Presentations spanned several themes among which trophic interactions and laboratory experiments on the population and community ecology of rotifers constituted 45% of the total presentations (Table 2). The lowest input was on aquacultural applications of rotifers. In the section on morphology and taxonomy, brilliant electron microscopic techniques for preparing rotifer specimens were shown by Wilko Ahlrichs. G Melone and his colleagues presented information on water loss and the associated morphological changes during desiccation in bdelloids. They believe that the reduced body size of a desiccated bdelloid rotifer is primarily due to elimination of body cavities. Data on the zoogeographical distribution of rotifers from different continents were also presented by some participants. Scott Mills discussed the future of rotifer taxonomy mainly based on the euryhaline Brachionus plicatilis complex. New species descriptions have been largely restricted to Brachionus (from Mexico) and Cephalodella (North-West Germany) and Dicranophorus (Belgium). Based on an ongoing project, Elizabeth Walsh and her colleagues (in USA and the counterpart in Mexico) presented some preliminary data on rotifer diversity in the Chihuahua desert springs.

The section on the trophic interactions and population ecology considered many diverse aspects. The most interesting from the point of salinity stress and the rotifer ecology was the invited talk by Peter Starkweather. Though many rotifer species are restricted to freshwaters, some do inhabit hypersaline desert endorheic water bodies. Salinity has strong effects on both density and diversity of rotifers. S. Nandini and her colleagues presented data on rotifer diversity and abundance through seasons and at different depths from one of largest drinking water reservoirs in Mexico (Valle de Bravo).

The importance of morphological and molecular data on the rotifer phylogeny was considered during this symposium. This was supplemented by the workshop on DNA barcodes by C.W. Birky Jr. Cross mating experiments within the different geographical populations appear to show the existence of a species complex in the rotifer Ephiphanes senta. The limited molecular work on Plationus did not consider other biological characteristics such as male or resting egg morphology, demography or cross mating or mate-recognition factors for deriving phylogenetic relationship within Brachionidae. Hence its taxonomic status still remains unresolved. Mark Welch presented a nice account on phylogenetics and ribosomal gene evolution in the bdelloid rotifers, a group where males are totally absent.

The aquacultural application of rotifers is not steadily increasing with the same pace as shrimp or fish production, where they are widely used as live food. Some reasons seem to be: a) mass culture techniques of rotifers are nearly stabilized on a global scale [⁶] and possibly, since Artemia cysts are relatively easy to procure, marine aquaculture largely employs these anostracans. Nevertheless, attempts to improve the nutritional quality of rotifers were presented during this symposium.

Ecotoxicological aspects of rotifers were represented by as many as seven different groups. Most of these contributions during this symposium considered population level effects of different toxic substances on monogonont rotifers. Field-based studies were poorly represented. The workshop on ecotoxicology co-chaired by Terry Snell and C?lia Joaquim-Justo invited lively discussion from the participants. There is a great practical application of rotifers in ecotoxicological evaluations and developing safety standards for water quality.

I thank Prof. Dr. Shiladitya DasSarma for inviting me to contribute this work. My wife Dr. S. Nandini offered many suggestions during the preparation of the manuscript. Three anonymous reviewers have critically evaluated this contribution. Ramiro Jes?s Sandoval and Ignacio Pe?alosa Castro extended full administrative support for the Symposium. Mexican National Council for Science and Technology (CONACyT) supported the event financially (DASJ 1100/590/05 ACAC-050187).