Mesosoma

Fet, Victor, Soleglad, Michael E. & Kovařík, František, 2009, Etudes on iurids, II. Revision of genus Calchas Birula, 1899, with the description of two new species (Scorpiones: Iuridae), Euscorpius 82 (82), pp. 1-72 : 9-14

Mesosoma

The Calchas sternum ( Fig. 4 ) conforms to the type

2 sternum as defined by Soleglad & Fet (2003 a). This structure is wider than long with a well defined posterior emargination forming two convexed lateral lobes. The apex is not particularly deep or offset from the lobes. The sternum tapers anteriorly. The entire sternocoxal area of C. gruberi , sp. nov., is illustrated in Soleglad & Fet (2003 a: fig. 8; referred to as C. nordmanni ).

The genital operculum exhibits considerable sexual dimorphism in Calchas . In the female (all three species are illustrated in Fig. 35 ), the individual sclerites are much wider than long and are fused medially most of their length. In the male, each sclerite is subtriangular in shape, roughly as long or longer than wide, separated most of their length. In addition, in the male, well-developed genital papillae are visible between the two plates, but not extending posterior of the operculum. Fet & Soleglad (2008: character 10 (state=0)) hypothesized this genital papillae configuration symplesiomorphic for family Iuridae (i.e., same configuration found in Iurus ) where it also existed for outgroup Chaerilus (parvorder Chaerilida ).

Unique to genus Calchas is a considerably well-developed prepectinal plate always found only in the females of all ages ( Figs. 5 , 35 ). This plate, situated between the genital operculum and the pectinal basal piece, is fully sclerotized and is as wide as or wider than an individual operculum sclerite. In species C. nordmanni and C. birulai , sp. nov., the prepectinal plate is somewhat swollen medially, making its length almost equal to that of the genital operculum. In species C. gruberi , sp. nov., this plate is a little less swollen medially, thus having a more slender appearance though still quite well developed. The prepectinal plate is not found in the male.

This structure was first identified by Birula (1911: 176) and can be clearly seen on the illustrations of C. nordmanni by Birula (1911, fig. 3; 1917a, fig. 12B; 1917b, Pl. II, fig. 2). It seems that after Birula, the prepectinal plate in Calchas has never been mentioned— although at least the Birula (1911) paper published in German was immediately accessible to the European scientists, and it clearly described this “…am Hinterrande der Genitalöffnung liegenden Querwulste; ein solcher Querwulst fehlt bei den anderen mir bekannten Skorpionen. [a transverse thickening at the posterior end of the genital opening; such a transverse thickening is absent in all scorpions known to me].” The English translations ( Birula, 1917a, 1917b), which appeared in the 1960s, describe this structure clearly: “an elliptical transverse thickening which is wanting in males…the transverse crest at the posterior end of the genital aperture is very well developed in females of any age” ( Birula, 1917b: 152–153, transl. B. Munitz, 1965) and “elliptic transverse thickening present in female i.e. immediately behind genital aperture; same thickening absent in male. …Transverse ridge behind genital aperture clearly developed in female… the abovementioned difference in structure of the genital area helps in distinguishing the sex of very small specimens of Calchas ” ( Birula, 1917a: 147–178, transl. J. Salkind, 1964). In the original Russian text, Birula also used nonspecific terms “utolshchenie [thickening]” or “valik” [ridge], clearly having no established terminology for this unique structure.

The modern term “prepectinal plate” originates from Kjellesvig-Waering (1986) who claimed its existence in some fossil and extant scorpions between the operculum (segment X) and the pectinal plate (segment XI). Existence of such a structure in fossil scorpions still has to be confirmed (J. Dunlop, pers. comm., 2008). This issue is important for general scorpion morphology since only seven mesosomal segments are currently accepted in scorpions, but Kjellesvig-Waering (1986) suggested that the prepectinal plate could indicate that the fundamental scorpion mesosoma should be considered as having eight segments; he also indicated existence of prepectinal plate in some males, but not females ( Calchas has a reverse situation) of the extant New World Buthidae . Sissom (1990: 148) and Farley (1999: 125; 2001: 20, 25) reviewed this structure based on Kjellesvig-Waering (1986) but did not mention Calchas . We use this term, keeping in mind that it is unclear whether the structure discussed by Kjellesvig-Waering (1986) is homologous to the prepectinal plate found in Calchas . The function of the prepectinal plate is not known.

