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In this review, we include rotifers, copepods, and cladocerans, including other groups not usually deemed as zooplankters: i.e., protists, acari, and large branchiopods. The objectives of this study were to integrate the dispersed literature on the taxonomy and diversity of these freshwater zooplankton groups and to explain (1) how these contributions can be arranged in distinct historical periods and (2) how this knowledge has allowed the detection of exotic and threatened species. We divided the freshwater zooplankton studies in Mexico into three historical periods: the first one comprised the 1840s to the 1940s when foreign researchers carried out most studies during several expeditions. Spanish researchers promoted surveys on different zooplankton taxa at the end of this first period. The second period, from the early 1950s to the end of the 1990s of the XX century, showed a remarkably increased research activity in its last ten years only (that is, during the 1990s to 2000), represented by contributions of a new generation of Mexican zooplanktologists. This period yielded more complete zooplankton listings and detailed morphological descriptions of rotifers, cladocerans, copepods, and large branchiopods. The third period started from the year 2000 to date. During this time, listings and online faunistic baselines based on integrative taxonomy have been the primary trend. An account of exotic zooplankters and conservation issues of several native species are discussed. The results of this review show that the knowledge of the freshwater zooplankton of this country has increased significantly over the last 40 years, with at least 408 first records of species for Mexico. Currently, the knowledge of Mexican freshwater zooplankton is among the most complete in the world. However, it is estimated that only a small fraction of the true diversity has been documented.

This paper presents a study of freshwater zooplankton biodiversity, deemed as a reliable indicator of water quality. The Guatemalan Lake Amatitlán, currently used as a water source, has shown signs of progressive eutrophication, with perceptible variations of the local zooplankton diversity. Biotic and abiotic parameters were determined at four sites of Lake Amatitlán (Este Centro, Oeste Centro, Bahía Playa de Oro, and Michatoya) in 2016 and 2017. The local composition, the species richness and abundance of zooplankton, and the system environmental parameters were analyzed during both years surveyed. Biological data suggesting eutrophication of this tropical system were obtained, including a high rotifer abundance (11 species: the rotifers Brachionushavanaensis (109 ind L−1) and Keratellaamericana (304 ind L−1) were the most abundant species in this lake). The presumably endemic diaptomid copepod species, Mastigodiaptomusamatitlanensis, was absent in our samples, but we report the unprecedented occurrence of two Asian cyclopoid copepods (i.e., Thermocyclopscrassus and Mesocyclops thermocyclopoides) for Lake Amatitlán and Guatemala. The presence of larger zooplankters like adults and immature copepods (i.e., Arctodiaptomusdorsalis) and cladocerans (Ceriodaphnia sp.) at site “Este Centro” indicates a relatively healthy zooplankton community and represents a focal point for managing the conservation of this lake.

Zooplankton biodiversity is deemed as a realiable indicator of water quality. For 40 years, the Guatemalan lake Amatitlan has shown signs of eutrophication, with measurable impacts on the local zooplankton diversity. Biotic and abiotic variables were surveyed at four sites of lake Amatitlan (Este Centro, Oeste Centro, Bahia Playa de Oro and Michatoya) in 2016 and 2017. The species richness and abundance of rotifers, cladocerans, and copepods were analyzed. The dynamic composition of zooplankton was studied and the system environmental parameters were analyzed in two seasons (rainy and dry season) for both years. Characteristical values of eutrophied tropical systems were obtained, with high rotifer diversity (11 species) and abundance. At present, the rotifers Brachionus havanaensis (109 ind/L) and Keratella americana (304 ind/L) were the most abundant species in the system. The copepod Mastigodiaptomus amatitlanensis considered as endemic in 1941 is absent nowadays, but we reported the unprecedented occurrence of two exotic copepods (i. e., Thermocyclops crassus, Mesocyclops thermocyclopoides) for lake Amatitan and all Guatemala. The presence of large zooplankton like adults and immature copepods (Arctodiaptomus dorsalis) and cladocerans (Ceriodaphnia sp.), in site “Este Centro”, indicates a relatively healthy community and represents a focal point for the conservation for this lake.