Wunderlich (2011) described Nemesia rastellata from a male specimen in the collection of the Senckenberg Museum in Frankfurt am Main. The specimen was collected by R. Kinzelbach in September 1963 on the Greek island of Karpathos. Wunderlich (2011) noted that the type specimen was in rather poor condition by stating that “the opisthosoma of the spider and the right pedipalpus have been separated, the opisthosoma is deformed” (sic). The female of the species was, and still is, unknown. At the time of Wunderlich's description, part of the mygalomorph spider collection was loaned out to the author of the present article and thus absent from the Senckenberg Museum collection. A request from the Senckenberg curator to return the loan in May 2022 triggered renewed attention for the contents of this loan collection and the discovery of three vials (four specimens) that were apparently incorrectly labelled as containing specimens identified as members of the family Atypidae. In fact, these vials appeared to contain four males of N. rastellata (fam. Nemesiidae). Moreover, the vial-labels indicated that these specimens, like Wunderlich's holotype, were collected on Karpathos by R. Kinzelbach. As these four specimens were absent from the Senckenberg collection at the time of Wunderlich's description of N. rastellata (2011), they are likely to have been collected together with the type specimen.

The four retrieved male specimens are here described, providing additional information for taxonomic recognition of the species and a first insight into intraspecific morphological variation in N. rastellata.

Material and methods

The sample consisted of four specimens in three separate vials. Two vials contained single specimens, the third vial contained two specimens (see paragraph ‘Studied material’ below). All specimens were studied with the aid of a Huvitz HSZ-645TR stereomicroscope equipped with a Lusis HC-20CU camera operating on Panasis software and an Euromex iScoop compact microscope equipped with a Euromex VC-3031camera. Both systems allow multiple focus photography and precision measurement. Figures were prepared with Adobe Photoshop elements 2022 and Helicon Focus 7. Terminology used and measuring methods follow Cassar et al. (2022). Measurements are given in millimetres. Size measurements (see below) are given as minimal–maximal values found across the sample of four specimens. Ratios (see below) provide an impression of the shape and relative size of different body parts. Ratios are also given as minimal–maximal ranges.

Terminology. The following terminology pertaining to male Nemesia morphology is used: 1) Clasper-hook (CH), this is the single strong, rigid, curved and sharp-pointed “hook” or “spur” placed on a prominent apophysis in a ventro-distal, prolateral position of tibia I (Fig. 2d-e). 2) Palp-tibia rake (PTR), this is a transverse row of particularly strong, distally directed spines along the dorso-distal margin of the palp-tibia. In some Nemesia species, or species groups, the one or more similar strong spines are present just proximal of the apical row (Fig. 2f). 3) Striae are fine, longitudinal ribs on the embolus found in most Nemesia species that occur in the eastern Mediterranean Region (Decae 2012).

Abbreviations. AME: anterior median eye(s), AR: width anterior eye-row; BuL: length bulb; CL: carapace length; CH: clasper-hook; CW: carapace width; diaALE: diameter anterior lateral eyes; diaAME: diameter anterior median eyes; diaPLE: diameter posterior lateral eyes; disAME: distance between anterior median eyes; EL: length eye-group; EmL: length embolus; Fem4: length femur IV; L1: length leg I; L1TiL: length tibia I; L1TiW: width tibia I; L2: length leg II; L3: length leg III; L4: length leg IV; LL: length labium, LW: width labium; Met4: length metatarsus IV; PL: length palp; PR: width posterior eye-row; PTR: apical rake on dorsal palp tibia; PTiL: length palp tibia; PTiW: with palp tibia; sd: standard deviation; SL: length sternum; SW: width sternum; T1–T4: respective lengths of tibiae I, II, III, IV; TBL: total body length; Tib4: length tibia IV.

Taxonomy

Fig. 1.

