Ephydra Hians in the Mono Basin - Article Example

Ephydra hians in the Mono Basin (Mono Lake) Introduction Mono Lake has numerous unique species of flies, birds, and other organisms. Ephydra hians also known as the brine fly, is the most visible type of insect found at the lake. Biologist argue that the rare fly thrives in Mono Lake since the lake provides a suitable breeding ground for it. Research indicates that the lake acts as a breeding ground to billions of Ephydra hians. The lake provides saline and alkaline conditions that favor the alkali fly while disfavoring many organisms that may otherwise compete with the flies for food, space and other resources. While they are not subject to much competition in their natural habitat, the alkali flies are food to predators such as birds and humans. The flies also must contend with certain environmental conditions such as water currents, waves, extremely high alkalinity, and cold temperatures. Description of the Species The alkali fly, is a rare species. This is attributable to the fact that the species breeds well only in certain habitats, especially in alkaline waters. This probably explains why the insect is called the alkali fly. Found in Mono Lake, California, and a few other Great Basin lakes, the fly breeds well on the surface and shore lands, as well as beneath the lake (Cash and Bradley 1994). Most of these populations of flies are dark brown in color with an adult measuring between 4 to 7 mm long. The fly has a segmented thorax, which is bluish in color, while the wings are brownish in color. Unlike ordinary flies, alkali flies normally spend most of their life cycles entirely beneath the water surface. This makes the fly unique in addition to the fact that it breeds well in alkaline environments. This paper discusses the Mono Lake alkali fly including its habitat, life cycles, and environmental factors that impact its survival. Reasons Why Mono Lake is a Preferred Habitat for the Alkali Fly Mono Lake is one of the renowned lakes in California. Circular in shape, Mono Lake draws most of its waters from its tributary streams. Since the lake has no outlet, however it is highly alkaline (Jiang, et al 2004). This is attributable to the continuous accumulation of salt in the lake. Research conducted more than three decades ago indicates a correlation between the alkalinity of Mono Lake and the availability of alkali flies. According to the research, the alkalinity of Mono Lake provides a suitable breeding ground for alkali flies (Jiang, et al 2004). Other researchers have also demonstrated that the salinity and alkalinity of Mono Lake has a significant impact on the algae found in the lake National Research Council, Herbst2 and Bradley2, 1989). The presence of these algae on the lake also influences the growth and development of the alkali fly. According to Wiens, et al. (1993), the salinity of the lake makes it difficult for algae to thrive. This leads to a reduction in the number of algae in Mono Lake, thereby compelling larvae to utilize high amount of energy to rummage. This normally allows very little osmoregualation to take place. Most species have no capacity to survive in highly saline water. However, alkali flies breed well in Mono Lake because the lake has a balance of alkalinity and salinity. Research conducted on the lake revealed that the alkaline concentration in Mono Lake is caused by both carbonate and bicarbonate ions drawn into the lake (Nixon 2012). As earlier stated, Mono Lake, has only inlets, and no outlets. As a result, all the carbonate and bicarbonate ions drawn into the lake ends up accumulating, resulting in increased alkalinity. The tributaries of mono lake include Rush Creek, Lee Vining Creek, and Mill Creek which flows through Lundy Canyon (United Nations Environment Programme 2014). Alkali flies tend to survive better in waters that are highly alkaline. At mono lake for example, the concentration of carbonate and bicarbonate ions is extremely high, making up about 40% of the dissolved solids as noted by Herbst2 (1990). Across the world, there is no lake that is higher in alkali levels that supports insect life. The alkali fly thrives in an highly saline environment. The level of salinity of the lake’s water directly affects the growth and development of the alkali fly and their rates of development. When the water is highly saline, the population of algae reduces and the larvae are forced to use more energy for foraging. This leaves little room for the occurrence of osmoregulation which makes it possible for the alkali fly to balance the quantity of salty in their bodies. Mono Lake Alkali Fly Life Cycle The Mono Lake alkali fly is an insect. Like all other insects, its typical life cycle involves developing from an egg to a larva and then to a pupa before undergoing a metamorphosis to become an adult that is capable of reproducing. For the alkali fly, the life cycle begins when a female fly that has mated with a male fly crawls beneath the water surface and goes to lay her eggs on substrate or benthic algal mats near the shore of the lake (Herbst1 1993). The eggs do not float but remain at the bottom of the lake because there are more dense compared to the water of the lake. To further ensure that the eggs are safe and have higher chances of hatching, the female fly may tuck her eggs