Description
Sphaeroma terebrans is a somewhat variable species (Harrison and Holdich 1984). Most authors consider Sphaeroma terebrans and S. destructor to be synonymous, but Kensley and Schotte (1989) state: 'There is no agreement on whether this species is synonymous with S. destructorr Richardson, 1897. This latter, if distinct, bores into wood pilings in estuarine water, while S. terebrans is found in the prop roots of the red mangrove tree, Rhizophora mangle.' Kensley (1997 personal communication) now considers the species synonymous.
Taxonomy
| Kingdom | Phylum | Class | Order | Family | Genus |
|---|---|---|---|---|---|
| Animalia | Crustacea | Malacostraca | Isopoda | Sphaeromatidae | Sphaeroma |
Synonyms
Invasion History
Chesapeake Bay Status
| First Record | Population | Range | Introduction | Residency | Source Region | Native Region | Vectors |
|---|---|---|---|---|---|---|---|
| 1962 | Unknown | Unknown | Introduced | Regular Resident | Western Atlantic | Western Pacific | Shipping(Fouling Community) |
History of Spread
Sphaeroma terebrans (Mangrove Isopod), a wood-borer, is now widely distributed in tropical-subtropical regions, including the Indo-Pacific, the West coast of Africa, the Mediterranean, the Atlantic coast of South America, and North America, where it has been recorded as far north as VA (Harrison and Holdich 1989; Kensley and Schotte 1989; Kuhne 1971; Schultz 1969; Van Name 1946). It was originally described from Brazil in 1866, but its close affinity to Indian Ocean species, its absence of planktonic larvae, and the well documented recent introductions of related Indo-Pacific species (S. annandalei, S. walkeri, S. quoyanum) indicate that S. terebrans was probably transported into the Atlantic in the hulls of wooden ships before 1850 (Carlton and Ruckelshaus 1997).
The first North American record of Sphaeroma terebrans (as S. destructor) was from the pilings of a bridge in freshwater of the St. Johns River, Palatka FL (Richardson 1897). The regular range of this isopod appears to be from SC or GA around FL to LA, also Cuba and Belize southwards to Brazil (Carlton 1997; Kensley and Schotte 1989; Menzies and Frankenberg 1966; Wallour 1960). In FL, S. terebrans is distributed around much of the peninsula, but was absent from about half the 51 sites surveyed, including the Keys and the southernmost tip (Conover and Reid 1975).
We know of only one definite record of S. terebrans from Chesapeake Bay, from the hull of a boat in Urbanna VA, near the mouth of the Rappahannock River (Miller 1968; Van Engel 1972; United States National Museum of Natural History collections). It was considered a 'stray, unlikely to become established' (Van Engel 1972). However, S. terebrans has been included in a list of 'Aquatic Invertebrates of the Washington D.C. area' (Banta 1997). Its occurrence in the tidal fresh Potomac is plausible, given the isopod's tolerance of fresh water and the frequent traffic of pleasure boats from FL, but we have not been able to obtain any details about this record. This species is probably transported occasionally into the region, but due to the absence of recent surveys of wood-boring organisms, it has not been detected.
History References - Banta 1997; Carlton and Ruckelshaus 1997; Conover and Reid 1975; Harrison and Holdich 1989; Kensley and Schotte 1989; Kuhne 1971; Miller 1968; Schultz 1969; United States National Museum of Natural History collections; Van Engel 1972; Van Name 1946; Wallour 1960
Invasion Comments
Population Status- This species is treated as 'population status unknown' because it is represented by only a single record. Possibly, S. terebrans should be considered a failed introduction, but the absence of recent surveys of wood-boring organisms makes that conclusion difficult. This species should be looked for near warm effluents. Sphaeroma terebrans is probably occasionally transported into the Bay by wooden boats and towed wooden structures.
