Isometrus sankeriensis Tikader & Bastawade 1983
Creators: name: Sulakhe, Shauri
name: Deshpande, Shubhankar
name: Gowande, Gaurang
name: Dandekar, Nikhil
name: Ketkar, Makarand
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Scorpiones
Buthidae
Isometrus
Isometrus sankeriensis

description: Isometrus sankeriensis Tikader & Bastawade, 1983
Figs 4–7, 18A, 19A, E, 26A, D, 21A, 23A, 25A; Table 1
Isometrus (Closotrichus) sankeriensis Tikader & Bastawade, 1983: 311.
Isometrus (Isometrus) sankeriensis – Kovařík 1994: 201; 1997: 8; 2003: 4. — Fet & Lowe 2000: 150.
Diagnosis (♂)
Total length 31.33–35.14 mm. Base colouration yellowish-brown and variegated with black-brown stripes and spots. Basal segments of chelicerae dorsally yellowish with blackish reticulation. Pectinal tooth number 15–18. Median supra ocular region with some coarse and some fine granules. Median ocelli anteriorly situated, with ratio 1: 2.2 (ratio of median ocelli to anterior margin/median ocelli to posterior margin). Tergites I–VI finely granular with strong median carina. All segments of metasoma longer than wide. Isometrus sankeriensis differs from all other Indian species of Isometrus based on the following set of morphological characters:
1. Surface of carapace coarsely and sparsely granular with some areas without granules (Figs 5C, 18A) as opposed to: coarsely and densely granular in I. tamhini; finely and densely granular in I. amboli; granular throughout with mixed granules, more closely granular in inter-ocular area and median posterior ocular area in I. kovariki; and granular throughout but obsolete in I. maculatus.
2. Chela length to width ratio in males 5.7–5.8 as opposed to 6.1–6.5 in I. tamhini and 5.0– 5.2 in I. thurstoni (Tables 1–3).
3. Lateral patches on mesosomal tergites V and VI with fine granulation along margins (Fig. 21A) as opposed to coarse granulation along margins in I. tamhini.
4. Metasomal length to carapace length ratio in males 5.9–6.1 as opposed to 8.8–9.1 in I. tamhini, 7.2–8.8 in I. amboli, 7.6–8.2 in I. thurstoni, 6.5–7.3 in I. kovariki and 9.6 in I. maculatus (Tables 1–3).
5. Lateral supramedian and ventral lateral carinae on metasomal segments II–IV strongly granular (Fig. 23A), as opposed to moderately to weakly granular in I. amboli, I. thurstoni and I. kovariki.
6. Telson length to width ratio in males 4.3 opposed to 3.7–4.0 in I. thurstoni (Tables 1–3).
7. Ventral median carina on telson vesicle weakly granular (Fig. 19D) as opposed to strongly granular in I. tamhini and moderately granular in I. amboli.
8. Spiniform granules of promedian carina of pedipalp patella moderately developed as opposed to strongly developed in I. thurstoni (Figs 24–25).
For comparisons of I. sankeriensis with the proposed new species described below in this study, refer to the diagnosis section of those respective new species.
Material examined
Holotype INDIA • ♂, adult; Karnataka State, Uttar Kannada, Karwar, Sunkeri [misspelled as Sankeri]; 25 Dec. 1975; U.A. Gajbe leg.; ZSI 5088/18.
Comments
The authors believe that the holotype of I. sankeriensis (adult male) (ZSI 5088/18) is lost as it was not traceable in any ZSI centres. To stabilize the taxonomy of the genus, we found it necessary to designate a neotype using the specimen under the voucher number BNHS SC 194. The neotype meets all the requirements of Article 75 of ICZN as it was collected from the exact type locality Sunkeri (erroneously given as Sankeri in Tikader & Bastawade 1983), Karwar, Karnataka, India. Our description of the neotype matches the description of the holotype in Tikader & Bastawade (1983). The allotype of I. sankeriensis (immature female) (ZSI 5089/18), collected in the Silent Valley Forest, Kerala, India, which is presumably also lost as it was not traceable in any ZSI centres, could be a different species considering the limited distributional ranges of species of Isometrus in India; however, this needs to be confirmed.
