Description of the glochidia of Westralunio albertisi Clench, 1957 (Bivalvia: Unionida: Hyriidae) from the Fly River system, Papua New Guinea

ABSTRACT Larvae (glochidia) of the freshwater mussel, Westralunio albertisi were obtained from the marsupia of a preserved female at the Western Australian Museum. Glochidial shells of W. albertisi are subtriangular and scalene in shape outline with a convoluted surface dotted with pores and have a protruding ventral apex. Glochidial shells (n = 60) measured 260.0 μm long (L) (±1.11 SE), 233.1 μm high (H) (± 1.32 SE), with a size of 246.6 μm (± 0.99 SE), hinge length (Hg) of 183.6 μm (± 0.99 SE), larval tooth length (LTL) of 53.6 μm (± 0.84 SE) and angle of obliquity (Á) of 12.9° (± 0.28 SE). Larval teeth are singular in each valve, lack microstylets, have convex or concave basal protuberances on opposing valves and terminate as blunt outward facing spoon-like to peg-like cusps. In comparison to Westralunio carteri, W. albertisi is smaller (d.f., 178; P < 0.001) for L (t = 33.85), H (t = 12.80), Size (t = 28.98), Hg (t = 21.32), H/L (t = −15.06) and Hg/L (t = −4.21). Westralunio albertisi also has a more acute Á than W. carteri (d.f., 71; t, 10.17; P < 0.001), but displays no difference in LTL (d.f., 6; t, 0.16, P = 0.44).