Comparison of brood size and juvenile weight between a blue strain and normal-coloured strains of the Australian freshwater crayfish Cherax Destructor Clark (Decapoda: Parastacidae)

A blue strain of the yabby Cherax destructor albidus was compared to two normal-coloured strains of C. d. destructor and C. d. albidus for brood size and juvenile weight. Reproductive performance of the blue strain was found to be significantly poorer than the two normal-coloured strains. Similarly, the weight of newly independent juveniles was also found to be significantly lower for the blue strain. No differences were detected between the two normal-coloured strains in either reproductive performance or size of newly independent juveniles. The phenotypic differences between the blue strain and normal-coloured strains are most likely genetic. However, further studies are needed to investigate whether these differences are due to pleiotropy or inbreeding effects.

Amplification of multiple copies of mitochondrial Cytochrome b gene fragments in the Australian freshwater crayfish, Cherax destructor Clark (Parastacidae: Decapoda)

Non-coding copies of fragments of the mitochondrial genome translocated to the nucleus or pseudogenes are being found with increasing frequency in a diversity of organisms. As part of a study to evaluate the utility of a range of mitochondrial gene regions for population genetic and systematic studies of the Australian freshwater crayfish, Cherax destructor (the yabby), we report the first detection of Cytochrome b (Cyt b) pseudogenes in crustaceans. We amplified and sequenced fragments of the mitochondrial Cyt b gene from 14 individuals of C. destructor using polymerase chain reaction (PCR) with primers designed from conserved regions of Penaeus monodon and Drosophila melanogaster mitochondrial genomes. The phylogenetic tree produced from the amplified fragments using these primers showed a very different topology to the trees obtained from sequences from three other mitochondrial genes, suggesting one or more nuclear pseudogenes have been amplified. Supporting this conclusion, two highly divergent sequences were isolated from each of two single individuals, and a 2 base pair (bp) deletion in one sequence was observed. There was no evidence to support inadvertent amplification of parasite DNA or contamination of samples from other sources. These results add to other recent observations of pseudogenes suggesting the frequent transfer of mitochondrial DNA (mtDNA) genes to the nucleus and reinforces the necessity of great care in interpreting PCR-generated Cyt b sequences used in population or evolutionary studies in freshwater crayfish and crustaceans more generally.

Preliminary study on the use of synthetic substrate for juvenile stage production of the yabby, Cherax destructor (Clark) (Decapoda: Parastacidae)

Juvenile Cherax destructor (commonly called the yabby) (mean weight 48.3 mg) were cultured intensively (stocking density 360/m²) under controlled conditions for 48 days. The animals were provided with a combination of food (high protein pellets and/or natural feed organisms attached to a conditioned synthetic substrate) and refuge. Fastest growth and highest yield was recorded when both pellets and the conditioned synthetic material were provided. Although the yabbies sheltered in the synthetic substrate, it did not increase survival. Juvenile yabbies (< 200 mg) were able to graze on small organisms attached to the synthetic material but this ability appeared to decline as the yabbies grew to a larger size. The use of artificial substrates in the intensive nursery phase production of juvenile freshwater crayfish is discussed.

Inheritance of molecular markers and sex in the Australian freshwater crayfish, Cherax destructor Clark

Inheritance of three kinds of molecular genetic markers (mtDNA, random-amplified polymorphic DNAs (RAPDs) and allozymes) and sex were investigated in crossbreeding experiments between three populations of the Australian freshwater crayfish Cherax destructor. Crossbreeding did not disrupt the ively maternally inherited, and allozyme and RAPD markers were transmitted following expected Mendelian principles for co-dominant and dominant traits respectively. Unlike these three markers, sex ratios were found to be distorted by crossbreeding in some families. Two crossbred families produced only females. The implications of these findings for freshwater crayfish population genetics, taxonomy and aquaculture are discussed.

"I could see, and yet, mon, I could na` see" : William Macewen, the agnosias, and brain surgery

Two little noticed cases in which William Macewen used symptoms of visual agnosia to plan brain surgery on the angular gyrus are reviewed and evaluated. Following a head injury, Macewen’s first patient had an immediate and severe visual object agnosia that lasted for about 2 weeks. After that he gradually became homicidal and depressed and it was for those symptoms that Macewen first saw him, some 11 months after the accident. From his examination, Macewen concluded that the agnosia clearly indicated a lesion in “the posterior portion of the operculum or in the angular gyrus.” When he removed parts of the internal table that had penetrated those structures the homicidal impulses disappeared. Macewen’s second patient was seen for a chronic middle ear infection and, although neither aphasic nor deaf, was ‘word deaf.’ Slightly later he became ‘psychically blind’ as well. Macewen suspected a cerebral abscess pressing on both the angular gyrus and the first temporal convolution. A large subdural abscess was found there and the symptoms disappeared after it was treated. The patients are discussed and Macewen’s positive results analysed in the historical context of the dispute over the proposed role of the angular gyrus as the visual centre.

Localisation and William Macewen`s early brain surgery part I: the controversy

Neurosurgery for the removal of brain tumours based on localising signs is usually dated from the 1884 operation by Bennett and Godlee. However, within weeks of that operation claims were made on behalf of William Macewen, the Glasgow surgeon, to have been the real pioneer of such surgery. According to Macewen's protagonists, he had conducted seven similar operations earlier than Bennett and Godlee and, in a notable 1888 address, Macewen described these seven pre-1884 cases and a number of others operated on after 1884. This paper, which is in two parts, contains an evaluation of the claims made for the priority of Macewen's pre-1884 operations. Part I deals mainly with Macewen's work in fields other than brain surgery that are relevant to it and sets out the facts of the controversy. It begins with a brief biography of Macewen, describes his pioneering work in antiseptic and aseptic surgery, his work on osteotomy and bone regeneration, and his use in brain surgery of the knowledge so gained. Part I concludes with an examination of the battle waged in the newspapers between Macewen's and Bennett's and Godlee's supporters, and of previously unpublished correspondence between Macewen himself, David Ferrier and Hughes Bennett. The primary records of the patients on whom Macewen operated, together with other materials relevant to the controversy, are examined in Part II.