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This volume reports on the findings of experts on tropical zooplankton gathered at a meeting in Kariba, Zimbabwe, in 1991. Some basic questions were asked on community composition and biodiversity in the tropics versus the non-tropics. Old ideas on the nature of zooplankton, which were found to be wider than the `classical' rotifers, cladocerans and copepods, as well as on the number of species in tropical waters, are now beginning to break down accordingly as more and more blank spots in the tropics are explored and as more in-depth studies on the zooplankton of tropical lakes are becoming available. This volume contains a mix of papers discussing the two alternative controls (bottom-up and top-down) of zooplankton community structure and these constitute another step towards a coherent theory of tropical ecosystem theory.

As in previous symposia, some current research topics were selected for review and eight invited papers were presented. For the first time a paper was presented on the historical aspects of Rotiferology, covering European research between 1680-1950. A special workshop session was devoted to a debate on a controversial topic: Rotifer Phylogeny. The workshop resulted in a very successful discussion and the integration of scattered evidence and hypotheses on the phylogenetic origin of rotifers, the relationships between major rotifer groups, and the mechanisms of evolution.

Mangrove ecosystems are typical formations found in coastal deposits of mud and silt throughout the tropics and some distance into the subtropical latitudes. The total wordwide mangrove area, which is estimated at about 170,000 km2 with some sixty species of trees and shrubs exclusive to the habitat, dominates approximately 75% of the world's coastline between latitudes 25(deg)N and 25(deg)S. Such unique intertidal ecosystems support genetically diverse communities of terrestrial and aquatic organisms that are of direct or indirect socioeconomic values. Mangrove forests play important roles as coastal stabilization and protection against winds and storms; producers of nutrients, forest resources and animal species of economic importance. Recently, the issues on the conservation, proper utilization and management of mangrove forests have been widely discussed. Unfortunately, overexploitation and destruction of mangroves seriously threatens the sustainability of such a unique ecosystem. This volume includes papers on three main areas: recent advances in mangrove ecology; application and utilization of mangrove resources; and conservation and management of the ecosystems.

Concentrations of dissolved organic matter (DOM) in lakes are often an order of magnitude greater than concentrations of particulate organic matter; nevertheless, the biogeochemical analysis of DOM is described in only a few textbooks on limnology (most thoroughly by Wetzel). The orgins of dissolved organic substances are largely photosynthetic; DOM is either autochthonously synthesized by littoral and pelagic flora through secretions and autolysis of cellular contents, or allochthonously generated in terrestrial systems of the drainage basin, composing largely of humic substances refractory to rapid microbial degradation. The role of DOM in lacustrine ecosystems, as energy source and system regulator, however, is still poorly known. The aim of this book is: (1) to present state-of-the-art reviews of the role of dissolved autochthonous and allochthonous organic matter in pelagial and littoral zones; and (2) to focus attention on poorly understood but critical topics and hence to provide direction for future research activity.

The origins of this volume date back to the 1978 American Society of Limnology and Oceanography (ASLO) meetings in Victoria, British Columbia. Interest in the ecology of mysids, particularly Mysis relieta. was growing rapidly, so a meeting of active workers was held at the ASLO conference. Although the small group of researchers attending that first meeting were primarily North American and interested in Mysis relieta. the group quickly expanded to include researchers from every continent with interests in all aspects of mysid biology (see Appendix). The group, informally called the Mysid Research Group, formed to serve two basic functions·. The first was to facilitate communication among mysid researchers by publishing a member­ ship list and periodic newsletters. The second was to organize an international symposium on mysid ecology. After several false starts, a symposium was successfully held in conjunction with the 1981 ASLO meetings in Milwaukee, Wisconsin. The symposium lasted over parts of two days with an evening workshop the second day. Altogether, 1 poster and 21 oral presentations were given by 42 researchers. This volume is an outgrowth of that symposium and includes 15 of the papers originally presented at the conference. In order to make the volume as comprehensive as possible, contributions from individuals who could not attend the symposium were solicited. Thus, a total of 22 original contributions make up the present work.