Ecology
Environmental Tolerances
| For Survival | For Reproduction | |||
|---|---|---|---|---|
| Minimum | Maximum | Minimum | Maximum | |
| Temperature (ºC) | ||||
| Salinity (‰) | 0.0 | 38.0 | 0.0 | |
| Oxygen | hypoxic | |||
| pH | ||||
| Salinity Range | poly-eu |
Age and Growth
| Male | Female | |
|---|---|---|
| Minimum Adult Size (mm) | ||
| Typical Adult Size (mm) | ||
| Maximum Adult Size (mm) | 10.0 | 11.5 |
| Maximum Longevity (yrs) | ||
| Typical Longevity (yrs |
Reproduction
| Start | Peak | End | |
|---|---|---|---|
| Reproductive Season | |||
| Typical Number of Young Per Reproductive Event |
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| Sexuality Mode(s) | |||
| Mode(s) of Asexual Reproduction |
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| Fertilization Type(s) | |||
| More than One Reproduction Event per Year |
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| Reproductive Startegy | |||
| Egg/Seed Form |
Impacts
Economic Impacts in Chesapeake Bay
Sphaeroma terebrans (Mangrove Isopod) has no apparent economic impacts in the Chesapeake region, due to its scarcity.
Economic Impacts Outside of Chesapeake Bay
Sphaeroma terebrans (Mangrove Isopod) is considered a major destroyer of wooden structures in tropical waters, particularly in low salinities where other borers, such as shipworms and Limnoria spp. are absent (Becker 1971). Atwood (1922) considered S. terebrans to be a less serious wood-boring pest than the former, because 'Its activities are confined to the tidal plane, and it is not often found at the greater depths in which the teredo and the limnoria work.' To the extent that S. terebrans might limit the growth of mangroves, it could have negative consequences on fisheries, as well as promoting coastal erosion. Since the introduced status of this species is not widely realized, the extent of its impacts on mangrove ecosystems is not fully understood (Carlton and Ruckelshaus 1997).
References- Atwood 1922; Becker 1971; Carlton and Ruckelshaus 1997
Ecological Impacts on Chesapeake Native Species
At present, the occurrence and abundance of Sphaeroma terebrans (Mangrove Isopod) in the Chesapeake region is uncertain, so this species has no significant ecological impacts.
In FL and in tropical regions, S. terebrans is important as a factor in the recycling of dead wood (Becker 1971) as a major factor regulating the growth of mangroves (Perry and Brusca 1989; Rehm and Humm 1973; Ribi 1982; Simberloff et al. 1978), and also as a borer in tidal marsh vegetation (Estevez 1994).
Herbivory- Sphaeroma terebrans apparently does not consume wood directly, but uses it for shelter, tunnelling into it and filter-feeding, and also probably feeding on bacteria, fungi etc. growing on the tunnel walls (Becker 1971; Estevez 1975). However, a cellulase has been reported from some wood-boring Sphaeroma spp, so direct consumption of wood cannot be ruled out (Becker 1971). Sphaeroma terebrans burrows into the aerial roots of Rhizophora mangle (Red Mangrove) (Humm and Rehm 1973), hollowing them out, and into the rhizomes of Juncus roemerianus (Black Needle Rush) plants in tidal marshes (Estevez 1994).
Habitat Change - Sphaeroma terebrans clearly has an important role in the dynamics of Rhizophora mangle (Red Mangrove) communities, but the precise nature of its effects on mangrove communities has been a subject of study and debate. Initially, it was regarded as destroyer of mangroves (Humm and Rehm 1973), but S. terebrans were also found to increase the frequency of root branching (Simberloff et al. 1978), and to differentially infest roots farther from established roots, resulting in increased density of roots near the stand (Ribi 1982). Perry and Brusca (1989), working with the similar Pacific S. peruvianum, found that the mangrove's responses to herbivory did not offset the loss of productivity due to Sphaeroma's burrowing. Sphaeroma terebrans effects on marsh vegetation could also encourage marsh erosion (Estevez 1994).
References - Becker 1971; Estevez 1994; Humm and Rehm 1973; Perry and Brusca 1989; Ribi 1982; Simberloff et al. 1978
Ecological Impacts on Other Chesapeake Non-Native Species
Sphaeroma terebrans (Mangrove Isopod) because of its scarcity, has no significant impacts on introduced biota in the Chesapeake region.
