Lecture Goals • Introduction to the major groups of zooplankton • Discussion of common and distinguishing characteristics of these groups • Important controls on distribution and abundance of zooplankton Approach to Freshwater Animals • Descriptions of major groups, organized taxonomically when possible • Some morphology, but I will focus on life history and ecology • Life History: changes experienced by an individual between birth and death that determine habitat requirements, ecology, and reproductive output • Ecology: interactions among species, or between the focal species (stage) and physical habitat What are zooplankton? • Microscopic animals that float freely in the water column • Very important as primary consumers – converting energy from phytoplankton to a form that can be used by larger animals • Important food base for secondary consumers, including fish Major groups of freshwater zooplankton • Rotifers • Cladocerans • Copepods Rotifers • 50 μm – 3 mm • Smallest metazoan Taxonomy Kingdom Phylum Class Order Family Genus Species http://tolweb.org/tree/ Rotifer Taxonomy Kingdom: Animalia Phylum: Rotifera Class Order Family Genus Species Rotifer Diversity **High diversity in morphology Cyclical Parthenogenesis* STRESS Resting Eggs Cyclical Parthenogenesis Rotifer Life Cycle No Molting → Cell Expansion Rotifer Colonies Major groups of freshwater zooplankton • Rotifers • Cladocerans • Copepods Cladocerans 0.5 mm – 3 mm Cladoceran Taxonomy Kingdom: Animalia Phylum: Arthropoda Class: Crustacea Orders: Cladocera Family: Daphniidae and Bosminidae Genus Species Cladoceran Families Daphniidae Bosminidae **High diversity in morphology Cyclical Parthenogenesis* Cladoceran Eggs Cladoceran Life Cycle Cyclical Parthenogenesis Ephippium Cyclical Parthenogenesis Major groups of freshwater zooplankton • Rotifers • Cladocerans • Copepods Copepods 1.0 mm – 8.5 mm Copepod Taxonomy Kingdom: Animalia Phylum: Arthropoda Class: Crustacea Orders: Cyclopoida, Calanodia, Harpacticoid Family Genus Species Copepod Orders Cyclopoid Calanoid Harpacticoid **Low diversity in morphology Copepod Egg Sacs Cyclopoid Copepod Egg Sacs Calanoid Copepod Egg Sacs Harpacticoid Copepod Life Cycle Controls on Zooplankton Distribution and Abundance • Temperature Nutrients • Physical Phactors Phish Phytoplankton • Vertical Migration • Parthenogenic ↔ Sexual Cycles • Predation among Zooplankton Controls on Zooplankton Distribution and Abundance • Temperature Nutrients • Physical Phactors Phish Phytoplankton • Vertical Migration • Parthenogenic ↔ Sexual Cycles • Predation among Zooplankton Zoop Distribution and Abundance: Temperature Nutrients Controls on Zooplankton Distribution and Abundance • Temperature Nutrients • Physical Phactors Phish Phytoplankton • Vertical Migration • Parthenogenic ↔ Sexual Cycles • Predation among Zooplankton Zoop Distribution and Abundance: Physical Phish Phytoplankton Zooplankton Population Dynamics Controls on Zooplankton Distribution and Abundance • Temperature Nutrients • Physical Phactors Phish Phytoplankton • Vertical Migration • Parthenogenic ↔ Sexual Cycles • Predation among Zooplankton Zoop Distribution and Abundance: Vertical Migration Pattern • Variation with stage and sex • Light is proximal cue • 3 main hypotheses Vertical Migration Hypotheses: Predation Vertical Migration Hypotheses: Food Quality Vertical Migration Hypotheses: Growth and Feeding Efficiency as a Function of Temperature “Hunt warm, rest cool” High Feeding Efficiency High Growth Efficiency Controls on Zooplankton Distribution and Abundance • Temperature Nutrients • Physical Phactors Phish Phytoplankton • Vertical Migration • Parthenogenic ↔ Sexual Cycles • Predation among Zooplankton Zoop. Distribution and Abundance: Parthenogenic -Sexual Cycles VS. Parthenogenic -Sexual Cycles Asplanchna Paramecium + Amictic ♀♀ = Amictic ♀♀ Parthenogenic -Sexual Cycles Chlamydomonas Asplanchna Paramecium + Amictic ♀♀ + Euglena = Parthenogenic -Sexual Cycles Enlargement = Mictic ♀♀ Large Mictic ♀♀ Mictic ♂♂ Mictic ♀♀ with “Humps” Controls on Zooplankton Distribution and Abundance • Temperature Nutrients • Physical Phactors Phish Phytoplankton • Vertical Migration • Parthenogenic ↔ Sexual Cycles • Predation among Zooplankton Zoop. Distribution and Abundance: Predation among zooplankton Predation Among Zooplankton Cyclomorphosis Cyclomorphosis: Elongation Cyclomorphosis: Enlargement Asplanchna Mictic ♀♀ Large Mictic ♀♀ Cyclomorphosis: Production of Lateral Spines Cyclomorphosis: Reduction in Spines Keratella Zooplankton in Streams and Rivers Low-Flow Areas Backwaters Reservoirs Alternate Copepod Life Cycle Cocopods Copepuffs