Australian tubeworm

Type Description

"The genus Ficopomatus is characterized by a symmetrical body, operculum and collar chaetae (coarsely serrated and simple) present, opercular peduncle without well developed distal wings and pseudoperculum (rudimentary operculum) absent (ten Hove and Kupriyanova, 2009).
The type species for the genus is F. macrodon (see Notes on Taxonomy and Nomenclature) and the complete description of this species is given by ten Hove and Kupriyanova (2009). Ten Hove and Weerdenburg (1978) made the revision of this genus and they described in detail the morphological characteristics of F. enigmaticus. The body length without the tube is approximately 44 mm; however, this measure is highly variable among sites. Individual lifespan is very variable, Obenat and Pezzani (1994) suggest up to 24 months in the Mar Chiquita coastal lagoon, ten Hove (1979) indicated a 4 to 8 years, and Fox (1963) mentioned 12 years for individuals maintained in an aquarium. The life cycle of F. enigmaticus follows the general pattern of the Serpulidae. The unfertilized oocytes are cup shaped to irregular (Fischer-Piette, 1937; Vuillemin, 1965). The morphology of the larvae in this species is similar to other Serpulidae species. After the fertilization, the negatively buoyant small eggs (60 µm) sink to the bottom where they undergo cleavage up to the blastula stage. Blastula is ciliated, mobile and develops into a larva with a prototroch consisting of a single ring of cilia. This stage undergoes significant morphological changes until the trochophore stage is reached. The trochophore continues to grow into the metatrochophore and finally to the larva ready to metamorphose to approximately 160 µm in size (Kupriyanova et al., 2001). The development time of larvae is approximately 20-25 days. The survival of the larvae in the water although has not been well determined, it appears to be very variable among habitats, probably due to the differences in environmental conditions. Fischer-Piette (1937) and Vuillemin (1965) estimated in 1-5 weeks, whereas Dixon (1981) indicated that it falls within the range of 1 to 3.5 months. Larvae act as the dispersal phase but the dispersion is mainly driven by currents since their own swimming speed generally does not exceed 5 mm/s (ten Hove, 1979). Then, larvae settle on hard substrates and grow as sedentary suspension feeder worms. The growth rate of the tubes varied among sites where it was measured. In Italy, tubes grew 0.4 mm per day (Bianchi and Morri, 1996) whereas the maximum was reported by Hartman-Schröder (1967) of 1.8 mm per day. For more details on the development see Kupriyanova et al. (2001)."

Habitat

"F. enigmaticus is mainly a brackish species that tolerates highly variable salinity, dissolved oxygen and temperature. The typical habitats invaded by this species include estuaries, coastal lagoons, harbours, and inland brackish waters, always in protected wave areas. This species can survive either in polluted or non-polluted habitats. Çinar et al. (2009) found Ficopomatus in low densities in the Golden Horn Estuary, Sea of Marmara and the authors hypothesized that was due to the pollution. Naylor (1959) observed colonies of Ficopomatus in the dock polluted by waste oil in Swansea, England.
F. enigmaticus is commonly found in shallow waters between 0.5 and 2 m where this species has the opportunity to build the reefs. However, it was reported living in deeper waters in Netherlands at 9 m (Sluys et al., 2005) and in Greece at 40 m (Antoniadou and Chintiroglou, 2005), the latter probably being an extreme environmental condition."

