Description

Order- In recent decades, many authors have doubted the validity of the Cladocera as a taxonomic unit, and have treated the four major cladoceran groups Ctenopoda, Anomopoda, Onychopoda, Haplopoda) as separate orders of the class Branchipoda (e.g. Smirnov 1992). However, recent molecular studies support treatment of the Cladocera as a monophyletic order, with the four groups as suborders (Rowe and Hebert 1999).

Family- The genus Ilyocryptus was formerly placed in the family Macrothricidae, but Smirnov (1992) transferred it to the new family Ilyocryptidae.

Potentially Misidentifed Species - The 3 species listed are all found in tidal fresh tributaries of Chesapeake Bay, together with I. agilis (Williams 1978). In analyses of the genus, Paggi (1992) and Kotov and Elías-Gutiérrez (2009), considered North and South American specimens of 'I. agilis', and many Eurasian populations to be members of a cosmopolitan species complex, following a pattern of cryptic speciation widely seen in freshwater cladocera (Frey 1982). Consequently, we consider the Chesapeake Bay specimens of I. agilis to be cryptogenic.

Taxonomy

Kingdom	Phylum	Class	Order	Family	Genus
Animalia	Crustacea	Branchiopoda	Cladocera	Ilyocryptidae	Ilyocryptus

Synonyms

Ilyocryptus sordidus var. longisetus

Invasion History

Chesapeake Bay Status

First Record	Population	Range	Introduction	Residency	Source Region	Native Region	Vectors
1974	Established	Unknown	Cryptogenic	Regular Resident	Europe	Eurasia	Shipping(Ballast Water),Ornamental(Aquatic Plant)

History of Spread

The cladoceran (water flea) Ilyocryptus agilis was described in 1894 from specimens collected in tanks containing the giant waterlily Victoria regia, in the Royal Botanic Gardens, Kew, England (Scourfield 1894). Since this was the site of discovery of two other well known freshwater introductions, the hydrozoan Craspedacusta sowerbii, and the oligochaete Branchiura sowerbii, (see histories of those organisms) Scourfield noted that 'its occurrence in the fauna does not give it a claim to be considered as British' (Scourfield 1894). However, based on further collecting, it appears to be a species with a broad Eurasian distribution (from Taiwan and Northern China, though southern Siberia and Turkey through most of Europe, except northern Scandinavia (Smirnov 1976). Introduction to the British Isles or other parts of this range is possible, however.

In 1974, Ilyocryptus agilis was identified by Williams for the first time in North America, from tidal tributaries of the Chesapeake Bay. She examined zooplankton samples from across North America, but found no specimens of I. agilis outside the Chesapeake region (Williams 1978). We regard the occurrence of this Eurasian cladoceran in North America as an introduction. It should be noted that benthic cladocerans as a group are relatively poorly known, so that there is still some possibility that this species could be overlooked. Also, Williams (1978) noted some small differences in size and morphology between American and European specimens. These differences may be environmental rather than genetic.

Ilyocryptus agilis was first found in the stomachs of Morone americana (White Perch) collected from the tidal fresh Potomac River, between Chain Bridge and Occoquan Bay (Williams 1978). In the summer of 1975, was collected near three electric power plants (Benning Road and Buzzards Point, DC, on the Anacostia River, and the Potomac River plant, Alexandria VA). Examination of preserved samples collected by the Academy of Natural Sciences of Philadelphia (no date given) moved the upriver range of I. agilis to the mouth of Watts Branch, ~10 miles upstream of Chain Bridge, the head of tide (Williams 1978). We have found no other published records of I. agilis. Storms (1981) sampled in Quantico Creek, upstream of Occoquan Bay and reported I. acutifrons, a species not reported by Williams. [I. acutifrons has a Holarctic distribution, and is found in both Eurasian and Eastern north America(Smirnov 1976)].

Ilyocryptus agilisI. agilis has also been collected in the James River system, in Tidemill Marsh, a tidal freshwater tributary of the lower James River in Hampton VA (Williams 1978).

We have found no further published references to I. agilis in the Chesapeake region or elsewhere in North America. Williams (1978) examined samples of cladocerans from across North America, but found no specimens outside the Chesapeake Bay drainage. In an analysiis of the genus, Paggi (1992) and Kotov and Elías-Gutiérrez (2009), considered North and South American specimens of 'I. agilis', and many Eurasian populations to be members of a cosmopolitan species complex, following a pattern of cryptic speciation widely seen in freshwater cladocera (Frey 1982). Consequently, we consider the Chesapeake Bay specimens of I. agilis to be cryptogenic.

History References - Scourfield 1894; Smirnov 1976; Storms 1981; Williams 1978; Paggi 1992; Kotov and Elías-Gutiérrez 2009

Invasion Comments

Vector(s) of Introduction- Accidental transport with aquatic plants was considered the likeliest vector for Ilyocryptus agilis into the Chesapeake Bay, given its description from water containing exotic plants (Scourfield 1894), and the low frequency of transatlantic ships entering the Potomac. Ballast water is also a possibility.