into the algal mat. The egg of the mono lake alkali fly assumes the shape of a football and is about 0.2 mm wide and about 0.8 mm long, on average according to Herbst2 (1990). The eggs hatch within a period of between one and three days depending on the temperature and salinity of the water (Herbst1 1993). The larvae that is hatched from the egg undergo a series of developmental stages, shedding their old skin between the stages (the first, second, and third instars). Depending on several factors including the temperature, salinity, amount of food available, and the quality of food that they feed on, the larvae takes between four and 20 weeks to get into the pupal stage (Herbst2 and Bradley2 1989). Research shows that when the temperature of water is maintained at 20OC, development of the larvae in the first instars takes four days, the second instars, seven days, and the third instars, 14 days (Herbst2 and Bradley2 1989). In the natural environment, temperatures usually vary greatly which affects the rate of development of organisms. This also applies to Mono Lake where temperatures are always below 200C which means that the alkali flies take longer to develop. At the end of the larva stage, the mature larva attaches itself to the underside of a stone using clamp-like claws. An ideal location for spending away the inactive pupal stage is where it is lee likely to be dislodged by turbulent water (Herbst1 1993). In the event that the pupa is dislodged from its location, it gets to float to the surface given that the puparium is always filled with air. The larva forms a case around it to form a pupa. The organism remains inactive as it goes through a complete structural change to emerge within three weeks as an adult fly. At the end of the pupal stage, the adult Mono Lake alkali fly floats to the surface of the lake enclosed in a bubble of air. Most of the adult life of the fly is spent along the shores of the lake where it feeds on algae and detrital sources of food. Part of the life of the adult alkali fly is dedicated to procreation with males and females mating randomly. The female fly lays 10 eggs on average over a two-week duration and go beneath the water surface to the benthic algal mats where they deposit their eggs (Herbst and Bradley 1989). The adult fly lives for between 10 and 14 days but can live longer during winter. Environmental Factors that Affect the Development, Survival and Reproduction of the Mono Lake Alkali Fly Food The Mono Lake alkali fly is a scraper gatherer as well as a herbivore-detrtivore (National Research Council and National Academy of Sciences 1987). Once the eggs hatch, the larvae feed on algae mats and grow very fast to the maturity of the larvae. The main food sources for the alkali fly include blue-green algae Oscillatoria, some protozoa, green algae Ctenocladus circinnatus, and benthic algae Nitzshia frustrulum. Worth noting is that the mono lake alkali fly egg and pupa do not need food. This means that food is only essential for the larvae and adult fly. So as to access high quality benthic algae, the adult fly often goes below the water surface. Generally, the population of algae in the Mono Lake is a factor of the population of the alkali fly and their size (Herbst2 1990). While they feed on detritus and benthic algae, they are fed on by birds that flock around the Mono Lake. Like every other living organism, high quality food is essential to the survival of the Mono Lake alkali fly. When they have no access to high quality food, the flies grow slowly, develop over a longer duration, end up smaller in size at maturity, and have a higher chance of dying. Furthermore, when the food they have access to be of low quality, the alkali fly tends to be less successful when it comes to reproducing. While no studies have been conducted with respect to the vitality of protozoa and bacteria in the diet of the alkali fly, recent studies show that green algae provide less nutrition to the flies. It has been established that one limiting factor with respect to population and size of Mono Lake alkali flies is food. From spring through autumn, the population of the flies is relatively high and competition for food is thus high. This may explain why during this period, the body size of the pupa and adult alkali flies reduce significantly. Some of the main factors that impact the availability of food during summer at the Mono lake region include the supply of nutrients and depth (Foley and White 1989). The population of benthic algae generally drops with increasing depth of the lake as this is directly related to the amount of light that penetrates the water. What this basically implies is that the alkali flies have more food at shallow waters. During spring and summer, the population of planktonic algae is limited by the low concentration of ammonium in the lake. Temperature Studies indicate that ambient temperature has a strong effect on the spacial and temporal patterns of the population of the alkali fly. Evidently, temperature many of the life processes of the organism are regulated to a great extent by temperature. In close relation to this, temperature affects egg laying, hatching, growth, development, pupation and metamorphosis (Mono Basin Research 2013). When the ambient temperature is low, the flies’ metabolic processes slow down the effect