Superstitionia donensis, Stahnke, 1940

Farley, Roger D., 2011, Pectine development in scorpion embryos and first and second instars, Euscorpius 120 (120), pp. 1-47 : 5

Superstitionia donensis ( Superstitioniidae )

The adults of this species are very small compared to the other scorpions of this investigation. The early stages of development were not examined, but a ventral view of a first instar is shown in Figure 14. This first instar of S. donensis looks much like the first instars of other species with apoikogenic development ( Farley, 2005, 2008). The coxapophyses of the first and second legs are slender, rounded structures that extend well forward to form the ventral wall of the preoral tube. After the first molt, the second instar coxapophyses are broad and flat ( Farley, 2005, 2008) as in the adult ( Farley, 1999). The genital operculum in Figure 14 is a distinct structure consisting of bilateral flaps. There is a sternum in the ventral prosoma, and the pedipalps are segmented and divided distally. The chelicerae are anterior to the mouth. Spiracles are usually prominent in first instar scorpions ( Farley, 2005, 2008). Their development may be delayed in this species since only one can be seen in opisthosomal segment 5, and/or possibly the magnification is not sufficient to show the spiracles.

Figure 14 shows that the pectines of this species are unusual in having only 6 teeth in each pectine. This is in comparison with 26 teeth per pectine in Figure 6 ( Smeringurus mesaensis ), 21 − 24 teeth for each pectine in Figure 7 ( Centruroides vittatus ), 14 − 17 teeth in Figure 13 ( Hadrurus arizonensis ), 17 teeth in Figure 23 ( Hadogenes paucidens ) and 14 teeth in Figure 32 ( Pandinus imperator ). Swoveland (1978) also noted six teeth per pectine for Superstitionia donensis in his comparison of pectine structure in ten adult scorpion species of North America. In that study, the tooth (dentes) number ranged from 6 to 38 per pectine.

Higher magnification of the region of the genital operculum (Fig. 15) shows that the gonopore (GP) is forming in the midline between the two flaps of the operculum. Just posterior to this in the basal plate (basal piece) of the pectines there is another small opening. This may be a transitory ancestral gonopore, labeled here as GP’. A similar structure was seen in advanced embryos of Centruroides vittatus ( Farley, 2005) .

A further indication of somewhat delayed development in this species is evident in Figure 16, the ventral surface of two pectinal teeth in a first instar. The peg sensilla are relatively few in number and at an early stage of development compared with sensory pegs on the pectinal teeth of embryos of Centruroides vittatus (Figs. 8, 9; Farley, 2005). Though somewhat delayed, the sequence of development of the peg sensilla in S. donensis is like that in C. vittatus and other scorpion species (Fig. 16; Swoveland, 1978; Farley, 2001c), i.e., a knob-like swelling in the ventral cuticle of the teeth and eventually a small pore in the center of the knob.