Mahogany as a genetic resource

The development of a strategy for the sustainable management and conservation of mahogany is an urgent priority. Such a strategy should be based upon clear information about the extent of genetic differentiation within and between populations, and on an understanding of the processes maintaining this variation. At present, such information is very limited for mahogany. Preliminary data are presented from two genetic tests of Swietenia macrophylla King (Meliaceae), indicating significant differences between provenances and half-sib progenies in both growth and form characteristics. In addition, the use of molecular markers for the characterization of genetic resources of mahogany is discussed. On the basis of the results available, the impacts of deforestation and logging activities on genetic resources are evaluated. Although both deforestation and selective logging may deplete genetic resources, no quantitative information on the extent of such depletion in mahogany is currently available. Additional research is therefore required before clear guidelines can be provided for the sustainable management of mahogany.     

The sipunculan genus Lithacrosiphon Shipley. A taxonomic review

A critical review of the sipunculan genus Lithacrosiphon , based on all of the type material and museum specimens with the exception of L. uniscutatus , results in the combining of nine species into three. L. maldivensis with its granular anal shield remains unchanged. L. cristatus with a grooved anal shield and both unidentate and bidentate hooks is redescribed and now includes L. altriconus, L. gurjanovae, L. indicus , and L. odhneri . The L. uniscutatus complex which allegedly has only unidentate hooks is discussed and now includes L. kukenthali and L. poritidis . This is a troublesome species as the pertinent specimens were either unavailable ( L. uniscutatus ) or with missing introverts ( L. kukenthali and L. poritidis ). An identification key is provided and the several morphological characters used for purposes of identification are reviewed and evaluated.     

Glycogen in Crustacean Fast and Slow Muscles

Ultrastructural examination of crayfish superficial (tonic)and deep (phasic) abdominal extensor muscles reveals a distributionand quantitative difference in glycogen between these muscles.Both superficial and deep fibers have a dense accumulation ofglycogen in the interfibrillar sarcoplasm. In addition, thesuperficial extensors, but not the deep extensors, contain glycogenin the I band region. The glycogen granules are of the ßtype and can be removed enzymatically. The superficial medialand lateral fibers contain more glycogen than the medial andlateral deep fibers. A possible functional role for this differenceis suggested.     

Dieldrin-resistant cabbage root fly in England

The existence of dieldrin resistance in Erioischia brassicae has been investigated in the main areas in England and Wales where brassicas are grown for human consumption. Dieldrin-susceptible and dieldrin-resistant flies were collected and bred as separate strains in the laboratory. In toxicity tests adult flies were treated with topically applied doses of insecticide in microdrops of cellosolve, and larvae were dipped in solutions of insecticide in 70% acetone and 30% water. Adults of the laboratory resistant strain showed a high level of resistance to dieldrin and aldrin and a lower level of resistance to γ-BHC. There was no cross-resistance with chlorfenvinphos or diazinon. Larvae of the resistant strain were shown to be resistant to dieldrin. Dieldrin resistance has been found in four areas in southern England, but not in a fifth major area, and resistant flies did not increase as rapidly in some areas as others. Sufficient migration of flies appeared to take place to produce similar percentages of resistant flies over areas of several square miles, but considerable differences were found in fly populations about 10 miles apart. It is suggested that the speed of development of insecticide resistance is affected by the proportion of brassica crops which are treated in an area, the amounts of insecticide applied to individual crops, and hence the insecticidal pressure applied to the E. brassicae population.     

FURTHER OBSERVATIONS ON THE BACTERIAL CONTENT OF WATER IN WATERCRESS BEDS

SUMMARY: Observations on two watercress beds in Kent have confirmed previous findings (Jones & Baker, 1955) that even in comparatively well-protected beds the coli-aerogenes content of the water may be high in summer. They have also shown that in spite of circumstances which would lead one to expect pollution, as in the case of one bed, the coli-aerogenes content can be low in winter. The season appears to influence the content in the water of coli-aerogenes bacteria, pectate liquefying bacteria and those capable of growing at 37°, but in the case of those growing at 22° other factors can play a more important part, as higher counts were not uncommon in winter. Seasonal effects were less marked with inlet samples; they were less influenced by atmospheric temperature, and little extraneous contamination occurred. Numbers increased as the sampling point moved from inlet to outlet.