31.12.2022

Davus sp. "Oaxaca" probably does not always originate from this Mexican state!

During one of our last visits to Oly Lenskes and Michael Heylen in Belgium, a dead adult male of a Davus species from Mexico preserved in alcohol was given to us for identification (Pic 1). The two had received the animal under the name Davus sp. "Oaxaca" from their supplier. The tarantula genus Davus has its range in Central America from Mexico down to Panama. They are mostly very nicely colored tarantula species, which have a striking pattern on the opisthosoma. The representatives of this genus from Mexico have been studied both genetically and morphologically in a detailed paper by Candia-Ramírez & Francke (2021). The specimens of this genus imported from Mexico over the years were mostly brought into the hobby as Davus pentaloris. However, Candia-Ramírez & Francke were able to show in their work that the numerous specimens they examined and analyzed from different areas of Mexico alone contain 13 morphospecies and, depending on the DNA analysis method used, even up to 16 different genetic species. Based on the combination of all genetic analyses and the available morphological data, they were able to discover 13 clearly definable species, 12 of which are new to science. Unfortunately, these 12 new Davus species have not yet been taxonomically described and given valid species names. Thus, for the determination of the male we followed the names of the analyzed species in the mentioned paper. These were given there in each case with abbreviations of the localities of the examined spiders.

If you compare the structure of the bulbs and keels prolateral (Pic 2) and retrolateral (Pic 3) of the present male as well as the structure of the tibia apophyses (Pic 4) with the same structures of the shown males on the pages 90 and 91 of Candia-Ramírez & Francke, it is easy to see that the examined male is most likely a male of the form from Tapachula (TAP), near the border to Guatemala, or a Davus pentaloris (DPE) from Guatemala, but in no case a male of the forms/species coming from the state of Oaxaca. Especially the resemblance of the present male compared to TAP and DPE in the shape of the bulb and the keeling on the embolus retrolaterally (Pic 5) and prolaterally (Pic 6), as well as the same structure of the tibial apophysis with these two forms (Pic 7) allows this conclusion. By the way, we are following the labeling of the keels in the work of Rogerio Bertani, who first homologized the different keels on the bulbs of the males in 2000 and gave them appropriate and nowadays universally accepted names (Bertani 2000). Comparing the male from Tapachula (TAP) and the male that Candia-Ramírez & Francke assign to Davus pentaloris sensu stricto (DPE), it is obvious that their genital morphological characters are highly similar structured. Also, both forms form a sister group relationship in the consensus tree of morphological and DNA data on p. 94 & 95 (Pic "map") whose localities are also quite close to each other, indicating the very close relationship or even conspecificity of both forms. This also results from the small genetic distance of only 5.2% difference in the 963bp of the CO1 sequence studied by the authors in their 2021 paper.

Besides, the photos on the bulb of D. pentaloris in Candia-Ramírez & Francke were taken from the work of Gabriel (2016) and flipped to ensure a comparative view. Unfortunately, the bulb of D. pentaloris (DPE) in prolateral view (Pic 6) does not correspond to the same angle as the other bulbs in prolateral position in the work of Candia-Ramírez & Francke, so one might have the impression that the bulb of DPE would be significantly different from TAP. However, if one imagines the bulb of D. pentaloris tilted slightly more anteriorly, it should be in high agreement with the prolateral bulb of TAP. High agreement with TAP and DPE, as mentioned, also applies to the bulb of the present male, which is virtually identical to the keels shown in Candia-Ramírez & Francke for TAP and DPE in terms of its structure, as well as the length, shape, and position of the posterior superior keel (PS), prolateral accessory keel (PAC), anterior keel (A), posterior inferior keel (PI), and retrolateral keel (R).

Resumè:

The adult male, named as Davus sp. "Oaxaca", which died shortly after its mature molt and was given to us for taxonomic study, could be classified to Davus pentaloris or to the Davus form that occurs around the Mexican locality of Tapachula, based on its bulb- and embolus structure, as well as the similarity in the structure of its keels and in the structure of the tibial apophysis. In no case, however, it has similarities to the Davus forms which occur in Oaxaca (see Pic "Map"). Whether Davus pentaloris (DPE) can be separated from the Davus form from Tapachula (TAP) in any way is at least more than questionable due to the high similarity of the male genitalia of both forms, the fact that they form a sister group relationship in the analyses of Candia-Ramírez & Francke, the high level of genetic similarity and their localities are geographically quite close to each other. For these reasons we think it would not be wrong to call this male Davus cf pantaloris (Simon, 1888). In any case, as a customer one should obviously be at least critical with the naming of tarantulas by the exporters! Whether all Davus sp. "Oaxaca" in the community do not originate from this Mexican state can not be generalized by our analysis of just this single male with this name which was examined by us. For this it is necessary to examine further Davus specimens using this name in the community!

Reference:

Bertani, R. (2000). Male palpal bulbs and homologous features in Theraphosinae (Araneae, Theraphosidae). Journal of Arachnology 28: 29-42.

Candia-Ramírez, D. T. & Francke, O. F. (2021). Another stripe on the tiger makes no difference? Unexpected diversity in the widespread tiger tarantula Davus pentaloris (Araneae: Theraphosidae: Theraphosinae). Zoological Journal of the Linnean Society 192(1): 75-104

Gabriel, R. (2016). Revised taxonomic placement of the species in the Central American genera Davus O. Pickard-Cambridge, 1892, Metriopelma Becker, 1878, and Schizopelma F. O. Pickard-Cambridge, 1897, with comments on species in related genera (Araneae: Theraphosidae). Arachnology 17(2): 61-92.