Ecology - Zooplankton Flashcards
Zooplankton
Defined as small aquatic invertebrates living in water columns of lakes or slow-moving streams.
Rotifers
Free-living planktonic pseudocoelomates characterised by as wheel of cilia called a corona at the anterior end
Where do rotifers inhabit?
Freshwater, associating with littorial substances, with some being planktonic.
Morphology of rotifer…
Elongated with distinct head, foot and mouth.
Function of corona….
Movement and generating currents to drag in food.
Where is food processed?
Muscular pharynx, a mastax, with a unique trophi which break down food particles.
How do rotifers feed?
Pulsating action of the coronal cilia, 12nm or less.
Feeding preferences of rotifer…
Selective feeding if planktonic, raptorial feeders and predate if large.
Parthenogenesis
A form of reproduction where an egg can develop into an embryo without fertilization by sperm.
Reproduction of rotifer..
Amicitc females produce amictic eggs, developing into amicitc females.
Male reproduction of rotifer…
Females produce an egg in a mictic female
Two fates of an egg?
If fertilized, a resting egg undergoes diapause, extremely resistant to envrionment
If NOT fertilized, a male rapidly develops, being short lived and sexually active within an hour of birth.
Conditions for rotifers to be most prominent…
Stentotherm in winters/early spring
Late summer in tandem with cyanobacteria population development
Rotifer tolerance to variable O2 concentration…
Allows occupation of spatial niches in metalimnion and hypolimnion, and winter seasonal survival
What does threshold food level of rotifers correlate with…
Body mass and growth rate.
Cladocerans
Majorly microzooplankton, distinguished by distinct heads, and a body covered by bivalve cuticular carapce.
Feeding of cladocerans…
Chitinized mandible for grinding and maxillules for pshing food between the mandibles.
Structures of cladocerans…
Sensory organs of a larger compound eye and a smaller ocellus
How do cladocerans feed?
Ventral thorax legs with hairs and setae, movement of which create currents that oxygenate the surface of the body and simultansouelsy incorpoate food particles.
Reproduction of Cladocerans…
Majorly parthenogenetic yet CAN go sexual reproduction.
Cladocerans sexual reproduction…
Eggs are produced and stored in a brood chamber in a cavity dorsal bound to he body by the carapace.
Copepods
Are small aquaitc crustaceans
Identifying copepods
They are identified with an anterior metasome, with a head region with five appendage parts and a thorax with six pairs of swimming legs.
Urosome
Abdomen or postabdomen of an arthropod
