Ephydra hians
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Collection of Ephydra hians on the shore of Mono Lake |
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| Say , 1830 |
Ephydra hians is a species of salt flies ( Ephydridae ). The species iscalled alkali fly in its North American homeland.
features
The small fly species reaches a body length of 4 to 7 millimeters and is therefore one of the larger species in its genus. The body is uniformly brown in color, but appears gray due to a more or less dense, waxy pollination. Only the forehead (mesofrons) is unpolluted and shiny, sometimes with a greenish metallic sheen. The species has quite dense and conspicuous hairs made up of black colored setae. The membrane of the wings is clouded smoke brown, with brown veins. The species can only be reliably distinguished from other species of the family by the detailed features of the bristles ( chaetotaxis ) and the morphology of the male reproductive organs .
The larvae of the third (last) larval stage are almost 10 to 12 millimeters long. They are cylindrical with a long, flexible, retractable breathing tube at the rear end; the first two front segments can also be retracted. The foremost section, which forms the rudimentary head, is mostly drawn in and not visible. The integument of the larva is whitish gray, somewhat leathery, reinforced and translucent, with an indistinct pattern of dark spots or transverse bands on the upper side, which is sculptured by tiny thorns. The fifth to eleventh body segment each has a pair of rather long, flexible pseudopods, each with a wreath of claws at the end. The twelfth segment is an odd pseudopod. The breathing tube at the rear end is divided in two towards the end, each of the branches with two weakly sclerotized open spiracles, it also has two long, thread-like retractable anal papillae near the base. The small, rudimentary head section is bilobed, with a pair of very small, tripartite antennae. The two mouth hooks are colored yellow and spoon-shaped. The pupa reaches a body length of about 7 to 8.5 millimeters, with an approx. 4 to 5 millimeter long breathing tube, similar to the larva. It is translucent brownish in color and stiff, the body curved upwards. The pseudopods of the seventh and eighth segment form a clamping device with those of the twelfth segment.
Ecology and way of life
The larvae of the species live and develop in shallow salt lakes in western North America, from Mexico to southern Canada. It is particularly typical of soda lakes with salty and at the same time lime-rich, alkaline water. In tide pools and lagoons on the American west coast, however, the species is absent; here it is replaced by other species of the genus Ephydra . The species is particularly characteristic of Mono Lake in California , where it is the only representative of the genus. In the Great Salt Lake in Utah it happens though, is here but far less frequently than Ephydra gracilis . According to an analysis of the ecological requirements and the distribution of the ephydra species in the Great Plains , ephydra hians is characteristic of very salty and alkaline, larger bodies of water. In salty, but carbonate-poor inland waters, it is replaced by Ephydra gracilis , in small and temporary waters, mostly of lower salinity, Ephydra auripes and Ephydra packardi predominate .
The larvae live on the bottom of the salt lakes, mostly near the shore, preferably on the hard, precipitated tufa crusts, but less often on soft substrates such as sand or silt, where they feed on algae and organic detritus . They have a long breathing tube with which they can take in atmospheric oxygen, but are not dependent on it. Often they live completely submerged, the breathing tube then acts as a gill. The pupae (actually puparia; pupae enclosed in the last larval skin) cling to hard objects such as branches that have fallen into water to transform. Often, however, there are not enough clamp structures, then they can simply sink to the floor. To lay their eggs, the females climb on a blade of grass or other overhanging structure, or on the hard, precipitated tuff limestone crusts into the water, whereby they remain enveloped by an air bubble, but often they simply land on the surface of the water and let the eggs sink to the bottom.
The larvae pass through the three larval stages in 15 to 58 days, in the absence of food and unfavorable conditions up to 120 days.
In the extreme ecosystems of the salt lakes, the larvae of this species, and other members of the genus with higher salinity, usually form the only higher life alongside the brine shrimp of the Artemia franciscana (the Mono Lake population is separated from some taxonomists as Artemia monica ). In this extremely species-poor ecosystem, however, they can reach enormous densities of individuals. More than 10,000 larvae per square meter of lake bed live on favorable subsoil ( tufa ), and even on unfavorable (sand) it is still around 550 per square meter.
