Long-bristled rotifer
Filinia longiseta
The long-bristled rotifer is a microscopic multicellular organism found globally in the zooplankton of freshwater bodies. It is characterized by a saccular body and three extremely long setae (bristles), with two located laterally at the anterior and one at the posterior end. These bristles allow for sudden, jumping movements, providing an effective defense mechanism against predators. The species is a filter feeder, primarily consuming bacteria and organic detritus.
Details
Identification
Three long, unsegmented bristles (setae); oval to egg-shaped body; corona at the anterior end for feeding.
Social behavior
Solitary living, but forms dense populations in the plankton under favorable feeding conditions.
Diet
Filters tiny particles such as bacteria, protozoa, and fine detritus from the water column.
Hunting strategy
Passive filter feeder; creates a food current using the ciliary wreath of the corona.
Spawning substrate
Pelagic; eggs are often briefly carried on the body or released directly into the water.
Overwintering
Overwintering as resting eggs (cysts) in the sediment of water bodies.
Ecology
Ecological role
Important consumer in the microbial loop; converts bacterial biomass for higher trophic levels.
Natural predators
Predatory zooplankton (e.g., Asplanchna), copepods, and predatory insect larvae.
Competitor species
Other filter-feeding rotifers of the genera Brachionus and Keratella.
Ecosystem service
Contributes to water purification by consuming bacteria and organic suspended matter.
Threats
Severe chemical pollution, extreme water acidification, and invasive predators.
Scientific profile
Profile
Distinguishing features
Possesses two antero-lateral setae and one posterior seta. In Filinia longiseta, the posterior seta is distinctly subterminal (inserted approx. 15-30 µm from the posterior end), distinguishing it from F. terminalis. The setae can reach 2 to 4 times the body length and serve as flotation appendages and for escape via jerky jumping movements.
Reproduction
Heterogony: For most of the year, reproduction occurs via obligate parthenogenesis. Under environmental stress (density, food shortage), mictic females appear, which produce resting eggs after fertilization.
Role in food web
Important link in the 'microbial loop'; transforms bacterial biomass and nanoplankton into energy available for higher trophic levels.
Protection & threats
Status not on standard scale
Main threats
No immediate threats known; tends to benefit from anthropogenic eutrophication, but is sensitive to toxic chemical pollution.