Akrav israchanani Levy, 2007

Fet, Victor, Soleglad, Michael E. & Zonstein, Sergei L., 2011, The genus Akrav Levy, 2007 (Scorpiones: Akravidae) revisited, Euscorpius 2011 (134), pp. 1-49 : 1-49

Akrav israchanani Levy, 2007

Akrav israchanani Levy, 2007: 92–95 , figs. 1–17.

Type series: Holotype: Israel, Ayyalon Cave , April 2006, leg. Israel Na’aman, HUJ Sc. 2673 (labeled “ Holotype ”); six paratypes (same data as for holotype); three paratypes labeled “ Paratype ” (Sc. 2674, Sc. 2675, Sc. 2676); three specimens not labeled as paratypes in HUJ collection but listed as such in Levy (2007: 92) (Sc. 2677, Sc. 2678, Sc. 2679), which therefore are paratypes as published. Gender of these and other specimens cannot be determined confidently.

Additional material (not type series): 13 specimens: three lots (Sc. 2681, Sc. 2683 and Sc. 2684) contain one specimen each; lots Sc. 2680 and Sc. 2682 are each a mixture of two specimens; one more lot (no accession number) contains a mixture of fragments from at least five specimens; and one dry embryo (no accession number). All data as for holotype, except for the specimen Sc. 2684, which was collected separately, on 8 May 2007 (not 2006). Most of the specimens are dismembered and fragmented .

RECORDS:

Akrav israchanani : Por, 2007: 3; Ćurčić, 2008: 332; Lubin & Gavish-Regev, 2008: 135; Negrea, 2008: 87; Volschenk & Prendini, 2008: 236 (Table I); Por, 2011a: 61; Por, 2011b: 452.

Akrab (misspelling) israchanani : Por, 2008: 107.

Genus/species diagnosis. The original diagnosis of the genus Akrav (and also of the species Akrav israchanani ) by Levy (2007: 91) is as follows: “Eyeless troglobite. Chelicerae without serrula on ventral edge. Fine elongated fingers of pedipalpi equipped with a nearly contiguous median row of denticles, a straight parallel row on their basal half, and inner and outer accessory denticles. Trichobothria ib-it positioned on fixed finger; series Vl-V4 extending to entire length of palm with little or no angling at the V2 juncture. Patella (tibia auct.) with all three ventral trichobothria positioned on ventral surface, and femur with trichobothrium d located slightly proximal to trichobothrium i. Metasomal segments longer than wide and bearing ventral carinae.”

We have two important corrections to this diagnosis: the pedipalp fingers are equipped with oblique median denticle (MD) groups along the entire length of the fingers; of the three patellar ventral trichobothria, v 3 is in fact found on the external surface, v 2 found on the ventroexternal carina, and v 1 is located on the ventral surface (see Figs. 13 and 15 ).

Morphology

The main goal of our study was to provide additional information to the original concise description by Levy (2007), and to illustrate the described morphology of Akrav by detailed photographic images. Below, we give a detailed description of all studied structures, commenting on their interpretation by Levy (2007), and augmenting his original description to correct errors and/or supply additional data. Extra detail and in-depth discussions on proposed taxonomically important structures are provided further below.

Levy’s description appears to be a composite one and does not refer to a specific type series specimen. It gives no measurements of any type specimens, and no photographic images except one, of a rather poorly reproduced original photograph by Israel Na’aman ( Levy, 2007, fig.1; see also our Fig. 1 ). Our description is based mainly on seven representative adult or subadult specimens: the holotype (Sc. 2673), four paratypes (Sc. 2674, 2675, 2678, 2679) and two specimens that do not belong to the type series (Sc. 2681, 2682), all of which were photographed by us .

Size. “Medium-sized troglobite about 50 mm in body length” ( Levy, 2007). The original description has no other measurements of the holotype or paratypes. We measured the type series (holotype and six paratypes) ( Table 2). In addition, measurements were taken of pedipalp chela of all other specimens ( Table 3). We can see variation in size, reflecting age differences.

