Heterometrus spinifer (Ehrenberg, 1828)

Kawai, Kazusa, Unnahachote, Thornthan, Suttisatid, Yossaphon & Tang, Victoria, 2023, А Review of Heterometrus in Thailand (Scorpiones: Scorpionidae), Euscorpius 373, pp. 1-25 : 11-13

Heterometrus spinifer (Ehrenberg, 1828)

( Figures 28–29 , 38–39 , 48–49 , 80–81 , 83 ) http://zoobank.org/urn:lsid:zoobank.org:act:55E9068D-

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Buthus (Heterometrus) spinifer Ehrenberg in Hemprich & Ehrenberg, 1828: pl. 1, fig. 2.

Heterometrus spinifer: Kovařík, 2004: 40–42 .

Heterometrus spinifer (in part): Prendini & Loria, 2020: 290– 302 , figs. 10, 23, 50, 67–69, 157, 184–188 (reference list until 2020).

TYPE LOCALITY AND TYPE DEPOSITORY. India (incorrect); ZMHB .

MATERIAL EXAMINED. Thailand, Narathiwat Province, Su-ngai Kolok District, Su-ngai Kolok Town [06.03°N 101.97°E], 1♂, 11 June 2021, leg. Azizi Mayi, TUPC ; Yala Province, Be Tong District, Tano Maero [05.87°N 101.11°E], 1♂, 28 June 2021, leg. K. Saechan, TUPC , 1♀, 20 September 2022, leg. P. Pawangkhanant, TUPC .

DIAGNOSIS (modified from Kovařík, 2004 and Prendini & Loria, 2020). Total length of adults 100–135 mm. Base color of adults uniformly black, cuticular surface highly lustrous. Carapace with dorsal essentially smooth but laterals granulated; dorsal profile rectangular ( Figs. 28–29 ). Tergites smooth with few granules and highly lustrous ( Figs. 80–81 ). PTC 15–19 in both sexes. Pedipalps relatively elongated in both sexes (similar in both sexes; cf. Prendini & Loria: figs. 184–185) among congeners, resembling that of female H. longimanus , differed from which with a more pronounced proximal lobe on cutting edge of pedipalp movable finger (cf. Prendini & Loria: figs. 177, 187); chelae of both sexes robust and moderately elongated, ChL/W: ♂ ♀ 2.4–2.6; FL/ CL: ♂ ♀ <0.74. Dorsal surface of chelal manus smooth in both sexes; prodorsal surface scattered with prominently large and acute spiniform granules ( Figs. 38–39 ); fixed finger shorter than manus ( Figs. 48–49 ). Proximal lobe on cutting edge of movable finger lacks pronounced sexual dimorphism, moderately developed in both sexes (cf. Prendini & Loria: fig. 187). Telson in adults orangish red to blackish red ( Figs. 80–81 ), become pitch black in elder individuals.

VARIATIONS. The internal spiniform granules of chela manus vary in size. The specimen collected from Yala Province has larger granules ( Fig. 38 ) than the one collected from Narathiwat Province ( Fig. 39 ); the latter also has a more elongated and flattened chela. An intraspecific variation was also observed in the relative position of trichobothrium Et 4. The specimen from Yala has the Et 4 closer to the anteroinferior margin of manus below the base of the fixed finger ( Fig. 48 ), while it is deviated therefrom in the specimen from Narathiwat ( Fig. 49 ).

DISTRIBUTION. This species is distributed in Thailand in the southern part near the border with Malaysia. This species also is widely distributes in the peninsular Malaysia and Tioman Island ( Prendini & Loria, 2020: 295).

COMMENTS.

Distribution of Heterometrus spinifer

This species was described by Ehrenberg in 1828 as Buthus spinifer , based on a specimen supposedly from India. “ India ” was considered an erroneous type locality by Kovařík (2004: 40, 42). Couzijn (1981: 91) did not find the holotype and presumed that it was destroyed during World War II, but he found an older mature male specimen, which resembled the illustration and description of the holotype, collected in “ India ” and labeled “ B.” for Buthus . However, this specimen had several differences from the original illustration, and Couzijn (1981) was not convinced that this specimen was the holotype. On the contrary, he designated a neotype collected in Kedah, Malaysia. Kovařík (2004) examined the male specimen from “ India ” and concluded that it was the holotype, which thus invalidated the neotype. The type locality of this species is thus not clarified; however, H. spinifer is abundant in Malaysia ( Prendini & Loria, 2020: 295, 298–299, 302).

Kovařík (2004: 40) reported H. spinifer from Thailand with records in Bangkok, Be Tong and Phang Nga. However, Kovařík (2004) also assumed the record in Bangkok was erroneous. The only species recognized by Prendini & Loria (2020: 240–241) from Phang Nga was “ H. laevigatus ” (now H. minotaurus ). They did not re-investigate the population in Be Tong. Interestingly, in their examined material list, Prendini & Loria (2020: 298) reported a male from “ Thailand, Burma, Southeast Asia ” collected in 1949, but they did not further discuss this record. We obtained specimens from in southern Be Tong (Yala Province) and confirmed them to be conspecific with H. spinifer , supporting this record mentioned by Kovařík (2004). Moreover, H. spinifer and H. cimrmani (ex. “ H. laevigatus ”) were also collected from Narathiwat Province in our survey, indicating a sympatric distribution therein without clear boundaries.