being a rise in mortality and time required for development. Below a certain temperature threshold, the flies stop to develop altogether. Low temperatures especially affect the flies at their pupal and egg stages. For example, below five degrees centigrade, the pupa stops to develop and may not survive for long. This explains why high pupae mortalities are experienced during winter seasons when the water temperatures often go below the 50C threshold. The same case would apply for eggs if not for the fact that adult alkali flies do not lay their eggs during the winter season. During the larval stage, the organisms can survive temperatures close to zero as they grow slowly at this time. The pupae and larvae of Mono Lake alkali flies are highest in number in water that is no more than three feet in depth (Foley and White 1989). They are also very rare to find below the thermocline which does not promote their growth and development for the low temperatures involved. During development, the body size of adult alkali flies and larvae change seasonally. The body sizes are largest when spring begins and smallest during autumn. These variations in body size based on seasons could be a factor of changes in metabolic processes as a consequence of temperature changes, or the availability of quality food. While the alkali flies have a short growing season owing to the generally low temperatures that characterize the Mono lake region, they develop and reproduce quite rapidly. In one season, the flies can produce between one and three generations. Salinity and Alkalinity Most aquatic organisms are subject to osmotic desiccation in highly saline waters since their body fluids have less salt compared to the surrounding water. While the pupa takes advantage of the puparium to overcome the issue of osmotic desiccation, the larva maintains a normal body salt level by excreting salt through special organs in its body (Herbst3 1999). Not much is so far known by scientists about how the Mono Lake alkali fly eggs osmoregulate. The fly is generally well adapted to high saline conditions although the energy it spends on osmoregulation is high leaving very little energy for growth and development. The higher the salinity of the environment beyond a given threshold, the lower the success rate of pupation, the rate of hatching success, and the rate of larval growth and development. Furthermore, the higher the concentration of salt in the water, the lower the productivity of algae which are fed on by the alkali flies. This implies that the quantity of food available to the flies will be lower. When food availability is low, the rate of growth and development of the flies are reduced and the mortality rate increases significantly. The larvae of alkali flies have a better chance of surviving in alkaline salt water compared to salty water that is non-alkaline. The larvae are well adapted to the environment and use their lime glands to excrete carbonate ions from their blood. Predation and Competition Mono Lake alkali-flies are the most secure species of flies. Alkali-flies at Mono Lake are not under immediate danger from other preys found around the lake. The fact that the lake is highly saline and alkaline makes it difficult for other insects or preys other than alkali-flies to survive. Additionally, the high concentration of carbonates and bicarbonates also minimizes diseases and parasites (Herbst1, and Bradley1 1993). Therefore, alkali-flies are free to breed in Mono Lake without any serious threat. This explains why the numbers of alkali flies have consistently remained higher in Mono Lake than alkali-flies breeding in other lakes. The fact that the alkali-flies are not under serious threat from other insects and competitors does not imply that they are free from prey. Rather, the flies are under threat of birds. Alkali-flies normally face serious threat from birds especially during the pupa stage, when they come onto the surface and become easily accessible to birds and other prey (Herbst1, and Bradley1 1993). This is, particularly so, during summer when numerous larvae and pupa find their way onto the surface in around Mono Lake. Grebes, halaropes, and gulls, that live near Mono Lake are some of the species that depend on alkali-flies for food. In addition, alkali-flies also face significant danger from the society leaving around Mono Lake. For instance, the Kutzadikaa people normally hunt alkali fly for food during winter periods (Herbst1 and Bradley1 1993). Further, human activities taking place around the lake continually pollutes the lake, thereby interfering with the breeding ground of this unique specie of flies. When the water of Lake Mono gets low in terms of salt concentration, the chances of the alkali fly dying as a result of predation goes high. Some of the organisms that may feed on alkali flies in low salinity conditions include beetles, dolichopodid larvae, and tabanid as evidenced in Lake Pyramid and Lake Walker in Nevada. A study conducted by the Mono Basin Research Committee revealed that in lake Abert, Oregon, between 60 and 70 percent of the population of alkali fly pupae that were dislodged and swept to the shore fell prey to the small wasp (Wirth 1971). What this implies is that the Mono Lake alkali fly is subject to high mortality if they are disloged and swept away by