Ecology

Environmental Tolerances

	For Survival		For Reproduction
	Minimum	Maximum	Minimum	Maximum
Temperature (ºC)			11.7	25.8
Salinity (‰)	0.0		0.0
Oxygen	hypoxic
pH
	Salinity Range	fresh-oligo

Age and Growth

	Male	Female
Minimum Adult Size (mm)		0.6
Typical Adult Size (mm)	0.6	0.8
Maximum Adult Size (mm)		1.2
Maximum Longevity (yrs)		0.2
Typical Longevity (yrs		0.1

Reproduction

	Start	Peak	End
Reproductive Season
Typical Number of Young Per Reproductive Event
Sexuality Mode(s)
Mode(s) of Asexual Reproduction
Fertilization Type(s)
More than One Reproduction Event per Year
Reproductive Startegy
Egg/Seed Form

Impacts

Economic Impacts in Chesapeake Bay

Ilyocryptus agilis is a food item for the economically important fish Morone americana (White Perch), but at the abundances reported by Williams (1978), it is unlikely to have detectable impacts on fish populations.

References- Williams 1978

Economic Impacts Outside of Chesapeake Bay

Ilyocryptus agilis, together with many other benthic cladocerans, probably constitute an important part of freshwater foodwebs throughout its range (Smirnov 1976). However, the individual importance of this species in fish feeding and recruitment, given the many others which share its habitat, is probably relatively small. References- Smirnov 1976

Ecological Impacts on Chesapeake Native Species

Ilyocryptus agilis is a food item of juveniles an important estuarine fish, Morone americana (White Perch), and probably of other planktivores in the Potomac estuary. However, its abundance in the water column (500 m-3, max.) and in fish guts (1-10 per fish) indicate that it was not a major food item, at least at the time of sampling (Williams 1978). Its relatively low abundance indicates that it was also not an important filter-feeder in the system.

Williams (1978) noted that the coexistence of 4 species of Ilyocryptus sp. in the Potomac estuary was unusual, and suggested that the high abundance of food might reduce competition among the species. Competive relations of I. agilis with the presumed native species [I. sordidus (cosmopolitan), I. gouldeni, and I. spinifer] have not been studied.

Refernces- Williams 1978

Ecological Impacts on Other Chesapeake Non-Native Species

Ilyocryptus agilis is a potential food item for larval and juvenile introduced fishes, including Dorosoma petenense (Threadfin Shad), centrarchids, and others. However, at the abundances reported by Williams (1978), it is unlikely to have detectable effects on their biology.

References- Williams 1978

References

Aladin, N.V. (1982) [Salinity adaptations and osmoregulation abilities of the Cladocera. 3. Forms from Bbackish and fresh waters.], Zoologicheskij Zhurnal 61: 851-860

Chirkova, E. N. (1970) Ephippia of the genus Ilyocryptus (Cladocera, Macrothricidae), Information Bulletin of the Institute of Biology of Inland Waters, Academy of Sciences, U.S.S.R. 8: 43-45

Chirkova, E. N. (1972) Latent eggs of species of the genus Ilyocryptus (Cladocera, Macrothricidae), Information Bulletin of the Institute of Biology of Inland Waters, Academy of Sciences, U.S.S.R. 14: 51-54

Chirkova, E. N. (1974) Reproduction of the parthenogenetic females of the genus Ilyocryptus, Transactions of the Institute of Biology of Inland Waters, Academy of Sciences, U.S.S.R. 28: 163-174

Kotov, Alexey A.; Elías-Gutiérrez, Manuel (2009) A phylogenetic analysis of Ilyocryptus Sars, 1862 (Cladocera: iIyocryptidae), International Review of Hydrobiology 94: 208-225

Paggi, Juan (1992) A new species of Ilyocryptus (Anomopoda: Macrothricidae) from Argentina, Hydrobiologia 231: 141-151

1999 Cladoceran Web Site. http://www.cladocera.uoguelph.ca/

Scourfield, D. J. (1894) On Ilyocryptus agilis (Kurz), a rare mud-inhabiting water-flea., Journal of the Quekett Microscopical Club : 429-432

Smirnov, N. N. (1976) Macrothricidae and Moinidae of the World's Fauna, , Leningrad. Pp.

Stifter, P. (1991) A review of the genus Ilyocryptus (Crustacea: Anomopoda) from Europe, Hydrobiologia 225: 1-8

Storms, Stephen E. (1981) Seasonal zooplankton distributions in Quantico Creek and the adjacent Potomac River, Journal of Freshwater Ecology 1: 327-340

Williams, Judith L. (1978) Ilyocryptus gouldeni, a new species of water flea, and first American record of I. agilis Kurz (Crustacea: Cladocera: Macrothricidae), Proceedings of the Biological Society of Washington 91: 666-680

Ilyocryptus agilis

Crustaceans