Wednesday, January 5, 2022

[Arachnida • 2022] Taksinus bambus • A New Genus of Bamboo Culm Tarantula (Araneae, Mygalomorphae, Theraphosidae) from Thailand

Taksinus bambus 
Songsangchote, Sippawat, Khaikaew & Chomphuphuang, 2022

บึ้งปล้องไผ่พระเจ้าตากสิน || DOI: 10.3897/zookeys.1080.76876

Bamboo plays an important role in the animal world, including providing a nutritious food source, shelter, and habitat. Inside of bamboo culm, we discovered a new genus of tarantula, which we describe here as Taksinus gen. nov. (♂♀). Specimens of this new tarantula were collected from Mae Tho, Mueang Tak district, Tak province, in Thailand, making it geographically distant from any other arboreal genera. Genital morphology was used to diagnose its genus, which is supported by distributional data, natural history, morphological characters, and photographic illustrations of the male and female. Diagnosis of the new genus was determined by distinguishing its different characters from those of other arboreal theraphosid spiders distributed throughout Southeast Asia. This tarantula’s specialization is that it lives in the stalks of the Asian bamboo Gigantochloa sp.

Keywords: Arboreal theraphosid, Lampropelma, Melognathus, Omothymus, Phormingochilus, Taksinus

Mygalomorphae Pocock, 1892
Theraphosidae Thorell, 1869
Ornithoctoninae Pocock, 1895

Included genera: Citharognathus, Cyriopagopus, Lampropelma, Melognathus, Ornithoctonus, Phormingochilus, Taksinus gen. nov.

 Taksinus Songsangchote, Sippawat, Khaikaew & Chomphuphuang, gen. nov.
Type species: Taksinus bambus Songsangchote, Sippawat, Khaikaew & Chomphuphuang, 2021
 from Tak, Thailand.

Diagnosis: The characteristics of Taksinus gen. nov. that differ from Ornithoctonus and Cyriopagopus are: a low caput, a clypeus that is less than the width of the median ocular quadrangle (Fig. 6A), and spermathecae with twin seminal receptacles (Fig. 7E, F) (Raven 1985; von Wirth and Striffler 2005; Smith and Jacobi 2015). The new genus differs from Citharognathus by the lack of incrassate tibia and metatarsus IV. Taksinus gen. nov. differs from Lampropelma by the absence of a dense brush of hair on the retrolateral side of the femora of the front limbs (von Wirth and Striffler 2005) and males by lack of apical embolus swelling (Fig. 5A–E; see Gabriel and Sherwood 2019: 143, figs 17, 18). Taksinus gen. nov. can be distinguished from Omothymus by male palpal bulb with a gently curved embolus with rounded embolic apex (Fig. 5A–E) vs palpal bulb steep angle embolus and apex with a sharp point in Omothymus (Fig. 5F–J; see Gabriel and Sherwood 2019: 139, figs 1–5). Taksinus gen. nov. differs from Phormingochilus by the lack of a single megaspine on the inside of the male tibial apophyses (Fig. 4A, B; see Smith and Jacobi 2015: 41, fig. 38; Gabriel and Sherwood 2019: 142, figs 14–16), a short embolus compared to palpal bulb length (1:1) (Fig. 5A–E), and the geographic distribution of Phormingochilus currently restricted to Borneo.

Etymology: The generic name was named Phraya Tak (governor of Tak province), which is in honor of Taksin the Great, king of the Thonburi Kingdom, in commemoration of his early career.

Taksinus bambus sp. nov. paratype ♀, TAK2 A dorsal view

Taksinus bambus sp. nov. paratype ♀, TAK2
 habitat in bamboo culm.

Taksinus bambus sp. nov. from Tak province, Thailand
A biotope, bamboo forests in mountainous slope areas B tarantula habitat in bamboo culm with entrance hole (below) and secondary entrance (upper)
 C, D tarantula in bamboo culm
 E tarantula building silk tube retreats on the cover culm F paratype ♀, TAK3 T. bambus alive.

 Taksinus bambus Songsangchote, Sippawat, Khaikaew & Chomphuphuang, sp. nov.

Etymology: The species name bambus refers to the species, which was discovered in a bamboo plantation and lives in Asian bamboo stalks. บึ้งปล้องไผ่พระเจ้าตากสิน 

Distribution and natural history: 
Specimens were collected from villages surrounding Tak province at approximately 1,000 m elevation. The biotope consists of a mixed deciduous forest dominated by bamboo that is rarely disturbed by human activity (Fig. 8A). The new arboreal tarantula shows a surprising specialization in that it lives in the stalks of Asian bamboo (Gigantochloa sp.) (Fig. 8B–E). All specimens were collected from bamboo internodes in mature culms, having nest entrances approximately 2–3 cm within a silk-lined tubular burrow at the entrance located in the branch stub or at the middle of the bamboo culms. Some specimens had a secondary entrance without silk at the hole (Fig. 8B). Tarantulas do not bore bamboo stems; instead, they depend on the assistance of other animals. Bamboo is attacked by numerous animals, the most common of which are insects from the orders Coleoptera, Lepidoptera, and Diptera (Varma and Sajeev 2015). Furthermore, we hypothesized that the tarantula might occupy the empty nest of insects, such as the bamboo-nesting carpenter bee Xylocopa, which creates a large hole. All the tarantulas living in the bamboo culms build silken retreat tubes that cover the stem cavity (Fig. 8C–E).

Chaowalit Songsangchote, Zongtum Sippawat, Wuttikrai Khaikaew and Narin Chomphuphuang. 2022. A New Genus of Bamboo Culm Tarantula from Thailand (Araneae, Mygalomorphae, Theraphosidae). ZooKeys. 1080: 1-19. DOI: 10.3897/zookeys.1080.76876