The pedipalp chelae of the specimens collected from both provinces (Narathiwat and Yala, located in the south of Thailand) tend to be thinner than those of the specimens collected from Malaysia. The several characteristics in pedipalps are different between the specimens collected from the two provinces which are separated by the Sankalakhiri Mountain Range (west of Narathiwat and east of Yala), but both near the border with Malaysia. Couzijn (1981: 91) also reported this species from Thailand in the following areas: Ban Laem (“Ban Lem Ngob”), Bangkok, Bang Saphan (misspelled as “Bangtaphan”) and Koh Chang. A subspecies, H. spinifer solitarius (= H. spinifer ), was also asserted to be rare in Thailand ( Couzijn, 1981: 96). Based on the current knowledge, we believe those to be the records of H. cimrmani and H. minotaurus .

Morphological comparison of Heterometrus spinifer with its congeners

H. spinifer is most similar to H. cimrmani and H. minotaurus among the species occurring in Thailand, sharing a lustrous cuticle and relatively elongated pedipalps. However, several characters can be applied to distinguish it from the latter two: (1) telson coloration: color changes from juveniles to elder adults in H. spinifer (white → whitish yellow → yellow → orange → orangish red → red → blackish red → black), but constantly brownish black to reddish black (or pitch black in elder individuals) in the other two species; (2) pedipalp sexual dimorphism and ratio: weak sexual dimorphism with less elongated pedipalps of ChL/W = 2.4–2.6 in both sexes in H. spinifer , but ♂ 2.6–2.8 ♀ 2.1–2.3 in H. cimrmani and ♂ 3.2– 3.4 ♀ 2.7–3.0 in H. minotaurus ; (3) body size: often larger in H. spinifer ; (4) chelal finger: proportionally longer when comparing with H. cimrmani (but similar with males of H. minotaurus ); (5) cuticle surface: more lustrous in H. spinifer .

Beyond Thailand, H. petersii (Thorell, 1876) is the most resemblant species with H. spinifer among all Heterometrus species in all aspects, and a cryptic species to H. spinifer that can only be distinguished by DNA ( Prendini & Loria, 2020: 278, 295, 298). Nevertheless, the possibility of H. petersii being the actual species of the two populations must be eliminated. Prendini & Loria (2020: 272–273) stated that there are “... no consistent morphological differences between H. petersii and H. spinifer ...”. However, pronounced spiniform granules on the prodorsal surface of the chela were visible in the photos of H. spinifer provided by Prendini & Loria (2020: figs. 187–188), while the female holotype of H. petersii showed a lack thereof ( Prendini & Loria, 2020: fig. 178). In the photograph of a male H. petersii used by Loria & Prendini (2020: fig. 1F), the spiniform granules were also less prominent than those of H. spinifer . We checked the original photograph series to which that photo belongs (iNaturalist, obs. ID = 13070334) and confirmed that the granules are very blunt and interfused compared with those of H. spinifer which are often expressed as explicit rows of sharp granules. Several other photos of presumably H. petersii from Singapore also revealed similar random configurations (iNaturalist, obs. ID = 32882891, 140218281, 145966755 and 148539827). Based on this character, the two specimens found in this survey were identified as H. spinifer for their pronounced spiniform granules, as well as the geography. However, this character can be intraspecifically variable between sexes and among populations and may not be reliable for diagnosis (pers. comm. of V. Tang to S. Loria). As above noted, the size of the spiniform granules of H. spinifer from Narathiwat and from Yala is slightly different.

Figures

Figures 83: Arm-span competition between males of Heterometrus spinifer from Yala (right) and Narathiwat (left).

Figures 20–29: Comparison of Heterometrus spp. in Thailand, prosoma in dorsal aspect. Figures 20–21. H. cimrmani, male from Trang (20) and female from Nakhon Si Thammarat (21), THNHM. Figures 22–23. H. minotaurus, male (22) and female from Surat Thani (23), THNHM. Figures 24–25. H. silenus, male from Chanthaburi (24) and female from Chonburi (25), TUPC. Figures 26–27. H. laoticus, male (26) and female from Lamphun (27), TUPC. Figures 28–29. H. spinifer, males from Yala (28) and Narathiwat (29), TUPC.

Figures 30–39: Comparison of Heterometrus spp. in Thailand, chela in dorsal aspect (trichobothria indicated by red circles). Figures 30–31. H. cimrmani, male from Trang (30) and female from Nakhon Si Thammarat (31), THNHM. Figures 32–33. H. minotaurus, male (32) and female from Surat Thani (33), THNHM. Figures 34–35. H. silenus, male from Chanthaburi (34) and female from Chonburi (35), TUPC. Figures 36–37. H. laoticus, male (36) and female from Lamphun (37), TUPC. Figures 28–29. H. spinifer, males from Yala (38) and Narathiwat (39), TUPC.

Figures 40–49: Comparison of Heterometrus spp. in Thailand, chela in external aspect (trichobothria indicated by red circles). Figures 40–41. H. cimrmani, male from Trang (40) and female from Nakhon Si Thammarat (41), THNHM. Figures 42–43. H. minotaurus, male (42) and female from Surat Thani (43), THNHM. Figures 44–45. H. silenus, male from Chanthaburi (44) and female from Chonburi (45), TUPC. Figures 46–47. H. laoticus, male (46) and female from Lamphun (47), TUPC. Figures 48–49. H. spinifer, males from Yala (48) and Narathiwat (49), TUPC.

Figures 80–81: Heterometrus spinifer, in vivo habitus and dorsal aspect.Figure 80. Male from Yala, TUPC.Figure 81. Male from Narathiwat, TUPC.