Description
Phylum- This phylum is often called 'Ectoprocta'.
Potentially Misidentifed Species - Victorellidae and related bryozoans are extremely difficult to identify because many important morphological features cannot be seen in preserved material, and because of the changing forms of colonies as they grow (Jebram and Everitt 1982). Victorella pavida has been perceived either as a naturally cosmopolitan species (Hyman 1959), or as one widely introduced worldwide (Carlton 1979), but some populations originally identified as V. pavida may be other species of Victorella pavida or other genera (Tanganella; Nolella; Bulbella; etc.) (Jebram and Everitt 1977). Wood et al. (2006) provide a detailed description, and describe some of the variability occurring under different growth conditions in wild and cultured colonies in freshwater in Thailand.
Osburn's (1932) identification of Victorella pavida from Chesapeake Bay was somewhat provisional; comments from British Musem taxonomists Harmer and Kirkpatrick were: 'Your example differs a good deal from the typical material; but on the other hand resembles closely the figures of Kraepelin. We are both inclined to think that you would not be far wrong if you named your specimen 'Victorella pavida.' So the determination stands and must reman until better preserved material can be properly studied' (Osburn 1932). Osburn (1944), Poirrer and Mulino (1977b) and other authors had noticed a correlation between decreasing salinity and decreasing salinity and decreased branching of 'Victorella pavida' colonies, but Jebram and Everitt (1982) suggest that this may represent differences among cryptic species. Wood et al. (2006) suggest that much of this variabiity may be environmnental, based on work with cultured colonies in Thailand.
The possible distinctions among multiple species potentially confused with Victorella pavida, are likely to be missed in earlier work and in most routine fouling surveys. Given the uncertainty over species identification, the Chesapeake and other records, as well as life history and community data, cited below, should be regarded as 'V. pavida 'sensu latu' (in the broad sense, ignoring possible cryptic speciation- 's. l.' for short) unless we have noted them as more closely identified. Dr. Judy Winston has identified 'Victorella pavida s. 1.', resembling Osborn's material from Chesapeake Bay, including material from the Smithsonian Environmental Research Center 'Invasions Group' settling plates (Winston personal communication).
Taxonomy
| Kingdom | Phylum | Class | Order | Family | Genus |
|---|---|---|---|---|---|
| Animalia | Bryozoa | Gymnolaemata | Ctenostomata | Victorellidae | Victorella |
Synonyms
Invasion History
Chesapeake Bay Status
| First Record | Population | Range | Introduction | Residency | Source Region | Native Region | Vectors |
|---|---|---|---|---|---|---|---|
| 1916 | Established | Stable | Cryptogenic | Regular Resident | Unknown-Marine | Unknown-Marine | Shipping(Fouling Community) |
History of Spread
The bryozoan Victorella pavida was first identified from the London docks by Kent (1870), and has subsequently been recorded from many European ports (Carrada and Sacchi 1965; D'Hondt 1983; Occhipiniti Ambrogi and D'Hondt 1981; Partaly 1979), from Israel (Massard et al. 1992), the Black and Caspian Seas (Mordukhoi-Boltovskoi 1964), India, Thailand Japan, and California (Carlton 1979; Menona and Nair 1967; Winston 1977; Wood et al. 2006), and the Atlantic and Gulf Coast of North America (Osburn 1944; Everitt 1975).
Many of these reports are complicated by the taxonomic problems described in the 'Taxonomy' section. Some of the V. pavida identified from the Atlantic coast of the U. S., including specimens illustrated by Osburn (1944) from Chesapeake Bay, may be Tanganella appendiculata, presumably a native North American species, first described in 1982 from Martha's Vineyard MA. Victorella pavida and Tanganella spp. can only be distinguished in living material, and consequently many 'Victorella' identifications are uncertain (Jebram and Everitt 1982). We will refer to records which could be V. pavida, T. appendiculata, or other related species as 'V. pavida s.l.' (for 'sensu latu', in the broad sense). Winston (1996, personal communication) has been examining live 'V. pavida s.l.' specimens from fouling plates from Baltimore Harbor, but has not yet determined the identity of the organisms.