Multiple use of natural waters and watersheds poses many practical problems, some of which are clearly limnological, relating for example to carrying capacities oflakes, deterioration of water quality and fisheries management. It is thus important to consider limnological aspects when making decisions in the field of water management. To further this attitude the Finnish Limnological Society considered 'Lakes and Water Management' to be a suitable theme for the Society's Jubilee Symposium, held in Helsinki on 22-23 September, 1980 at the Viikki Campus of the University of Helsinki, to mark the Society's 30th Anniversary. The Finnish Limnological Society has arranged nationallimnological symposia everyone or two years. The papers presented at these symposia have been published in the series 'Limnologisymposion' (in Finnish or Swedish, with short summaries in an internationally spoken language). Due to financial difficulties, the series was terminated as of the symposium in 1979. When preparing the 30th Anniversary of the Finnish Limnological Society, the Governing Board of the Society decided to arrange an international symposium on a theme relevant to modern limnology both in Finland and elsewhere. The selected results of the successful meeting on lakes and water management, which was attended by 220 people from 7 countries, are presented in this volume.

At the First International Symposium on Aquatic Oligochaete Biology in Sidney, B. C. , the suggestion was made to hold the second in Pallanza, on Lake Maggiore, at the C. N. R. -Istituto Italiano di Idrobiologia. At the same time it was decided that there should be a symposium every third year. The organization of the symposium was made considerably easier by the Senior Editor's having been in personal contact with several Russian colleagues (courtesy of a kind invitation from the U. S. S. R. Academy of Sciences), the 'Hamburg Group' and the Junior Editor. Correspondence with various students of Oligochaeta also furnished many useful suggestions. The Second International Symposium on Aquatic Oligochaete Biology was therefore held in Pallanza in late September 1982 and was attended by 53 scientists from 16 countries in Europe, North America, Asia and Australia. No review papers were formally invited as this had already been done at the first symposium: all the papers were accordingly allotted the same time for oral presentation. These proceedings contain all papers Hrabe and Slepukhina, which were given in absentia, as it presented at the symposium, including those by was impossible for the authors to join the group. The main topics were taxonomy and evolution of Oligo chaeta, life-cyle and population studies, the role of Oligo chaeta in assessing water pollution, physiolog­ ical studies, community and distribution studies. Special taxonomic workshops took place in the evenings.

At the end of the first international Symposium on Rotifers diately accepted to do this, and kindly made an entire in Lunz, Austria, September 1976, entousiastic pleas were special volume of its Journal 'Hydrobiologia' available made for a second gathering of possibly the same format for this purpose. Also, arrangements were made to have and spirit that had made the first one such a great success. the proceedings out as quickly as possible. The proceedings include all papers that were presented One of us (HJD), 'supported' herein by his friends Charles E. King and Jens Petter Nilssen in particular, tentatively in Gent, and two communications by collegues who could suggested that Gent University might host a meeting of not attend in person. They thus amount to 23 original con­ this kind, having in mind that since the Xlth congress of tributions, including the summaries of the workshops. All SIL in 1950, no other SIL activity had take places in have been reviewed by the editors, and many, in addition Belgium. In view of the relatively large number of Be1gian by one or more referees. Manuscripts have been adjusted, rotifer workers, many among which are or were active in wherever needed, for grammar, clarity of meaning, and Gent, this proposal sounded acceptable to the attendance length. However, where possible, the flavor of some per­ of the Lunz meeting, who then gave each other rendez sonal styles was left unaltered.

Turbellarian platyhelminths (or, as they are known now among cladistic systematists, free-living Platyhelminthes) comprise a widely distributed assemblage of lower worms found in marine, freshwater, and even occasionally in terrestrial habitats. The phylum Platyhelminthes may be more widely known for its parasitic members since the major parasitic groups of the tapeworms, flukes, and their relatives are more speciose and have greater impact on everyday human life; but the turbellarians are more diverse and, as inhabitants of virtually any aquatic habitat, are more widespread as well. Many of the lower turbellarians are rather simple in morphology and have served as models for ancestors of the Bilateria, i.e., the bulk of the animal phyla. Others are quite complex organisms, especially in the morphology of their reproductive systems which are highly specialized. The majority are free-living in aquatic habitats but a number of interesting parasitic and commensal species are found scattered among the higher turbellarian taxa. But turbellarians are more than just taxonomic curiosities. They have served as illustrative models in research on a variety of basic life processes. For example, their high capacity for regeneration has made them the subject of a large literature in developmental biology, the occurrence of mixoploidy and other karyological oddities among turbellarians has been important in understanding evolution of the genome, and the fine structure and biochemistry of the nervous system in turbellarians is revealing important principles of the organization of so-called primitive neural systems.

