Arachnologische Mitteilungen 58

Arachnologische Mitteilungen / Arachnology Letters 58: 1-3 Karlsruhe, September 2019 The spider genus Porrhomma Simon, 1884 is one of the most unpopular among arachnologists, because of the difficulty of species identification. Differentiating species represents a problem, particularly among females with similar genitalia. Usually, dorsal and ventral views of the vulva are provided (Thaler 1991); this is, however, insufficient in some cases. Růžička (2018) added lateral and caudal views to understand the spatial structure of the copulatory ducts and spermathe- cae in Porrhomma . To comprehend the complicated structure of copulatory ducts in Hahnia C. L. Koch, 1841, Kovblyuk et al. (2017) used a schematic illustration of the copulatory ducts consisting of one line, which followed the spatial course of the ducts. We were inspired by Qing et al. (2015), who recommended 3D models and 3D prints to visualize impor- tant morphological characters in nematodes. Here, we (1) re- commend the use of 3D models to describe and distinguish female genitalia in spiders and (2) document the advantage of 3D models in distinguishing two pairs of similar species belonging to the genus Porrhomma . Material and methods Specimen preparation and study Spiders were examined with an Olympus SZX-12 stereomi- croscope in 80 % ethanol. The vulva was separated from the opisthosoma using a scalpel and passed through 40 %, 20 % ethanol and distilled water to 10 % sodium hydroxide, which digests soft structures at room temperature. Subsequently, it was coloured in an ethanol solution of chlorazol black (for details see Růžička 2018). Further details were studied with an Olympus BX-40 compound microscope, and photographs were taken with an Olympus C-5060 wide zoom digital camera mounted on the microscope. The photos were montaged using CombineZP image stacking software.The photo was used as a background layer in the Inkscape Vector Drawing Program, the line dra- wing was prepared and the printed image was detailed by hand. A 3D model was created in Blender 3D, based on the combination of photos and line drawings. Spermathecae are brown, copulatory ducts are blue (cf. Figs 1 and 2 with Fig. 4 in Růžička 2018). The final model can be rotated and obser- ved in the program from any angle. Female genitalia The female genitalia usually consist of sclerotized plates, co- pulatory ducts, spermathecae and fertilisation ducts. In Porr­ homma , copulatory ducts start with a copulatory opening in the aperture. Behind a side loop, they continue by an ascen- ding (in ventral view) part above the aperture wall to the me- dian plane, closely under the integument. The spermatheca is formed at the end of the copulatory duct. It consists of a broader main sack with a slender appendix. Results Porrhomma egeria Simon, 1884 versus Porrhomma campbelli F. O. Pickard-Cambridge, 1894 In these two species, the spermathecae are formed immedi- ately behind the side loop under the ventral body wall, star- ting at the midway of the ascending part of the copulatory ducts. Appendices of P. egeria are oriented usually to the side (see Fig. 633.3 in Thaler 1991), appendices of P. campbelli are oriented usually to the median line (see Fig. 634.3 in Thaler 1991), but not in all cases; cf. Figs 8a and 9a inThaler (1968). The main sacks of these two species are hardly distinguishable in ventral and dorsal views (Figs 1c, d; cf. also Figs 8a, b and 9a, b in Thaler 1968, and Figs 21D, F and 15D, F in Růžička 2018). The principal difference between the form of the main sacks of these two species is visible in caudal view. In P. egeria , the main sacks end at the base of the appendices and the axes of their end part are convergent; i.e. they are directed towards the centre of the opisthosoma (Fig. 1a). In P. campbelli , the main sacks reach deeper inside the opisthosoma, they are cur- Three-dimensional modelling in arachnology as exemplified using Porrhomma -species (Araneae: Linyphiidae) Vlastimil Růžička & Adam Růžička doi: 10.30963/aramit5801 Abstract. Three-dimensional modelling has shown its importance in many fields, including zoological systematics. It is difficult to dis- tinguish females of Porrhomma egeria Simon, 1884 and P. campbelli F. O. Pickard-Cambridge, 1894 according to only dorsal and ventral views of the vulva. The same is true for the pair P. microps (Roewer, 1931) and P. profundum Dahl, 1939. A caudal view is necessary to distinguish the vulvae of these species pairs. A 3Dmodel combines all important views of the female genitalia (ventral, dorsal, lateral and caudal) into a single unit. Keywords: 3D modelling, female genitalia, Porrhomma egeria, Porrhomma campbelli, Porrhomma microps, Porrhomma profundum, spiders Zusammenfassung. Dreidimensionale Modelle in der Arachnologie am Beispiel von Porrhomma -Arten (Araneae: Linyphiidae). Dreidimensionale Modelle haben in vielen Bereichen eine Bedeutung, einschließlich der zoologischen Systematik. Die Weibchen von Porrhomma egeria Simon, 1884 und P. campbelli F. O. Pickard-Cambridge, 1894 sind lediglich nach der dorsalen und ventralen Ansicht der Vulva schwierig zu unterscheiden. Gleiches gilt für das Artenpaar P. microps (Roewer, 1931) und P. profundum Dahl, 1939. Die caudale Ansicht ist zur Unterscheidung der Vulven dieser Artenpaare notwendig. Ein 3D-Modell vereint alle wichtigen Ansichten des weiblichen Genitals (ventral, dorsal, lateral und caudal). This contribution was presented at the 31st European Congress of Arachnology, Vác, Hungary, 2018 July 8–13 Vlastimil RŮŽIČKA, Czech Academy of Sciences, Biology Centre, Institute of Ento- mology, Branišovská 31, CZ-370 05 České Budějovice, Czech Republic; E-Mail: vruz@ entu.cas.cz Adam RŮŽIČKA, Mánesova 21, CZ-370 05 České Budějovice, Czech Republic; E-Mail: ruzicka.adam@email.cz submitted 12.11.2018, accepted 20.2.2019, online 18.6.2019