30.11.2021

Theraphosinae sp. "Cusco" is a Thrixopelma species!

After we could clarify the species affiliation of the tarantula Species, which is called Theraphosinae sp. "Piura" in the community, as Thrixopelma pruriens, the question was obvious, which genus or species it would be then with that tarantula species, which is called Theraphosinae sp. "Cusco" in the community. Fortunately, there is a preserved adult male of this Species in our collection. Also, we have a few images of the spermatheca of this Species in our archives.

Examination of the male showed two differently sized tibial apophyses (Pic 2: Retrolateral Branch = RB & Prolateral Branch = PB) each with an internal spine (Pic. 1, 2, 3). -> Clear agreement to the structure of the tibia apophyses in Thrixopelma as seen in the recent work of Sherwood (Sherwood et al. 2021) on this genus.

Furthermore, the structure of the bulb is interesting. Theraphosinae sp. "Cusco" also shows a distinct and elongated "Prolateral inferior keel" (PI) with two distinct "crests" as well as a distinct "Tegular heel" (TH) (Pic 4 & 5). -> Completely typical and a generic feature of the genus Thrixopelma!

The spermathecae of the females show the very strongly sclerotized two receptacula typical for Thrixopelma which are clearly rounded at the tip (Pic 8 ).

Thus, there is no doubt that Theraphosinae sp. "Cusco" is also a Thrixopelma!

Due to the clear agreement in the spermathecae shape, as well as the high structural agreement in the shape of the bulb, this form should belong to the very close relationship of Thrixopelma pruriens Schmidt, 1998. However, it shows a more distinct PI whose "crests" are also much more distinct than in T. pruriens (compare Pic 4 & 5 with Pic 6).

In contrast, the spermathecal shape of Theraphosinae sp. "Cusco" (Pic 8 ) is almost identical - within the range of variation - to Thrixopelma pruriens (Pic 7). Also, the claws on tarsus IV of Theraphosinae sp. "Cusco" (Pic 9) are similarly strongly dentate as in Thr. pruriens (Pic 10).

Resumé:

Based on the clear correspondence of the generic characters to Thrixopelma, we are certain that the tarantula Species referred to in the community as Theraphosinae sp. "Cusco" is a representative of the genus Thrixopelma, obviously very closely related to Thrixopelma pruriens. Whether it is really a Thrixopelma pruriens Schmidt, 1998, further investigations e.g. of the DNA sequences and/or further useful taxonomic characteristics must show. For the time being, we plead for this form to be listed as THRIXOPELMA sp. "Cusco" in the future.

Reference:

Sherwood, D., Gabriel, R., Kaderka, R., Lucas, S. M. & Brescovit, A. D. (2021). Stabilizing a chaotic taxonomy: redescription and redefinition of the genera Lasiodorides Schmidt & Bischoff, 1997 and Thrixopelma Schmidt, 1994 (Araneae: Theraphosidae). Arachnology 18(8): 893-917.