Hexagenia populations have disappeared and later re-established in the area. It is also found throughout Canada, its range extends to just south of Alaska and Nunavut. It is the most widespread burrowing mayfly species in North America. (Giberson and Rosenberg, 1994; Green, et al., 2013; McCafferty, et al., 2012; Shipley, et al., 2012), a species of burrowing mayfly, sometimes called the giant mayfly, is native to the Nearctic region. It is widespread across the entirety of the United States, having been documented in every state except Arizona and Alaska. It is particularly prevalent in the Great Lakes region. Populations near Lake Erie have been the focus of much research and attention throughout the last few decades, as
As their common name suggests, giant mayflies can grow rather large, from 8.7 to 27.3 mm in length. Like all adult mayflies, they are soft-bodied, with large forewings and a smaller pair of hindwings, which are held together above the body when at rest. Two hairlike tails extend from the abdomen and they have small antennae. Burrowing mayflies of family Ephemeridae can be distinguished by their 4-segmeted hind tarsi, as well as their wing venation, most notably an abrupt distal bend in the base of the M2 vein in the forewing. Imagos, the sexually mature adults, can be differentiated from subimagos by their clear wings. Female imagos have lighter yellow bodies and smaller eyes than males and are typically several millimeters longer than males. Female imagos can also be twice the mass of males. They have a large variety in coloration (anywhere from yellow to white to shades of brown), patterns, and size. (Bachteram, et al., 2005; Borror and White, 1970; Bustos and Corkum, 2013; Corkum, 2010; Corkum, et al., 1997; Green, et al., 2013; Hunt, 1951; Reynoldson and Hamilton, 1993)
Nymphs of Hexagenia rigida. Male imagos of these two mayfly species can be distinguished by their genitalia; has penis lobes that hook, while H. rigida has penis lobes that are elongate and straight. also has a dark band along the outer edge of the hind wing that H. rigida lacks. Otherwise, it can be tricky to differentiate between Hexagenia species. (Bachteram, et al., 2005; Borror and White, 1970; Bustos and Corkum, 2013; Corkum, 2010; Corkum, et al., 1997; Green, et al., 2013; Hunt, 1951; Reynoldson and Hamilton, 1993)are elongate, with a cylindrical body. They have 3 tail filaments extending from the end of the abdomen and gills line the outer edges of the abdomen. Nymphs also have modified mandibles with sclerotized tusks for burrowing. When they hatch, nymphs are 1 mm long and males can grow to lengths of 23 mm, while females grow to lengths of 30 mm. Later nymphal instars have dark, prominent wing pads. Eggs are 0.3 mm by 0.2 mm and ellipsoid in shape. They are a white color and transparent enough to see the embryo inside. Non-viable eggs are dark or black. often inhabits the same area as another burrowing mayfly,
Like all mayflies, is hemimetabolous. It develops from an egg into a nymph, also called a naiad, with several instars, then molts into a sexually immature adult called a subimago or dun, then molts into a sexually mature adult called an imago or spinner. Eggs are laid in water by newly-mated females and either drop into the sediment or are dispersed by flowing water. Most eggs overwinter, as eggs of can survive in cold temperatures (8 degrees Celsius) for over a year. Development and hatching depend on exposure to anoxia and water temperatures. After the surrounding water reaches the appropriate temperature, eggs hatch a couple days to 2 or 3 weeks later. Some eggs may hatch within a few weeks of oviposition, without overwintering. Nymphs that hatch early experience little growth and few molts before winter. (Bustos and Corkum, 2013; Corkum, 2010; Corkum, et al., 2006; Corkum, et al., 1997; Giberson and Rosenberg, 1994; Green, et al., 2013; Shipley, et al., 2012)
Nymphs undergo as many as 30 molts and development time can take anywhere from 14 to 22 months. (Bustos and Corkum, 2013; Corkum, 2010; Corkum, et al., 2006; Corkum, et al., 1997; Giberson and Rosenberg, 1994; Green, et al., 2013; Shipley, et al., 2012)traditionally has a two year life cycle, the bulk of which is spent as a nymph, though in colder regions these mayflies may have a 3 or 4 year life cycle. Nymphal development time is temperature dependent. The final nymphal instar swims to the surface and molts into a sexually immature subimago. Because nymphal development time varies greatly, the period of subimago emergence can occur over an extended time, anywhere from spring to early fall. Subimago emergence also depends on temperature and does not occur until water temperatures have reached 20 degrees Celsius. The subimago moves on shore where it rests for 24 to 48 hours. One final molt produces the adult imago. The imago lives for up to two days, in which time it must find a mate and breed, before dying. Peak emergence of adults is during June and July, though they can emerge anytime from late spring to early fall. The life history of is complicated by protracted emergence, multiple cohorts, delayed hatching of eggs, and a wide variability of growth in individuals from the same egg mass.
