Corophium curvispinum Sars, 1895; Corophium sowinskyi, Corophium devium Wundsch 1912

Chelicorophium curvispinum may aggregate on stones, wooden structures, dead and living shells (including those of Dressenid mussels), sandy sediments, clay sediment, and submerged aquatic vegetation (den Hartog et al. 1992; van den Brink et al. 1993; Czarnecka et al. 2014; Kurina and Seleznev 2019). It can also be found in association with the green alga Cladophora (Kotta et al. 2006). In European waters, C. curvispinum density has been extremely variable, with some studies observing 100,000–750,000 individuals/m2 (highest at 2–3 m depths) (den Hartog et al. 1992; van den Brink et al. 1993), and others observing much lower densities (13–50,000/m2) (Harris and Bayliss 1990; Schöll 1990; Kurina 2017; Barabashova et al. 2021). Average densities in more recently invaded territory (Gulf of Finland) were reported to be between 125–1425 individuals/m2 (Kotta et al. 2006).

Chelicorophium curvispinum is a tube-dwelling amphipod; it collects minerals and organic particles from the water column and secretes a 1–4 cm thick layer of muddy tubes on colonization surfaces (Paffen et al. 1994). Mud used to build these tubes has ranged from 61 to 609 grams dry weight/m2 stone surface, smothering previously established organisms (van der Velde et al. 1994). Oxygen consumption, and therefore metabolism, of individuals within tubes (39 µmol/g/h) is approximately twice as high as that by free swimming individuals (22 µmol/g/h) outside of tubes (Muskó et al. 1998; Harris and Muskó 1999).

This amphipod is a suspension feeder, filtering phytoplankton, especially diatoms, and other suspended matter from the water (van den Brink et al. 1993). This feeding strategy results in population densities being highest where current velocities are strongest (e.g., 1–1.23 m/s), allowing C. curvispinum to most efficiently filter the largest quantity of food and obtain the greatest amount of oxygen for metabolism (van den Brink et al. 1993; van der Velde et al. 2000). This species is an important food source for a variety of fish species, including sculpin, eels, perch, ruffe, and pike perch (van den Brink et al. 1993). Other predators include birds, crayfish, and other predatory macroinvertebrates (Biro 1974; Kelleher et al. 1998, 1999; Marguillier et al. 1998).

Reproduction in C. curvispinum occurs from May to October in the Black Sea (Bortkevitch 1988) and from April to September in the Baltic (van den Brink et al. 1993). These are the warmest periods of the year (water temperature 12–20°C). Sex ratios exhibit a female bias—females outnumber males at all times of year and at many times more than double the male population (van den Brink et al. 1993). Large females (5.00–6.30 mm) become ovigerous a few weeks before smaller individuals (3.80–4.75 mm). Three generations of offspring are produced each year, following an overwintering period—the first in April to May, the second in June to July, and the third in September to October (den Hartog et al. 1992). The progeny of the first generation of summer animals (generation 2), along with the late autumn brood (generation 3), make up the next overwintering generation (Rajagopal et al. 1998).

Brooded egg sizes range from 360 x 280 µm (Stage I) to 520 x 440 µm (Stage IV). The number of eggs carried by females and total female body length are correlated, ranging in the Rhine from 3 to 34 eggs (mean = 12) (van den Brink et al. 1993) and in Lake Balaton from 1 to 25 (mean = 6) (Muskó 1990). These differences in clutch size are thought to be due to differences in food availability. Both average clutch size (Rajagopal et al. 1998) and growth rate (Rajagopal et al. 1997) have been positively correlated with the availability of chlorophyll a, which leads to increased planktonic development and greater food availability. Embryonic development lasts about two weeks and larval development takes approximately four weeks. Most rapid growth rates occur from May to August, when water temperatures range from 15–20°C (van den Brink et al. 1993). The life span of C. curvispinum lasts no longer than 8 months (van der Velde et al. 2000).