This species is quite slender in overall proportions, all metasomal segments considerably longer than wide; even the basal two segments are more than twice as long as wide, L/W = 2.163, 2.245 (here and below, for the holotype). The pedipalp is also slender, the femur, patella, and chela are much longer than wide, L/ W 3.646, 4.323, 5.579; the fingers are long and tenuous, the movable finger longer than both the carapace and metasomal segment V, in ratios 1.533 and 1.070. The sternum is longer than wide, in a ratio 1.24 .

Coloration. Levy (2007) says that Akrav is “brown coloured”.

Prosoma. “…completely eyeless without any lenticel remnants.” ( Levy, 2007). We confirm complete anophthalmy – absence of median and lateral eyes; even under high magnification we find no trace of eyes. In some scorpions, smaller lateral eyes can be confused with numerous round granules covering the carapace, but granulation in Akrav is very minimal.

“Carapace encircled by fine raised edges; anterior margin notched by a moderate concavity, and a narrow, deep median groove running along posterior part; carinae absent” ( Levy, 2007, fig. 2).

Mesosoma. “Sternum pentagonal, longer than wide, with angular anterior margin and posteriorly with a narrow depression flanked by slightly distended sides” ( Levy, 2007, fig. 3; “type-2 of Soleglad & Fet, 2003a”). The length to width ratio of the sternum is 1.24.

“Internal bifurcated process projecting from posterior median edge of sternum” ( Levy, 2007, fig. 3a). This is also illustrated in our Figure 9 , which shows the internal view of the sternum where the two posterior emargination processes are visible.

“Genital opercula fused along median indentation” ( Levy, 2007, figs. 3–4). The sclerites are wider than long and are quite rounded on their inner posterior edges.

“Tergites of mesosoma without carinae” ( Levy, 2007). Tergites I–VI are generally smooth as reported by Levy, but there are slight traces of the lateral pair of carinae visible on tergite VII (see Fig. 10 ).

“Spiracle slits on sternites slightly crescent-shaped” ( Levy, 2007).

Pectines. “Pectines consisting of basal dilated, long anterior marginal and middle lamellae, a terminal piece, four distinct fulcra, and five relatively large teeth (fig. 5). Ventral surface of anterior two-thirds of each pectinal tooth covered by short setae, and posterior third perforated by fine dense pores.” ( Levy, 2007).

The number of pectinal teeth (five) given by Levy does not refer to a particular specimen. We confirm, however, that all analyzed specimens in which pectinal organs were found, had exactly five pectinal teeth; in total, we counted 17 pectines (including the embryo, which also had five teeth). Such a fixed value of this meristic trait could be expected in the completely isolated and inbred population of Akrav ; it would be more surprising to find variation in number.

Metasoma. “Metasomal segments longer than wide and bearing, in part, low tuberculated carinae or carinalike embossments. Segment V bearing a pair of ventrolateral carinae and a single, partly indicated, ventromedian (axial) carina” ( Levy, 2007, species description). At the same time, Levy’s genus diagnosis says, somewhat differently, “Metasomal segments longer than wide and bearing ventral carinae”, and the family diagnosis mentions “Metasomal segment V with single ventromedian carina.” We observe the following: segments I–IV with granulated dorsal and dorsolateral carinae; ventrolateral carinae are smooth on I to granulated to crenulated on IV; ventromedian carinae are obsolete to smooth. Segment V: we observe a granulated to crenulated dorsolateral carinae, granulated ventrolateral carinae, and weak to granulated single ventromedian carina. Also, all Recent scorpions, with the sole exception of Pseudochactas , have a single ventromedian carina on segment V, so it not clear why this was mentioned by Levy as a diagnostic character of the genus.

Telson. “Stinger without subaculear tubercle (fig. 6)” ( Levy, 2007). The vesicle is large and globular in shape, considerably longer than the short highly curved aculeus (see Fig. 10 ).

Chelicerae. “Chelicerae with a fixed finger armed with two separate basal-most teeth, and a movable finger with five teeth and smooth dorsal and ventral edges without comb-like serrula” Levy, 2007, fig. 7). In addition, the family diagnosis states: “movable finger with one subdistal denticle; median and basal denticles of fixed finger not conjoined on a common trunk.”

