News — A new weevil species was discovered in Japan’s pristine subtropical forests on Ishigaki Island and Yanbaru National Park in Okinawa.
The Ryukyu Islands, situated between mainland Japan and Taiwan, are widely recognized for their extraordinary biodiversity. This chain of subtropical islands possesses a unique and captivating insect fauna, which thrives due to its relatively secluded evolutionary past.
Since 2015, the Okinawan Institute of Science and Technology (OIST) has conducted ongoing insect monitoring on Okinawa Island using net traps. Various insects, such as beetles, flies, wasps, and bees, have been captured during these efforts. These specimens are carefully preserved in ethanol, dried, and stored within the esteemed OIST insect collection. Notably, a newly discovered species of beetle, Acicnemis ryukyuana, was successfully identified through meticulous microscope analysis and dissection by Jake H. Lewis, an entomologist and the Collection Manager in the OIST Environmental Science and Informatics Section.
Upon my arrival at OIST in 2022, I enthusiastically immersed myself in the exploration of the OIST weevil collection. During my thorough examination, a particular species instantly grabbed my attention. It undeniably belonged to the Acicnemis genus, yet it possessed distinct characteristics not observed in any other known species from East Asia," recalls Lewis. "The elongated scales and remarkable coloration of this species set it apart from other Japanese species previously documented."
Given that the Acicnemis genus encompasses more than 180 species, verifying the discovery of a new species within this genus necessitates a comprehensive examination of existing literature and museum collections. As the "type specimens" - the original specimens used for species description - of the Acicnemis genus are held in European and Japanese museums, Lewis had to collaborate with multiple institutions to validate the classification of Acicnemis ryukyuana as a newly identified species. He reached out to esteemed organizations such as the Kyushu University Museum in Japan, the Natural History Museum in London, United Kingdom, and the Senckenberg German Entomological Institute in Germany to authenticate the status of Acicnemis ryukyuana.
According to the available information, Acicnemis ryukyuana is considered endemic to the Ryukyu Islands. To highlight its status as a unique component of the Ryukyu biodiversity, the entomologist chose to name this species ryukyuana [derived from Ryukyu] and リュウã‚ュウカレã‚ゾウムシ [pronounced as Ryuku-kareki-zoumushi], which translates to "Ryukyu dead-tree weevil" in Japanese. This naming strategy aims to emphasize its exclusive association with the biodiversity of the Ryukyu Islands.
Weevils constitute a remarkably diverse group of animals on Earth and predominantly subsist on plants. Certain weevil species exhibit high levels of specialization, feeding exclusively on a limited selection of plants. The specific host plant(s) for this recently discovered species is still unidentified, prompting Lewis to pursue additional field studies in order to explore this matter further.
The distinctive features of Acicnemis ryukyuana
The distinguishing characteristics of Acicnemis ryukyuana are readily noticeable, such as the yellow bands adorning its shoulders and the distinctive arrangement of grey, black, and yellow scales on its robust fore wings. Upon closer examination using a microscope, additional distinctive features become apparent, including the presence of elongated scales (hairs) on its dorsal side and the distinct shape of the final leg segment.
Lewis explains that upon observing the distinctive combination of features present in this newly discovered species, A. ryukyuana, it seems to have a close relationship with certain species found in Southeast Asia. However, to confirm this hypothesis, DNA analyses will be necessary.
Lewis expresses their fascination with Okinawa as a destination due to the abundance of unidentified weevil species in the area, in contrast to their home country of Canada, where weevils have been extensively studied. The prospect of residing in Okinawa and having Yanbaru National Park as their backyard fills Lewis with excitement, considering the park's abundance of undiscovered endemic species. They describe the Ryukyu Islands as an irresistible playground for taxonomists, boasting a wealth of species found exclusively in that region.
The beetles’ sensitivity to human presence
Despite OIST researchers placing insect traps in various locations throughout Okinawa Island, including densely populated and disturbed areas, A. ryukyuana was exclusively discovered in an undisturbed and specially protected section of Yanbaru National Park. Additionally, specimens of the new species were collected from well-preserved subtropical forest regions on Ishigaki Island and were even found by Lewis within the collection of the Kyushu University Museum. Based on these collection sites, it appears that this particular weevil species displays heightened sensitivity to human disturbance when compared to other commonly encountered Acicnemis species in the Ryukyu Islands.
Lewis suggests that the recently found beetle, A. ryukyuana, could be regarded as a vulnerable and endemic component of the Ryukyu fauna, akin to other unique creatures such as the flightless bird Okinawa rail, the Yanbaru long-armed scarab beetle, and the Okinawa spiny rat. They anticipate that taxonomists, conservation biologists, and local nature enthusiasts in Okinawa will be intrigued to learn about the discovery of yet another extraordinary species within the Ryukyu Islands.
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