Female body size is positively correlated with fecundity, each female contains 4,000 eggs on average, though this can range from 2000 to 7000. Due to their short life, they are semelparous, as they only lay one batch of eggs and die shortly after. Eggs may be dispersed by flowing water after oviposition. When strong wings are present, these female swarms have been observed being pushed ashore by the wind, then ovipositing their eggs under street lights rather than in the water. This may be because they are attracted to light, or because the streetlights may mimic moonlight reflected on water. Eggs that are deposited on cement are no longer viable, as they are prone to desiccation. Artificial insemination of eggs has been achieved in the laboratory by placing the male genitalia to an unfertilized egg mass, though the hatching rate is not as successful as natural insemination. (Bustos and Corkum, 2013; Corkum, 2010; Corkum, et al., 2006; Green, et al., 2013; Hunt, 1951)
Females of (Green, et al., 2013)provide provisioning in the eggs, and lay the eggs in a body of water that will provide a suitable habitat for the eggs and nymphs to grow and develop. Since adults live only for a day or two, they do not provide any further parental care.
Adults are poor fliers and often have to rely on winds to move them ashore after emerging from the water. They have been recorded traveling about 1.2 km on average away from their emergence site. Nymphs mainly remain in burrows. (Corkum, et al., 2006; Green, et al., 2013)
Adult mayflies have large eyes and can perceive their environment and others visually. They are also attracted to light. However, nymphs are photophobic and actively stay away from light, which is not typically an issue in their underwater burrows. (Bustos and Corkum, 2013; Gallon, et al., 2008)
Many aquatic animals prey on Macromia illinoiensis, and many freshwater fish species, including yellow perch, lake whitefish, and smallmouth bass. Though the nymphs burrow deep into the sediment, this behavior does not seem to prevent them from being preyed upon by dragonfly larvae. Many bird species, such as tree swallows and other aerial predators, such as adult dragonflies, can prey on the adult mayfly swarms. These swarms, as well as synchronous emergence of adults from immature stages in large groups is one defense against predators, as it decreases the risk of predation on any one individual. (Clady and Hutchinson, 1976; Corkum, et al., 2006; Corkum, et al., 1997; Fincke and Tylczak, 2011; Giberson and Rosenberg, 1994; Papp, et al., 2007)nymphs, such as dragonfly larvae including
Populations of Hexagenia species and the state of the lake caused people to reevaluate dumping phosphorous and other nutrients. After this was curbed and the lake was restored to habitable conditions, reappeared in the 1980s and is once again very prevalent in the region. As a source of prey for many fish, birds, and insects in the area, its disappearance could have had a significant impact on the other fauna of the ecosystem. Also in Lake Erie, populations are dealing with the effects of invasive zebra mussels (Dreissena polymorpha) and quagga mussels (Dreissena bugensis) that have spread throughout and now dominate the Great Lakes. Numbers of nymphs are lower in areas where the mussels have a high density, due to the buildup of mussel shells on the sediment, which prevents construction or maintenance on the burrows in which the nymphs live. However, the mussels do produce feces that the nymphs might feed on, which could be beneficial. (Freeman, et al., 2011; Green, et al., 2013)in Lake Erie have received considerable research attention, as this species disappeared from the region for over 30 years due to pollution and subsequent eutrophication and hypoxia episodes. The disappearance of this and other
Nymphs are significant agents of bioturbation in their benthic habitat. Through the currents they create with their gills, as well as their burrow building, nymphs likely cause some sediment bound chemicals such as cadmium to stay in the water, instead of sinking into the sediment. This may cause a slower recovery of contaminated areas. Their respiration activities may also play a role in oxygen depletion in the sediment-water interface area in which they live. Hexagenia rigida, another burrowing mayfly, particularly in Lake Erie and the eastern range of its habitat, they are often studied together. Whichever of the two is dominant often changes from season to season and the two species can often be found co-dominating a habitat. has been the dominant species in the last few years, which may be due to larger body size, allowing for better dispersal, as well as higher fecundity. Crepidostomum cooperi, a trematode that matures in sunfish of family Centrarchidae, uses nymphs of as a second intermediate host. (Bachteram, et al., 2005; Corkum, 2010; Edwards, et al., 2009; Marcogliese, et al., 1990)is often found in the same habitat as
Swarms of Hexagenia species can be huge and are often a nuisance to communities. Swarms were a problem particularly in the 1950s in the Lake Erie region, and as the populations have re-established in that region, are again causing problems. Since mayflies are attracted to lights, swarms often collect at street lights, causing power outages when swarms collect at illuminated power transformers. The dead bodies of mayflies can also quickly pile up. (Corkum, 2010; Corkum, et al., 2006; Reynoldson and Hamilton, 1993)and other
In July 1999, a swarm of mayflies made up of Hexagenia rigida on the shore of Lake Erie was so large that it was visible on Doppler radar. The swarm was thought to be 3 to 6 km wide, 16 to 25 km long, and 125 to 250 m in height. (Corkum, 2010)and
Angela Miner (author), Animal Diversity Web Staff, Leila Siciliano Martina (editor), Animal Diversity Web Staff.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats decomposed plants and/or animals
particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
union of egg and spermatozoan
a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.
mainly lives in water that is not salty.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
fertilization takes place within the female's body
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
Having one mate at a time.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
breeding is confined to a particular season
remains in the same area
offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
uses sight to communicate
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