Culmenella lineata

Culmenella lineata is a small species of freshwater gastropod in the family Planorbidae. It is native to South and Southeast Asia.

Culmenella lineata
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Superorder:	Hygrophila
Family:	Planorbidae
Genus:	Culmenella
Species:	C. lineata
Binomial name
Culmenella lineata (H. F. Blanford, 1871)[2]
Synonyms[3]
Camptoceras lineatum H. F. Blanford, 1871

Taxonomy

Culmenella lineata was originally discovered in 1869 by Henry Haversham Godwin-Austen near Nazirpur, India alongside Camptoceras austeni.^[4] It was subsequently described in 1871 as Camptoceras lineatum by Henry Francis Blanford.^[2]

Description

The dark brown, oval-shaped shell of Culmenella lineata measures about 2.3 mm (0.091 in) in diameter and 4.2–4.5 mm (0.17–0.18 in) in height. The aperture (shell opening) measures about 3.5 by 1.7 mm (0.138 by 0.067 in). The oval-shapedaperture 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 (body) whorl is unfused.^[2][5] A 3-dimensional structure (sculpture) is present, made of dark-colored raised lines, as well as small hairs (chaetae).^[2][5][6]

The foot (an organ used for locomotion) is relatively short, and the eyes are set at the base of tentacles.^[5]

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.^[1]

This species may be found up to a depth of 4 m (13 ft) in lakes, ponds, wetlands, and streams with vegetation. This vegetation includes both aquatic species like Hydrilla verticillata (which it is most highly associated with), Vallisneria spiralis, and Potamogeton octandrus, as well as emergent species like Panicum auritum.^[1][5] The species was always observed in substrates with more clay than those with more sand.^[5] It shares similar habitats with Camptoceras austeni, and may live alongside it. Like C. austeni, C. lineata may cling to vegetation.^[2][4][5] It has been observed to eat periphyton (microbial growth) 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.^[5]

Reproduction and development

Culmenella lineata may lay egg capsules on the leaves of aquatic vegetation such as Vallisneria and Hydrilla. Each capsule is circular, measuring about 1 mm (0.039 in) in diameter. Between 6 and 10 eggs may be found in each capsule, which are set in a gel-like substance. The eggs are hexagonal and transparent, displaying a yellow embryo inside. After one day, the embryos will have grown hair-like structures called cilia, allowing them to move around the egg. At 2 days old, the embryos stop moving as much, and the color becomes much fainter and more transparent. At 3 days old, the embryos will have a shell, eyes, and mouth. At 5 days, the embryos hatch into juveniles, and at about 20–25 days, become adults. This species has been observed to lay eggs in captivity, though with low survivability into adulthood.^[5]