Metabolic rates and movements of the male tarantula Aphonopelma anax during the mating season

Abstract

Tarantulas exhibit sexual dimorphism in their resting metabolic rate (RMR). The significantly higher RMRs observed in sexually mature males may be an adaptive strategy to support their higher energetic demands when searching for females. In this study, we investigated how intrasexual differences in male RMR may affect their locomotory activity and behavior during the mating season. Over a 2-year period, we radio-tagged male Texas tan tarantulas ( Aphonopelma anax (Chamberlin, 1940)), measured their movements, and periodically recorded their metabolic rates in an open-flow respirometery system over the course of the breeding season. Differences found in search speed, search-area size, and movement patterns were not sufficiently explained by the small amount of intrasexual variation exhibited in RMR. Individuals were capable of searching areas up to 29 ha and moved up to 365 m/day. In addition, metabolic rate measured over a 24 h period showed no circadian periodicity and remained constant over the season. Lastly, the body condition of new captures stayed constant throughout the season, corroborating observations of males feeding and drinking.

Consequences of sexual size dimorphism on energetics and locomotor performance ofGrammostola rosea(Araneae; Teraphosidae)

“…In the other ambulation experiments with G. rosea , no sexual differences are found in A t , in agreement with the results reported for other spiders (Stoltey & Shillington, ), whereas, despite the high variability, d is significantly longer in males than in females, revealing a high tracking efficiency. This means that smaller males may travel longer distances.…”

“…Janowski‐Bell & Horner () report that the Texas brown tarantula Aphonopelma hentzi may travel up to 95 m in 1 day, a result in contrast to that for G. rosea in 1 h of experimental trials. Stoltey & Shillington () report that males of A. anax (Texas tan tarantula) may travel 90–259 m in a day and do not find a relationship between M b and distance recorded by telemetry, which appears to be more consistent with the results for G. rosea . However, a negative M b relationship is found for G. rosea when the distance travelled by both males and females is included, which can be explained by the large body mass of females.…”

“…Sexual differences in behaviour and several life-history characteristics are also associated with sexual size dimorphism (Ghiselin, 1974;Vollrath & Parker, 1992;Elgar & Fahey, 1996;Hormiga et al, 1995Hormiga et al, , 2000. When spiders reach sexual maturity, the males locate the females and reproductive events occur (Shillington & Peterson, 2002;Stoltey & Shillington, 2009;Foelix, 2011). The energetic budget associated with these different sexual behaviours could be the origin of differences in traits such as metabolic rates and physiological performance (Shillington, 2005).…”

When landscape modification is advantageous for protected species. The case of a synanthropic tarantula, Brachypelma vagans

“…Like other burrowing tarantulas (Janowski-Bell and Horner 1999;Pérez-Miles et al 2005), males of the species are responsible for long-range gene dispersal, by walking large distances among female aggregations and crossing nonhabitat features such as roads (Shillington and Verrell 1997;Yáñez and Floater 2000;Pérez-Miles et al 2005). Although dispersal distances for B. vagans remain unknown, Stoltey and Shillington (2009) showed that males of Aphonopelma anax Chamberlin 1940 (Araneae, Theraphosidae) were capable of walking at a speed of 365 m/day, covering an area of up to 29 ha during the breeding season. In contrast, Janowski-Bell and Horner (1999) showed that A. hentzi Girard 1852 walks at a speed of 94.9 m/day.…”

Padrões bioenergéticos das aranhas de teia: considerações sobre a unidade e a diversidade do fenômeno

“…Os estudos de V O 2 Max em aranhas é ainda mais complicado do que com vertebrados (Anderson & Prestwich, 1985;Shillington & Peterson, 2002;Stoltey & Shillington, 2009). Além da dificuldade experimental, no caso das aranhas a V O 2 Max pode não possuir o significado biológico desejado devido ao possível compromisso entre locomoção e trocas gasosas necessárias à respiração (Wilson & Bullock, 1973).…”