Leuckart's Cyclops
Thermocyclops leuckarti
Thermocyclops leuckarti is a small, pelagic copepod primarily found in standing freshwater bodies. The species is characterized by a slender body shape and specific morphological features on its swimming legs and furcal rami. It is one of the most common zooplankton species in eutrophic and mesotrophic lakes across Central Europe. Population densities typically peak within the epilimnion during the warmer summer months.
Details
Identification
Slender body; terminal segment of the endopodite of the 4th swimming leg more than three times as long as wide; short furcal rami.
Social behavior
Solitary, but forms dense aggregations in open water during peak population periods.
Diet
Adults are predatory, feeding on smaller zooplankton such as rotifers; nauplii and early copepodids are filter feeders.
Hunting strategy
Ambush predator that detects prey via mechanoreceptors on the antennae and actively seizes it.
Spawning substrate
Eggs are carried in two separate egg sacs attached to the female's abdomen.
Overwintering
Diapause as a copepodid stage (usually stage IV or V) within the bottom sediments of water bodies.
Ecology
Ecological role
Important consumer in the aquatic food web; regulates rotifer populations and serves as food for fish.
Natural predators
Planktivorous fish, predatory zooplankton (e.g., Leptodora kindtii), and insect larvae (e.g., Chaoborus).
Competitor species
Other cyclopids such as Mesocyclops leuckarti or predatory calanoids.
Ecosystem service
Support of nutrient cycling and provision of biomass for higher trophic levels.
Threats
Eutrophication (in extreme cases), acidification of water bodies, and chemical pollutants.
Scientific profile
Profile
Distinguishing features
The terminal segments of the 5th leg (P5) bear two appendages of approximately equal length. The connecting plate of the 4th swimming leg (P4) features characteristic sharp prominences (spines). The receptaculum seminis of females is hammer-shaped with short lateral arms. The furcal rami are relatively short (approx. 2-3 times as long as wide).
Reproduction
Sexual reproduction; females carry two lateral egg sacs. Development proceeds through naupliar and copepodid stages.
Role in food web
Important link between primary producers/microzooplankton and higher trophic levels (fish); regulates rotifer populations through predation.
Protection & threats
Status not on standard scale
Main threats
General degradation of water quality, extreme acidification, and invasive species that massively increase predation pressure in the pelagic zone.