Potential pathway(s) of introduction: Trans-oceanic shipping

Chelicorophium curvispinum is indigenous and widespread throughout the Ponto-Caspian region and recently has invaded the Baltic Sea and many large European river systems (Bij de Vaate et al. 2002). In Europe, shipping—including transport by ballast water and hull fouling—has been the primary vector of dispersal of this species outside of its native range (Harris 1991; den Hartog et al. 1992; van der Velde et al. 2000; Leppäkoski and Olenin 2001). Introduction to Great Britain, for instance, likely occurred via ballast water released from ships trading with ports on the Elbe River in northern Germany (Harris 1991). The discovery of C. curvispinum west of the Rhine River system before it was discovered in the Rhine lends further support to shipping mediated spread (den Hartog et al. 1992), as this sort of “jump” dispersal is a common indicator of human-mediated transport (MacIsaac et al. 2001).

As Great Lakes shipping traffic commonly originates in areas where this species has become established, Ricciardi and Rasmussen (1998) identified C. curvispinum as a species likely to be transported to the Great Lakes via ballast water. The discovery (but not subsequent establishment) of a related Ponto-Caspian amphipod, Corophium mucronatum, in a benthic sample collected from Lake St. Clair in 1997, suggests that C. curvispinum may at least have the potential for introduction to the Great Lakes (Grigorovich and MacIsaac 1999; Ricciardi and MacIsaac 2000). Corophium spp. appear to be unaffected by flow-through salinity shock experiments (increase of roughly 5 ppt from ambient salinity), but undergo ~35% mortality in empty-refill treatments after 48 hours of exposure (Johengen et al. 2005). However, given this species’ physiological salinity constraints, under current mandatory ballast water regulations (saltwater flushing of at least 30 ppt), the risk of its entry into the Great Lakes has been modeled as having low likelihood (Grigorovich et al. 2003).

Chelicorophium curvispinum has a moderate probability of establishment if introduced to the Great Lakes (Confidence level: High).

This species has been one of the most successful macroinvertebrate invaders in Europe, establishing populations much larger than those of any native invertebrate species within a few years of colonization (den Hartog et al. 1992; van den Brink et al. 1993; Bij de Vaate et al. 2002). Densities have reached 750,000 individuals/m2 in some areas of the Rhine (van den Brink et al. 1993). With a high fecundity (see Ecology), reproducing populations are now established throughout all major European river systems and as far west as Great Britain (Bij de Vaate et al. 2002). This species is able to readily disperse through ballast water transport, ship hull fouling, passive drift, and active migration (van der Velde et al. 2000; van Riel et al. 2006), with secondary spread across Europe occurring in a pattern similar to, though at a much slower rate than, that of the zebra mussel (Dreissena polymorpha) (Tittizer et al. 1994).

Chelicorophium curvispinum is a non-specific feeder (Bij de Vaate et al. 2002), filtering diatoms, organic particles, and small minerals from the water column. Its superior competitive abilities—including spatial adaptation, gregarious behavior, and relatively short lifespan and generation time—have contributed to this species’ invasion success (van den Brink et al. 1993; Bij de Vaate et al. 2002). Competition with other macroinvertebrate species has been well documented, most notably with the highly successful Great Lakes invader, the zebra mussel. However, it is heavily consumed by the Ponto-Capsian amphipod Dikerogammarus villosus (another predicted Great Lakes invader) in invaded habitat. Thus, the establishment of C. curvispinum in the Great Lakes may be restricted by the co-invasion of D. villosus (Bovy et al. 2015; Barrios-O'Neill et al. 2015).

The water temperature (up to 31.8°C) and salinity (<6 ppt) ranges tolerated by C. curvispinum are well within those of the Great Lakes and have allowed this species to be extremely successful in invasions of European rivers. Furthermore, C. curvispinum produces overwintering populations of smaller individuals (van den Brink et al. 1993) in waters of the Ponto-Caspian basin with very similar climatic conditions to those of the Great Lakes. However, its physiological tolerance (see Ecology) is restricted by other factors, such as ion concentrations, oxygen availability, chlorophyll a concentrations, flow rate, and organic pollution levels (van der Velde et al. 2000). Individuals’ ability to retain and replace Na+ and Cl- varies among populations in different locations, and some populations have adapted to freshwater by means of lower ion permeability (Harris 1991; van der Velde et al. 2000). The changing conditions of the Rhine River throughout the 20th century, specifically increases in temperature and salinity, have created more suitable conditions for the invasion of foreign species originating in brackish waters, including C. curvispinum (den Hartog et al. 1992; van den Brink et al. 1993). These conditions are consistent with the physical changes forecast for the Great Lakes as a result of climate change (Rahel and Olden 2008), suggesting that this species may benefit from the resulting habitat shifts if introduced.

