"Bay barnacle European acorn barnacle"

Type Description

"Full details of morphology and anatomy of adults can be found in Darwin (1854); Pilsbry (1916); Broch (1924); Tarasov and Zevina (1957, in Russian); Henry and McLaughlin (1975); and Southward (2008). For details of larval morphology see Jones and Crisp (1954); Korn (1991); Elfimov (1995); and Murina and Grintsov (1995).
A. improvisus has a low, cone-shaped or semi-globe shape. It may be cylinder-shaped in crowded populations, but according to Southward (2008) it does not react to crowding by production of very tall specimens.
The calcareous shell is made up of white to greyish plates. Walls never ribbed or folded longitudinally. Uneroded calcareous shells have a smooth surface and may be covered by a thin yellowish epidermis, which is often more resilient on the radii. The radii are narrow and oblique and do not completely cover the alae that is nearly horizontal. The carina is lower than the rostrum. The operculum situated off centre, so that terga are close to the carina. The operculum is rounded at the rostral end. In water the opening is narrow and diamond shaped with partly- erect tergoscutal flaps. In juveniles' opening (Southward, 2008) a white ground is crossed by five black bands of speckles, whereas adults display the same dark bands, but the ground colour is white speckled with purple.
The variant “assimilis” has longitudal white hyaline lines (Darwin, 1854).
Base of the shell calcareous, flat and thin. Canals inside run radially to the place (approximately centre of the basal plate) where cyprid antennas were attached (Tarasov and Zevina, 1957; Leppäkoski, 1999) forming a star-like pattern.
A. improvisus normally grows to around 10 mm in diameter, the largest specimens reaching 23 mm (Tarasov and Zevina, 1957).
The shells can remain in place long after the animal that constructed and inhabited it is dead."

Habitat

"Habitat type and substrate use is similar in native and invaded habitat. A. improvisus occurs in a very wide range of habitats with brackish water conditions, from bays and estuaries to shallow marine habitats with preferably stony and stony-sandy bottoms (Jarvekiulg, 1979). Vertical distribution can vary, generally reflecting the difference in tidal range at each location, usually 0-80 cm.
The species is known for its ability to tolerate high levels of pollution, such as thick oil film in the Caspian Sea (Tarasov and Zevina, 1957). It can tolerate intermittent exposure to fresh water (Darwin, 1854) and often goes further up estuaries than other native species (Southward, 2008).
The species can often be found on ship hulls, sluices and oil platforms. On ships it tolerates places with strong water flow (Tarasov and Zevina, 1957).
Within the habitat range the species tends to colonize all available substratum suitable for a cyprid larva settlement. Many authors noted an ability of A. improvisus to live on a wide range of hosts.
In northern Europe the species can be found attached to algae (such as bladder wrack, Fucus vesiculosus) (Birshtain et al. 1968; Hayward and Ryland 1995; Weidema, 2000; Southward, 2008). In Brazil it attaches directly to mangrove roots from the lower region to shallow sublittoral places (Farrapeira, 2010).
A. improvisus is often found attached to bivalve shells and dead molluscs. On sandy beaches of the northwestern Black Sea it colonised almost all bivalve shells at 2-10 m depth (Vinogradov, 1956). In the Baltic it has been found on Mytilus edulis (Laihonen and Furman, 1986) and Mya arenaria (Olszewska, 2000). In the southern Baltic A. improvisus is the only representative of the Cirripedia which grows on the mussel Mytilus trossulus, which is the dominant element of the bottom fauna in this area. The sporadic occurrence of this barnacle on another Baltic bivalve species, the cockle Cerastoderma glaucum, has also been noted (Olszewska, 1999).
In September 1999 the species was found on shells of the soft-shell clam Mya arenaria on the beach near Brzezno (Gulf of Gdansk). The presence of A. improvisus on M. arenaria could be further evidence of the tendency of barnacles to colonise all available habitats, even if they are not always optimal (Olszewska, 2000).
In the Caspian Sea it uses an endemic bivalve Didacna sp. (Riedel et al., 2006). In Brazil it attaches directly to living oysters and mussels, as well as on stones and empty shells on the muddy sediment (Farrapeira, 2010). In the Sea of Japan it settles on the native bivalve Corbicula japonica, which may live in freshwater, and on the oyster Crassostrea gigas, but also on seagrass and macroalgae (Ovsyannikova, 2008).
Apart from mollusc shells, A. improvisus has been reported growing on other hosts, such as the carapace of fresh-water beetles and crayfishes in northern Iran (Southward, 2008). In Florida it has been found on a brackish water turtle, the diamond-backed terrapin (Ross and Jackson, 1972). In South America Farraepeira (2009; 2010) has reported it on numerous organisms."

