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Dolania americana. Photo by Greg Courtney. Image may be subject to copyright.
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Dolania americana Edmunds and Traver, 1959

American Sand-burrowing Mayfly

Federal Protection: No US federal protection

State Protection: No Georgia state protection

Global Rank: G4

State Rank: SU

SWAP High Priority Species (SGCN): No

Element Occurrences (EOs) in Georgia: 0

Habitat Summary for element in Georgia: Large rivers and their tributaries in shifting sand with fairly swift current


Description

The American Sand Burrowing Mayfly (Family: Behningiidae) is among the smallest species of mayflies, with membranous forewings only 10-13 mm (0.4-0.5 inches) in length. As a subimago and imago, Dolania americana are pale brownish purple in color. The mouthparts are vestigial. The eyes are large, especially in males. Their large, triangular net-veined forewings and smaller hind wings are held straight above the body at rest. The forelimbs of the imago are long, but the two outer tails at the end of the abdomen are longer, often more than twice the length of the rest of the body. The middle terminal tail is considerably shorter and thinner.

As a nymph, the body is cylindrical. The head is flat with antennae projecting from the ventral side. Nymphs possess razor sharp palps that are used to manipulate prey. The legs are all clawless, as they are not used to crawl, but rather for defensive (hindlegs) and raptorial (forelegs) purposes. The abdomen usually bears three (sometimes 2) long tails and six pairs of gills ventrally.

Similar Species

Dolania americana has many characteristics that distinguish it from other mayflies.

Habitat

Not much is known about the specific aquatic requirements of Dolania americana. Nymphs can be found in the streams and rivers of the coastal plains of the southeastern United States where they burrow into the sandy riverbed.  Adults appear briefly, flying over the water surface. Based on field and laboratory observations, a primary requirement of this species is the presence of beds of coarse sand substrate in which the nymphs live. One study (McCafferty 1975) showed that nymphs will burrow in clean, well-aerated sand to a depth of 10 to 30 cms, although shallower depths have been reported since (Tsui and Hubbard 1979).  

Diet

The D. americana  nymph is very unusual in being predaceous, one of just seven mayfly species known to be predatory in this life stage. The diet is comprised of midge larvae which survive in the same habitat, but may also include micro-crustacea, biting midge larvae, nematodes, and occasionally tardigrades.  After the nymph develops into an imago and subimago, it does not eat.

Life History

Dolania americana  spend a vast majority of their life as a nymph, getting its nutrients through predation on other small sand-dwelling organisms. They can spend up to two years as a nymph before emerging from the river in the subimago state. It is in this state that D. americana is most vulnerable to predation, as subimago females are the favorite food of many fish and whirligig beetles, as well as a variety of sparrows, bats, dragonflies, and spiders. While the females never grow past their subimago state, the males will moult into imagos, and within five minutes of doing so will set out frantically across a stretch of river in search of a mate. After mating with a female, male imagos will continue for up to 30 minutes, until he collapses into the river from exhaustion and drowns. The females live even shorter adult lifespans. Stuck in their slow subimago state, females can live up to five minutes, and must rely on a male to find them if they are to successfully mate before they die. Once mated, a female can produce up to 60 eggs before dying and subsequently sinking back to the sandy riverbed, where the relatively large eggs will, if they haven’t been eaten, hatch within a year.

Survey Recommendations

The American Sand Burrowing Mayfly has the shortest adult lifespan of any organism recorded. Therefore, we recommend constant surveillance during the summer months when adults are active, as well as continued inventories across Georgia’s large rivers in an effort to document new populations. The Sand-Burrowing Mayfly has only two confirmed populations in the Georgia, while South Carolina has as many as six, and Florida over nine. The species is yet to be recorded along the shores of the Chattahoochee river, a large river with adequately clean water and sediment to support at least twelve other species of mayfly.

Range

Dolania americana is known from Alabama, Florida, Georgia, Louisiana, North Carolina, South Carolina, and Wisconsin. Specific regions in Georgia include the upper Savannah River and the Satilla River. Because of the specific conditions required for this species to survive, it is possible that there is a population in the Chattahoochee River, although there are no recorded sightings.

Threats

All populations studied are from “clean” shifting sand and high quality fresh water. Therefore any degradation in water quality or sedimentation can have drastic effects on the survival of this species, which is by far their greatest threat.

Georgia Conservation Status

There are only two confirmed populations in the state; one in the upper Savannah River, and another in the Satilla River. Due to this lack of information, the species is currently listed in Georgia as SU (Subnation Unrankable). However, in our two neighboring states with the largest recorded populations, South Carolina and Florida, it is listed as vulnerable (S3).

Conservation Management Recommendations

The habitats where the two known populations occur should have their water and sand tested periodically for any changes, and strict care should be taken not to alter the river sediment or water quality in any way. Oxygen should be monitored for both the sediment and the water, as the nymphs and their prey are sensitive to oxygen levels. Care should be taken to prevent run-off and erosion, as well as pesticide use in areas near known populations, as these can affect the cleanliness of the water and the texture of the sediment in which the nymphs burrow.

References

Jackson, D.R. “American Sand-Burrowing Mayfly .” NatureServe Explorer 2.0, 30 June 2014, explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.120259/Dolania_americana.

Fink, T.J., T. Soldan, J.G. Peters and W.L. Peters. 1991. The reproductive life history of the predacious, sand-burrowing mayfly Dolania americana. Pages 211-230. In: Advances in Ephemeroptera Biology, J. F. Flannagan and K. R. Marshall, Editors. Plenum. New York, New York.

McCafferty, W.P. 1971. Systematics of the mayfly superfamily Ephemeroidea (Ephemeroptera). Unpublished Ph. D. Dissertation. University of Georgia. Athens, Georgia.

McCafferty, W.P 1975. The Burrowing mayflies (Ephemeroptera: Ephemeroidea) of the United States. Transactions of the American Entomological Society. 101:447-504.

McCafferty, W.P. 2004. Higher classification of the burrowing mayflies. (Ephemeroptera: Scapphodonta). Entomological News. 115, No. 2 84-90

Tsui, T.P and M.D. Hubbard. 1979. Feeding habits of the predaceous nymphs of Dolania americana in northwestern Florida (Ephemeroptera: Behningiidae). Hydrobiologia 67:119-123.

 

Authors of Account

Adam Smith

Date Compiled or Updated

May 4, 2020