The flies, some of which live in extreme densities, and their larvae and pupae are of great importance in the local ecosystem. Three bird species, Wilson's treadmill , black-necked grebe and California gull , occur in high densities at salt lakes such as Mono Lake, which can be explained by this favorable food supply. In earlier times, the indigenous people of the Paiute also harvested the dolls as food insects for human consumption.
Taxonomy and systematics
The genus Ephydra is distributed almost worldwide, mainly Holarctic , in Eurasia, Africa and North America, it occurs south to Mexico and is absent in South America (and in Australia). It forms the tribe Ephydrini with about ten other genera .
The species belongs to the subgenus Hydropyrus Cresson and is its type species.
Diving ability
The adults of the species are notable for the fact that, enclosed in an air bubble, they can submerge in water without being wetted and thereby wet. This behavior was described more than 150 years ago by the writer Mark Twain on a visit to Mono Lake. Experimental studies have shown that the combination of dense, short hair and the body surface, which cannot be wetted by embedded long-chain hydrocarbons, explains the effect. Since the carbonate-rich alkaline water of salt lakes such as Mono Lake significantly increases the wettability compared to pure water, the species has a significantly lower wettability compared to other fly species. Nevertheless, large numbers of flies in the habitat are killed when the surface tension is reduced, for example by substances formed during the decomposition of plant material.
Individual evidence
- ^ A b Willis W. Wirth (1971): The Brine Flies of the Genus Ephydra in North America (Diptera: Ephydridae). Annals of the Entomological Society of America 64 (2): 357-377.
- ^ Karl W. Simpson (1976): The mature larvae and puparia of Ephydra (Halephydra) cinerea Jones and Ephydra (Hydropyrus) hians Say (Diptera: Ephydridae). Proceedings of the Entomological Society of Washington 78: 263-269.
- ↑ Wesley A. Maffei: Brine Flies. in: Baylands Ecosystem Species and Community Profiles: Life histories and environmental requirements of key plants, fish and wildlife. Prepared by the San Francisco Bay Area Wetlands Ecosystem Goals Project, 2000. PR Olofson, editor. San Francisco Bay Regional Water Quality Control Board, Oakland, California.
- ↑ a b David B. Herbst (1999): Biogeography and physiological adaptations of the brine fly genus Ephydra (Diptera: Ephydridae) in saline waters of the Great Basin. Great Basin Naturalist 59 (2): 127-135.
- ^ A b David B. Herbst (1990): Distribution and abundance of the alkali fly (Ephydra hians) Say at Mono Lake, California (USA) in relation to physical habitat. Hydrobiologia 197: 193-205.
- ^ Mono Basin Ecosystem Study Committee, Board on Environmental Studies and Toxicology, National Research Council: The Mono Basin Ecosystem: Effects of Changing Lake Level. National Academy Press, Washington, DC 1987. ISBN 0-309-54281-2 ( download ).
- ↑ J. Schrader, DGAB Oonincx, MP Ferreira (2016): North American entomophagy. Journal of Insects as Food and Feed 2 (2): 111-120. doi: 10.3920 / JIFF2016.0003 .
- ^ A b Wayne N. Mathis (2008): Two new neotropical genera of the shore-fly tribe Ephydrini Zetterstedt (Diptera: Ephydridae). Zootaxa 1874: 1-15.
- ↑ Wane N. Mathis & Luciane Marioni (2016): Revision of Ephydrini Zetterstedt (Diptera: Ephydridae) from the Americas south of the United States. Zootaxa 4116, 1-110.
- ↑ Floris van Breugel & Michael H. Dickinson (2017): Superhydrophobic diving flies (Ephydra hians) and the hypersaline waters of Mono Lake. PNAS 114 (51): 13483-13488. doi: 10.1073 / pnas.1714874114
Web links
- Mono's Alkali Fly www.monolake.org (The Mono Lake Committee)
- This fly survives a deadly lake by encasing itself in a bubble. by Elizabeth Pennisi. November 20, 2017, www.sciencemag.org.