Reproductive Information

F. enigmaticus has separate sexes but there is evidence of protandric hermaphrodism. True gonads are absent and the germ cells are produced by a germinal epithelium associated with genital blood vessels in the intersegmental septa. This species has external fertilization and spawning occurs through the specialized ducts in abdominal setigers of both males and females (Obenat et al., 2006b). Temperature is one of the most important factors affecting the reproduction and fecundity in F. enigmaticus and is the most commonly studied variable. In general, development time increases with decreasing temperature (Kupriyanova et al., 2001). The minimum water temperature required for (or associated with) successful reproduction of F. enigmaticus differs among populations. In the Thames estuary (UK) it is about 18ºC (Dixon, 1981), whereas in the Emsworth lagoon (UK) and Tunis lagoon (Tunisia) it is 10ºC (Vuillemin, 1965; Thorp, 1995). In Mar Chiquita lagoon (Argentina) the proportion of sexually undifferentiated and gametogenic, but immature, worms was highest during the winter (June-August), when water temperature is below 16ºC (Obenat et al., 2006b). In this lagoon, the highest proportion of mature worms was registered when temperatures were above 16ºC (September to May); however, individuals at all stages were found all the year round (Obenat et al., 2006b). In Mar Chiquita coastal lagoon sexual maturity is reached at an age of approximately four months, and there are three oocyte generations each year (Obenat et al. 2006b), as observed in some other populations of F. enigmaticus (Vuillemin, 1965; Gambi et al., 2001). Sex ratio was observed to be male-biased throughout the year in Mar Chiquita coastal lagoon (Obenat and Pezzani, 1994). The fecundity of Ficopomatus is reported to vary between 1,000 and 10,000 (Kupriyanova et al., 2001). In Mar Chiquita coastal lagoon the maximum size of sexually undifferentiated worms was 26 mm. Sexually mature males ranged between 5 and 48 mm, and females between 8 mm and 51 mm (Obenat et al., 2006b). In Japan, mature eggs and sperm were first observed in individuals of 6-8 mm (Kupriyanova et al., 2001), whereas in France this species becomes mature at 9-10 mm (Fischer-Piette, 1937). This species has two periods of spawning and recruitment in most regions where it was studied, one in spring-summer and the other one during the autumn. In Mar Chiquita coastal lagoon, recruitment occurred in November-December and in April-May (Obenat and Pezzani, 1994). Recruitment in southeastern England starts in June and continues through October (Dixon, 1981). Settlement peaks in North Adriatic (Italy) occur in June-July and in September (Bianchi and Morri, 1996) and in Japan occurs in May and October (Kupriyanova et al., 2001). Bianchi and Morri (1996) also observed that growth and settlement are inversely related; months with heavy settlement showed reduced growth and vice-versa. The growth of the tubes was found to be variable among regions. Bianchi and Morri (1996) in Italy observed that tubes grew 30-35 mm in 90 days, Vuillemin (1965) in Tunisia recorded a tube growth of 54 mm in 108 days and Hartmann-Schröder (1967) in Germany reported 30 mm in 16 days. In some conditions with calm and shallow brackish waters Ficopomatus build reefs with different shapes including fringing reefs and microatolls (Bianch and Morri, 1996; Fornós et al., 1997), and circular shapes up to 7 m in diameter (Schwindt et al., 2004a). In these cases where the reefs are circular is particularly interesting to note that most of the reef structure is dead due to the accumulation of sediment trapped inside the reef, live individuals are found around the edges where larval settlement occurs between the calcareous tubes (Obenat and Pezzani, 1994). The bottom part of a reef is gradually buried in anoxic black sediment while the reef grows and the nucleus usually can be found right in the centre. Little is known about the growth rate of the reefs. In Mar Chiquita coastal lagoon the growth rate was studied at different spatial and temporal scales. On a large scale, the density of reefs increased by 24% in 24 years (from 1975 and 1999), neighbouring reefs coalesced with each other forming platforms several metres (up to 12 m) long (E Schwindt, CENPAT-CONICET, Argentina, personal communication, 2009) and their density also increased in a 12.5% in the same period (Schwindt et al., 2004a). On a smaller scale, the growth rate of reefs of different sizes was measured during three years. Smaller reefs (average diameter of 0.5 m) increased their size by 24% while the larger reefs (3 m in diameter) only increased by 16% (Schwindt et al., 2004). In addition, the monthly growth rate was measured during a year resulting in a increasing of the reef size at 1.6 cm per month, this growth being higher in summer and lower in winter (Schwindt et al., 2004a)  

Lifecycle

Ficopomatus enigmaticus may have two periods of spawning and recruitment. Its first takes place in the summer yeilding early cohorts with a 24 month life span and two spawning periods, while late cohorts have a 20 month life span with only one spawning period. Larvae are tochophore and planktotrophic, developing in the plankton and settling to a nucleus substrate or an established colony, after 20-25 days where they form a calcareous tube secreted by the collar gland. Maturation of oocytes takes about 4 months (Obenat, 1994; Cohen, 2005; Muniz, 2005; Bianchi, 2001).

Nutrition Information

Ficopomatus enigmaticus feeds on suspended detritus and phytoplankton with its crown of ciliated gill plumes, which it extrudes from its tube opening. Cilia move water currents thereby oxygenating blood within, while others capture food particles and pass them down to the mouth (Obena, 1994).

General Impact Information

Ficopomatus enigmaticus grows very fast and abundantly and inflicts significant change in ecological and sedimentary dynamics. Referred to as an ecosystem engineer it modifies resources and physical environment. These reefs affect water movement, generate topographic heterogeneity, and ameliorate physical conditions by accumulating sediments. These changes modify distribution abundance of infaunal organisms and food supply dramatically affecting native benthic communities. F. enigmaticus increases oxygen and nutrient levels which may be viewed as beneficial, but these changes can have adverse effects on native communities. Changes in geomorphology pose a threat to recreational and aesthetic values of water bodies. Since it faces little competition in relatively confined waters with variable salinity, it is able to flourish in these characteristically highly productive habitats. In the presence of native competitors, abundant populations F. enigmaticus is known to deplete resources from and even replace them. (Fornos, 1997; Schwindt, 2004; Orensanz, 2002; JNCC, 1997; Hove,1978).

General Management Information

"Preventative measures: As with most marine invasive species prevention of establishment is the best and sometimes only means of management of Ficopomatus enigmaticus. De-oxygenation of ballast water tanks using nitrogen gas may prove effective in reducing introductions of F. enigmaticus as one study found this treatment to kill 80% of its larvae (Tamburri, 2001). Physical removal of F. enigmaticus by scrapping it from ships hulls may reduce new introductions (JNCC, 1997).
Physical: The use of freshwater has been employed in the cooling system of Otahuhu Power Station on the Tamaki Estuary, Auckland to combat fouling by F. enigmaticus (Read, 1991). Others propose heat treatment as a means of eliminating fouling of cooling systems (Jenner, 2004). Scraping of F. enigmaticus from harbour surfaces is a short term solution to fouling (JNCC, 1997).

Chemical: F. enigmaticus is resistant to anti-marine borer timber preservative CCA. Its susceptibility to other antifouling and biocide treatments has not been documented (Brown, 2001)."

General Pathway Information

The opportunistic species that adapt easily to a new environment and increase their population densities in a short time tend to expand their distributional ranges by the transport by shipping. These species are also resistant to unsuitable conditions through the transport (i.e. ballast water) (Carlton, 1985).

Notes

References