water currents and waves especially during pupalage. On the other hand, adult alkali flies were eaten by damselflies and beetles among other insects, and birds. During summer, the birds that prey on Mono Lake alkali flies have a plentiful supply of fresh food given that pupae and larvae are dislodged from their original locations by windrows and drifts that constantly rock the waters of the lake. In this respect, research shows that during summer, roughly one metric ton of Mono Lake alkali fly larvae and pupae can end up floating on the lake. Substrate The habitat of the alkali fly falls within the definition of benthic-littoral as noted by Clark and Bradley (1994). The habitat consists of hard substrate such as beach rock, mudstone bedrock, and tufa; and soft substrate such as silt, sand, and mud. The alkali flies have a preference for hard substrate, more especially, tufa, compared to soft substrate going by the density of their pupae and larvae in the substrates according to Stine (1992). The hard substrate offers several advantages to the alkali flies including the presence of more food (algae) and protection from several harmful factors. Some of the harmful factors in this respect include shifting sands, currents, waves, and predators. In addition, hard substrate offers the alkali flies an environment to securely attach themselves especially when they are in their pupal stage. In as much as a lot of alkali fly larvae feed on detrital and algal mats, they are to less sheltered from waves and find nowhere to attach themselves firmly on soft substrate. The larvae of alkali flies tend to be more densely populated on hard substrate vis-s-vis soft substrates. While this is the case, soft substrate located near tufa tend to be more densely populated than those that are far from tufa as noted by Mono Basin Research (2013). The possible reason for this trend is that tufa provides greater recruitment, the availability of more quality food, higher accumulation of detritus, and lower wave action effects. As previously noted, substrate that are hard and that provide shelter for alkali fly larvae and pupae include free standing tufa, mudstone, bedrock, tufa-covered pumice blocks, and beachrock. In as much as mudstone covers a wider area compared to its counterparts on Mono Lake, its is not a preferred choice of shelter for alkali fly pupae and larvae according to Mono Basin Research (2013). This is because it is relatively soft and has no micro-crevices which act as shelter to them. Tufa-covered pumice stones which occupy the second largest area compared to other hard substrates are more preferred by alkali flies as a place of shelter. These blocks provide good shelter against waves and are relatively rough to the extent that they provide good holding surfaces for the larvae and pupae of alkali flies. Free standing tufa blocks while constituting a small type of habitat, are very important for alkali flies (Mono Basin Research 2013). These substrates primarily consist of calcium carbonate compounds and other mineral compounds that precipitate as a result of the mixing of fresh spring water and saline lake water. The bottom of Mono Lake is mainly covered in tufa. Apart from covering the lake bottom, tufa also often encrusts vegetation and man made objects such as tins and cans over time. Beachrock which comprises cobbles, gravel, and sand cemented by tufa provides a good habitat for alkali flies in their early life stages. However, they are considered to be of little significance given that they are not well distributed in and around Mono Lake and similar environments occupied by alkali flies. The most preferred hard substrates for alkali flies in their pupal and laval stages are tufa, irrespective of type. Studies reveal that the densities of larvae and pupae on tufa far exceed those found on other soft and hard substrates (Mono Basin Research 2013). It is thought that this is the case considering that tufa has a rough surface which translates to better footholds. Tufa also serves as a prominent place for the growth of algae in addition to providing deeper crevices in which the larvae and pupae find shelter against tides, predators and waves. Given that tufa towers rise above the bottom surface of the lake, they provide shelter to alkali fly larvae and pupae from abrasion and burial by moving sand. The Kutzadikaa People Several years before the first European Americans arrived at the Mono Lake Basin, the Kutzadikaa people had established settlements along the Mono Lake basin. The Kutzadikaa people who followed annual cycle of gathering food depended greatly on the mono lake for their food (Mono Basin Ecosystem Study Committee of the National Research Council 1987). The shallow waters provided the people with a steady supply of alkali fly pupae. Rich in protein and fat, the pupae larvae could be easily stored for future consumption. They often dried the pupae in the sun before removing the shells as part of preparation before they consumed the flies. The Mono Lake Paiute used the dried pupae to make a salty, calorie packed, proteinuos biscuits or soup that they called kutsavi (Mono Basin Ecosystem Study Committee of the National Research Council 1987). It is because they ate alkali flies that the people who settled around the Mono Lake got the name Kutzadikaa , which means “eaters