Reproductive Information

"Although hermaphroditism is universal in sessile barnacles, only a few species are known to be facultative self-fertilisers. Furman and Yule (1990) tested the ability of A. improvisus to self-fertilise. Individuals were observed to carry well-developed ovaries and well-developed testes at the same time. Fertilisation took place and the eggs developed to larvae in both isolated and communal individuals. Self-fertilisation appears to take place somewhat later than cross-fertilisation. These laboratory results on self-fertilisation are supported by field observations, in which isolated individuals were found with fertilised egg masses. A. improvisus can thus be added to the list of facultatively self-fertilising cirripedes. The ability to self-fertilise is especially advantageous for individuals of a species such as A. improvisus, which often has sparse and isolated populations (Weidema, 2000).
Prior to copulation the barnacle acting as male briefly stops pumping water and beating the cirri, and the extremely long penis is extended into the mantle cavity of the recipient barnacle (Crisp and Southward, 1961). Eggs form in the mantle cavity. Egg size is about 180 µm, and contrary to other species, there is little geographic variation in this size (Barnes and Barnes, 1965). A. improvisus may produce 1000 to 10,000 eggs per season (Costlow and Bookhout, 1957) and gives several generations in a year. Embryos are brooded in an ovisac inside the mantle cavity. Development to hatching takes about 21 days at 18°C (Furman and Yule, 1990). "

Lifecycle

Amphibalanus improvisus is a filter feeder. It extends its six pairs of modified legs called cirri to catch plankton and other organic material floating past. It is a hermaphrodite and sperm is passed into the cavity of a neighbouring barnacle through a long penis. The eggs are fertilised and brooded in the cavity and hatch into nauplius larvae which drift with the currents. After six naupliar stages occupying two to five weeks, these become cyprid larvae and find a suitable surface on which to settle. Here they cement themselves to the substrate and undergo metamorphosis into juveniles. There may be several broods in the year but usually just two in the cooler waters of the Baltic and only one in low salinity environments.

Nutrition Information

"Adult A. improvisus is a filter/suspension feeder which feeds on microplankton and deitritus (Olenin, 2006). Additionally, in the splash zone mineral pieces constitute up to 60% of gastric content (Kuznetsov, 1978). According to Resnichenko et al. (1976), level of consumption of A. improvisus is 1.5 higher than other crustaceans, giving rapid growth and reproduction.
The barnacle creates a feeding current by pumping movements of the opercular plates and regular beating of the “cirri”, modified thoracic legs, and filters edible particles with the setae on these cirri. The current speed and the strength of the beating of the cirri can be adjusted to the concentration and size of food particles (Crisp and Southward, 1961; Rainbow, 1984). In laboratory experiments they feed on phytoplankton, but had slower body growth than in the field (Costlow and Bookhout, 1953, 1957).
In field experiments, consumption of Enteromorpha intestinalis promoted the growth and settlement success of A. improvisus (Kotta et al., 2006b). In laboratory experiments examining larval survival and growth under different algal feeding regimes, development time was shortest (6 days) with a mixed diet of Chaetoceros calcitrans, Chlorella vulgaris and Scenedesmus quadricauda (Nasrolahi et al., 2007). Highest mortality occurred for monoalgal diets of S. quadricauda while the highest survival was achieved with a monoalgal diet of C. calcitrans. "

