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Isidorella newcombi (A. Adams and Angas, 1864)

Diagnostic features

Globose shell with about 4 convex whorls, narrowly umbilicate, with fine spiral striae and periostracal hairs. Reaches about 20 mm in length.


Isidorella newcombi (A. Adams and Angas, 1864)

Common name: Newcomb's Pouch Snail.

Class Gastropoda

Subclass Heterobranchia

Order Hygrophila

Superfamily Planorboidea

Family Planorbidae

Genus Isidorella Tate, 1896

Original name: Physa newcombi A. Adams and Angas, 1864. Adams, A. & Angas, G. F. (1864). Descriptions of new species of freshwater shells collected by Mr F.G. Waterhouse during J. McDonald Stuart's overland journey from Adelaide to the north-west coast of Australia. Proceedings of the Zoological Society of London 1863: 414-418.

Type locality: Ponds, Mt. Margaret, South Australia.

Synonyms: Lymnaea physopsis Cooke, 1887

Biology and ecology

This species lives on aquatic vegetation in ponds, billabongs, swamps and sluggish streams and rivers. Locally common. Capable of aestivation, biology generally unstudied. Development direct.

Additional information on the biology and ecology of members of this family can be found in Fauna of Australia, vol. 5B, p. 1072-1074.


Isidorella newcombi occurs throughout much of far inland, arid to semi-arid parts of Australia, but does not range far into Western Australia and is absent from Victoria.


Some forms of Glyptophysa - particularly those in Tasmania - are very similar to Isidorella species, but the penial apparatus has a penial stylet and an accessory flagellum. Isidorella lacks a stylet and an accessory structure but the penis has two lobes. A possible subspecies with more pronounced spiral cords, relatively high spire and narrower shell occurs at Hugh River and Jay Creek in the Lake Eyre Division of the Northern Territory. The taxonomy of Isidorella is very poorly understood. A number of species-group names are available and it is quite possible that more species of Isidorella occur in Australia. Another species name - Isidorella hainesii (Tryon,1866) - has been used to describe a relatively smooth - shelled form from NSW and eastern Queensland which lacks an umbilicus and which lives in more or less permanent water bodies however this form appears to intergrade with I. newcombi and the two forms are often difficult to separate. I. newcombi generally has a larger shell with an open umbilicus.

This genus is in need of revision, as the species concepts we have used have not been rigorously tested and can only be resolved by additional molecular and morphological studies involving dense sampling.

Further reading

Hubendick, B. (1955). Phylogeny of the Planorbidae. Transactions of the Zoological Society of London 28: 453-542.

Smith, B. J. (1992). Non-marine Mollusca. Pp. i-xii, 1-408 in W. W. K. Houston. Zoological Catalogue of Australia, 8. Canberra, Australian Government Publishing Service.

Stevens, M. M., Faulder, R. J. & Coombes, N. E. (1996). Microcosm assessment of potential molluscicides for control of the rice snail Isidorella newcombi sens. lat.(Gastropoda: Basommatophora: Planorbidae). Crop and Pasture Science 47: 673-680.

Stevens, M. M. (2002). Pests of rice, with particular reference to Isidorella newcombi. Pp. 217-351 in G. M. Barker. Molluscs as Crop Pests. Wallingford, UK, CAB International.

Walker, J. C. (1988). Classification of Australian buliniform planorbids (Mollusca: Pulmonata). Records of the Australian Museum 40: 61-89.