Tuesday, September 19, 2023

[Arachnida • 2023] Chilobrachys natanicharum • A New Electric-blue Tarantula Species of the Genus Chilobrachys Karsh, 1892 (Araneae: Mygalomorphae: Theraphosidae) from Thailand

Chilobrachys natanicharum  
Chomphuphuang, Sippawat, Sriranan, Piyatrakulchai & Songsangchote, 2023

The enchanting phenomenon of blue coloration in animals arises from the fact that blue is one of the rarest colors found in nature, and it is a structural color that is produced by the arrangement of biological photonic nanostructures, rather than pigments. This unique coloration has evolved independently in many different species, adding to the fascination and diversity of coloration patterns in the animal kingdom. This study describes a new species of Chilobrachys Karsch, 1892 from southern Thailand that exhibits a blue-violet hue resembling the color of electrical sparks. Photographic illustrations, a morphological description, and the natural habitat of the new species are given. The diagnosis, palpal-bulb structures, spermathecae, and stridulatory organ morphology of related species are discussed.

Key words: Arboreal theraphosid, habitat, mangrove forests, mountainous, rainforests

Mygalomorphae Pocock, 1892

Theraphosidae Thorell, 1869
Selenocosmiinae Simon, 1889

Chilobrachys Karsh, 1892

Chilobrachys natanicharum sp. nov. live
A paratype ♀ ELB03 B holotype ♂ THNHM-At-00000062.

Chilobrachys natanicharum sp. nov.
A type locality B habitat in the type locality of THNHM-At-00000062: Bang Nai Si, Takua Pa District Phang-Nga, elevation 5 m C habitat in the type locality of ELB02: Khuekkhak, Takua Pa District Phang-Nga, elevation 57 m D juvenile build asymmetric funnel webs live in tree holes.

 Chilobrachys natanicharum Chomphuphuang, Sippawat, Sriranan, Piyatrakulchai & Songsangchote, sp. nov.
Diagnosis: C. natanicharum sp. nov. was included in Chilobrachys based on the maxillary lyra of the stridulation organ comprising 1–3 rows of heavy claviform bacillae (West et al. 2012). The male of C. natanicharum sp. nov. can be distinguished from C. dominus, C. hardwickei, C. himalayensis, C. hubei, C. jonitriantisvansickleae, C. liboensis, C. lubricus, and C. qishuoi, by the wide base of the embolus, which is flat and knife-like in shape (Figs 6–9) (long and slender in all other known congeners). Chilobrachys natanicharum sp. nov. similar to those of C. dominus, C. guangxiensis, C. hubei, C. jinchengi, C. liboensis, C. lubricus, and C. qishuoi, in having developed apical (A), prolateral inferior (PI), and prolateral superior keels (PS), but it can be distinguished by the presence of parallel longitudinal keels of PI and PS on the distal spine of the embolus (Fig. 8A, C) (not parallel on the distal spine in other species) and the appearance of a groove at the beginning tip of the apical keel (Fig. 9A, B). The males of C. natanicharum sp. nov. can be further distinguished from those of C. dominus by the angle between the lowest and highest points of the embolus (ALH), which is 40° (Fig. 14A–D) (compared to 90° in C. dominus). Females of C. natanicharum sp. nov. resemble C. fimbriatus in the form of the spermathecae, which have fused spermathecae. However, they can be distinguished from C. fimbriatus by the shape of the spermathecae. In C. natanicharum sp. nov., the spermathecae are raised and trapezoidal, with a thick, rounded upper edge (Fig. 12A, B). On the other hand, C. fimbriatus has M-shaped spermathecae, characterized by a shallow hump and a middle hollow (see West et al. 2012: fig. 30). Females of this species can be distinguished from several other species, namely C. assamensis, C. dyscolus, C. guangxiensis, C. hardwickei, C. hubei, C. huahini, C. jonitriantisvansickleae, C. khasiensis, C. lubricus, C. nitelinus, C. paviei, C. qishuoi, C. sericeus, and C. stridulans, by the presence of two separate spermathecae receptacles. Chilobrachys natanicharum sp. nov. differs from all other Chilobrachys species, except C. jonitriantisvansickleae Nanayakkara, Sumanapala & Kirk, 2019, in that female and male juveniles have a metallic color on the legs, carapace, and chelicerae. The new specieds differs from C. jonitriantisvansickleae in terms of color shades. Chilobrachys natanicharum sp. nov. shows a violet-blue metallic color (Fig. 1), whereas C. jonitriantisvansickleae has a shade of metallic grayish-turquoise-blue sheen (Nanayakkara et al. 2019: fig. 1a).

Etymology: Chilobrachys natanicharum sp. nov. The specific epithet for this species was provided by Nichada Properties Co., Ltd., Thailand, the winner of the auction campaign for choosing the scientific name of the new species. The name is a combination of the names of Mr Natakorn Changrew and Ms Nichada Changrew, who are company executives. 
All proceeds from the auction were donated to support the education of Lahu children in Thailand and poor cancer patients. The Lahu people are an indigenous hill tribe in northern Thailand (Musoe) and are known for their vibrant culture and traditional way of life. Unfortunately, many Lahu children are denied access to education due to poverty, leaving them with limited opportunities for their future. The goal is to help change this by providing educational opportunities for Lahu children, giving them a chance to break out of the cycle of poverty. Additionally, cancer remains a significant public health issue globally, affecting millions of people each year. Many cancer patients struggle with financial hardship, which can make accessing quality care even more difficult. We believe that everyone deserves access to quality healthcare, regardless of their financial situation.

Metallic-blue and violet coloration of Chilobrachys natanicharum sp. nov.

 Narin Chomphuphuang, Zongtum Sippawat, Patipan Sriranan, Paveen Piyatrakulchai and Chaowalit Songsangchote. 2023. A New Electric-blue Tarantula Species of the Genus Chilobrachys Karsh, 1892 from Thailand (Araneae, Mygalomorphae, Theraphosidae).  ZooKeys. 1180: 105-128. DOI: 10.3897/zookeys.1180.106278