Pedipalps. “Pedipalpi with trichobothriotaxy conforming to type C pattern ( Figs 12–16 ; see also diagnosis of genus)” ( Levy, 2007). The genus diagnosis says: “Fine elongated fingers of pedipalpi equipped with a nearly contiguous median row of denticles, a straight parallel row on their basal half, and inner and outer accessory denticles. Trichobothria ib-it positioned on fixed finger; series V1–V4 extending to entire length of palm with little or no angling at the V2 juncture. Patella (tibia auct.) with all three ventral trichobothria positioned on ventral surface, and femur with trichobothrium d located slightly proximal to trichobothrium i.” Our detailed discussion of trichobothria pattern is given below.

“Long, slender, slightly bent fingers of pedipalpi terminating with curved tips” ( Levy, 2007, figs. 12–14). The illustrations of chelal fingers by Levy in his figs. 12–14, especially fig. 13, exaggerate the distal curvature of these fingers. In addition, the distal tip of the fixed finger overlaps the movable on its internal edge, not external as shown by Levy. See our Figs. 17–18 , 20 .

“Fingers with a median row of denticles arranged in a straight contiguous line, partly broken up at distal part into a few groups, and basal half armed with two straight parallel rows of denticles. Inner and outer denticles distributed alongside median row” ( Levy, 2007, fig. 15). We see that the chelal finger median denticle (MD) row groups are not continuous but are oblique and imbricated the entire length of the finger; see more details below. Of special interest is the fact that we also see inner accessory denticles (IAD) on both the fixed and movable fingers; see discussion below (see Fig. 21 ).

Constellation array on fixed finger of pedipalp chela, not reported by Levy, and barely visible without SEM, can be distinguished at the highest magnification ( Fig. 19 ) and appears to include five or six sensilla, close to numbers known in chactoids ( Fet et al., 2006).

Legs. “Legs bearing two sclerotic basitarsal (pedal) spurs: a dilated white retrolateral spur and a brown spine-like prolateral spur” ( Levy, 2007, figs. 16–17). These observations seem problematic, since Levy’s depiction of two spurs is schematic, and they are described as unusually different in shape and color. As it turns out, the retrolateral spur is indeed missing, and the unusual “dilated white” spur described by Levy is a swollen intersegment membrane. Its “spine point” is

formed by the triangular-shaped cuticle of the basal ventral portion of the tarsus.

“Tarsi bearing paired ventral setae.” ( Levy, 2007, figs. 16–17). Levy’s depiction of tarsal setation is schematic, and proves to be imprecise. His figures show 9 pairs of socketed setae, with setae of each pair very widely removed from each other. In fact ( Fig. 11 ), two rows of setae are positioned in a more usual, submedian formation and with less than 9 pairs (see below).

An Embryo

Levy (2007: 91) wrote: “The internal contents of the scorpions’ carcasses have been completely cleared out. This may have been carried out by mites, as the remains of an unidentified mite were found inside a dry carcass.” Presence of mites is also mentioned by Por (2007: 3; “… as yet unidentified mites”) and Negrea (2008: 87, “some unidentified species of mites”). Ćurčić (2008: 331) even talks about “living populations of … mites”. In fact, all this information about Ayyalon mites comes from the sole “unidentified mite” mentioned by Levy. As it happens, however, this specimen was misidentified.

We analyzed the specimen labeled “Mite (Acari)”, taken from inside of one of the Akrav specimens, and deposited in the same box in HUJ collection. A close examination proved that this specimen is a late-stage scorpion embryo. It is unequivocally recognized by a combination of unique scorpion features, absent in all other arthropods: well-developed pectinal organs and a long metasoma, as well a typical late-stage embryonic setation.

