[
WormBook,
2009]
Caenorhabditis elegans has orthologs for most of the key enzymes involved in eukaryotic intermediary metabolism, suggesting that the major metabolic pathways are probably present in this species. We discuss how metabolic patterns and activity change as the worm traverses development and ages, or responds to unfavorable external factors, such as temperature extremes or shortages in food or oxygen. Dauer diapause is marked by an enhanced resistance to oxidative stress and a shift toward microaerobic and anaplerotic metabolic pathways and hypometabolism, as indicated by the increased importance of the malate dismutation and glyoxylate pathways and the repression of citric acid cycle activity. These alterations promote prolonged survival of the dauer larva; some of these changes also accompany the extended lifespan of insulin/IGF-1 and several mitochondrial mutants. We also present a brief overview of the nutritional requirements, energy storage and waste products generated by C. elegans.
[
WormBook,
2006]
Spermatogenesis creates functional sperm from an initially undifferentiated germ cell. In the nematode Caenorhabditis elegans, both males and hermaphrodites engage in spermatogenesis. The hermaphrodite germ line, like that of the male, initiates spermatogenesis during the L4 larval stage. The hermaphrodite germ line differs from that of the male because it ceases spermatogenesis and switches to oogenesis during the adult stage. Each hermaphrodite stores her sperm and uses them to fertilize her oocytes. Many mutants have been identified where hermaphrodite self-fertility is disrupted. If such a self-sterile hermaphrodite is mated to a wild-type male, mutant hermaphrodites that either lack sperm or contain defective sperm will produce outcross progeny. Easily implemented tests are then applied to identify the subset of these mutants that produce defective sperm. Currently, more than 44 genes are known that are required for normal spermatogenesis. This chapter discusses the 25 best-understood genes that affect spermatogenesis and mutants are grouped based on the cellular structure or process that is affected. C. elegans spermatozoa lack an acrosome and a flagellum, which are organelles found in the spermatozoa produced by most other species. Like other nematodes, C. elegans spermatozoa move by crawling using a single pseudopod. Wild-type spermatogenesis and its defects in mutants can be studied in vivo because the animal is transparent and in vitro because a simple, chemically defined medium that supports development has been discovered. Unlike nearly all other C. elegans cells, homogeneous sperm can be obtained in sufficient quantities to permit biochemical analyses.