Taxonomic Implications of Variation in Sperm Head Morphology of the Australian Delicate Mouse, Pseudomys delicatulus.

Abstract

The structural organisation of the sperm head of individuals included within the species Pseudomys delicatulus, and P. patrius, which has recently been separated from P. delicatulus, is detailed here. P. patrius has a sperm type with three hooks - a feature shared with most other species of Pseudomys including all three other pebble-mound mice. By contrast, P. delicatulus has a very different sperm type that lacks the three hooks and in this species two morphotypes appear to be present. One is highly variable, generally pear-shaped with a basal attachment of the sperm tail, and is present in individuals which occur on the mainland of the Northern Territory and Western Australia. The other, which is present in individuals in Queensland and on West Island and Groote Eylandt off the north coast of Northern Territory, is bilaterally flattened with a single, attenuated, blunt apical hook and tail attached to the lower concave surface. These results (1) support the recent separation of P. patrius from P. delicatulus and, (2) suggest the presence of a cryptic species or subspecies within Pseudomys delicatulus as presently constituted.