The 12th Congress of SIDUO took place in Iguazu Falls, Argentina, where participants could enjoy the scenery of the magnificent Falls. The organization was sponsored by the University Department of Oph­ thalmology, Buenos Aires; the University Department of Ophthalmology, EI Salvador; SAUMB (Socieded Argentina de Ultrasonografia en Medecina y Biologia) and CLEO (Club Latinoamericano de Ecografia OftalmoI6gica). The Honorary President was Professor Horacio Soriano from Buenos Aires. The local organizing committee consisted of the following persons: President Roberto Sampaolesi Vice President Atilio Lombardi Scientific Secretary: Eduardo Mayorga Treasurers Guillermo Iribarren Abelardo Cavatorta We are particularly grateful to Doctor J S Hillmann, Professor K C Ossoinig and Doctor nvf Thijssen, who have helped with their counsel and advice. I would also like to thank our congress secretaries Graciela Massonat and Cristina Taegl for their enormous help in organizing SIDUO XII. To Doctor Javier Cassiraghi and Doctor Walter de Gregory our thanks for their outstanding help in organizing the scientific sessions. Thanks are due to the commercial exhibitors and most of all to our sponsors: Laboratorios Pfoertner Cornealent and Biophysic Medical. Our special thanks to Doctor Tomas Pfoertner for his great administrative expertise and counsel and to Christine Warren from Biophysic for her help in financing these proceedings. The 12th SIDUO thanks for their generous support: Pupilent Plastic Lens Argentina, Grafica SA and Laboratorio Optico Santamarina.

Members of the gastropod family Littorinidae are common throughout the world. They form a very abundant component of many intertidal and shallow subtidal ecosystems and, by their grazing, often play a central role in shaping these communities. They also display a wide range of life history strategies and many are polymorphic, making them attractive model organisms for ecologists, evolutionary biologists and physiologists alike. Areas of particular interest include ecological interactions with other animals and with algae, the effects of pollutants and the use of littorinids as sentinel species for monitoring pollution, the effects of parasites on growth and ecology, taxonomy, and the study of genotypic/phenotypic responses to environmental factors. There is still much to be done, and the littorinids are proving to be an ideal group on which to work. Audience: Primarily targeted at the research level. Will also provide useful information for advanced first-degree students conducting research projects.

A major concern among ecologists in and outside the ASEAN region is the degradation of the environment, and the overexploitation of freshwater and marine resources. There is as yet no indication that freshwater and marine resources are being managed on a sustainable basis, and loss of wetlands, whether freshwater swamps or mangrove swamps, is a major problem in the ASEAN region. Reclamation of mangrove swamps for aquaculture and agriculture seems to be a continuous activity here and the status of marine parks should also be examined in the light of recent resort development acitivities on small islands. This volume contains numerous recommendations for the promotion of ecological studies and regional cooperation in marine, freshwater ecology and conservation, with special emphasis on the common water masses like the Strait of Malacca, Gulf of Thailand and the South China Sea.

Proceedings of a Conference on Rutland Water, held in Leicester, 1-3 April 1981

Industrial seaweed use started in Brittany in the XVII century. Today, 700 species have been identified along 1000 km of shoreline, producing 10 million tons of biomass. In the Fourteenth International Seaweed Sumposium the latest developments in the area are discussed. The blending of molecular biology with traditional taxonomy is improving our understanding of phylogeny and species relationships among many of the important algae. A new generation of biologically-based management models is gradually incorporating field testing, concepts from ecological theory and principles from population biology. Prediction is being improved, and an appropriate balance is being struck between commercial exploitation and the preservation of wild seaweed resources. Cell and tissue culture of seaweeds is entering the mass-production phase. Field farming is now entering the large-scale production area. New, biologically active compounds are being described, obtained from algae, and new tools for the characterisation of phytocolloids are described. Microalgal blooms and toxins are also experiencing a flourish of new results.

Ecotones are interface zones between different ecosystems. Their ecological role and significance with regard to ecological management and conservation has become increasingly appreciated. For the management of freshwater resources, for example, an improved understanding of the role of land/inland water interfaces, will be essential for reducing negative human impacts by engineering, nutrient loading, siltation, etc. The management of ecotones, on the other hand, offers the possibility to control aquatic system processes via stock control of fish populations. Fish apparently are both excellent indicators of ecotone quality as well as determiners of its structure and function.