Erichsonella attenuata is a small, slender, elongate idoteid isopod.
Like other isopods, E. attenuate has seven pairs of legs. Two
pairs of antennae are present, and one of these is notably elongated
(around half the body length). It is a member of the suborder Valvifera,
whose members posess two door-like structures below the abdomen that serve
to protect the delicate gill structures (Rupert and Fox 1988).
Potentially Misidentified Species
The slender, elongate body and small body size aid in distinguishing
Erichsonella attenuata from other Florida marine isopods.
HABITAT AND DISTRIBUTION
Bostršm and Mattila (1999) report the US distribution of E.
attenuate extending from New Jersey to Florida (possibly
discontinuously) and the Gulf of Mexico. The GBIF database
[http://us.mirror.gbif.org/species/13792768] indicates a somewhat broader
western Atlantic distribution, from Maine south along both coasts of
Florida and west along the Gulf of Mexico to south Texas.
Erichsonella attenuata may be found in seagrass habitats throughout the IRL system (Kensley et al. 1995, Bostrom and Mattila 1999).
LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan
Lipson and Lipson (2006) indicate Erichsonella attenuata is a small
isopod, attaining a length of approximately 13 mm.
Kensley et al. (1995) indicate Erichsonella attenuata is one of the
three most common invertebrate species in Indian River Lagoon Halodule
beaudettei seagrass beds. It is also a numerical dominant in Zostera
marina and Ruppia maritime beds of lower Chesapeake Bay, representing more
than 40% of total macroinvertebrate secondary production (Fredette et al.
1990). Marsh (1973) includes E. attenuate as one of the 5 most
abundant non-colonial epifaunal inhabitants of the York River, VA,
Zostera community he studied.
Details on the reproductive ecology of Erichsonella attenuata from
the literature are lacking. General information on reproduction in marine
isopods is provided by Barnes (1987). Sexes are separate, and
fertilization is internal. Males use modified copulatory pleopods to
inject sperm into each of the female's two sternal gnopores. Eggs are
fertilized in the oviduct and brooded in a marsupium. In many species,
copulation occurs during or following a female molt.
Eggs and embryos are brooded in a marsupium and there is no free-living
larval stage. Rather, young emerge as a postlarval stage called the manca
stage whose last pair of legs is incompletely developed (Barnes 1987, SERTC
Marsh (1973) notes that a number of epifaunal species, including
Erichsonella attenuate, appear to migrate into bottom sediments
during the winter months in the York River, VA, but does not indicate
whether this is a response to low temperature, dieback of above-ground
seagrass biomass, or both.
Erichsonella attenuata is a euryhaline estuarine species. Its
presence within the gut contents of young-of-the-year yellow perch
(Perca flavescens) captured from the Severn River, a low salinity
Chesapeake Bay tributary, suggests E. attenuate can persist at
salinities of 7 ppt, and possibly as low as 2 ppt (Muncy 1962). Similarly,
Hoese (1960) reports the presence of E. attenuate at salinities
ranging from 13.4 ppt down to as low as 2.4 ppt in Mesquite Bay, TX.
Erichsonella attenuata is an epiphyte-grazing organism and is an
important link in seagrass food webs due to its abundance. Although it
appears to feed primarily on epiphytic microalgae, E. attenuate may
also be capable of directly utilizing seagrass as a food resource in the
absence of alternatives (Howard and Short 1986, Bostršm and Mattila 1999).
Duffy et al. (2001) experimentally demonstrated that E. attenuate
was quite capable of reducing the epiphyte load on seagrass by grazing.
Surface scrapings of Zostera marina by Marsh (1973) revealed
epiphytic material consisted of nematodes, rotifers, diatoms and other
microorganisms, sediment and detritus. The author noted E.
attenuate as among the grazers utilizing this heterogeneous resource.
