19.09.2021

Grammostola anthracina (C. L. Koch, 1842) 

Recently we received some exuviae from Justine Ruf (Pic 7). She always posts rare tarantulas on her Facebook site "Arachnoaddict" and so we felt the need to examine these partly rare species and to find out if they are really these rare species or to get to know the characteristics of these species. So the first species was the exuvia of a Grammostola anthracina. Unfortunately, the animal was missing the carapace, so we could not examine its dimensions. The holotype of this species is in the ZMB, but was not borrowed for this study, as there are two recent publications by Fukushima et al. & Montes de Oca et al. on this species (see references). The comparison of the present exuvia with these publications and descriptions of the holotype showed some similarities but also differences.

- The basic shape of the spermathecae is the same, but the base of the two receptacles is much broader in the present exuviae (Pic 1) compared to the holotype (Pic 1 a)

- The stridulatory organ (arrows) on the coxae of leg I prolaterally (Pic 3) looks very similar to that of the holotype (Pic 3 a). The complementary on the coxa of the palpi retrolateral to the holotype is unfortunately not shown in either publication and therefore cannot be compared with that of the exuvium (Pic 2, circle).

- The distribution of the scopula on the metatarsi I - III covers half of the leg limb in the holotype. This is different in the exuvia. There it covers even about 3/4 of the leg limb (Pic 4).

- The labium of the holotype contains about 120 cuspules, in the exuvia it is 172, which is much more (Pic 5, green dots).

- The holotype has the urticating hair types III and IV, as it is also the case with the exuvia (Pic 6).

Resumé:

Due to the ultimately sparse redescription of the holotype by Fukushima et al., owed to the fragile condition of the holotype of Grammostola anthracina, and the resulting lack of comparability of ALL features in question, as well as the deviation of some features compared to the type, we consider the animal and its exuvia to be at least closely related to Grammostola anthracina, because there are features which agree (stridulation organ, urticating hairs, leg length ratio: exuvia I: 52; IV: 55) as well as those which are clearly different (fine structure of the spermatheca, scopulation of the metatarsi, number of labial cuspules). We therefore suggest for calling the animal Grammostola cf anthracina for the time being. 

References:

Fukushima, C. S., Pérez-Miles, F. & Bertani, R. (2011). On the Avicularia (Araneae: Theraphosidae: Aviculariinae) species from Uruguay. Journal of Arachnology 39: 528-532.

Montes de Oca, L., D'Elía, G. & Pérez-Miles, F. (2016). An integrative approach for species delimitation in the spider genus Grammostola (Theraphosidae, Mygalomorphae). Zoologica Scripta 45(3): 322-333.