Fluviopupa gracilis is separated from F. ramsayi in having an elongate-pupoid shell and the distal end of the penis is longer (not shorter) than the accessory lobe. In F. gracilis pupa the mantle and head-foot are darkly pigmented and the pupoid shell has about 4 whorls which have impressed sutures and the operculum has a well-developed white smear on the inner side.
Fluviopupa gracilis pupa (Iredale, 1944)
Class Gastropoda
Infraclass Caenogastropoda
Order Littorinida
Suborder Rissoidina
Superfamily Truncatelloidea
Family Tateidae
Genus Fluviopupa Pilsbry, 1911
Original name: Pupidrobia pupa Iredale, 1944. In Iredale,T. (1944) The land Mollusca of Lord Howe Island Australian Zoologist 10: 299-334.
Type locality: Creeks at Old Settlement, Lord Howe Island.
In pools of small creeks on and under stones and leaves.
Creeks behind Old Settlement Beach, Lord Howe Island.
The Lord Howe Island Fluviopupa species are rather similar in appearance but the different taxa are in distinct geographical locations on Lord Howe Island.
Iredale, T. (1944). The land Mollusca of Lord Howe Island. Australian Zoologist 10: 299-334, pls XVII-XX.
Ponder, W. F. (1982). Hydrobiidae of Lord Howe Island (Mollusca: Gastropoda: Prosobranchia). Australian Journal of Marine and Freshwater Research 33: 89-159.
Zielske, S., Ponder, W. F. & Haase, M. (2017). The enigmatic pattern of long‐distance dispersal of minute freshwater gastropods (Caenogastropoda, Truncatelloidea, Tateidae) across the South Pacific. Journal of Biogeography 44: 195-206.
