Sperm Morphology of Murid Rodents From New-Guinea and the Solomon-Islands - Phylogenetic Implications

Abstract

Observations on sperm morphology from most species of murid rodents from New Guinea and the Solomon Islands, based on light microscopy, are presented. Transmission electron microscopy of spermatozoa for three species in two genera are also given. All Rattus species, Melomys lanosus, M. rattoides, Lorentzimys nouhuysi and Coccymys ruemmleri have sickle-shaped sperm heads and long sperm tails. In contrast, most of the other species have sperm with a broader lateral face and three ventral processes. These processes vary somewhat in size and shape, and in two Pogonomys and one Chiruromys species there is an extension of the nucleus into the most caudal of the three processes. Species of Anisomys and Hyomys have a sperm head with a broad lateral face but with only a single apical process. Abeomelomys sevia and Solomys salebrosus each have a distinct sperm head morphology unlike that of any other Australian murid; the latter species also has an extremely short sperm tail. Taxonomic and phylogenetic inferences are drawn from these data. Some of the phylogenetic conclusions are markedly divergent from traditional views, which are based on craniodental anatomy.