David J. Stanton

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There is growing evidence that transitions from sexual to asexual reproduction are often provoked by internal genetic factors rather than extrinsic selection pressures. In the cladoceran crustacean Daphnia pulex, the shift to asexuality has been linked to sex-limited meiosis suppression. Most populations of this species reproduce by obligate(More)
Allozyme studies of the cladoceran Daphnia pulex have shown that most populations reproduce by obligate parthenogenesis, although some cyclically parthenogenetic populations remain throughout the southern portion of its range. Clonal diversity within the obligate parthenogens is extremely high and has been attributed to the polyphyletic origin of(More)
The concept of intensive therapy has developed since the early 1950s following the poliomyelitis epidemic when patients required respiratory assistance. Intermittent positive pressure ventilation and the development of large integrated general intensive therapy units where all critically ill patients could be managed has resulted. The environment in the(More)
The mitochondrial genome ofDaphnia pulex (Crustacea, Cladocera) was cloned as a single fragment into the plasmid vector pUC12. The genome size, estimated from restriction endonuclease fragment lengths, is 15,400±200 base pairs. The GC content, estimated from thermal denaturation studies, is 42%. The positions of 39 cleavage sites were mapped for 14(More)
In the present study, spermatozoon ultrastructure was documented in two species of hangingflies, Bittacus strigosus Hagen (Mecoptera: Bittacidae) and B. stigmaterus Say. Structures considered important to phylogenetic assessment that were observed in B. strigosus and B. stigmaterus included a short bilayered acrosome, elongated nucleus, tube-like(More)
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