A unique feature of the genus Drosophila is the formation of unusually long sperm tails. Sperm lengths of millimeters are common within this group, with the 1.8 mm sperm of D. melanogaster being fairly typical. This marked expansion in sperm length reflects an unusual aspect of spermatogenesis in these organisms: in contrast to other species in which an intraflagellar transport system is used for growth of the sperm flagellum (Scholey, 2006), Drosophila sperm axonemes are assembled in syncytial cysts by a mechanism that does not require, and is not limited by, this system (Han et al., 2003;Sarpal et al., 2003). This unusual sperm axoneme development and the resulting expansion of sperm tail length have led to distinctive features of spermatogenesis not found in other species. In D. bifurca, a special 'sperm roller' has evolved to package its 6-centimeter-long gametes (Joly et al., 2003). In D. melanogaster, a highly evolved individualization process that generates 64 individual sperm from an elongate cyst containing 64 syncytial spermatids has been identified and studied (Noguchi and Miller, 2003;Tokuyasu et al., 1972a). The distinctive molecular mechanisms needed for this process include a motile filamentous actin system (the investment, or actin, cones) that traverses the entire length of the sperm tails, removing excess cytoplasm and investing each sperm in its own plasma membrane. A specialized microtubulerich structure (the dense complex) is also associated with the sperm nuclei and functions to position the basal body and also possibly to strengthen the nuclei as they undergo extreme condensation (A. D. Tates, Cytodifferentiation during spermatogenesis in Drosophila melanogaster, PhD thesis, Rijksuniversiteit Leiden, The Netherlands, 1971) (Tokuyasu, 1974).We have identified a locus, yuri gagarin (yuri), that we show here has multiple roles in the generation of elongate individualized sperm. The gene is only highly conserved in the genus Drosophila, suggesting specialized roles in these organisms. Interestingly, yuri was initially identified through its function in another specialized organ system of insects and arthropods: the chordotonal organs. These are complex mechanosensory structures with roles in proprioception and graviperception. The first mutation at the locus, yuri c263 , was identified in a screen for mutants affecting gravitaxis. Altered gravitaxis was shown to result from perturbed expression of yuri in subsets of chordotonal neurons (Armstrong et al., 2006). The molecular functions of the locus identified here suggest that yuri mediates specialized actin-and microtubule-related activities in Drosophila tissues. ResultsThe yuri locus in D. melanogaster and other Drosophilids In addition to the cDNA (GH14032) encoding a ~30 kDa protein that we used previously (Armstrong et al., 2006), we identified 11 further yuri ESTs/cDNAs from adult testis, ovary, S2 cells and embryos through FlyBase. Sequencing of these new cDNAs established that three major transcript classes are generated from yuri (Fig...

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The lipid kinase PI3K plays key roles in cellular responses to activation of receptor tyrosine kinases or G protein coupled receptors such as the metabotropic glutamate receptor (mGluR). Activation of the PI3K catalytic subunit p110 occurs when the PI3K regulatory subunit p85 binds to phosphotyrosine residues present in upstream activating proteins. In addition, Ras is uniquely capable of activating PI3K in a p85-independent manner by binding to p110 at amino acids distinct from those recognized by p85. Because Ras, like p85, is activated by phosphotyrosines in upstream activators, it can be difficult to determine if particular PI3K-dependent processes require p85 or Ras. Here, we ask if PI3K requires Ras activity for either of two different PI3K-regulated processes within Drosophila larval motor neurons. To address this question, we determined the effects on each process of transgenes and chromosomal mutations that decrease Ras activity, or mutations that eliminate the ability of PI3K to respond to activated Ras. We found that PI3K requires Ras activity to decrease motor neuron excitability, an effect mediated by ligand activation of the single Drosophila mGluR DmGluRA. In contrast, the ability of PI3K to increase nerve terminal growth is Ras-independent. These results suggest that distinct regulatory mechanisms underlie the effects of PI3K on distinct phenotypic outputs.

Effective disease monitoring and prevention is critical to the success of captive amphibian care. Nematodes, including the genera Rhabdias and Strongyloides, are known to contribute to mortality in captive amphibians and have been identified in the Houston Zoo's endangered Houston toad (Bufo [Anaxyrus] houstonensis) captive assurance colony. Five years of fecal data for the toad colony were compiled and analyzed in order to investigate the efficacy of two anthelminthic medications, fenbendazole (FBZ) and levamisole (LMS), which were used to control nematode infections. Both FBZ (dusted onto food items) and topical LMS (6.5 to 13.5 mg/kg) significantly reduced the number of nematode eggs, larvae, and adults observed by fecal parasitologic examination. There were no significant differences between treatments, and egg reappearance periods were difficult to compare as a result of low sample size. No adverse effects from either anthelminthic treatment were observed. Both topical LMS and oral FBZ appear to be safe and efficacious treatments for the reduction of the internal nematode burden in captive Houston toads.