 50%, and 57% vs. 30%, respectively). Scorpions attacked tarantulas in 25.5% of occasions, but they were never successful, and were killed in 9% of occasions. We conclude that tarantulas are potential predators of scorpions. Moreover, in villages where tarantulas are abundant they might prevent the presence of scorpions. Thus the presence of this non-aggressive tarantula may be beneficial from the human perspective.
Canal, M., D. Figueroa, C. Alfaro, T. Kawamoto, H. Torres-Contreras, P. Sabat & C. Veloso. 2011. Effects of diet and water supply on energy intake and water loss in a mygalomorph spider in a fluctuating environment of the central Andes. Journal of Insect Physiology, Article in Press, Uncorrected Proof. DOI: 10.1016/j.jinsphys.2011.07.016
Abstract. The metabolic and water evaporation strategies in spiders may be part of a set of physiological adaptations to tolerate low or unpredictable food availability, buffering spiders against environmental fluctuations such as those of the high mountains of the central Andes.
The aim of this study is to analyze experimentally the variations in metabolic rate and the rate of evaporative water with food and/or water restriction in a high mountain mygalomorph spider population (Paraphysa sp.).
We found that the low metabolism of this spider was not affected by water restriction, but its metabolism was depressed after 3 weeks of food deprivation. The spider did not show seasonal metabolic changes but it presented seasonal changes in the rate of evaporative water loss at high temperatures.
Females with egg sacs reduced their metabolic rate and evaporative water at high temperatures.
These findings constitute a set of possible adaptations to a highly fluctuating Mediterranean environment, which is completely covered with snow for many months and then progresses rapidly to a very dry climate with high temperatures.
Wang, Z. Y., J. T. Wang, A. H. Ji, H. K. Li & Z. D. Dai. 2011. Movement behavior of a spider on a horizontal surface. Chinese Science Bulletin 56: 2748–2757. DOI: 10.1007/s11434-011-4584-y
Abstract. Studying the locomotive behavior of animals has the potential to inspire the design of the mechanism and gait patterns of robots (“bio-inspired robots”). The kinematics characteristics of a spider (Ornithoctonus [sic] huwena), including movement of the legs, movement of the center of mass (COM) and joint-rotation angle, were obtained from the observation of locomotion behaviors recorded by a three-dimensional locomotion observation system. Our results showed that one set of the stance phase consists of four legs, which were leg-1 and leg-3 on one side and leg-2 and leg-4 on the other side. Additionally, two sets of the stance phase comprised eight legs alternately supporting and driving the motion of the spider’s body. The spider primarily increased its movement velocity by increasing stride frequency. In comparison to other insects, the spider, O. [sic] huwena, has superior movement stability. The velocity and height of COM periodically fluctuated during movement, reaching a maximum during alternation of leg phase, and falling to a minimum in the steady stance phase. The small change in deflection angle of the hind-leg was effective in driving locomotion, whereas each joint-rotation angle of the fore-leg changed irregularly during locomotion. This research will help in the design of bio-inspired robots, including the selection of gait planning and its control.
Machkour-M’Rabet, S., Y. Hénaut, S. Calmé & L. Legal. 2011. When landscape modification is advantageous for protected species. The case of a synanthropic tarantula, Brachypelma vagans. Journal of Insect Conservation. Online publication date: 24-Aug-2011. DOI: 10.1007/s10841-011-9434-3
Abstract. Landscape fragmentation usually has a considerable effect on the genetic and demographic viability of most species because it reduces population size and increases isolation among populations. This situation provokes loss of genetic diversity and increased inbreeding that can lead to population or species extinctions. Some studies also show that landscape fragmentation may have no effect on or even positive consequences for species genetic diversity. The protected tarantula, Brachypelma vagans, exhibits a particular situation in the Mexican Caribbean, which has experienced high lowland and coastal fragmentation because of recent increases in agricultural, urban and touristic development. This modified landscape structure creates favorable conditions for establishment of B. vagans populations in rural settlements. Populations of this tarantula have high densities of individuals, principally females and juveniles, and gene dispersion is assumed by the rare males. Within this context, we studied the influence of natural and anthropogenic fragmentation on the genetic diversity of six B. vagans populations (five continental, one insular), together with their spatial organization. Our approach used seven inter simple sequence repeat markers, which are highly polymorphic markers. The 76 loci selected revealed high genetic variability for continental populations and a low, but not critical situation, for the insular population. We detected a good level of gene exchange among continental populations, and an evident and recent isolation of the island population. This species exhibits a metapopulation structure in the lowlands with numerous local populations where mature females exhibit high birth site fidelity. We conclude that this protected species does not exhibit characteristics to warrant its current conservation status, and we propose complete revision of the ecological and genetic situation for B. vagans in particular, and for all species within the genus Brachypelma in general.
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