Monday, July 30, 2018

[Entomology • 2018] Aphaenogaster gamagumayaa • The First Troglobiotic Ant (Hymenoptera: Formicidae: Myrmicinae) from Ryukyu Archipelago, Japan

Aphaenogaster gamagumayaa 
Naka & Maruyama, 2018

「洞窟性アリ」DOI: 10.11646/zootaxa.4450.1.10 

Aphaenogaster gamagumayaa sp. nov., a new troglobiotic (true cave-dwelling) ant species, from a limestone cave on the island of Okinawa (Okinawa-jima), Ryukyu Archipelago, Japan is described. This is the first discovery of a troglobiotic ant in Japan and the second verified record worldwide. This species has only been found in a cave area with heavy guano deposits, and some worker ants were observed carrying guano. The evidence for categorizing this new species as troglobiont is discussed.

Keywords: Hymenoptera, cave-dwelling species, guano, island, limestone cave, Myrmicinae, Okinawa-jima, Ryukyu Archipelago, troglobiont.

FIGURES 1–4. holotype worker of Aphaenogaster gamagumayaa sp. nov. 1) whole body in lateral view; 2) head; 3) head capsule; 4) mesosoma and fore segments of abdomen. Scales= 1.0 mm.

FIGURES 5–8. habitat photos of Aphaenogaster gamagumayaa sp. nov.5) guano hall where the type series found; 6) the nest entrance; 7) two workers walking together; 8) worker carrying a guano ball.

Aphaenogaster gamagumayaa Naka & Maruyama, sp. nov.

Diagnosis. This species is distinguished from the other East Asian species by having the most elongate body, the longest antennae and legs, and the most reduced eyes. Among the Japanese species, it is most similar to A. irrigua Watanabe & Yamane, 1999 described from Ryukyu Archipelago. It differs from A. irrigua in lighter color, smaller eyes (EL 0.19 x TmL vs. 0.38 x TmL), basal margin of mandible with weaker serration, and scapes more elongate and slim (SL 2.28 x HW vs. 1.53 x HW).

Etymology. The specific epithet is a Ryukyuan dialect “gamagumayaa” (= cave-dwelling hermit), referring to the habitat of the new species.

Biological notes. The type series of Aphaenogaster gamagumayaa is based on workers probably from a single nest, collected in a limestone cave on the island of Okinawa. All specimens were found in a guano hall (Fig. 5), an area of approximately 25 m2 (2–3 m in height), approximately 20 m from the cave entrance. The hall is completely dark, and during the study period (August to October 2017), it was consistently cooler (< 25°C during the day) than the exterior of the cave (28–32°C). The cave contains no pools or streams but is generally wet, and the substrate is clay soil.  

Takeru Naka  and Munetoshi Maruyama. 2018.  Aphaenogaster gamagumayaa sp. nov.: The First Troglobiotic Ant from Japan (Hymenoptera: Formicidae: Myrmicinae). Zootaxa. 4450(1); 135–141.  DOI: 10.11646/zootaxa.4450.1.10

日本で初めて、世界で 2 例目となる「洞窟性アリ」の発見 

1 comment:

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