MATING BEHAVIOR OF GRAMMOSTOLA DOERINGI HOLMBERG 1881 (ARANEAE: THERAPHOSIDAE), A BUROWING SPECIES FROM ARGENTINA.

FERRETTI, N., S. COPPERI, G. POMPOZZI, F. PÉREZ-MILES

Alexandoupoli, Grecia

Congreso; 25th European Congress of Arachnology; 2009

Democritus University of Thrace Department of Molecula Biology and Genetics

The Theraphosidae are widely distributed in tropical and subtropical regions of the world, but their biology is poorly known. Due to theraphosid basal phylogenetic location among spiders, the studies of their biology can provide important perspective for evolutionary hypotheses. Studies on the mating behavior of this family have been limited to a few species, namely Acanthoscurria suina, Aphonopelma chalcodes, Brachypelma klassi, Catumiri uruguayense, Eupalaestrus weijenberghi, Grammostola mollicoma, Grammostola schulzei, Plesiopelma longisternale and Sickius longibulbi. A common pattern emerges from the available literature on theraphosids: male courtship includes body vibrations and palpal drumming, usually followed by clasping, hooking female´s fangs with the male tibial apophysis. Mating always occurs with the male located in front of the female, and raising the female´s body. In this position, the male is able to reach the genital opening with his palpal organs. Grammostola doeringi is a large and burrowing tarantula that lives in the suburbs of Bahía Blanca, Buenos Aires province, Argentina. This species make their burrows always in meadows and males can be seen seeking for females at late spring (October). Here we describe the mating behavior of Grammostola doeringi heretofore unknown in laboratory conditions based on 11 successful matings. Six males and eight females were collected by hand during October – November 2008 at the locality of Bahía Blanca (38º 42´ 2.77" S, 62º 16´ 9.21" W), Buenos Aires, Argentina. A total number of 30 encounters were carried out in rectangular cages of 30 x 35 and 30 high. The cages had a substrate of 10 cm and a burrow was excavated simulating natural conditions and allowing for observation of female´s behavior. All interactions were videotaped and analyze. All males initiated courtship when touched the female´s silk over the substrate. The courtship involved palpating as the first unit registered, that consisted in the two palps moving up and down in an alternating phase hitting the soil at constant velocity, quite different from palpal drumming where the bout started at low velocity and increased sequentially. Males made a mean number of 30.72 ± 29.74 SD, being highly variable with a range of 2 to 114 bouts per courtship and had a mean duration of 1.46 s ± 0.57 SD. He also made body vibrations caused by the contraction of the third pair of legs. The mean number of this unit per courtship was 15.66 ± 28.65 SD (range = 2 – 117) and the mean duration was 1.88 s ± 0.36 SD. The male sometimes beat the substrate with legs I, that consisted in elevating a leg, extended it and lowered rapidly over the soil. Males made a mean number of 24.57 ± 21.79 SD (range = 2 – 71) bouts. The courtship duration in minutes was 12.64 ± 15.76 SD (range = 1.89 – 56.3). Then, the male approached the female, touching her with the first pair of legs and beating spasmodically with legs II over the female´s body. In G. doeringi, when the female raised her body and opened fangs, then the male clasped onto her fangs using the tibial apophysis and legs III and IV were maintained over the substratum. After the contact, latency was observed, where the pair stayed motionless. Then, the male pushed the female to reach an angle of 80° approximately and began a series of palpal insertions on the female genital opening. The mean number of insertions was 11.45 ± 8.72 SD (range = 3 – 26). The mean duration of each insertion was 11.89 s ± 5.65 SD. Palpal insertions usually were difficult to see, but seemed to occur with many fail insertions, where the bulb tried to enter and undo. The mean duration of copulation in minutes was 5.65 ± 3.20 SD (range = 2.13 – 11.88). Afterwards the male unclasped beating spasmodically and moved away from the female. The mean number of spasmodicals beats during clasping and unclasping was 13.25 ± 9.54 SD per courtship. For several minutes, the female stayed totally immobile. Afterwards, she recovered and walked into the burrow. The mean duration in minutes of this immobile condition was 33.39 ± 14.36 SD (range = 6.96 – 48.52). The mating took place at the burrow entrance. Females accepted males by leaving the burrow because mating does not occur inside it. Moreover, males tried to take out females entering the burrows and courting inside. In conclusion, the mating behavior of G. doeringi was similar to the prevalent theraphosid pattern. Males of Grammostola doeringi made a large number of insertions as other species of theraphosids. The failed insertions were also observed in Grammostola mollicoma. The duration of copulation of G. doeringi was short even with fail insertions that consumed time, but that was related with shorter duration of each effective insertion.