Chapters authored
Adverse Effects of Herbicides on Freshwater Zooplankton
Part of the book: Herbicides
Ultrastructural and Morphological Description of the Three Major Groups of Freshwater Zooplankton (Rotifera, Cladocera, and Copepoda) from the State of Aguascalientes, Mexico
An ultrastructural and morphological description of the three major groups of freshwater zooplankton (Rotifera, Cladocera, and Copepoda) from the state of Aguascalientes using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) was performed. The main characteristics used for identification keys for each group were particularly investigated and also the cellular morphology of rods and spermatozoids in males of the rotifer Brachionus bidentatus has also been investigated. It is noteworthy to mention that in the state of Aguascalientes, three endemic species of rotifers new to science have been described: Keratella mexicana, Brachionus araceliae, and Brachionus josefinae. Regarding the suborder Cladocera, the analysis of the first and second pair of antenna, rostrum, cephalic pores, postabdomen, and the five pairs of swimming legs has resulted in the description of seven species new to science from the state of Aguascalientes: four species of Macrothrix, two species of Alona, and one species of Karualona. Regarding the subclass Copepoda, four species of Cyclopoida group new to science have been described from Aguascalientes. The taxonomical description of these species included the morphological analysis of the buccal parts and the five pairs of swimming legs with emphasis on the fifth pair of legs. The ultrastructural and morphological analysis of each characteristic has been an exhaustive task. The use of SEM and TEM was crucial to identify all these new species. SEM has allowed focusing in the study of new micro-details that have been used for taxonomical clarity, while TEM allows for studies of cellular composition and the physiological functioning of these zooplankton species. The state of Aguascalientes inventory today comprehends more than 100 rotifer species and about 50 cladoceran and 30 copepod species (of which 14 were new to science in all three groups), leading us to believe that the number of species for this inventory could be increased, adding new species to science, in the process.
Part of the book: The Transmission Electron Microscope
Rotifers as Models in Toxicity Screening of Chemicals and Environmental Samples
An important objective of aquatic ecotoxicology is to determine the effects of toxic compounds in organisms that play a central role in aquatic communities where rotifers have a large impact on several important ecological processes. The contribution of the rotifers to secondary production in many aquatic communities is substantial as they are often the larger fraction of zooplankton biomass at certain times of the year. In addition to the importance of their ecological roles in aquatic communities, the rotifers are attractive organisms for ecotoxicological studies by its short life cycles and rapid reproduction, their small size, and little volumes needed for culture and toxicity assays. The main end points used in ecotoxicological studies are mortality, reproduction, behavior, and biomarkers. Such parameters are included in international regulations from all over the world, where different species are used to evaluate the effect of environmental samples or chemical compounds. The high diversity of rotifers is an important issue because it can modify their relative susceptibility to toxicants. Thus, more studies are needed to know the relations and mechanisms involved in clonal variation, sensitivity, and development, which can be all assessed by state-of-the-art procedures.
Part of the book: Invertebrates