The pectines in Calchas are fully developed, exhibiting all major substructures common to most scorpions ( Figs. 4 , 6 ). Three anterior lamellae are present, the most basal significantly longer than the middle and distal lamellae. Middle lamellae are present but only extend below the basal anterior lamellae, the area below the middle and distal lamellae is occupied by these lamellae. The number of middle lamellae ranges from two to six (the largest number of six found in a male C. gruberi , sp. nov., from the Greek island of Samos). Well-developed fulcra are present between the inner bases of pectinal teeth. The pectinal teeth are well-developed in Calchas , exhibiting well-defined sensorial areas on their inner distal edges. The sensorial areas are densely populated with peg sensilla, which are shaped as uniform elongated cylinders (see close-up in Fig. 6 ). The pectinal basal piece is well-developed in Calchas , longer than the genital operculum in the female. Anterior edge exhibits a somewhat wide deep indentation.

Birula (1917a) says the following for the sternopectinal area in C. nordmanni :

“…sternum with a deep groove, running from the posterior margin to its middle and divided into three parts by shallower grooves … the sternum is pentagonal, anteriorly noticeably narrowed … the genital opercula of the male have the shape of a triangle with unequal sides … the genital opercula of the female are very narrow and have the shape of transverse, elongate-oval … in addition, there is a convex elliptical crest behind the genital pore of the female …”.

In the species-level descriptions of C. birulai , sp. nov., and C. gruberi , sp. nov., we illustrate the sternopectinal area of both genders ( Figs. 47, 52 and Figs. 64, 70 ).

The lung stigmata (spiracles) in Calchas are somewhat small, suboval in shape ( Fig. 7 ). They are angled roughly 45º toward anterointernal direction. The fine structure of the posterior spiracle margin ( Kamenz et al., 2005) can be seen in Fig. 7 .

Figures

Figure 4: Sternopectinal area of Calchas birulai, sp. nov., female, Nemrut Dağı, Turkey, showing sternum, genital operculum, prepectinal plate, basal piece, and pectines.

Figure 5: Prepectinal plate in Calchas. Top. Close-up of prepectinal plate of Calchas birulai, sp. nov., female, Nemrut Dağı, Turkey. Bottom. Detached prepectinal plate of C. gruberi, sp. nov., female, Antalya, Turkey, and close-up showing surface of the plate.

Figure 6: Pecten of Calchas gruberi, sp. nov., female, Antalya, Turkey, showing close-up of peg sensilla.

Figure 7: Fourth left lung stigma in Calchas gruberi, sp. nov., female, Antalya, Turkey.

Figure 35: Sternopectinal area in Calchas species showing the genital operculum, prepectinal plate (in female), and genital papillae (in male). Note, in the male, the large long subtriangular shaped genital operculum with separated sclerites exposing significant genital papillae, as compared to the female, we see a narrow operculum with fused sclerites. Top-Left. C. nordmanni, female, Tortum, Turkey. Top-Right. C. birulai, sp. nov., female, Mardin, Turkey. Bottom-Left. C. gruberi, sp. nov., female, 12 km S. Akseki, Turkey. Bottom-Right. C. nordmanni, male, Turkey.

Figures 44–53: Calchas birulai, sp. nov. 44–50. Male holotype (NMW), Mardin, Turkey. 44. Carapace showing close-up of lateral eyes. 45. Leg IV (left, ventral view), showing the tibial spur. 46. Stigma IV. 47. Sternum, genital operculum, and pectines. 48. Chelal fixed and movable finger dentition. 49. Telson and metasomal segments IV–V, lateral view. 50. Metasomal segment V and telson, ventral view. 51–52. Female paratype (NMW), Mardin, Turkey. 51. Telson, ventral view. 52. Sternum, genital operculum, prepectinal plate, and pectines. 53. Female paratype (HNHM), Kavurma Köyü, Diyarbakır Province, Turkey. Chelicerae, ventral and dorsal views.

Figures 61–70: Calchas gruberi, sp. nov. 61–67. Female holotype (NMW), Mamure Kalesi, Anamur, Turkey. 61. Carapace showing close-up of lateral eyes. 62. Leg IV (left, ventral view), showing the tibial spur. 63. Stigma III. 64. Sternum, genital operculum, prepectinal plate, and pectines. 65. Chelal fixed and movable finger dentition. 66. Telson and metasomal segments IV–V, lateral view. 67. Metasomal segment V and telson, ventral view. 68–70. Male paratype (NMW), Anamur, Turkey. 68. Telson, ventral view. 69. Chelicerae, vental and dorsal views. 70. Sternum, genital operculum, and pectines (note lack of prepectinal plate conspicuous in female).