Culmenella lineata
Culmenella lineata is a small species of freshwater gastropod in the family Planorbidae. It is native to South and Southeast Asia. This species lives streams, lakes, and wetlands with aquatic vegetation, where it grazes on microbial growth called periphyton. It is known to survive dry periods by aestivating. It lays eggs in clusters of 6–10, which hatch after 5 days and reach maturity after 20–25 days.
Taxonomy
Culmenella lineata was originally discovered in 1869 by Henry Haversham Godwin-Austen near Nazirpur, India alongside Camptoceras austeni. It was subsequently described in 1871 as Camptoceras lineatum by Henry Francis Blanford. Type specimens, or those used in Blanford's original description, are held in the collections of the Natural History Museum of London.Description
The dark brown, oval-shaped shell of Culmenella lineata measures about in diameter and in height. The aperture measures about. The oval-shaped aperture protrudes above the surface of the shell. There are 2.5 whorls, or revolutions of the shell. Most whorls are fused, though in some cases a small fraction of the final whorl is unfused. A 3-dimensional structure is present, made of dark-colored raised lines, as well as small hairs.This snail has red blood, giving it a slightly pink color. The foot and tentacles are dotted with black, white, and olive colored spots. The head is dark in color with similarly colored dots and stripes. The foot is relatively short, coming to a blunt point. It is nearly hidden by the extended aperture. The eyes are set at the base of thin tentacles, which widen slightly towards the tips. The animal's snout is also relatively short and blunt.
The radula is similar to Camptoceras hirasei and Culmenella subspinosum. This species possesses teeth in rows of 43, with one central rachidian tooth bordered on each side by 9 lateral teeth and 12 poorly developed marginal teeth. The jaws are made of 3 parts, with one wide piece bordered by 2 long skinny pieces.
Distribution, habitat, and ecology
Culmenella lineata may be found across much of South Asia and parts of Southeast Asia, including northern India, Nepal, and Bangladesh. Its range likely extends into Bhutan, Myanmar, and Thailand. It is rare in Nepal. Specific occurrences have been recorded from at least 3 river systems, including the Ganges, Brahmaputra, and Irrawaddy Rivers.This species may be found up to a depth of in lakes, ponds, wetlands, and streams with vegetation. This vegetation includes both aquatic species like Hydrilla verticillata, Vallisneria spiralis, and Potamogeton octandrus, as well as emergent species like Panicum auritum. The species was always observed in substrates with more clay than those with more sand. It shares similar habitats with Camptoceras austeni, and may live alongside it. Like C. austeni, C. lineata may cling to vegetation. It has been observed to eat periphyton and decomposing plant matter. In an Indian wetland, it was found in population densities of up to 45 per square meter, or as low as 11 per square meter.
This species is known to survive dry periods through a process called aestivation. It can create a structure called an epiphragm, sealing the shell opening and preventing the snail from drying out.