The Lepocreadiidae (Digenea) of fishes from the north-east Atlantic: a review of the genusLepidapedon Stafford, 1904

The genusLepidapedon is subdivided into several species groups and subgroups of species based on the vitelline distribution and the length of the excretory vesicle. The species in each of the subgroups are listed and keys to the species in most subgroups are given. The following north-eastern Atlantic species are described or redescribed:Lepidapedon rachion fromMelanogrammus aeglefinus, Gadus morhua, Aspitrigla cuculus, Merlangius merlangus andPollachius pollachius; L. cambrensis fromEnchelyopus cimbrius; L. sommervillae n. sp. fromTrachyrincus scabrus, T. murrayi andCoryphaenoides guentheri; L. elongatum fromGadus morhua; L. gaevskayae fromCoryphaenoides (Nematonurus) armatus; L. discoveryi n. sp. fromCoryphaenoides (Nematonurus) armatus; L. arlenae n. sp. fromTrachyrincus scabrus andT. murrayi; L. mariannae n. sp. fromGaidropsarus argentatus; Lepidapedon spp. innom (Elongatum-group) fromCoryphaenoides guentheri andCoryphaenoides (Chalinura) leptolepis; L. desclersae n. sp. fromLepidion eques; L. beveridgei fromCoryphaenoides (Nematonurus) armatus andC. (Chalinura) mediterraneus; andL. zubchenkoi fromCoryphaenoides (Chalinura) leptolepis andC. (C.) profundicolus. The phylogeny, host-specificity and zoogeography of the genus are briefly discussed.     

Insecticidal effectiveness ofMammea Americana (Guttiferae) extracts on larvae ofDlabrotica Virgifera Virgifera (Coleoptera:Chrysomelidae) andTrichoplusia Ni (Lepidoptera:Noctuidae)

Seed and leaf extracts ofMammea americana (mamey apple) have a historical use as a biopesticide with the active components previously characterized. We reexamined the utility of this natural bioinsecticide in light of existing sources of material as a by-product of the fruit processing industry. Our results addDiabrotica virgifera virgifera andTrichoplusia ni to the list of insects which are susceptible to the insecticidal ingredients ofM. americana and confirms earlier reports of activity againstBlatella germanica, Periplaneta americana, andPlutella xylostella. We report LD5Os for crude hexane extracts ofM. americana leaves and seeds againstT. ni. These materials represent renewable sources of bioinsecticides for agriculture, and should regenerate interest in coumarin-type compounds for novel pesticidal action.     

Nutritional Aspects of Dissimilatory Sulfate Reduction in the Human Large Intestine

In contrast to other anaerobic ecosystems, such as marine and estuarine sediments, there is a lack of information on the nutritional requirements of human gut sulfate-reducing bacteria (SRB). Various substrates stimulated sulfate reduction in mixed culture, including short-chain fatty acids and other organic acids, alcohols, and amino acids (but not sugars or aromatic compounds). However, the use of sodium molybdate as a specific inhibitor of sulfate reduction caused an accumulation of ethanol and malonate only, and reduced the rate of utilization of lactate. This indicates the importance of these electron donors for sulfate reduction. Since ethanol and lactate are primarily utilized by members of the Desulfovibrio genus, the results suggest a physiologically important role for this group.  Experiments with two strains of Desulfovibrio desulfuricans isolated from human feces demonstrated that both were able to reduce sulfite, thiosulfate or nitrate in the absence of sulfate. In addition, one strain (DsvUC1) was able to grow by fermentative metabolism, although the second strain (DsvFD1) showed more restricted fermentative growth. The data indicate that desulfovibrios are ecologically the most significant group of SRB in the human colon, and that colonic isolates belonging to this genus are versatile, in terms of both the electron acceptors and donors that they are able to utilize. Received: 24 March 1997 / Accepted: 10 June 1997     

Genome amplification and gene expression in the ciliate macronucleus

The focus of this review is on the micronucleus and macronucleus in the ciliated protozoa and the organization and function of the DNA molecules within them. We present (1) some of the structural and functional differences which are known, (2) the genetic evidence for macronuclear units, (3) two hypotheses for the organization of the DNA molecules in the macronucleus to explain these units, and (4) experiments designed to discriminate between these hypotheses. We conclude that the size of the genome is not reduced in the macronucleus and that there are 45 copies of the haploid genome present in the macronucleus of normal strains of Tetrahymena pyriformis and 800 copies in the macronucleus of Paramecium aurelia. The ciliate genome is relatively simple in terms of repeated sequences. However, not all copies of the genes present in the macronucleus may be identical since fractions of differing thermal stability appear after renaturation.The work reported in this paper has been supported by a research grant, GM 15879, from the National Institute of General Medical Sciences, U.S. Public Health Service, and by grants from the Science and Medical Research Councils of Great Britain. We are also grateful to the Center for Human Growth and Development, University of Michigan, for a summer fellowship facilitating collaboration.