Cercopagis pengoi - Fishhook Waterflea

Information Last Reviewed Spring 2007

The fishhook waterflea, a native of the Ponto-Caspian region, is a predatory zooplankton and a recent invader of the Laurentian Great Lakes and Finger Lakes regions.

Taxonomy

General Biology

Identification

Life Cycle

Habitat Characteristics

Taxonomy

Phylum: Arthropoda

Superclass: Crustacea

Class: Branchiopoda

Superorder: Cladocera

Order: Onychopoda

Family: Cercopagidae

General Biology

Adult Morphology

Body length of males (Figs. 1 and 2) can range from 0.8 to 1.6 mm

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Body length of females (Figs. 3 and 4) can range from 0.6 to 2.4 mm
North American specimens are generally smaller than counterparts collected in their native region

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North American specimens are generally smaller than counterparts collected in their native region
Caudal (i.e., tail) process may exceed the body length by more than five times (Fig. 5)
Distinctive "loop" at the end of the caudal process (Fig. 6)
Head is composed primarily of one large, compound eye

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Well-developed second pair of antennae (Fig. 7) Four pairs of thoracic legs with the first pair of legs three to four times the length of the second (Fig. 8) Males possess paired penes behind the last thoracic legs (Fig. 2) and toothed hook on the first pair of legs
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Identification

Distinguishing Characteristics

Similar in appearance to the spiny waterflea Bythotrephes (Fig. 9), but with the following differences:
Presence (Cercopagis) and absence (Bythotrephes) of the loop on the caudal process
Presence (Bythotrephes) and absence (Cercopagis) of gnathobasic process on the thoracopod
Cercopagis have seven setae on each ramus of the antennae whereas Bythotrephes have eight on the outer ramus of antennae and seven on the inner (Fig. 7)
Morphology of the penes differ between genera (Cercopagis – long, smooth; Bythotrephes – shorter, containing minute setae)
Dorsal brood pouch of Cercopagis is pointed at apex in instar III females (Fig. 9)

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Life Cycle

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Cercopagis grows allomentrically (i.e., increases in body length exceed increases in caudal process length between molts)
Shape and size of the dorsal brood pouch varies between instars (i.e., developmental stages of growth)
Resting eggs (produced by sexual females) and embryos (produced by parthenogenetic females) develop in dorsal brood pouch
Resting eggs remain dormant over the winter
Parthenogenetic females reproduce at instars I through III
Sexual females reproduce at instars II and III
Cercopagis ossiani (Fig. 10) is believed to be a vernal, morphologically distinct generation of C. pengoi (emerging only from resting eggs) although further research is needed to define its taxonomic status

Reproduction

Monocyclic
Mainly parthenogenetic throughout growth season
Sexual reproduction during late growth season (as water temperature declines); sexual females are reproductive only at instars II and III, producing 1-4 resting eggs
Parthenogenetic females produce between 1 and 24 embryos; average clutch size decreases gradually from instar I to instar III and from early to late stage of brood development

Habitat Characteristics

Preferred Environment

Naturally occurs in fresh and brackish waters
Prefers to inhabit pelagic zone

Temperature

Occurs at water temperatures between 8°C and 29°C, although population maxima observed between 18°C and 24°C

Salinity

Euryhaline
Resting eggs are capable of tolerating inhospitable conditions (e.g., inside ballast tanks)
In native range are found to be more abundant at lower salinities (less than 10 ppt)

Distribution

Native Range

Caspian Sea, Azov Sea, Aral Sea, estuarine regions of Black Sea

North American Distribution

See Fig. 11

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Probable Means of Introduction

Ballast water discharged by transatlantic ships originating from Eastern Europe

Diet

Consume various zooplankton (e.g., Daphnia, Ceriodaphnia, and Leptodora) at a rate of up to 16 individuals per day

Impacts

Negative

Competes with planktivorous invertebrates and vertebrates for food
Has potential to affect small and juvenile fish populations
Has potential to impact native plankton assemblages including carniverous onychopods
Presence of Cercopagis has the potential to affect the abundance and condition of predatory fish (e.g., herring, smelt)
Interference with angler activities (i.e., fouling fishing lines and trawls)
Presence results in economic losses at fish farms

Positive

Although not all zooplanktivorous fish prefer to consume Cercopagis, some of the larger species do

Management

Control Measures

Do not release bait or bait water into waterbody or transport from one waterbody to another
Following good containment measures is important in controlling the spread of adult Cercopagis, but resting eggs are capable of surviving desiccation and freezing (even for periods of several years) and therefore:
Rinsing boat and equipment with hot water (>40°C), high-pressure water spray, or drying boat and equipment for at least 5 days before re-entering waterbody will help to control the spread of adult Cercopagis
Thoroughly draining and cleaning motor; bilge, transom, and live wells; bait buckets; and fishing apparatus and gear will help to control the spread of adult Cercopagis and resting eggs

Literature

Gorokova, E., Aladin, N., and Dumont, H. J. 2000. Further expansion of the genus Cercopagis (Crustacea, Branchiopoda) in the Baltic Sea, with notes on the taxa present and their ecology. Hydrobiology 429:207-218.