Carlton (1979), while acknowledging taxonomic difficulties, has suggested that V. pavida is a species of Indo-Pacific origin which has been transported worldwide by ships, first to Britain and elsewhere in Europe, then to the east coast of North and South America, and later to the West Coast (Lake Merritt; Oakland Ca; 1967) by way of Japan. However, Mordukhoi-Boltovskoi (1964) regarded this bryozoan as native to the Ponto-Caspian region and introduced worldwide, as was the hydroid Cordylophora caspia. It appears that careful comparisons of morphology of live organisms and genetic studies will be needed to determine the origins of this species or species complex. Victorella pavida probably was introduced in England. Marine biology was such a widespread interest there in the late 1800's, that native populations would have been recognized much earlier if they existed.
On the East Coast of the U.S., the number of professional and amateur bryozoologists was smaller than in Europe, and tended to concentrate on rocky intertidal habitats from NJ to New England (Winston 1996), rather than the estauries to the south. Consequently, there is a strong probability that a bryozoan in Chesapeake Bay or southward would have been overlooked. Because of taxonomic difficulties and the late development of bryozoan studies, Victorella pavida's status as an introduced species in Chesapeake Bay and North America is uncertain. We treat this bryozoan as cryptogenic.
Biologists from Johns Hopkins; including S. F. Clarke and W. K. Brooks did examine fouling communities in Curtis Creek, Baltimore harbor in 1877, and found abundant Cordylophora caspia, but made no mention of bryozoans or other organisms (Clarke 1878). However, Bibbins (1893), studying Cordylophora in Furnace Creek, Baltimore Harbor, noted 'dense and beautiful growths of bryozoans', most likely Victorella pavida (s. l.)., since this is the only bryozoan occurring there now (Ruiz et al., unpublished).
Victorella pavida (s. l.) was identified in material collected in a biological survey of Chesapeake Bay in 1915-1922 (Cowles 1930; Osburn 1932). Victorella pavida (s. L.) has also been reported from NC, LA, and MS (Everitt 1975; Pourrier and Mulino 1977; Winston 1977), but Chesapeake Bay appears to be its northern limit on the Atlantic Coast The first collections of Victorella pavida (s. l.) were in the mid-to-lower Bay, at locations between James Island MD and Cape Charles City VA, where salinities averaged (Cowles 1930; Osburn 1932), but Osburn (1944) later reported that it ranged over 3-27 ppt, with an optimum around 10-14 ppt. 'Where it is abundant, it is a nuisance in fouling the bottoms of boats... Oysters and barnacles may be covered to the edges of their shells' (Osburn 1944). However, some of Osburn's material may have been actually been Tanganella appendiculata, presumably a native North American species, first described in 1982 from Martha's Vineyard MA (Jebram and Everitt 1982).
Victorella pavida (s.1.) has been reported in abundant in fouling studies, primarily in the upper-mid Bay and tributaries, including Surry Nuclear Power Plant, James River (Thompson 1993), Calvert Cliffs Nuclear Power Plant (Abbe 1987), and the Patuxent River (Cory 1967), but also in Hampton Roads (Calder 1966). In the ongoing Smithsonian Environmental Research Center 'Invasions Group' fouling studies, V. pavida (s.1.) was found primarily in Upper Bay locations (Gunpowder-Rhode Rivers), but at least once in a lower Bay location (Gloucester Point) (Ruiz et al. unpublished).
History References - Abbe 1987; Bibbins 1993; Calder 1966; Carlton 1979; Carrada and Sacchi 1965; Clarke 1878; Cory 1967; Cowles 1930; D'Hondt 1983; Everitt 1975; Jebram and Everitt 1982; Kent 1870; Massard et al. 1992; Menon and Nair 1967; Mordukhoi-Boltovskoi 1964; Occhipinti Ambrogi and D'Hondt 1981; Osburn 1932; Osburn 1944; Partaly 1979; Poirrier and Mulino 1977b; Thompson 1993; Winston 1977; Winston 1996
Invasion Comments
First Record - Specimens were collected in a biological survey of Chesapeake Bay, in 1915-1922 (Cowles 1930); 1916 was considered the likeliest year because dredging for hydroids occurred on several of that year's cruises. These specimens were collected at 4 stations from James Island MD to Cape Charles City VA (Cowles 1930; Osburn 1932).
