The interaction between the coastal brown ant,Pheidole megacephala (Fabricius), and other invertebrate fauna of Mt Coot-tha (Brisbane,Australia)

Abstract Sampling of invertebrate fauna was carried out on Mt Coot-tha, between 25 February and 11 March 1992, to determine whether the presence of the coastal brown ant, Pheidole megacephala (Fabricius), affected die abundance and diversity of other invertebrates. Four plots were sampled; in two the coastal brown ant was present and in two it was absent. The overall abundance of invertebrates did not differ significantly between plots. The abundance of Collembola did vary significantly, but intraplot variability was large. Mite numbers did not differ significantly between plots, except for the family Laelapidae. Abundance of other ant species did not differ significantly between plots, but there was a difference in species composition; Dolichoderinae and Ponerinae were absent or poorly represented in plots where the coastal brown ant was present.     

Melanosomal Tyrosine Transport in Normal and Pink-eyed Dilution Murine Melanocytes

Tyrosine is the endogenous substrate for melanin production within melanosomes, but the method of tyrosine transport into the melanosome has not been investigated. In the mouse, melanogenesis is disrupted by mutations in the p gene resulting in the pink-eyed dilution phenotype; it has been suggested that the p gene codes for a tyrosine transport protein. We determined that normal (melan-a) melanosome-rich granular fractions take up 10 μm [³H]tyrosine at 21.1 ± 6.1 (SEM, standard error of the mean) pmol/min/mg protein (N=7) compared with 21.3 ± 5.8 SEM pmol/min/mg protein (N=5) for pink-eyed dilution, whose plasma membrane tyrosine transport was also normal (K_m 89 μM; V_max 302 pmol/min/mg cell protein). We also demonstrated that pink-eyed dilution melanosomes are immature by virtue of their low density, high hexosaminidase activity, and lack of pigment. These data indicate that a tyrosine transport system exists in the melanosomal membrane and that the p gene does not encode a tyrosine transporter of critical importance.