Grigorovich, I. A., MacIsaac, H. J., Rivier, I. K., Aladin, N. V., and Panov, V. E. 2000. Comparative biology of the predatory cladoceran Cercopagis pengoi from Lake Ontario, Baltic Sea and Caspian Lake. Archiv für Hydrobiologie 149:23-50.

Grigorovich, I. A., Pashkova, O. V., Gromova, Y. F., and van Overdijk, C. D. A. 1998. Bythotrephes longimanus in the Commonwealth of Independent States: Variability, distribution and ecology. Hydrobiologia 379:183-198.

Johannsson, O. E., Millard, E. S., Ralph, K. M., Myles, D. D., Graham, D. D., and Taylor, W. D. 1998. The changing pelagia of Lake Ontario (1981-1995): A report of the DFO long-term biomonitoring (Bioindex) program. Canadian Technical Report of Fisheries and Aquatic Sciences 2243:I-IX 278 pp.

Krylov, P. I., Bychenkov, D. E., Panov, V. E., Rodionova, N. V., and Telesh, I. V. 1999. Distribution and seasonal dynamics of the Ponto-Caspian invader Cercopagis pengoi (Crustacea, Cladocera) in the Neva Estuary (Gulf of Finland). Hydrobiologia 393:227-232.

MacIsaac, H. J. and Grigorovich, I. A. 1999. Ponto-Caspian invaders in the Great Lakes. Journal of Great Lakes Research 25:1-2.

MacIsaac, H. J., Grigorovich, I. A., Hoyle, J. A., Yan, N. D., and Panov, V. E. 1999. Invasion of Lake Ontario by the Ponto-Caspian predatory cladoceran Cercopagis pengoi. Canadian Journal of Fisheries and Aquatic Sciences 56:1-5.

Makarewicz, J., Grigorovich, I., Mills, E., Damaske, E., Cristescu, M., Pearsall, W., LaVoie, M., Keats, R., Rudstam, L., Hebert, P., Halbritter, H., Kelly, T., Matkovich C., and MacIsaac, H. 2001. Distribution, fecundity and genetics of Cercopagis pengoi (Ostroumov)(Crustacea, Cladocera) in Lake Ontario. Journal of Great Lakes Research 27:19-32.

Mills, E. L., O’Gorman, R., Roseman, E. F., Adams, C. and Owens R. W. 1995. Planktivory by alewife (Alosa pseudoharengus) and rainbow smelt (Osmerus mordax) on microcrustacean zooplankton and dreissenid (Bivalvia: Dreissenidae) veligers in southern Lake Ontario. Canadian Journal of Fisheries and Aquatic Sciences 52:925-935.

Ricciardi, A. and MacIsaac, H. J. 2000. Recent mass invasion of the North American Great Lakes by Ponto-Caspian species. Trends in Ecology and Evolution 15:62-65.

Rivier, I. K. 1998. The predatory Cladocera (Onychopoda: Podonidae, Polyphemidae, Cercopagidae) and Leptodorida of the world. Backhuys Publishers, Leiden, Netherlands. 214 pp.

Simm, M. and Ojaveer, H. 1999. Occurrence of different morphological forms of Cercopagis in the Baltic Sea. Proceedings of the Estonian Academy of Science, Biology and Ecology 48:169-172.

Sprules, G. W., Riessen, H. P., and Jin, E. H. 1990. Dynamics of the Bythotrephes invasion of the St. Lawrence Great Lakes. Journal of Great Lakes Research 16:346–351.

Web Sites

http://venus.uwindsor.ca/courses/biology/macisaac/pages/cercopagis.htm

Comparative Biology of the Predatory Cladoceran Cercopagis pengoi from Lake Ontario, Baltic Sea, and Caspian Sea

http://www.protectyourwaters.net

Stop Aquatic Hitchhikers

This report was prepared by Danielle M. Crosier and Daniel P. Molloy (New York State Museum) with assistance from Igor A. Grigorovich (University of Windsor).