History of Spread - A population of Victorella spp. in the Salton Sea CA, had been considered to be V. pavida (Carlton 1979), but has since been named as a new species, V. pseudoarachnida by Jebram and Everitt (1982). Jebram and Everitt (1982) found Victorella-like forms (Tanganella apendiculata and Bulbella abscondita) from Martha's Vineyard MA.
Ecology
Environmental Tolerances
| For Survival | For Reproduction | |||
|---|---|---|---|---|
| Minimum | Maximum | Minimum | Maximum | |
| Temperature (ºC) | 0.0 | 37.8 | 12.3 | 25.7 |
| Salinity (‰) | 0.0 | 30.0 | 30.0 | |
| Oxygen | hypoxic | |||
| pH | 6.8000000000 | 8.6000000000 | ||
| Salinity Range | fresh-poly |
Age and Growth
| Male | Female | |
|---|---|---|
| Minimum Adult Size (mm) | ||
| Typical Adult Size (mm) | ||
| Maximum Adult Size (mm) | 120.0 | 120.0 |
| Maximum Longevity (yrs) | ||
| Typical Longevity (yrs |
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
Victorella pavida (s. l.) was found in one of the earliest comprehensive biological surveys of the Chesapeake Bay (Cowles et al. 1930). Consequently, impacts of its possible invasion are difficult to assess.
Industry - Victorella pavida (s. l.) is an important fouling organism in power plants and other industrial users of estuarine waters. (Nauman and Cory 1969; Partaly 1979).
Boating - Victorella pavida (s. l.) is 'a nuisance fouling the bottom of boats' (Lippson and Lippson 1984; Osburn 1944).
References - Cowles et al. 1930; Lippson and Lippson 1984; Nauman and Cory 1969; Osburn 1944; Partaly 1979
Economic Impacts Outside of Chesapeake Bay
Victorella pavida (s. l.) is a common fouling organism in warm-temperate harbors and estuaries, affecting power plants and other industrial water use (Hyman 1959; Partaly 1979).
References- Hyman 1959; Partaly 1979
Ecological Impacts on Chesapeake Native Species
The bryozoan Victorella pavida(s. l.) was found in one of the earliest comprehensive biological surveys of the Chesapeake Bay (Cowles et al. 1930). Consequently, impacts of its possible invasion are difficult to assess.
Habitat Change - Victorella pavida (s. l.) colonies provide habitat for a wide variety of small motile animals (amphipods, polychaetes, etc.) (Ruiz et al. unpublished observations).
Competition - Victorella pavida (s. l.) is one of the dominant fouling organisms in summer in Chesapeake Bay (Abbe 1987; Cory 1967; Lippson and Lippson 1984; Osburn 1944) and is presumed to compete for space with other fouling taxa. These observations from the Sea of Azov may be applicable to Chesapeake Bay as well 'Thus, larvae of bryozoan foulings settle in the Sea of Azov in the summer and appear in biocoenosis with a high number of mature barnacles and growing hydroids. The bryozoans settle on the remaining free area of barnacles and growing hydroids. The bryozoans settle on the remaining free area of barnacles and hydroids and depress them.' (Partaly 1979).
Food - Victorella pavida (s. l.) is a likely but not documented food of nudibranchs (see 'Comments').
References - Abbe 1987; Cory 1967; Cowles et al. 1930; Lippson and Lippson 1984; Osburn 1944; Partaly 1979; Ruiz et al. unpublished observations
Ecological Impacts on Other Chesapeake Non-Native Species
Victorella pavida (s. l.) was found in one of the earliest comprehensive biological surveys of the Chesapeake Bay (Cowles et al. 1930). Consequently, impacts of its possible invasion are difficult to assess.
Competition - Victorella pavida (s. l.) is presumed to compete for space in mesohaline fouling communities with the introduced hydroids Cordylophora caspia and introduced Garveia franciscana, which are also frequently dominant in fouling communities (Abbe 1987; Cory 1967; Nauman and Cory 1969; Ruiz et al. unpublished data).
References- Abbe 1987; Cory 1967; Cowles et al. 1930; Nauman and Cory 1969; Ruiz et al. unpublished data
References
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Bibbins, Arthur (1892) On the distribution of Cordylophora in the Chesapeake estuaries, and the character of its habitat, Transactions of the Maryland Academy of Sciences 1: 213-228
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