References
Atwood, W. G. (1922) Marine borers, Proceedings of the American Society of Civil Engineers 48: 1408-14241996 09.522 Field and lab methods in water quality analysis- Fall 1996.. http://gurukel.ucc.american.edu/banta/qf_aalltxhhtml
Becker, Gunther (1971) On the biology, physiology, and ecology of marine wood-boring crustaceans., In: Gareth Jones, E. B.//Eltringham, S. K.(Eds.) Marine borers, fungi, and fouling organisms of wood.. , Brussels. Pp. 303-326
Carlton, James T.; Ruckelshaus, Mary H. (1997) Nonindigenous marine invertebrates and algae of Florida, In: Simberloff, Daniel, Schmitz, Don C., Brown, Tom C.(Eds.) Strangers in Paradise: Impact and Management of Nonindigenous Species in Florida. , Washington, D.C.. Pp. 187-201
Conover, David O.; Reid, George K. (1975) Distribution of the boring isopod Sphaeroma terebrans in Florida, Florida Scientist 38: 65-72
Estevez, Ernest D. (1994) Inhabitation of tidal salt marshes by the estuarine wood-boring isopod Sphaeroma terebrans in Florida., In: Thompson, M.-F. and Nagabhushanam, R.(Eds.) Recent developments in biofouling control. , New Delhi. Pp. 97-105
Harrison, K.; Holdich, D. M. (1984) Hemibranchiate sphaeromatids (Crustacea: Isopoda) from Queensland, Australia, with a world-wide review of the genera discussed, Zoological Journal of the Linnean Society 81: 275-387
Kensley, Brian; Nelson, Walter G.; Schotte, Marilyn (1995) Marine isopod biodiversity of the Indian River Lagoon, Florida, Bulletin of Marine Science 57: 136-142
Kensley, Brian; Schotte, Marilyn (1989) Guide to the marine isopod crustaceans of the Caribbean., , Washington, D.C.. Pp.
Kuhne, Helmut (1971) The identification of wood-boring crustaceans., In: Gareth Jones, E. B., and Eltringham. S.K.(Eds.) Marine Borers, Fungi, and Fouling Organisms of Wood.. , Paris. Pp. 65-88
Miller, Milton A. (1968) Isopoda and Tanaidacea from buoys in coastal waters of the continental United States, Hawaii, and the Bahamas (Crustacea), Proceedings of the United States National Museum 125: 1-53
Perry, Diane M.; Brusca, Richard C. (1989) Effects of the root-boring Sphaeroma peruvianum on red mangrove forests., Marine Ecology Progress Series 57: 287-292
Rehm, Andrew; Humm, Harold J. (1973) Sphaeroma terebrans: a threat to the mangroves of southwestern Florida., Science 182: 173-174
Ribi, Georg (1982) Differential colonization of roots of Rhizophora mangle by the wood boring isopod Sphaeroma terebrans as a mechanism to increase root density., Pubblicazioni della Stazione Zoologica di Napoli I: Marine Ecology 3: 13-19
Richardson, Harriet (1897) Description of a new species of Sphaeroma., Proceedings of the Biological Society of Washington 11: 105-107
Richardson, Harriet (1905) A monograph on the isopods of North America, United States National Museum Bulletin 54: 1-727
Schultz, G.A. (1969) The Marine Isopod Crustaceans, , Dubuque, Iowa. Pp.
Schultz, George A. (1978) Four marine isopod crustaceans from St. Catherines Island with a list of other species from Georgia, Georgia Journal of Science 36: 1-17
Simberloff, Daniel; Brown. Becky J.; Lowrie, Stuart (1978) Isopod and insect borers may benefit Florida mangroves., Science 201: 630-632
Van Engel, W. A. (1972) Subclass Cirripedia, Virginia Institute of Marine Science, Special Scientific Report 65: 143
Van Name, Willard G. (1936) The American land and fresh-water isopod Crustacea, Bulletin of the American Museum of Natural History 71: 1-535
Wallour, Dorothy Brown (1960) Thirteenth progress report on marine borer activity in test boards operated during 1959, , Duxbury, Massachusetts. Pp. 1-41