A. pertexta differs from the other species of Alathyria in being less elongate (height/length ratio less than 56%). Two subspecies are recognised, with the shell of the typical subspecies differing from A. pertexta wardi in having a less truncate posterior end and a generally stronger hinge, as well as lacking a posterior ventral sinuation and in having a marked anterior dorsal excavation. Uneroded beaks are sculptured with nodules.
Glochidia have a larval filament, smooth shells dotted with pores that are sub-triangular with an angle of obliquity of 9.5°, have an average length of 257-268 μm, average height of 242-250 μm, average hinge length of 175-191 μm and singular sigmoidal (s-shaped) hooks on each valve that are each around 70 μm in length. Glochidia are released in amorphous mucous conglutinates that dissociate in water.
Alathyria pertexta pertexta Iredale, 1934
Common name: Purple nacre mussel
Class Bivalvia
Infraclass Heteroconchia
Cohort Palaeoheterodonta
Order Unionida
Superfamily Unionoidea
Family Hyriidae
Subfamily Velesunioninae
Genus Alathyria Iredale, 1934
Original name: Alathyria pertexta pertexta Iredale, 1934. In Iredale, T. (1934). The freshwater mussels of Australia. Australian Zoologist 8: 57-78.
Type locality: Upper Brisbane River, Queensland.
Synonyms: Unio shuttleworthi Lea, 1856 (non Unio shuttleworthi Küster, 1855). Alathyria morti Iredale, 1943.
The last major taxonomic revision of Australian freshwater mussels was conducted by McMichael & Hiscock (1958). Based on recent molecular results, Walker et al. (2014) suggested that a reassessment of Australian hyriids is needed.
Shallow burrower in sand or gravel. Suspension feeder. Larvae (glochidia) are brooded in marsupia in the gills of females. Although the post-brooding phase of the life cycle of this species has not been reported, they presumably become parasitic on fish gills or fins where they undergo metamorphosis before dropping to the sediment as free-living juvenile mussels.
Coastal river systems and northern parts of the Murray-Darling drainage in mid-Queensland and northern New South Wales including the upper Condamine River (Graf et al. 2015). Also present in part of the Lake Eyre drainage in Queensland.
Another subspecies, Alathyria pertexta magnifica McMichael & Hiscock, 1958, occurs in Papua.
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