Erichsonella attenuata is an important food resource for predatory
seagrass community members. At times, they are consumed in large numbers
by seagrass-associated fish predators. A study by Ryer and Orth (1987) in
lower Chesapeake Bay, for example, reveals E. attenuate to be the
fall seasonal dominant prey item for seagrass-associated northern pipefish
(Syngnathus fuscus). In another lower Chesapeake Bay study, Orth
and Heck (1980) determined E. attenuate was also a component in the
diets of juvenile black sea bass (Centropristis striata).
In the presence of a predatory fish, E. attenuate has been observed
under experimental conditions to occupy habitat based on refuge value over
food value. In the absence of immediate predation threat, food value was
the primary determinant of habitat preference (Bostršm and Mattila 1999).
E. attenuate is also preyed upon by other macroinvertebrates.
McDermott (1976) reported predation on E. attenuate by the nemertean
worm Zygonemertes virescens under laboratory conditions.
Erichsonella is a tropical to warm-temperate genus occupying
vegetated marine habitats from the intertidal to 20 m (Pires 1984, Ruppert
and Fox 1988). E. attenuate preferentially selects habitats based
largely on food value (Bostršm and Mattila 1999). Field manipulations
conducted in Waquoit Bay, MA, Zostera beds revealed an increase in
macroalgal density appeared to increase the abundance of E.
attenuate and other free-swimming macroinvertebrates (O'Brien et al.
No information is available at this time
Barnes. 1987. Invertebrate Zoology. 5th edition. CBS College Publishing,
NY. 893 p.
Bostrom C and J Mattila. 1999. The relative importance of food and shelter
for seagrass-associated invertebrates: A latitudinal comparison of habitat
choice by isopod grazers. Oecologia 120:162-170.
Duffy JE, MacDonald KS, Rhode JM, and JD Parker. 2001. Grazer diversity,
functional redundancy, and productivity in seagrass beds: An experimental
test. Ecology 82:2417-2434.
Fredette TJ, Diaz RJ, Van Montfrans J, and RJ Orth. 1990. Secondary
production within a seagrass bed (Zostera marina and Ruppia
maritime) in lower Chesapeake Bay. Estuaries 13:431-440.
Hoese HD. 1960. Biotic changes in a bay associated with the end of a
drought. Limnology and Oceanography 5:326-336.
Howard RK and FT Short. 1986. Seagrass growth and survivorship under the
influence of epiphyte grazers. Aquatic Botany 24:287-302.
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University Press, MD. 324 p.
Kensley B, Nelson WG, and M Schotte. 1995. Marine isopod biodiversity of
the Indian River lagoon, Florida. Bulletin of Marine Science 57:136-142.
Marsh AG. 1973. The Zostera Epifaunal Community in the York River,
Virginia Chesapeake Science 14:87-97.
McDermott JJ. 1976. Observations on the food and feeding behavior of
estuarine nemertean worms belonging to the Order Hoplonemertea. Biological
Muncy RJ. 1962. Life history of the yellow perch, Perca flavescens,
in estuarine waters of Severn River, a tributary of Chesapeake Bay,
Maryland. Chesapeake Science 3:143-159.
Kristin MA, O'Brien M, Deegan LA, Finn JT, and SG Ayvazian. 1990. The
effects of macroalgae on the abundance and diversity of free-swimming
invertebrates in eelgrass beds of Waquoit Bay. Biological Bulletin
Orth RJ and KL Heck. 1980. Structural components of eelgrass (Zostera
marina) meadows in the lower Chesapeake Bay: Fishes. Estuaries
Pires AM. 1984. Taxonomic revision and phylogeny of the genus
Erichsonella with a discussion on Ronalea (Isopod,
valvifera). Journal of Natural History 18:665-683.
Rupert EE and RS Fox. 1988. Seashore Animals of the Southeast. A Guide to
Common Shallow-Water Invertebrates of the Southeastern Atlantic Coast.
University of South Carolina Press. 429 p.
Ryer CH and RJ Orth. 1987. Feeding ecology of the northern pipefish,
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Bay. Estuaries 10:330-336.
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