Chlorophyll a concentrations required by this species are currently present only in Lake Erie’s central basin, with less than 3 µg/L typically occurring in the other lake basins (U.S. EPA 2012). This is consistent with the predicted distribution of C. curvispinum in the Great Lakes according to the Genetic Algorithm for Rule-Set Production (GARP) model, which incorporates variable chlorophyll a levels (U.S. EPA 2008). However, anoxic conditions have recently been present in the central basin of Lake Erie, dropping below 0.5 mg/L at certain times of year (U.S. EPA 2012). As a result, C. curvispinum distribution is likely to be restricted to areas with sufficient flow rates, high dissolved oxygen levels, and high phytoplankton productivity.

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Beneficial

This species plays an important role in the food web of the Rhine as well as other invaded areas, driving prey switching among some fish predators (van der Velde et al. 2000). Due to the reduction in invertebrate diversity in areas where C. curvispinum has invaded, a decline in the number of predators, such as leeches, has been observed (van der Velde et al. 2000). It has been hypothesized that the prevalence of C. curvispinum in invaded rivers may lead to alterations of entire food webs (Ricciardi and Rasmussen 1998), although its role as a food source for predatory macroinvertebrates (e.g., as crayfish) requires further study (Rajagopal et al. 1997).

The population explosion of C. curvispinum in the Rhine from 1989–1991 coincided with a decrease in the levels of total organic carbon and total suspended matter (van den Brink et al. 1993). An increase in water clarity due to particle filtration by large populations of C. curvispinum is thought to have expanded the euphotic zone, increasing the transfer of energy and nutrients to the benthos and leading to greater levels of benthic production (Rajagopal et al. 1997).

There is little or no evidence to support that Chelicorophium curvispinum has the potential for significant socio-economic impacts if introduced to the Great Lakes.

The resulting reduction in macroinvertebrate abundance associated with C. curvispinum invasions may have a negative impact on the diet of native fish species, however, predation pressure on exotic amphipods changes rapidly depending upon prey availability. Hence, further biological monitoring is necessary in order to determine the full extent of the impact of C. curvispinum on fish diet and subsequent effect on commercial fisheries (van der Velde et al. 2000).

Chelicorophium curvispinum has the potential for moderate beneficial effect if introduced to the Great Lakes.

In areas where these species have colonized together, C. curvispinum has either greatly reduced or eliminated D. polymorpha populations by smothering settled individuals and larvae with a thick layer of dense, muddy material used for construction of tubes (van der Velde et al. 1994). After introduction of C. curvispinum to the Rhine, zebra mussel populations were seen to decrease from 1000s of individuals/m2 to 100s of individuals/m2 within four years (Paffen et al. 1994; van der Velde et al. 1994; Rajagopal et al. 1997). This species has also potentially prevented populations of another Great Lakes invader, Echinogammarus ischnus, from forming dense populations in the Rhine (van der Velde et al. 2000). Additionally, C. curvispinum along with D. villosus displaced E. ischnus from the Upper Danube River due to substrate competition (Žganec et al. 2015). While populations of previously established invaders in the Great Lakes may be reduced by the introduction of this species, its effectiveness as a control agent is likely to be limited due to independent negative ecological consequences.

Chelicorophium curvispinum is fed upon by many fish genera, including those with species represented in the Great Lakes (van den Brink et al. 1993). In the past, this species was intentionally introduced to large rivers in the Ponto-Caspian region to increase faunal diversity and to feed fish (Mordukhai-Boltovskoi 1979; Jazdzewski 1980). However, its potential beneficial impact as a food source for commercial fisheries in the Great Lakes is unknown. Lastly, while water clarity is increased by the presence of large populations of this species (Rajagopal et al. 1997), the positive impact of this effect for humans and/or native species is likely limited.

*Ballast water regulations applicable to this species are currently in place to prevent the introduction of nonindigenous species to the Great Lakes via shipping. See Title 33: Code of Federal Regulations, Part 151, Subparts C and D (33 CFR 151 C) for the most recent federal ballast water regulations applying to the Great Lakes and Hudson River.

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
There are no known chemical control methods for this species.

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.