Skistodiaptomus pallidus
Herrick, 1879
Common Name:
A calanoid copepod
Synonyms and Other Names:
Diaptomus pallidus
Identification:
The endopod of the first leg of this copepod species is bifurcate. Unlike some other diaptomids, the antepenultimate segment of the right first antenna has no distinct appendage and is not produced into a blunt point in males. The male left fifth leg is shorter than the right, reaching to the end of or slightly past the first segment of the right exopod. There is a scythe-like inner process on the terminal exopod segment of the male left fifth leg. Females have 3 urosomal segments, rounded metasomal wings with small sensilla, and a somewhat expanded genital segment (Pennak 1989; Lesko et al. 2003).
Size:
Females are around 0.8–1.2 mm long while males are around 0.7–1 mm long (Geddes and Cole 1981; Torke 2001; Lesko et al. 2003).
Native Range:
Skistodiaptomus pallidus is native to the north central plain states, northeast to New York, southern United States in the Mississippi River basin, Texas, and west to Colorado (Pennak 1989; Mills et al. 1993; Torke 2001; Thum and Sternberger 2006).
See Remarks for important details.
Great Lakes Nonindigenous Occurrences:
Skistodiaptomus pallidus was first recorded from Lake Ontario in 1967. In the 1970s, it was recorded from Lake Erie, Lake St. Clair, Lake Huron and the Saginaw River. The occurrences in the Lake Huron drainage were discovered upon re-examining archived specimens from 1974 and 1975 (Mills et al. 1993; Torke 2001; Lesko et al. 2003). Skistodiaptomus pallidus has expanded its range in North America westward (Duggan et al. 2006). It has been introduced outside of North America, possibly via the aquarium trade.
Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Skistodiaptomus pallidus are found here.
Full list of USGS occurrences
Table last updated 4/20/2024
† Populations may not be currently present.
Ecology:
Found in freshwater lakes. Skistodiaptomus pallidus occurs in beta-mesotrophic to eutrophic habitats with higher total phosphorus and total nitrogen in comparison with those inhabited by two congeners in the United States, S. pygmaeus and S. oregonensis. Skistodiaptomus pallidus can also tolerate more suspended solids and greater turbidity than the latter two. Skistodiaptomus pallidus is typically found in waters with a pH range of 7.5–8.6 and a conductivity range of 77–660 μS cm-1. This species prefers to dwell in cool waters <12ºC and was found at 10 m in June and below 16 m in July, underneath the thermocline in Belews Lake, North Carolina (Chapman et al. 1985; Marcogliese and Esch 1992; Torke 2001; Thum and Stemberger 2006).
Skistodiaptomus pallidus produces some eggs that go through a diapause stage before they hatch and some that do not. Breeding in general takes place from around March to November and females can produce up to around 20 eggs per brood. Diapausing eggs produced between June and October hatch from December to June of the following year. When production of diapausing eggs occurs in the summer it may aid populations to avoid fish predation. These eggs have been known to reach densities of 105 per m2 in the sediments of some habitats. Such high densities may help mitigate the effects of a poor year in reproduction and recruitment. It may take around 7 weeks for resting stages to hatch. One study found that it takes around 66 days at 10ºC and 15 days at 25ºC for development to the adult stage. There are 2–5 generations per year in different parts of this species’ range (Geiling and Campbell 1972; Chapman et al. 1985; Dowell 1997; Torke 2001; Lesko et al. 2003; Wonham et al. 2005).
Skistodiaptomus pallidus feeds on phytoplankton, especially individual algae >53 μm in size. It can also selectively and intensely prey on some rotifer species (Geiling and Campbell 1972; Williamson and Butler 1986; Torke 2001).
Skistodiaptomus pallidus has been known to reach densities of 10,000 individuals per m3 in a coastal marsh in Lake Erie (Krieger and Klarer 1991).
Means of Introduction:
Uncertain -- however, S. pallidus could have been introduced accidentally in bait buckets, in fishing equipment, by recreational boaters, with hatchery stock from the Mississippi River basin, or through dispersal (Mills et al. 1993; Lesko et al. 2003; Reid and Hudson 2008).
Status:
Considered established, but see Remarks.
Great Lakes Impacts:
Summary of species impacts derived from literature review. Click on an icon to find out more...
Current research on the environmental impact of Skistodiaptomus pallidus in the Great Lakes is inadequate to support proper assessment. Potential:
Skistodiaptomus pallidus is an efficient omnivorous predator, with the ability to prey on preferred rotifers and microzooplankton from large distances. It also consumes algae and practices cannibalism, which may allow populations to persist when resource availability is low (Williamson and Butler 1986; Williamson and Vanderploeg 1988). It has also been known to attain very high densities in suitable habitats, reaching 10,000 per m3 in a Lake Erie marsh to unknown consequences (Krieger and Klarer 1991). Skistodiaptomus pallidus became the primary calanoid copepod in a particularly eutrophic portion of Lake Tahoe, dominating two previously common species, Leptodiaptomus tyrrelli and Epischura nevadensis (Byron and Saunders 1981).
Additionally, based on evidence from an Ohio lake, it has been suggested that S. pallidus is an intermediate host for the parasitic worm Tanaorhamphus longirostris, although study of this occurrence has been limited (Hubschman 1983). Documented evidence combined with its record of spread across the U.S. (Byron and Saunders 1981) have led some recently colonized areas, like New Zealand, to express concern over the potential effects of S. pallidus on native ecosystems (Duggan et al. 2006).
There is little or no evidence to support that Skistodiaptomus pallidus has significant socio-economic impacts in the Great Lakes.
There is little or no evidence to support that Skistodiaptomus pallidus has significant beneficial effects in the Great Lakes.
Management:
Regulations (pertaining to the Great Lakes)
There are no known regulations for this species. Note: Check federal, state/provincial, and local regulations for the most up-to-date information.
Control
Biological
There are no known biological control methods for this species.
Physical
There are no known physical control methods for this species.
Chemical
The Great Lakes and Mississippi River Interbasin Study (GLMRIS 2012) suggests that alteration of water quality using carbon dioxide, ozone, nitrogen, and/or sodium thiosulfate could be effective in preventing upstream and downstream movement of copepods. It should be noted that the effectiveness of these methods is likely significantly diminished against copepod ephippia.
Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.
Remarks:
There have been no recent records of this species in the Great Lakes. Persistent populations of S. pallidus may be lacking in the main water bodies of the Great Lakes, although individuals are probably washed into the lakes during floods. Its native range could extend into tributaries and coastal wetlands within the basin (Mills et al. 1993; Lesko et al. 2003; Reid and Hudson 2008).
References
(click for full reference list)
Author:
Kipp, R.M., A.J. Benson, J. Larson, T.H. Makled, and A. Fusaro
Contributing Agencies:
Revision Date:
9/12/2019
Citation for this information:
Kipp, R.M., A.J. Benson, J. Larson, T.H. Makled, and A. Fusaro, 2024, Skistodiaptomus pallidus Herrick, 1879: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI, https://nas.er.usgs.gov/queries/greatlakes/FactSheet.aspx?Species_ID=169&Potential=N&Type=0&HUCNumber=DHuron, Revision Date: 9/12/2019, Access Date: 4/20/2024
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.