General Impact Information

"The compounds of anti- fouling paints used on ships and hydrotechnical constructions are highly toxic to the marine environment as a whole (Weidema, 2000; Leppakoski, 2002).
A. improvisus tends to form dense layers on the surface of artificial structures and other substrata, inhibiting water flow, attracting associate fauna and producing organic debris (Leppäkoski, 1999; Weidema, 2000). The increase in biodeposition and mechanical trapping of organic material caused by A. improvisus may result in increasing eutrophication of semi-enclosed systems, providing an important source of material to the benthic environment, including the important detritus food chain (Kotta et al., 2006a, b; Weidema, 2000). This may potentially increase the energy flows from pelagic system to benthos and cause a shift from pelagic production to benthic production.
A. improvisus may be involved in competition for food and/or space with local or introduced species. For example, Jarvekiulg (1979) observed competition for attachment places and food between the filter feeders A. improvisus, Mytilus edulis (sea forms) and Dreissena polymorpha (zebra mussel, brackish water form) in the Pernu Bight. Salinity is the main factor on which the result of competition depends: increased salinity is favourable for the two sea forms and not for zebra mussels. Durr and Wahl (2004) also described A. improvisus as a strong competitor for space, but mentioned that it does not have a negative effect on community diversity in the Baltic. The same authors detected that while A. improvisus had no significant effect on recruitment of species, a negative synergistic effect of blue mussels and barnacles on species richness and diversity H-1 (Shannon Index) may be significant in the Western Baltic.
A. improvisus can affect biodiversity and community structure. Leppäkoski and Olenin (2000) noted that the barnacle was facilitating settlement of other organisms in the Baltic, changing community structure. In dense populations of A. improvisus, biodiversity of associated species such as hironmide larvae, ostracod and copepod crustaceans and juvenile bivalves increase compared to adjacent sites without the barnacle (Leppäkoski, 1999). Additionally, empty shells of the barnacle serve as new microhabitats for small annelids, crustaceans and chironomids.
The overall impact of A. improvisus on habitats and communities requires further investigation. After introduction of A. improvisus (along with more than 100 other species) in the Baltic sea during the last two centuries, no extinction of native species had been recorded in 2002 (Leppakoski et al., 2002). Reise et al (2006) state than they found “no evidence that they (non-native) species generally impair biodiversity”, but that the species expand ecosystem functioning adding new ecological traits, increasing functional redundancy and intensifying existing traits. Aladin et al. (2002) concluded that, despite some negative effects of certain non-native species, in general they contribute to rich biodiversity in the Caspian Sea."

General Management Information

"Physical/mechanical control
Mechanical methods may be simple and effective, and, perhaps, pose less risk for the environment than chemical control. The following methods are widely used to control A. improvisus and other barnacles:
Ballast waters: mid ocean exchange of ballast water is necessary to get rid of planktonic larvae.
Fishing and other equipment and infrastructure (nets, trays, etc); Onshore washing, manual cleaning (scrubbing and/or brushing); air drying; lowering below the photic zone during major spawning; oxygen deficiency.
Aquaculture stock: manual and mechanical cleaning; hot water, freshwater, or chemical solution treatment; lowering lines below the photic zone during major spawning.
Chemical control
Use of anti fouling components in coating is a basic chemical method of prevention (Hellio, 2009; Banerjee et al., 2011) which is continually being developed and improved in terms of effectiveness and economic cost.
Some antifouling compounds such as tri-butyl-tin and copper are now considered as dangerous for marine environments. There has been some research carried out trying to identify natural substances that may specifically hinder settling of A. improvisus. Some of these studies have been successful and anti-barnacle compounds are patented. Toth and Lindeborg (2008) found that water-soluble compounds from the breadcrumb sponge Halichondria panicea deters attachment of the barnacle. Pinori et al. (2011) indicated that protection from A. improvisus is achieved by trace amounts of a macrocyclic lactone (ivermectin) included in rosin-based coatings."

General Pathway Information

Through ships as fouling organisms, ship ballast waters.

Notes

References