Systematic Position / Classification
Phylum: Retaria
Class: Globothalamea
Order: Rotaliida
Family: Elphidiinae
Genus: Elphidium
Species: Elphidium crispum
Habit and Habitat
- It is a free-living, marine, shelled-protozoan or foraminiferan.
- It occurs in the littoral zone of the sea down to about 600 meters.
- It is commonly found creeping about on sea weeds.
- It also occurs in brackish waters.
- It has many chambered shells and thread-like axopods.
- It mainly feeds on small algae and bacteria.
General Characteristics
- The size of Elphidium crispum ranges from 200 to 500 micrometers in diameter.
- It is a shelled protozoan.
- It exhibits the phenomenon of dimorphism, i.e., Elphidium exists in two distinct forms—large megalospheric and small microspheric forms.
- The microspheric form is small and multinucleate.
- The microspheric form exhibits the asexual mode of reproduction.
- The megalospheric form is large and uninucleate.
- The megalospheric form exhibits the sexual mode of reproduction.
- The shell of Elphidium crispum is disc-shaped, flattened, and slightly elongated in one direction.
- The aperture, or the opening in the shell, is on one side.
- Elphidium crispum is a benthic species, which means it lives on the sea floor.
- Elphidium crispum reproduces asexually by dividing into two daughter cells.
- It can also reproduce sexually by producing gametes.
Locomotion / Movement
- Elphidium crispum creeps slowly over the substratum on the sea bottom with the help of its reticulopodia.
- The reticulopodia are arranged in bundles around the shell.
- With the contraction of distally placed bundles, the body is pulled or dragged forward.
Nutrition / Food and Feeding
- Elphidium crispum is typically holozoic.
- It feeds upon minute organisms like diatoms, other protozoans, crustacean larvae, etc.
- The net-like reticulopodia are thought to secrete an external mucous layer to trap the food organisms.
- The mucous layer contains proteolytic secretions which paralyze the prey and initiate its digestion even during capture.
- The captured food, enclosed in a food vacuole, is drawn into the endoplasm by the withdrawal of reticulopodia filaments towards the interior of the body.
- Digestion is normally completed outside the shell and the products of digestion pass into the endoplasm.
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