Testicular and spermatozoan parameters in the pukeko (Porphyrio porphyrio melanotus)

The pukeko (Porphyrio porphyrio melanotus) is widespread in New Zealand, and is the closest living relative to the endangered takahe (Porphyrio mantelli), which has a relatively high rate of infertility. In this study, sperm collected from a number of pukeko was analysed in order to model the reproductive physiology of the male takahe. In addition, testicular parameters were measured. To ascertain the best method of sperm collection five techniques for harvesting sperm were used on two occasions during the breeding season. All five techniques resulted in the successful recovery of sperm. However, the float-out technique produced the best quality samples. Following collection, the morphometry of unstained sperm was assessed. Our findings suggest that pukeko sperm is non-motile in the male reproductive tract. We found the mean sperm head length in the pukeko is 16.9 μm, but sperm head length varied significantly between birds. Testicular weight and length was significantly correlated with bird weight (P < 0.05). Within each bird, testes weights were asymmetric. However, testes length was significantly correlated (P < 0.05). There was a significant difference (P < 0.05) in testes length between birds. The methodologies presented for obtaining and analysing pukeko sperm morphometry can be used to assist opportunistic studies of the reproductive biology of other New Zealand native birds.