of flies”. The Kutzadikaa people never restricted their lives around the Mono Lake Basin. During autumn, they often moved and camped at the hills that are situated east and north of the Mono Lake. While staying at these places, they survived on Pinyon nuts that are rich in carbohydrates, fats, and proteins (Mono Basin Ecosystem Study Committee of the National Research Council 1987). The people also fed on the nuts, which they stored in the winter, during winter. They also hunted rabbits for their meat and skins. They used the rabbit skins for clothing while they consumed the meat as food. Another source of food for the Kutzadikaa people was the pronghorn antelopes which they trapped through the corrals. During the winter seasons, they moved to the valleys and during spring, they camped along the Rush Creek or along sources of fresh water. The shallow streams that fed the Mono Lake were preferred sites for the dwelling of the Kutzadikaa people as their women easily collected alkali flies from them. Conclusion The Mono Lake region is has a rich ecosystem in spite of it having an environment that is harsh to many species. The lake has extremely high levels of salinity and alkalinity that make it unsuitable for habitation by many aquatic animals such as fish. The lake provides a conducive environment for habitation to alkali flies, most especially the brine flies or Ephydrahians. The alkali flies have several adaptations that make them able to survive in the environment that is mostly devoid of flora and fauna. The flies that mainly feed and breed on blue and green algae that thrive in the lake are a rich source of food to at least 100 species of birds. Some of the bird species that flock around the mono lake either temporarily or permanently include: red-necked phalaropes, flamingoes, egrets, Wilsons phalaropes, horned lark, bank swallow, dusky flycatcher, and stellers jay. Many of the birds that flock around the lake are migratory birds that originate several thousands of kilometers away from the Lake. Like the birds that find the alkali flies useful for feed, the Kutzadikaa people, an Indian tribe, collect and dry alkali fly pupae and use it for food. Humans also find the Mono Lake region an attractive place for its tufa mounds and beautiful birds. Tufa mounds line the shores of Mono Lake as well as occur beneath its waters. The mounds form as a result of the precipitation of carbonate minerals in lacustrine settings or fluvial channels. Although the Mono Lake region is a great attraction, it is has not escaped from destruction by humans through pollution and diversion of waters that would otherwise end up in the lake for private and commercial use. Works Cited Cash, C. & Bradley, T., 1994. External morphology of the alkali fly (Ephydrahians) Say at Mono Lake, California (USA) in relation to physical habitat. Journal of Morphology v. 219 no.3 pp. 309-318. Foley, C. & White, B., 1989. Occurrence of Ephydra hians Say (Diptera: Ephydridae) in deep water in Mono Lake, California. Bulletin Southern California Academy of Sciences, v. 88, no. 1, pp. 40-41. Herbst1, D. & Bradley1, T., 1993. A population model for the alkali fly at Mono Lake: Depth distribution and changing habitat availability. Hydrobiologia, v. 267 no. 1-3, pp. 191-201. Herbst1, D., 1986. Comparative studies of the population ecology and life history patterns of an alkaline salt lake insect: Ephydra (Hydropyrus) hians Say (Diptera: Ephydridae). Ph.D. thesis, Oregon State University, Corvallis. pp. 206 Herbst2, D. and Bradley2, T., 1989. Salinity and nutrient limitation on growth of benthic algae from two alkaline salt lakes of the western Great Basin (USA). Journal of Phycology, v. 25 pp. 667-673. Herbst2, D., 1990. Distribution and abundance of the alkali fly (Ephydrahians Say) at Mono Lake, California (USA) in relation to physical habitat. Hydrobiologia v. 197, pp. 193-205. Herbst3, D., 1999. Biogeography and physiological adaptations of the brine fly genus Ephydra (Diptera: Ephydridae) in saline waters of the Great Basin. Great Basin Naturalist, v. 59, no. 2, pp. 127-135. Jiang, S., Steward, G., Jellison, R., Chu, W., Choi S., 2004. Abundance, Distribution, and Diversity of Viruses in Alkaline, Hypersaline Mono Lake, California.Microb Ecology, v. 47 no. 1, pp. 9-17. Mono Basin Ecosystem Study Committee of the National Research Council, National Academy of Sciences, 1987. The Mono Basin ecosystem: effects of changing lake level. Washington, D.C.: National Academy Press. Mono Basin Research 2013. EIR Appendix I. Natural History of the Mono Lake Alkali Fly. 551/APPD-I I-1 http://www.monobasinresearch.org/images/mbeir/dappendix/app-i-text.pdf Nixon, E., 2012. Geologic History of the Mono Basin. G188/G190. http://www.iub.edu/~sierra/papers/2012/Nixon.pdf Stine, S., 1992. Distribution of "substrate types" at Mono Lake. Report to Jones and Stokes Associates. United Nations Environment Programme, 2014. Endorheic Lakes: Waterbodies That Dont Flow to the Sea. UNEP Division of Technology, Industry and Economics. Wiens, J., Patten, D. &Botkin, D., 1993. Assessing Ecological Impact Assessment: Lessons from Mono Lake, California, Ecological Applications, v. 3 no. 4, pp. 595-609. Wirth, W., 1971. The brine flies of the genus Ephydra in North America. Annals of Entomological Society of America v. 64, pp. 357-377. Read More