As mentioned by Levy, this specimen was found inside a dry scorpion exoskeleton, which would indicate a gravid female. There are several adult females in the collection, but we cannot match one of them with the embryo. This dried Akrav embryo is illustrated here ( Figs. 22–24 ), and its morphology is addressed below.

c

Morphology of late embryonic stages is not well documented in chactoid scorpions. The overall arrangement of the Akrav embryo and detail of structure development is similar to late-stage embryos of the apoikogenic chactoid Smeringurus mesaensis ( Vaejovidae ) illustrated by Farley (1999, 2001a). For the general information on scorpion embryonic development, see the most recent reviews by this author ( Farley, 1999, 2001a) and his other important works ( Farley, 2001b, 2005, 2008). Recently, our research group ( Kovařík et al., 2010) published a detailed description, based on 16 late-stage embryos, of the apoikogenic iuroid Iurus dufoureius Brullé ( Iuridae ). While only remotely related to chactoids, this description illustrates some rarely observed late embryonic features in scorpions also discernable in Akrav embryo.

The late-stage embryo in scorpions is generally very similar to the newborn animal. As confirmed and discussed by Farley (2005), a newborn scorpion (also called a first stadium, first instar, pronymph, or pullus) represents continuation and extension of embryological development. The newborn are kept on mother’s dorsum, and possess a number of distinct embryonic features. The first ecdysis (molt) of this first instar results in a drastic transformation of an embryo-like newborn to an adult-like second instar (= second stadium, nymph); see Farley (2005: figs. 9–10).

The Akrav embryo was preserved in a typical “supine position” (such as depicted for iuroids Hadrurus arizonensis in Farley, 1999, fig. 23, and Iurus dufoureius by Kovařík et al., 2010, figs. 235–236); i.e., when the metasoma and telson as well as the legs and pedipalps were folded over the ventral aspect of the mesosoma.

The size of the embryo (without metasoma) is 3. 60 mm, i.e. ~ 8 % of the adult’s size of 44–45 mm (Table I). (Compare to Iurus , where a late embryo without meta-soma was 14.55 mm long, while an adult female size was ca. 90 mm; Kovařík et al., 2010) Although the embryo is dry and distorted, and some structures are missing (notably pedipalps), many typical scorpion structures are clearly visible from ventral aspect ( Figs. 22–24 ). We can easily distinguish prosoma (sternopectinal area), with both well-developed pectines visible, each having five teeth. Remnants of basal plate, genital operculum and pentagonal sternum are clearly visible, as well as remnants of all four right legs and four left legs (some leg segments are well preserved). Coxosternal area is preserved, with all coxae of legs and pedipalps. We also observe ventral view of mesosoma with attached tapering metasoma (telson is not formed), folded under posterior edge of mesosoma toward left side of the body. Left and right lung spiracles visible on mesosomal sternites III and IV. Large embryonic setae (lost after first molt) are clearly visible on metasomal sternites II, III, IV, on legs (including coxae), as well as on sternum and genital opercula. An interesting morphological feature of this stage ( Farley, 2005) is a marked heterochrony: advanced embryonic development of some structures combined with the delayed development of others. In Akrav , as in other scorpions, we see advanced development of pectines compared to telson and metasomal segmentation.

Phylogenetic Considerations

In this section, we discuss the phylogenetic position of genus Akrav among the Recent scorpions. Key to this discussion is the determination of which characters are of phylogenetic importance and which characters may be the product, in part, of cave adaptation (troglomorphism).

Figures

Figure 1: Akrav israchanani, dead specimens on cave surface, Ayyalon Cave, Israel. Photos courtesy of Israel Na’aman.

Figure 9: Akrav israchanani. Internal view of the sternum showing the two posterior emargination processes, diagnostic of the type 2 sternum (see Soleglad & Fet, 2003: 9). The genital operculum, somewhat folded over, is seen just posterior of these processes. “Non-type” specimen Sc. 2682.

Figure 10: Akrav israchanani. Miscellaneous metasomal segments and telson from six specimens. Last mesosomal segment and metasomal segment I: Paratype Sc. 2675 (344). Metasomal segments: paratypes Sc. 2674 (317-318), Sc. 2675 (354, 358), non-type specimen Sc. 2682 (163). Telson: holotype Sc. 2673 (283), non-type specimen Sc. 2682 (164). Telson and metasomal segment V: paratype Sc. 2676 (372-373), non-type specimen Sc. 2678 (442-443).

