22.09.2023
A Grammostola that turned out to be Euathlus
Recently Volker v. Wirth visited the well known Belgian tarantula breeder Samuel Spreuwers. During this visit Samuel handed over some exuviae of which he did not know which species they were, with the request to identify them. The very first exuvia, named "Grammostola sp.", turned out to be something completely different from a Grammostola species and shows once more how many tarantulas in the tarantula community have a wrong name.
Species of the genus Grammostola show typical stridulatory setae on the prolateral coxae I and retrolateral coxa of Palp. Females also have a typical spermathecae consisting of two receptacula seminis with a rounded apex. How these structures look like can be seen very well in an ARTICLE on our website.
The present exuvia of the spider, which Samuel Spreuwers said he had received from another tarantula keeper under the term "Grammostola grossa", shows none of these characters. On the palpcoxa retrolateral the stridulations setae (Pic 1) are missing as well as on the coxa I prolateral (Pic 2). Furthermore, although the spermatheca consists of two separate receptacula seminis (Pic 3), these are structured completely differently than in Grammostola. So it cannot be a Grammostola species. But, what is it then?
Because of the shape of the spermathecae we immediately suspected that it must be a species from the Euathlus-Phrixotrichus complex, because only they have this shape of the spermathecae with two Receptacula seminis with a lateral spheroid chamber, which we found when examining the exuviae (Pic 3). Furthermore, the spiders from these two genera do not possess a stridulatory organ on the palpcoxa and coxa I, as is typical for Grammostola. Euathlus shares with Phrixotrichus the very similar shape of the spermatheca, but differs from Phrixotrichus in having a much longer sternum compared to its width and in having spines on the palptibia and femur prolaterally, where Phrixotrichus has no spines. In addition, Phrixotrichus possesses two patches of urticating hairs on the opisthosoma, one on the right and one on the left, while Euathlus possesses only one patch of urticating hairs, dorsally on the opisthosoma.
Examination of the present exuvia of a putative Grammostola sp. shows, as mentioned, no stridulating setae on coxa I prolaterally (Pic 2) and palpcoxa retrolaterally (Pic 1), which would be typical for Grammostola. Furthermore, the exuvium has a significantly longer sternum compared to its width (Pic 4). There are also numerous spines on the palptibia and palpfemur prolaterally (Pic 5, green circles). Both last mentioned characters speak clearly for a Euathlus. Unfortunately, the opisthosoma of the exuvium could not be reconstructed completely, so that we cannot say whether there are one or two patches of urticating hairs. However, based on the described combination of features, it can be assumed that only one patch will be present dorsally on the opisthosoma.
Resumé:
The exuvium of a spider of Samuel Spreuwers from Belgium, which was named "Grammostola sp." and which he said he had acquired from a tarantula keeper as "Grammostola grossa", could indeed be identified as Euathlus sp. on the basis of the above feature combination. The shape of the spermatheca could suggest a relationship to Euathlus atacama Perafán & Pérez-Miles, 2014 . Once again this example shows how often our tarantulas are given wrong species names and that a correct identification is only possible on the basis of a detailed exact taxonomic examination of an exuvia of an adult female or on the basis of adult, dead preserved tarantulas.
References:
Pic 1.jpgPic 2.jpgPic 3.jpgPic 4.jpgPic 5.jpg