Neotype (designated here) INDIA • ♂, adult; Karnataka State, Uttar Kannada, Karwar, Sunkeri; 14.80° N, 74.18° E; 30 m a.s.l.; 30 Aug. 2019; Makarand Ketkar, Shauri Sulakhe, Shubhankar Deshpande and Mayuresh Kulkarni leg.; BNHS SC 194.
Other material
INDIA • 1 ♂, adult; same locality as for neotype; 4 Nov. 2020; Makarand Ketkar, Shauri Sulakhe, Shubhankar Deshpande and Swayam Thakkar leg.; INHER 288.
Description (neotype, ♂, measurements in Table 1)
COLOURATION (Fig. 4A–B). Body and appendages yellowish brown and variegated with blackish brown stripes and spots; metasomal segment V yellowish to dark brownish, darker on posterior portion; pedipalp fingers dark brownish at base. Ventral surfaces uniformly yellow and sternite VII with very few dark spots. Basal segments of chelicerae yellowish dorsally with blackish reticulation ending anteriorly in a blackish transverse patch; ventral portion of chelicerae yellowish brown; fingers of chelicerae yellowish brown with tip of fingers blackish brown. Telson yellowish to dark brownish.
CARAPACE (Figs 5C, 18A). Surface coarsely and sparsely granular with some areas without granules. Carapace without carinae, median supra-ocular area with some coarse and some fine granules. Pair of median ocelli situated anteriorly, with median ocelli to anterior margin/median ocelli to posterior margin ratio of 1: 2.2. Antero-lateral ocular tubercle granular with type 5 lateral ocelli. Three pairs of large major ocelli and two small minor ocelli situated behind major ocelli. Median longitudinal furrow throughout carapace. Lateral margins finely crenulated below lateral ocelli. Posterior margin almost entirely smooth.
CHELICERAE (Fig. 4D). Characteristic of Buthidae. Basal segments and movable fingers with short and firm setae on basal and ventral surfaces.
PEDIPALPS (Figs 6, 25A). Femur with five carinae (prodorsal, retrodorsal, promedian, retromedian and proventral). All carinae crenulated. Intercarinal surfaces smooth except ventral surface with a few dense granules on proximal portions. Patella with seven distinct carinae (dorsomedian, prodorsal, retrodorsal, retromedian, retroventral, promedian and proventral). Intercarinal surfaces almost entirely smooth on ventral surface and weakly granular on dorsal surface. Chela acarinate. Fixed finger with one smooth and obsolete dorsal median and retrodorsal carina. Movable and fixed fingers with six rows of prolateral and retrolateral denticles in pairs and one additional single row of retrolateral denticles on proximal portion. Trichobothrial pattern typical for genus (chela dorsal 12, chela ventral 2, patella dorsal 6, patella retrolateral 7, femur dorsal 7 and femur prolateral 4).
LEGS (Fig. 4A–B). Femur and patella carinated. All carinae granular. Tibiae III and IV carinated, without tibial spurs. All legs with a pair of pedal spurs. Tarsomere covered with long delicate setae arranged in parallel rows on ventral side. Tarsomere I (basitarsus) carinated dorsally with tuft of short, stout blackish setae on ventral side. Tarsomere II (telotarsus) compressed laterally and ventrally with paired row of short, pointed, anteriorly directed, closely placed setae.
GENITAL OPERCULUM (Fig. 4C). Wider than long, elliptical, separated, with a pair of short male genital papillae.
PECTINES (Fig. 4C). Basal piece rectangular, deeply notched on anterior median margin. Posterior margin of basal piece curved and smooth. Marginal lamellae of 3/3 digits and median lamellae of 6/7 digits, outer margin armed with a row of stout, short red setae and few setae on surface. Fulcra 14/15, roughly triangular, each armed with a few short red setae, placed in between adjacent pectinal teeth. Teeth 15/16, strong and stout.