Figure 11: Akrav israchanani. Legs from three specimens: holotype Sc. 2673 (286, 292), and non-type specimens Sc. 2678 (440), Sc. 2682 (140, 142, 175). pps = prolateral pedal spur, is = intersegment membrane.

Figure 12: Akrav israchanani. Chelal trichobothrial pattern. Composite of four specimens: non-type specimen Sc. 2682 (24, 26- 29), holotype Sc. 2673 (256), paratype Sc. 2674 (303), and paratype Sc. 2676 (387). Of particular interest, we see that trichobothrium Dt is located at the base of the fixed finger, the large gap between V2 and V3, and trichobothria Eb3, db, and dsb are petite in size.

Figure 13: Akrav israchanani. Pedipalp patella, external view. Note, all standard 13 external orthobothriotaxic trichobothria are visible. In addition, the three ventral trichobothria are also shown on the left image. Of particular interest, the esb series slants “upwards” towards the distal aspect of the patella. Also of note, ventral trichobothrium v 2 is located directly on the ventroexternal carina (VE c), and v 3 is located on the external surface of the patella. See Fig. 15 for additional images of these trichobothria. Paratype Sc. 2676 (386) and non-type specimen Sc. 2682 (148).

Figure 14: Akrav israchanani. Pedipalp patella (UV photo), dorsal view, where the two dorsal trichobothria and one internal trichobothrium are identified. Note that the internal trichobothrium, i, is located directly on the dorsointernal carina (DIc). Non-type specimen Sc. 2682.

Figure 15: Akrav israchanani. Pedipalp femur and patella (UV photo), ventral view, where three ventral trichobothria of the patella are identified. Note that the ventral trichobothrium v 2 is located on the ventroexternal carina (VEc) and v 3 is located on the external surface of the patella. See Fig. 13 for additional images of these trichobothria. Non-type specimen Sc. 2682.

Figure 16: Akrav israchanani. Pedipalp femur, basal area. Left (UV photo), dorsal view showing three standard orthobothriotaxic trichobothria. Right, internodorsal view. Of particular interest, trichobothrium e is located on the dorsal surface of the femur as indicated by the dorsoexternal carina (DE ). Non-type specimen Sc. 2682 (two pedipalps, one reversed).

Figure 17: Akrav israchanani. Chela, three basic views, showing trichobothria. Views from two paratypes, Sc. 2676 and Sc. 2678.

Figure 18: Akrav israchanani. Various images of the chelal fingers from six specimens, showing the unusual curvature of the finger distal tips and finger dentition. See Figs. 20–21 and 27–28 for further discussion on finger dentition. Holotype (265), paratypes Sc. 2674 (302, 303, 324-326), Sc. 2675 (352), Sc. 2676 (393), and non-type specimens Sc. 2679 (220), Sc. 2682 (48).

Figure 19: Akrav israchanani. External view of chelal fixed finger distal area showing the constellation array. Non-type specimen Sc. 2682.

Figure 20: Akrav israchanani. Three chelae showing the curvature of the fingers and the distinct overlap of the enlarged highly curved fixed finger distal denticle (DD). Non-type specimen Sc. 2682.

Figure 21: Akrav israchanani. Chelal finger dentition. Fixed finger on the left (non-type specimen Sc. 2682; UV photo) and movable finger on the right (paratype Sc. 2674).

Figure 22: Akrav israchanani, Ayyalon Cave, Israel. Embryo, ventral view showing sternopectinal area. Note both pectines are visible, the right pecten (left side) exhibits five teeth, the distal teeth 4 and 5 are somewhat out of focus.

Figure 23: Akrav israchanani, Ayyalon Cave, Israel. Embryo, ventral view showing sternites II, III and IV. Stigma, embryonic setae, legs III and IV, and metasoma are indicated.

Figure 24: Akrav israchanani, Ayyalon Cave, Israel. Embryo, ventral view of prosoma showing various angles. Top. Sternopectinal area. Bottom, Left. Left side of prosoma. Bottom, Right. Sternopectinal area, right angled view.