Agrenia bidenticulata

(Tullberg, 1876)

Agrenia bidenticulata is the type of the Agrenia, a in the Isotomidae. It belongs to the bidenticulata species group, characterized by the presence of a mucronal seta. show considerable morphological variation across their range, with Buryatian mountain forms differing from typical arctic populations in claw length. The species exhibits sexual (epitoky) and cyclomorphosis.

Pronunciation

How to pronounce Agrenia bidenticulata: /əˈɡriːniə ˌbaɪˌdɛntɪˈkjuːˌleɪtə/

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Identification

Distinguished from other Agrenia by the presence of a mucronal seta (placing it in the bidenticulata-group versus the agilis-group). Separation from closely related forms within the A. bidenticulata sensu lato complex requires examination of claw index and Tibiotarsus/Claw ratio, which vary with latitude. The of the provides additional diagnostic characters for species-level separation.

Appearance

Small, elongated with diagnostic mucronal seta on the . lacks sublobal hairs on the outer lobe. Dens bears and a long subapical macrochaeta on the inner side. Unguis possesses a tunica. Claw varies geographically: typical arctic have relatively shorter claws, while South Siberian mountain populations exhibit much longer claws.

Habitat

Arctic, sub-arctic, and montane environments. Occurs in High Arctic regions and mountainous areas of South Siberia. Strictly northern hemisphere distribution in and montane zones.

Distribution

Holarctic. Palearctic: High Arctic, sub-Arctic, Europe, Mediterranean region, northeastern Eurasia including Buryatia (Russia, East Siberia) and South Siberian mountains. Nearctic: northern North America.

Life Cycle

Cyclomorphosis reported.

Similar Taxa

Agrenia agilis-group speciesLack mucronal seta; A. bidenticulata possesses this diagnostic structure
Other forms in A. bidenticulata sensu lato complexDiffer in Claw index and Tibiotarsus/Claw ratio; Buryatian have much longer claws than typical arctic A. bidenticulata

More Details

A. bidenticulata sensu lato complex

Buryatian of a form similar to A. bidenticulata differ sufficiently from the typical arctic that a broader A. bidenticulata sensu lato complex has been proposed. This complex comprises several local forms varying in Claw index and associated Tibiotarsus/Claw ratio, with these indexes showing dependence on latitude.