MESOSOMA (Figs 4A–B, 5A–B, 21A). Tergites I–VI finely granular with short median carina. Lateral patches on mesosomal tergites V and VI with fine granulation along posterior margins. Posterior and lateral margins granular. Tergite VII narrowed posteriorly, granular with two pairs of lateral granular carinae, diverging laterally. Broad median carina limited to posterior half. Sternites III–VI almost entirely smooth with a pair of spiracles. Sternite V exceptionally smooth and emarginated on median part. Sternite VII smooth on posterior margin, while finely crenulated to serrated on lateral margins; two pairs of granular carinae with median and lateral carinae present on posterior two-thirds.
METASOMA (Figs 4A–B, 5A–B, 23A).All segments longer than wide. Segment I with five pairs of granular carinae (dorsal lateral, lateral supramedian, lateral inframedian, ventral lateral and ventral submedian). Intercarinal surfaces weakly granular, anterior margin smooth. Segments II–IV with five pairs of carinae (dorsal lateral, lateral supramedian, ventral lateral, ventral submedian and lateral inframedian). Lateral supramedian and ventral lateral carinae strongly granular. Lateral inframedian carina granular, present only on posterior one-third. Intercarinal surfaces weakly granular, lateral supramedian and dorsal lateral carinae posteriorly ending in very weak subtriangular tubercles. Segment V with seven carinae (dorsal lateral, lateral supramedian and ventral lateral pairs and a single ventral median). Intercarinal surfaces more granular than on segments I–IV. Anal rim very weakly granular.
TELSON (Fig. 19A, D). With stout vesicle, bulbous on distal portion and smooth on dorsal surface. Lateral surface demarcated with weakly granular ridge. Ventral median carina weakly granular, ending in triangular, subaculear, pointed nodule, armed with two pairs of minute denticles on inner margin. Ventral portion with two pairs of sparsely and finely granular carinae. Intercarinal surfaces weakly granular. Aculeus elongated, sharp and moderately curved.
Distribution, habitat and ecology (Figs 7, 26)
Isometrus sankeriensis is currently known only from the type locality near Karwar, India. It is found in the degraded forests and scrub around Sunkeri village, Karwar. We also observed some individuals on the way to Jamba Falls near Sunkeri village. This forest habitat is under tremendous stress due to mass tourism and all factors commonly responsible for land degradation (Buckingham & Weber 2016). Our surveys recorded a small population of this species. The population also reaches the forest close to the buffer zone of Anshi National Park, which gives some hope for survival of this species. Currently the species appears to be distributed only in the lowlands in the coastal scrub forest around Karwar, Karnataka. However, more sampling from the protected area needs to be done to confirm the population density of this species. The ecology of this species is congruent with that of bark scorpions.
Remarks
Our diagnosis of I. sankeriensis, based on specimens we collected at the type locality, shows strong morphological divergence from that of I. thurstoni. The two species differ from each other based on the following morphometric ratios (Table 1, meristic and morphometric data sourced from Sulakhe et al. 2020a): chela length to width ratio in males of I. sankeriensis 5.7–5.8 as opposed to 5.0– 5.2 in I. thurstoni; metasomal length to carapace length ratio in males of I. sankeriensis 5.9–6.1 as opposed to 7.6–8.2 in I. thurstoni; telson length to width ratio in males of I. sankeriensis is 4.3 opposed to 3.7–4.0 in I. thurstoni. The two species also differ in qualitative characters: lateral supramedian and ventral lateral carinae on metasomal segments II–IV strongly granular in I. sankeriensis as opposed to weakly granular in I. thurstoni (Figs 22A, 23A); spiniform granules of promedian carina of pedipalp patella moderately developed as opposed to strongly developed in I. thurstoni. The two species differ from each other by a raw genetic divergence of 13.6–14.2% based on COI and 10.1% on 16S (Tables 6–7). In consideration of all the above evidence, we resurrect I. sankeriensis.
description: Published as part of Sulakhe, Shauri, Deshpande, Shubhankar, Gowande, Gaurang, Dandekar, Nikhil & Ketkar, Makarand, 2022, Arboreal gems: resurrection of Isometrus sankeriensis Tikader & Bastawade, 1983 and descriptions of two new species of Isometrus Ehrenberg, 1828 (Scorpiones: Buthidae) from the Western Ghats, India, pp. 1-50 in European Journal of Taxonomy 811 (1) on pages 15-21, DOI: 10.5852/ejt.2022.811.1725, http://zenodo.org/record/6448654