Nemesia rastellata male, general somatic characters. a. SMF18e, general appearance; b. SMF11e, lateral carapace, note flat cephalic part and prominent ocular process (cf. Wunderlich 2011: fig. 25); c. SMF21e1, dorsal prosoma, note anterior narrowing carapace and fovea with prominent central groove (cg) (cf. Wunderlich's (2011) median notch on fig. 24); d. SMF11e, eye-group, note large anterior eyes and black pigmented ring around AME (br); e. SMF18e, ventral chelicerae ventro-lateral view, note rastellum (ra) and smooth fang-ridge (sr); f. SMF11e prolateral tibia and patella III, note three spines in line (ps) on the patella, other specimen have either two or three spines in this row; g. SMF11e, spinnerets, note knob-shape of PMS. Scale bars = a. 2.0 mm, b, c, f. 1.0 mm, d, e, g. 0.5 mm

Discussion

Wunderlich named the species after three prominent ‘rastella’ (rows or groups of particularly strong spines) that he found to be present: 1) on the distal chelicerae, just above the base of the fang (Fig. 1e), 2) on the dorso-distal palp-tibia (Fig. 2f) and 3) on the cymbium (Fig. 2f). It should be noted that Wunderlich’s three ‘rastella’ are a general feature of Nemesia males (at genus level), and therefore have no practical value in the diagnostics of Nemesia species. Furthermore it is customary that only the group of strong and ridged spines at the apex of the basal segment of the chelicerae (Fig. 1e) is referred to as the rastellum (e.g. Main 1967: 9, Ubick et al. 2005: 270, Jocqué & Dippenaar-Schoeman 2006: 24, Foelix 2011: 336). The cheliceral rastellum, that is functional in burrow construction, is a common feature in fossorial mygalomorph spiders of various genera and families. Personal observations indicate that the rastellum is not used for digging-up soil, but rather for compressing soil in the burrow walls and entrance region during burrow construction, and in shaping (molding) the trapdoor. Compressing the soil in the burrow wall and entrance results, probably in combination with a cementing secretion from the mouth (personal observation), in the formation of a sturdy plastered clay lining of the burrow shaft (Nascimento et al. 2021). Burrow construction is exclusively preformed by juvenile and female spiders, which leaves the functionality of the male rastellum an open question. In contrast to the cheliceral rastellum present in juveniles, females and males, rastella on the palp tibia and cymbium described by Wunderlich are exclusively present in adult males. These structures, together with the CH and modified metatarsus I (Fig. 2d-e) are apparently parts of the male defensive equipment which is functional in sexual encounters (personal observation).

Fig. 2.

Nemesia rastellata male, sex related characters. a-b. Right-side copulatory organs of two different specimens viewed under different rotation angles; a. SMF11e, note longitudinal ribs (striae) on the embolus (st); b. SMF18e, note the blunted embolus tip (bt) with apical pore (cf. Wunderlich 2011: fig. 31); c. SMF.21e1, general palp morphology, note relatively simple pyriform bulbs with short, distally pointed emboli (cf. Decae 2012: fig. 1); d. SMF11e, left distal leg I retrolateral view, note short apophysis clasper-hook (sa) (contra Wunderlich 2011: fig. 27); e. clasper-hook (CH) in ventral view, note weakly sigmoid shape (sh); f. distal palp in dorsal view, note the four strong spines of the PTR and spine-group on the cymbium (cs) (cf. Wunderlich 2011: fig. 29). Scale bars = a, b. 0.2 mm, c, e, f. 0.5 mm, d. 0.5 mm.

The clasper-hook (Fig. 2d-e) is functional in locking the female fangs during copulation. The terminology here used is function-oriented and preferred over ‘megaspine’, the purely structural description of this structure proposed by Raven (1980). The CH is present in all Nemesia and Iberesia males and is a main diagnostic character to distinguish these two nemesiid genera from two other Mediterranean nemesiid genera: Brachythele (forked CH) and Amblyocarenum (CH absent).

The dark eye-ring around the AME (Fig. 1d), here proposed as a possibly species level diagnostic character, might be an artefact of preservation in which the cuticle of the carapace has become slightly loose from the deeper lying prosoma.